HK1111655B - A method and system for wavelength specific thermal irradiation and treatment - Google Patents

Abstract

A system for direct injection of selected thermal-infrared (IR) wavelength radiation or energy into articles for a wide range of processing purposes is provided. These purposes may include heating, raising or maintaining the temperature of articles, or stimulating a target item in a range of different industrial, medical, consumer, or commercial circumstances. The system is especially applicable to operations that require or benefit from the ability to irradiate at specifically selected wavelengths or to pulse or inject the radiation. The system is particularly advantageous when functioning at higher speeds and in a non-contact environment with the target.

Description

Method and system for wavelength specific thermal irradiation and treatment

Technical Field

Is free of

Background

The present invention relates to the injection of selected thermal Infrared (IR) wavelength radiation or energy directly into a target entity for a wide range of heating, treatment or therapeutic purposes. As described below, these purposes may include: heating, raising or maintaining the temperature of an article, or stimulating a target item in a range of different industrial, medical, consumer, or commercial environments. The methods and systems described herein are particularly applicable to operations that require or benefit from the ability to irradiate or pulse or inject radiation at specifically selected wavelengths. The invention is particularly advantageous when the object is moving at a high speed and in a contactless environment with the object. The present invention provides an infrared system having a selected narrower wavelength that is highly programmable for a wide range of end-use applications. The present invention teaches a new and novel type of infrared illumination system consisting of an engineered array of the most preferred new class of narrower wavelength solid state Radiation Emitting Devices (REDs), one variant of which will be specifically referenced later in this document.

More particularly, the present invention is directed to a novel and efficient way of injecting infrared radiation of an optimal wavelength into a target for affecting the temperature of the target in some way. By way of a few example samples, the "targets" for infrared injection may be a variety of targets, from individual components in a manufacturing operation, to a processing area for a continuous roll of material, to food in a cooking process, to a human patient in a medical environment.

Although the specific embodiments of the invention described below are examples that relate specifically to plastic bottle preform reheating operations, the principles contained therein may also be applied to many other known situations. It also applies to single-stage plastic bottle blow-moulding operations, in which the injection-moulding operation is carried out continuously before the blow-moulding operation. For example, in this deployment, the method and apparatus of the present invention provide similar advantages to known techniques, but will use different sensing and control at the entrance of the reheat section of the process to handle the change in initial temperature.

In general, an ideal infrared heating system optimally raises the temperature of the target with minimal energy consumption. Such a system may include such an apparatus: it may convert its electrical energy input directly to a radiant electromagnetic energy output having a selected single or narrow band of wavelengths for the target such that the energy comprising the irradiation is partially or fully absorbed by the target and converted to heat. The more efficient the conversion of electrical input to radiated electromagnetic output, the more efficient the system can perform. The more efficiently the radiated electromagnetic wave is directed to expose only the desired area on the target, the more efficiently the system will do this. The radiation emitting device selected for use should have both instant "on" and instant "off" features so that when the target is not being illuminated, no input and output energy is wasted. The more efficiently the exposed target absorbs radiant electromagnetic energy to convert it directly into heat, the more efficiently the system can operate. For an optimal system, care must be taken to properly select so that a set of system output wavelengths matches the absorption characteristics of the target. These possible wavelengths will be chosen differently for different target applications of the invention to best suit the different absorption characteristics of the different materials and to suit different desired results.

In contrast, the use of a range of different types of radiant heating systems for a wide range of processes and treatments is well known in the art and in the industry. Techniques previously available for such purposes produce a relatively broad band spectrum of emitted radiant electromagnetic energy. It may be referred to as an infrared heating, treatment, or treatment system, and in practice, it often produces radiant energy outside the infrared spectrum.

The infrared portion of the spectrum is typically divided into three wavelength classes. These fractions are generally classified into near-infrared, mid-infrared, and long-infrared wavelength bands. Although the exact cut-off point is not clearly established for these general regions, it is believed that the near infrared region spans a range between visible and 1.5 microns. The mid-infrared region spans a range from 1.5 to 5 microns. The long wave infrared region is generally considered to be between 5 and 14 microns and above.

Radiant infrared sources that have previously been used in industrial, commercial and medical, thermal processing or processing equipment produce a broad band of wavelengths that are rarely limited to one portion of the infrared spectrum. Although its broad-band output may peak in a particular range of the infrared spectrum, it typically has a large number of output tails extending into adjacent regions.

For example, quartz infrared heating lamps, which are well known in the art and are used for various process heating operations, will typically produce peak outputs in the 0.8 to 1 micron range. Although the output may peak between 0.8 and 1 micron, these lamps have a significant amount of output in a broad contiguous set of wavelength bands of about 3.5 microns from the Ultraviolet (UV) through the visible and out into the mid-infrared. It is clear that although the peak output of quartz lamps is in the near infrared range, there is a large amount of output in the visible and mid infrared ranges. Thus, existing broad spectrum infrared sources cannot be selected to be the preferred wavelength most needed for any given heating, treatment or therapeutic application. This is inherently a broad spectrum treatment or process and has been widely used since there has been no practical alternative prior to the present invention. The major temperature rise in many targets is due to absorption of thermal IR energy having one or more narrow band wavelengths. Thus, much of the broadband IR energy output is wasted.

Nonetheless, quartz infrared lamps are widely used in both the discrete component industry and the continuous materials handling industry. Various methods are commonly used to assist in directing the emission from the quartz lamp to the target in the process, including various reflector types. Regardless of how the energy is concentrated on the target, quartz lamps are usually powered continuously. Whether the object in the process is a continuously produced article or a discrete assembly. The reason for this is mainly due to the relatively low thermal response time of quartz lamps, which is usually measured in seconds.

The field in which improved energy injection is particularly needed relates to blow molding operations. More specifically, plastic bottle stretch blow molding systems thermally condition preforms prior to a stretch blow molding operation. One aspect of this process is referred to in the art as a reheat operation. In the reheat operation, the preforms formed by the injection molding or compression molding process are allowed to thermally stabilize to room temperature. The preforms are then fed into a stretch blow molding system, where the preforms are heated to a temperature at an earlier stage of the system, with the thermoplastic preform material at a temperature that is optimal for a subsequent blow molding operation. This condition is met when transporting the preforms along a path through a heating section to a blow molding section of a machine. In the blow molding portion, the preform is first mechanically stretched and then blown into a larger capacity vessel or container.

The energy consumption cost is a large percentage of the cost of a finished article manufactured using a blow molding operation. More specifically, the prior art to date requires considerable energy to heat or thermally condition polyethylene terephthalate (PET) from ambient temperature to 105 ℃ in the reheat section of a stretch blow molding machine. From all of the manufacturing efficiency considerations, it is apparent that it would be advantageous from an economic and environmental standpoint to reduce the energy consumption rates associated with the operation of the thermal conditioning portion of the stretch blow molding system.

U.S. Pat. No. 5,322,651 describes an improvement in the method of heat treating thermoplastic preforms. In this patent, the conventional practice of using broadband Infrared (IR) radiant heating for the thermal treatment of plastic preforms is described. The text in this patent is cited, "heating using infrared radiation gives a favorable output and allows for increased productivity, compared to other heating or heat treatment methods using, for example, convection and conduction, and taking into account the low thermal conductivity of the material.

The particular improvement to the prior art described in this patent relates to the manner in which the excess energy emitted during the IR heating of the preforms is managed. In particular, this patent focuses on the energy emitted during the heating process (by absorption, conduction, and then convection at a location outside of the preforms) which ultimately results in an increase in the air temperature in the oven volume surrounding the conveyed preforms. It has been demonstrated that convective heating of the preforms by a hot gas flow results in non-uniform heating of the preforms and thus has a detrimental effect on the manufacturing operation. Patent 5,322,651 describes a method of counteracting the effects of inadvertent heating of the air flow surrounding the preform during the IR heating operation.

It may be expected that the transfer of thermal energy from historical prior art IR heating elements and systems to the target preforms is not a completely efficient process. Ideally, 100% of the energy expended in thermally conditioning the preform will end up in the volume of the preform in the form of thermal energy. Although not specifically mentioned in the above referenced patents, current prior art blow molding machines claim typical conversion efficiency values (energy into the transported preforms/energy consumed by the IR heating elements) ranging between 5% and 10%. Any improvement to the method or components associated with infrared heating of preforms that improves the conversion efficiency values would be highly advantageous and represent a substantial reduction in energy costs to users of stretch blow molding machines.

There are many factors that work together to establish the energy conversion efficiency performance of the IR heating elements and systems used in current prior art blow molding machines. As noted above, conventional thermoplastic preforms, such as PET preforms, are heated to a temperature of about 105 ℃. This is typically accomplished in prior art blow molding machines using commercially available broadband quartz infrared lamps. In high speed/high productivity machines, these typically take the form of large banks of very high wattage bulbs. The resultant energy consumption of all banks of quartz lamps becomes a huge current consumption, which is up to several thousand kilowatts on the fastest machines. Two factors associated with these types of IR heating elements that contribute to the overall energy conversion efficiency performance of the overall heating system are the color temperature of the filament and the optical transmission characteristics of the filament bulb.

Another factor that has a significant impact on the overall energy conversion performance of the thermal conditioning subsystem of current prior art blow molding machines is flux control or lensing measures that are used to direct the IR radiation emitted by the heating element into the volume of preforms that are transported through the system. In most prior art blow molding machines, certain measures are deployed to direct the IR radiation flux emitted by the quartz lamps into the volume of the preforms. In particular, metallized reflectors work effectively to reduce the amount of emitted IR radiation wasted in these systems.

Yet another factor that has an impact on the energy conversion efficiency performance of the IR heating subsystem is the degree to which energy is input to the generally stationary IR heating element in synchronization with the movement of preforms moving through the heating system. More specifically, if the stationary IR heating element continuously consumes a fixed amount of input energy, even in the absence of preforms in the immediate vicinity of the heater due to their continuous movement through the system, then the energy conversion efficiency performance of the system is clearly not optimized. Indeed, the low physical response time of commercial quartz lamps and the relatively fast preform transfer speed in prior art blow molding machines preclude any attempt to successfully modulate the lamp input power to synchronize it with discrete part movement and thus achieve an improvement in overall energy conversion efficiency performance.

U.S. patent No. 5,925,710, U.S. patent No. 6,022,920, and U.S. patent No. 6,503,586B1 all describe similar methods to increase the percentage of the energy emitted by the IR lamp that is absorbed by the transported preforms used in the blow molding process. All of these patents describe in varying amounts of detail the general practice in the prior art reheat blow molding machines to use quartz lamps as IR heating elements. In a reheat blow molding process, preforms that were previously injection molded and allowed to stabilize to room temperature are reheated to blow temperature just prior to the blow molding operation. These above-referenced patents describe how polymers in general and PET in particular can be heated more efficiently by IR absorption than is possible using conductive or convective means. These patent documents represent the measured absorption coefficient of PET as a function of wavelength in the figures. Many strong molecular absorption bands occur in PET, mainly in the IR wavelength band above 1.6 microns. Quartz lamps are known to emit radiation over a broad spectrum, the exact emission spectrum being determined by the filament temperature as defined by planck's law.

As used in prior art blow molding machines, quartz lamps operate at filament temperatures around 3000 ° K. At this temperature, the lamp has a peak radiation emission of around 0.8 microns. However, because the emission is a blackbody type emission, as is known in the art, quartz filaments emit a continuous spectrum of energy, from X-rays to very long IR. At 3000 ° K, the emission rises through the visible region, peaks at 0.8 microns, and then gradually decreases as it begins to overlap with a significant PET absorption region starting around 1.6 microns.

What is not described in any of these patents is the effect of the quartz bulb on the emission spectrum of the lamp. The quartz material used to make bulbs for commercial quartz lamps has an upper transmission limit of about 3.5 microns. Beyond this wavelength, most of any energy emitted by the enclosed filament is absorbed by the quartz glass envelope enclosing the filament, and therefore is not directly available for preform heating.

For the reasons outlined above, in existing prior art blow molding machines that use quartz lamps to reheat PET preforms to blow molding temperatures, the range of absorptive heating occurs between 1 and 3.5 microns. The above-referenced set of patents (5,925,710, 6,022,920, and 6,503,586B1) all describe different methods and means for altering the natural absorption characteristics of the preform, thereby improving the overall energy conversion efficiency performance of the reheat process. In all of these patents, foreign materials are described as being added to the PET preform stock, with the sole purpose of increasing the absorption coefficient of the mixture. These described methods and means are intended to affect the material optical absorption properties in the range from near IR around 0.8 microns out to 3.5 microns. While a viable means of increasing the overall energy conversion efficiency performance of the reheat process, changes in the absorption characteristics of preforms that are very beneficial in reducing the manufacturing cost of the container can also have a detrimental effect on the appearance of the finished container. This reduction in the optical clarity of the container (sometimes referred to as haziness of the container) makes this general approach a non-optimal solution to this manufacturing challenge.

U.S. Pat. No. 5,206,039 describes a one-stage injection molding/blow molding system consisting of improved means of conditioning and transporting preforms from the injection stage to the blow stage of the process. In this patent, the independent operation of an injection molding machine and a blow molding machine, each of which adds a significant amount of energy to the process of thermally conditioning the thermoplastic material, is described as being wasteful. This patent teaches that using a single stage manufacturing process reduces the overall rate of energy consumption and manufacturing costs. This reduction in energy consumption is primarily due to the fact that most of the thermal energy required to perform the blow molding operation is retained by the preforms after the injection molding stage. More specifically, in the one-stage process described in the' 039 patent, the preform is not allowed to stabilize to room temperature after the injection molding process. Rather, the preform moves directly from the injection molding stage to the thermal conditioning portion and then continues to move into the blow molding portion.

The thermal conditioning section described in the' 039 patent has the following characteristics: a smaller amount of thermal energy can be added and the preform subjected to a controlled stabilization period. This is in contrast to the requirement of the thermal conditioning section of a reheat blow molding machine during the 2-stage process, where a relatively large amount of energy is required to heat the preforms to the blow temperature. Although the operation of single stage molding/blow molding machines is known in the art, the quality issues of finished containers continue to exist for these machines. These quality problems are linked to temperature variations between preforms as the flow of preforms enters the blow molding stage. Despite the advantages described in the' 039 patent, by using the prior art IR heating and temperature sensing means and methods to date, the process of thermally conditioning preforms immediately after they are removed from the injection molding process still results in preforms having varying heat capacities entering the blow molding stage. Variations in the heat capacity of the incoming preforms result in finished containers having varying properties and qualities. Due to inefficiencies in the ability to custom tune the IR heating process on a preform-by-preform basis, manufacturers choose to use a reheat blow molding process to achieve the desired quality level. For this reason, the industry's reliance on reheat methods continues for the highest productivity applications. Also, because preforms are typically manufactured by commercial converters and sold to end users who will blow and fill containers, the reheat process has been more prevalent.

The prospect of an overall improvement in the efficiency and/or functionality of the IR heating section of a blow molding machine is clearly advantageous from an operating cost as well as product quality standpoint. While several attempts have been made to present improvements to prior art IR heating subsystems, there are still significant drawbacks. It is an object of the present invention to overcome these drawbacks by introducing a novel IR heating element and method.

Solid state reflectors or LEDs are well known in the art in the field of solid state electronics. It is known that photon or flux emitters of this type are commercially available and operate at various wavelengths, from the Ultraviolet (UV) to the near infrared. LEDs are constructed from semiconductor materials doped with appropriate N and P dopants. A volume of semiconductor material appropriately processed to contain a P-doped region in direct contact with an N-doped region formed of the same material is given the generic name "diode". Diodes have many important electrical and optoelectronic properties that are well known in the art. For example, it is well known in the art that at the physical interface between the N-doped and P-doped regions of the semiconductor diode being formed, there is a characteristic band gap in the material. This band gap relates to the difference in the energy level of electrons in the conduction band located in the N region from the energy level of electrons in the lower effective P region orbital. When electrons are induced to flow across the PN junction, transitions of electron energy levels from the N-region conduction orbital to the lower P-region orbital begin to occur, resulting in the emission of a photon for each such electron transition. The exact energy level or wavelength of the emitted photon corresponds to the energy drop of the conducted electron.

In short, LEDs operate as direct current to photon emitters. Unlike filament or other blackbody type emitters, there is no need to convert the input energy into an intermediate form of heat before the output photons can be extracted. Because of this direct current-to-photon behavior, LEDs have the property of being extremely fast acting. LEDs have been used in many applications where extremely high pulse rate UV, visible and/or near IR light generation is required. One particular application where the high pulse rate characteristics of LEDs are particularly useful is in automated discrete part vision sensing applications, where visible or near infrared light is used to form a lens focused image, which is then viewed in a computer.

Unlike filament-based sources, LEDs emit over a relatively limited range of wavelengths corresponding to the particular band gap of the semiconductor material used. This characteristic of LEDs is particularly useful in applications requiring wavelength selective operation such as component lighting, status indication, or optical communication. More recently, large groups of LEDs have been used for larger scale forms of visible illumination, or even for signaling lights such as automobile tail lights or traffic lights.

Disclosure of Invention

The present invention provides for the construction of small or large numbers of infrared radiation devices that are highly wavelength selective and can facilitate the use of infrared radiation for entirely new types of applications and technologies that have not been available in the past.

It is an object of the present invention to provide a molding or other processing or treatment system having a thermal IR heating system that possesses improved IR energy conversion efficiency performance.

It is another object of the present invention to provide an IR heating system having IR penetration depth properties tuned to the particular material to be treated or targeted.

It is another object of the present invention to provide a thermal IR radiation system that can incorporate an engineering mix of REDs that can produce IR radiation in those selected narrow wavelength bands that are optimal for certain types of applications.

It is another object of the present invention to provide an IR heating system that can be driven in a pulsed mode; the pulse pattern is particularly suited to provide IR heat to discretely manufactured parts as they are transported during the manufacturing process, or to facilitate simultaneous tracking of an irradiation target.

It is another object of the present invention to provide an IR heating element that can be more easily directed via a metallized reflector element.

It is another object of the present invention to provide an IR heating system that can cooperate in conjunction with a preform temperature measurement system to provide preform-specific IR heating capabilities.

It is another object of the present invention to provide an IR heating element that is fabricated as a direct current to photonic IR solid state emitter or array of Radiation Emitting Diodes (REDs).

It is a further advantage of the present invention to provide an infrared illumination system that has substantial radiant output at single or multiple narrow wavelength bands that are highly targeted.

Yet another advantage of the present invention is functionality that generates powerful thermal infrared radiation and is highly programmable for at least one of location, intensity, wavelength, on/off rate, directionality, pulse frequency, and product tracking.

Yet another advantage of the present invention is that it facilitates a more efficient method of inputting energy for injecting thermal energy than current wide band sources.

Yet another advantage of the present invention in heating bottle preforms is the ability to maintain efficient heating without the need for additives that would reduce the visual clarity and appearance quality of the finished container.

It is a further object of the present invention to combine programmability and pulsing capability to provide a general radiant heating system for a wide range of applications for which it is applicable to provide increased functionality of wavelength selective infrared radiation.

Yet another advantage of the present invention is the ability to facilitate very fast very high intensity bursts with much higher instantaneous intensity than steady state intensity.

Yet another advantage of the present invention is that waste heat can be easily conducted to another location where it is needed or can be conducted out of the use environment to reduce unintended heating.

Yet another advantage of the present invention is that RED devices can be packaged at high density to produce solid state thermal IR output power levels heretofore impractical to implement.

Drawings

Fig. 1 is a cross-sectional view of a portion of an exemplary semiconductor device constructed in one embodiment of the invention.

Fig. 2 is a cross-sectional view of a buffer layer of an exemplary semiconductor device constructed in one embodiment of the invention.

Fig. 3 is a cross-sectional view of a quantum dot layer of an exemplary semiconductor device constructed in one embodiment of the invention.

Fig. 4 is a cross-sectional view of a radiation emitting diode including a quantum dot layer constructed in one embodiment of the present invention.

Fig. 5 is a cross-sectional view of a radiation emitting diode including a quantum dot layer constructed in an embodiment of the present invention.

Fig. 6 is a cross-sectional view of a radiation emitting diode including a quantum dot layer constructed in an embodiment of the present invention.

Fig. 7 is a cross-sectional view of a laser diode containing a quantum dot layer constructed in an embodiment of the present invention.

Fig. 8 shows a diagrammatic representation of a single RED semiconductor device.

Fig. 9 and 10 show the relative percentage of infrared energy transmitted through a 10mil thick portion of PET as a function of wavelength.

Fig. 11a, 11b and 11c show a typical collection of individual RED emitters packaged together into a RED heater element.

Fig. 12a and 12b show a preferred deployment of RED heater elements within a blow-molding machine.

Figure 13 shows a preferred method of heat treatment of the preforms described by the present invention.

FIGS. 14-16 show an alternative method of heat treatment of thermoplastic preforms in accordance with the present invention.

Fig. 17 shows a RED heater element advantageously applied to a dynamically transported component.

Detailed Description

The benefits of providing wavelength specific illumination can be illustrated by referring to the hypothetical radiant heating example. Assume that a material that is substantially transparent to electromagnetic radiation from the visible range to the mid-infrared range requires process heating to support a certain manufacturing operation. It is also assumed that such substantially transparent materials have a narrow but significant molecular absorption band between 3.0 and 3.25 microns. The examples described above are representative of how the presently described embodiments may be most advantageously applied within the industry. If the parameters of this particular process heating application dictate the use of radiant heating technology, then the current prior art will require the use of quartz lamps operating at a filament temperature of 3000 ° K. At this filament temperature, the basic physical calculation yields the following results: only about 2.1% of the total emitted radiation energy of the quartz lamp falls within the band of 3.0 to 3.25 μm, wherein a favorable energy absorption will occur. The ability to produce only wavelength specific radiant energy output described in this disclosure holds the prospect of greatly improving the efficiency of various process heating applications.

The present invention is directed to a novel and novel method capable of directly outputting a large amount of infrared radiation having a selected wavelength for use in place of such a wide band type device.

Recent advances in semiconductor processing technology have made it possible to use direct electron-to-photon solid state emitters that operate in the general mid-infrared range above 1 micron (1,000 nanometers). These solid state devices operate in a similar manner to ordinary Light Emitting Diodes (LEDs) except that they do not emit visible light, but instead emit true thermal IR energy at the longer mid-infrared wavelengths. These are an entirely new class of devices that utilize quantum dot technology, breaking the barrier of not being able to produce a viable, cost-effective solid state device that can act as a direct electron-to-photon converter whose output is pseudo-monochromatic and in the mid-infrared wavelength band.

To distinguish this new class of devices from conventional shorter wavelength devices (LEDs), it is preferable to describe these devices as Radiation Emitting Diodes (REDs). The device has the property of emitting radiant electromagnetic energy in a tightly confined wavelength range. Furthermore, through appropriate semiconductor processing operations, RED can be tuned to emit at a particular wavelength that is most advantageous for a particular radiation processing application.

In addition, innovations have been developed in the area of RED technology that involve: a doped planar region is formed in contact with an oppositely doped region formed as a randomly distributed array of small areas of material or quantum dots for the generation of photons in and possibly beyond the target IR range. Full application of this fabrication technique, or other techniques such as the development of novel semiconductor compounds, will yield suitable pseudo-monochromatic solid-state mid-ir emitters for the present invention. Alternative semiconductor technologies may also be used in the mid-infrared, as well as in the long wavelength infrared, which would be a suitable building block for practicing the present invention.

The direct electron (or current) to photon conversion contemplated within these described embodiments occurs within a narrow wavelength range (often referred to as a pseudo-monochromatic) consistent with the inherent bandgap and quantum dot geometry of this fabricated diode emitter. It is expected that the half-power bandwidth of the candidate RED transmitter will fall in the range of 20-500 nanometers. The narrower width of such type of infrared emitter should support the various wavelength-specific illumination applications identified throughout this disclosure. A series of RED devices and techniques for making these devices are the subject of the following separate patent applications: samar Sinharoy and Dave Wilt are U.S. application No. 60/628,330 entitled "Quantum dot Semiconductor Device" (attorney docket No. ERI.P. US0002; express mailing label No. EL 726091609US) filed on 16/11/2004 by assigned inventors, which is incorporated herein by reference.

Semiconductor devices are known in the art in accordance with this "Quantum Dot Semiconductor Device" application. It is used in photovoltaic cells that convert electromagnetic radiation into electricity. These devices may also be used as Light Emitting Diodes (LEDs), which convert electrical energy into electromagnetic radiation (e.g., light). For most semiconductor applications, semiconductors are prepared for a desired band gap (electron volts) or a desired wavelength (micrometers) and in a manner such that the semiconductor can conform to the desired band gap range or wavelength range.

The ability to achieve a particular wavelength of emission or electron volt of energy is not trivial. In practice, semiconductors are limited by the choice of particular materials, the energy gap of the particular materials, their lattice constant, and their inherent emissive capabilities. One technique for tuning semiconductor devices is to use binary or ternary compounds. By varying the compositional characteristics of the device, a technically useful device can be designed.

The design of the semiconductor device may also be manipulated to adjust the behavior of the device. In one example, quantum dots may be included within a semiconductor device. These dots are considered quantum confined carriers and therefore alter the energy of photon emission compared to a sample of the same semiconductor. For example, U.S. Pat. No. 6,507,042 teaches a semiconductor device including a quantum dot layer. In particular, it teaches indium arsenide (InAs) quantum dots deposited on an indium gallium arsenide (InxGa1-xAs) layer. This patent discloses that the emission wavelength of photons associated with quantum dots can be controlled by controlling the amount of lattice mismatch between the quantum dots (i.e., InAs) and the layer on which the dots are deposited (i.e., InxGa 1-xAs). This patent also discloses the fact that the lattice mismatch between the InxGa1-xAs substrate and the InAs quantum dots can be controlled by varying the indium content within the InxGa1-xAs substrate. As the amount of indium within the InxGa1-xAs substrate increases, the degree of mismatch decreases and the wavelength associated with photon emission increases (i.e., the energy gap decreases). Indeed, this patent discloses that an increase in the amount of indium within the substrate from about 10% to about 20% may increase the wavelength of the associated photons from about 1.1 μm to about 1.3 μm.

While the techniques disclosed in U.S. Pat. No. 6,507,042 may prove useful in providing devices that can emit or absorb photons having a wavelength of about 1.3 μm, the ability to increase the amount of indium within an InxGa1-xAs substrate is limited. In other words, as the content of indium increases above 20%, 30% or even 40%, the extent of defects or flaws within the crystal structure becomes limiting. This is particularly true when the InxGa1-xAs substrate is deposited on a gallium arsenide (GaAs) substrate or wafer. Therefore, a device that emits or absorbs photons of longer wavelengths (lower energy gap) cannot be realized by using the technology disclosed in U.S. Pat. No. 6,507,042.

Therefore, since a device that emits or absorbs photons having a wavelength longer than 1.3 μm is required, a semiconductor device having such properties is still required.

In general, RED provides a semiconductor device comprising an InxGa1-xAs layer, wherein x is a mole fraction of indium from about 0.64 to about 0.72 weight percent, and quantum dots are located on the InxGa1-xAs layer, wherein the quantum dots comprise InAs or AlzIn1-zAs, wherein z is a mole fraction of aluminum less than about 5 weight percent.

The present invention also includes: a semiconductor device comprising quantum dots (including InAs or AlaIn1-zAs), wherein z is a mole fraction of aluminum less than 5 wt%, and a capping layer contacting at least a portion of the quantum dots, wherein lattice constants of the quantum dots and the capping layer are mismatched by at least 1.8% and less than 2.4%.

The semiconductor device includes a quantum dot layer comprising indium arsenide (InAs) or indium aluminum arsenide (AlzIn1-zAs, where z is 0.05 or less) quantum dots on an indium gallium arsenide (InxGa1-xAs) layer, which may be referred to as InxGa1-xAs matrix cladding. The dots and lattice constants of the InxGa1-xAs matrix layer are mismatched. The lattice mismatch may be at least 1.8%, in other embodiments at least 1.9%, in other embodiments at least 2.0%, and in other embodiments at least 2.05%. Advantageously, the mismatch may be less than 3.2, in other embodiments less than 3.0%, in other embodiments less than 2.5%, and in other embodiments less than 2.2%. In one or more embodiments, the lattice constant of the InxGa1-xAs matrix cladding is less than the lattice constant of the dots.

In those embodiments where the dots are located on an InxGa1-xAs cladding matrix, the molar concentration of indium (i.e., x) within this cladding matrix layer may be from about 0.55 to about 0.80, optionally from about 0.65 to about 0.75, optionally from about 0.66 to about 0.72, and optionally from about 0.67 to about 0.70.

In one or more embodiments, the InxGa1-xAs cladding matrix is located on an indium phosphorous arsenide (InP1-yAsy) layer that is lattice matched to the InxGa1-xAs cladding matrix. In one or more embodiments, the InP1-yAsy layer on which the InxGa1-xAs cladding is deposited is one of a plurality of graded (continuous or discrete) InP1-yAsy layers that exist between the InxGa1-xAs cladding and the substrate on which the semiconductor is supported. In one or more embodiments, the substrate comprises an indium phosphide (InP) wafer. The semiconductor may also include one or more other layers, such as InxGa1-xAs layers, located between the InxGa1-xAs cladding and the substrate.

One embodiment is shown in fig. 1. Fig. 1, as well as the other figures, are schematic representations and are not drawn to scale with respect to the thickness of each layer or component, or comparatively, with respect to the relative thickness or dimension between each layer.

Device 1000 includes substrate 1020, optional conduction layer 1025, buffer structure 1030, capping layer 1040, and dot layer 1050. As is understood by those skilled in the art, certain semiconductor devices operate by converting electrical current to electromagnetic radiation or converting electromagnetic radiation to electrical current. The ability to control electromagnetic radiation or current within such devices is known in the art. The present disclosure does not necessarily alter these conventional designs, many of which are known in the art of manufacturing or designing semiconductor devices.

In one embodiment, substrate 1020 comprises indium phosphide (InP). The thickness of the InP substrate 1020 may be greater than 250 microns, in other embodiments greater than 300 microns, and in other embodiments greater than 350 microns. Advantageously, the thickness may be less than 700 microns, in other embodiments less than 600 microns, and in other embodiments less than 500 microns.

In one or more embodiments, contemplated semiconductor devices may optionally include an epitaxially grown layer of indium phosphide (InP). The thickness of this epitaxially grown indium phosphide layer can be from about 10nm to about 1 micron.

In one embodiment, optional conduction layer 1025 comprises indium gallium arsenide (InxGa 1-xAs). The molar concentration of indium (i.e., x) within this layer may be from about 0.51 to about 0.55, optionally from about 0.52 to about 0.54, and optionally from about 0.53 to about 0.535. In one or more embodiments, conduction layer 1025 is lattice matched to the InP substrate.

Conduction layer 1025 may be doped to a given value and have an appropriate thickness to provide sufficient conductivity for a given device. In one or more embodiments, the thickness can be from about 0.05 microns to about 2 microns, optionally from about 0.1 microns to about 1 micron.

In one or more embodiments, buffer layer 1030 includes indium phosphorous arsenide (InP 1-yAsy). In a particular embodiment, the buffer layer 1030 includes at least two, optionally at least three, optionally at least four, and optionally at least five InP1-yAsy layers, wherein the lattice constant of each layer increases as the layer increases in distance from the substrate 1020. For example, and as depicted in fig. 2, buffer structure 1030 includes first buffer layer 1032, second buffer layer 1034, and third buffer layer 1036. Bottom layer surface 1031 of buffer structure 1030 is adjacent substrate 1020 and top planar surface 1039 of buffer structure 1030 is adjacent barrier layer 1040. The lattice constant of second layer 1034 is greater than first layer 1032, and the lattice constant of third layer 1036 is greater than second layer 1034.

As will be appreciated by those skilled in the art, the lattice constant of the individual layers of buffer structure 1030 can be increased by varying the composition of the successive layers. In one or more embodiments, the concentration of arsenic within the InP1-yAsy buffer layer increases in each successive layer. For example, first buffer layer 1032 may include about 0.10 to about 0.18 mole fraction arsenic (i.e., y), second buffer layer 1034 may include about 0.22 to about 0.34 mole fraction arsenic, and third buffer layer 1036 may include about 0.34 to about 0.40 mole fraction arsenic.

In one or more embodiments, the increase in arsenic between adjacent buffer layers (e.g., between layer 1032 and layer 1034) is less than 0.17 mole fraction. It is believed that any defects formed between successive buffer layers that may be caused by a change in lattice constant due to an increase in arsenic content are not detrimental to the semiconductor. Techniques for using critical component fractionation in this manner are known, as described in U.S. patent No. 6,482,672, which is incorporated herein by reference.

In one or more embodiments, first buffer layer 1032 can be from about 0.3 to about 1 micron thick. In one or more embodiments, the top buffer layer is typically thicker to ensure that the lattice structure is completely relaxed.

In one or more embodiments, individual buffer layers (e.g., buffer layer 1036) at or near the top 1039 of buffer structure 1030 are designed to have a thickness from aboutTo aboutOptionally from aboutTo aboutThe lattice constant of (2).

In one or more embodiments, the individual buffer layers (e.g., buffer layer 1032) at or near the bottom 1031 of buffer structure 1030 are preferably designed to be within the confines of a critical composition grading technique. In other words, because the first buffer layer (e.g., buffer layer 1032) is deposited on an InP wafer, the amount of arsenic present in the first buffer layer (e.g., layer 1032) is less than 17 mole fraction.

Cladding layer 1040 includes InxGa 1-xAs. In one or more embodiments, this layer is preferably lattice matched to the in-plane lattice constant of the top buffer layer at or near the top 1039 of the buffer structure 1030. The term "lattice matched" refers to successive layers characterized by lattice constants that are within 500 parts per million (i.e., 0.005%) of each other.

In one or more embodiments, capping layer 1040 can have a thickness from about 10 angstroms to about 5 microns, optionally from about 50nm to about 1 micron, and optionally from about 100nm to about 0.5 microns.

In one or more embodiments, quantum dot layer 1050 includes indium arsenide (InAs). Layer 1050 preferably includes wetting layer 1051 and quantum dots 1052. The thickness of the wetting layer 1051 may be one or two monolayers. In one embodiment, the thickness of the dots 1052 measured from the bottom 1053 of the layer 1050 and the peaks of the dots 1055 may be from about 10nm to about 200nm, optionally from about 20nm to about 100nm, and optionally from about 30nm to about 150 nm. Also, in one embodiment, the average diameter of the dots 1052 may be greater than 10nm, optionally greater than 40nm, and optionally greater than 70 nm.

In one or more embodiments, quantum layer 1050 includes a plurality of dot layers. For example, as shown in fig. 3, quantum dots 1050 may include first dot layer 1052, second dot layer 1054, third dot layer 1056, and fourth dot layer 1058. Each layer comprises indium arsenide InAs and contains wetting layers 1053, 1055, 1057, and 1059, respectively. Each dot layer also contains dots 1055. The characteristics of each dot layer (including the wetting layer and the dots) are substantially similar, although they need not be the same.

Disposed between each of dot layers 1052, 1054, 1056, and 1058 are intermediate cladding layers 1062, 1064, 1066, and 1068, respectively. These intermediate cladding layers comprise InxGa 1-xAs. In one or more embodiments, the InxGa1-xAs intermediate cladding is substantially similar or identical to cladding 1040. In other words, the intermediate capping layer is preferably lattice matched to the barrier layer 1040, and the barrier layer 1040 is preferably lattice matched to the top buffer layer 1036. In one or more embodiments, intermediate layers 1062, 1064, 1066, and 1068 may have a thickness from about 3nm to about 50nm, optionally from about 5nm to about 30nm, and optionally from about 10nm to about 20 nm.

As described above, the various layers surrounding the quantum dot layer may be positively doped or negatively doped to manipulate current. Techniques for manipulating current within semiconductor devices are known to those skilled in the art, as described in, for example, U.S. patent nos. 6,573,527, 6,482,672, and 6,507,042, which are incorporated herein by reference. For example, in one or more embodiments, a region or layer may be doped "p-type" by using zinc, carbon, cadmium, beryllium, or magnesium. On the other hand, a region or layer may be doped "n-type" by using silicon, sulfur, tellurium, selenium, germanium, or tin.

Contemplated semiconductor devices may be prepared by using techniques known in the art. For example, in one or more embodiments, the various semiconductor layers can be prepared by using organometallic vapor phase epitaxy (OMVPE). In one or more embodiments, the dot layer is prepared by using a self-forming technique such as Stranski-Krastanov mode (S-K mode). This technique is described in U.S. Pat. No. 6,507,042, which is incorporated herein by reference.

One embodiment of a Radiation Emitting Diode (RED) including a quantum dot layer is shown in fig. 4. RED 1100 comprises base contact 1105, infrared reflector 1110, semi-insulating semiconductor substrate 1115, n-type Lateral Conduction Layer (LCL)1120, n-type buffer layer 1125, cladding layer 1130, quantum dot layer 1135, cladding layer 1140, p-type layer 1145, p-type layer 1150, and emitter contact 1155. Base contact 1105, infrared reflector 1110, semi-insulating semiconductor substrate 1115, n-type Lateral Conduction Layer (LCL)1120, n-type buffer layer 1125, cladding layer 1130, quantum dot layer 1135, and cladding layer 1140 are similar to the semiconductor layers described above.

Base contact 1105 may comprise a number of highly conductive materials. Exemplary materials include gold, gold-zinc alloy (especially when adjacent to the p-region), gold-germanium alloy or gold-nickel alloy, or chrome-gold (especially when adjacent to the n-region). Base contact 1105 may have a thickness of from about 0.5 to about 2.0 microns. A thin layer of titanium or chromium may be used to increase the adhesion between the gold and the dielectric material.

Infrared reflector 1110 comprises a reflective material, and optionally a dielectric material. For example, silicon oxide may be used as the dielectric material, and gold may be deposited thereon as the infrared reflective material. The thickness of reflector 1110 can be from about 0.5 to about 2 microns.

Substrate 1115 comprises InP. The thickness of substrate 1115 may be from about 300 to about 600 microns.

Lateral conduction layer 1120 comprises InxGa1-xAs that is lattice matched (i.e., within 500 ppm) to InP substrate 1115. Also, in one or more embodiments, the doped layer 1120 is n-doped. The preferred dopant is silicon and the preferred degree of doping concentration may be from about 1 to about 3e19/cm³. The thickness of lateral conduction layer 1120 may be from about 0.5 to about 2.0 microns.

Buffer layer 1125 comprises three graded layers of InP1-yAsy in a manner consistent with that described above. Layer 1125 is preferably n-doped. The preferred dopant is silicon and the doping density can be from about 0.1 to about 3e9/cm 3.

Cladding layer 1130 comprises InxGa1-xAs that is lattice matched to the in-plane lattice constant of the top of buffer layer 1125 (i.e., the third level or sublayer thereof) (i.e., within 500 ppm). In one or more embodiments, InxGa1-xAs cladding 1130 comprises from about 0.60 to about 0.70 mole fraction% indium. The thickness of the cover layer 1130 is about 0.1 to about 2 microns.

Quantum dot layer 1135 comprises InAs dots as described above with respect to the teachings of the present invention. As with the previous embodiment, the intermediate layers between each dot layer include InxGa1-xAs cladding layers similar to cladding layer 1130 (i.e., lattice matched). In one or more embodiments, the amount of indium in one or more successive intermediate capping layers may be less than that included in capping layer 1130 or a previous or lower intermediate layer.

Cladding layer 1140 comprises InxGa1-xAs that is lattice matched (i.e., within 500 ppm) to the top of buffer layer 1125 (i.e., the third level or sublayer thereof).

Confinement layer 1145 comprises InP1-yAsy, which is lattice matched to InxGa1-xAs layer 1140. Further, in one or more embodiments, layer 1145 is p-doped. The preferred dopant is zinc and the doping concentration can be from about 0.1 to about 4e19/cm 3. The confinement layer 1145 may have a thickness from about 20nm to about 200 nm.

Contact layer 1150 comprises InxGa1-xAs that is lattice matched to confinement layer 1145. Contact layer 1150 is preferably p-doped (e.g., with zinc). The doping concentration may be from about 1 to about 4e19/cm³. Contact layer 1150 has a thickness of from about 0.5 to about 2 microns. Contact layer 1150 may be removed from the entire surface except under layer 1155.

The emitter contact 1155 may comprise any highly conductive material. In one or more embodiments, the conductive material comprises a gold/zinc alloy.

Another embodiment is shown in fig. 5. The semiconductor device 1200 is configured as a radiation emitting diode with a tunnel junction in the p-region. This design advantageously provides a lower resistive contact portion and lower resistive current distribution. Many aspects of the semiconductor 1200 are similar to the semiconductor 1100 shown in fig. 4. For example, contact 1205 can be similar to contact 1105, reflector 1210 can be similar to reflector 1110, substrate 1215 can be similar to substrate 1115, lateral conduction layer 1220 can be similar to conduction layer 1120, buffer layer 1225 can be similar to buffer layer 1125, cladding layer 1230 can be similar to cladding layer 1130, dot layer 1235 can be similar to dot layer 1135, cladding layer 1240 can be similar to cladding layer 1140, and confinement layer 1245 can be similar to confinement layer 1145.

Tunnel junction layer 1247 comprises InxGa1-xAs, which is lattice matched to confinement layer 1245. The tunnel junction layer 1247 is about 20 to about 50nm thick. The tunnel junction layer 1247 is preferably p-doped (e.g., with zinc), and the doping concentration may be from about 1 to about 4e19/cm³. Tunnel junction layer 1250 includes InxGa1-xAs that is lattice matched to tunnel junction 1247. The thickness of the tunnel junction layer 1250 is from about 20 to about 5,000 nm. The tunnel junction layer 1250 is preferably p-doped (e.g., silicon) and has a doping concentration from about 1 to about 4e19/cm³。

Emitter contact 1255 may comprise a variety of conductive materials, but preferably includes those materials preferably used for the n-region, such as chrome-gold alloy, gold-germanium alloy, or gold-nickel alloy.

Another embodiment of RED is shown in fig. 6. Semiconductor device 1300 is configured as a radiation emitting diode in a manner similar to the RED shown in fig. 5, except that electromagnetic radiation may be emitted through the substrate of the semiconductor device due, at least in part, to the absence of a base reflector (e.g., the absence of an emitter such as 1210 shown in fig. 5). Furthermore, the semiconductor device 1300 shown in fig. 6 includes an emitter contact portion/infrared reflector 1355, which is a "full contact" covering the entire surface (or substantially the entire surface) of the device.

In other aspects, device 1300 is similar to device 1200. For example, contact 1305 may be similar to contact 1205, substrate 1315 may be similar to substrate 1215, lateral conduction layer 1320 may be similar to conduction layer 1220, buffer layer 1325 may be similar to buffer layer 1225, cladding layer 1330 may be similar to cladding layer 1230, dot layer 1335 may be similar to dot layer 1235, cladding layer 1340 may be similar to cladding layer 1240, confinement layer 1345 may be similar to confinement layer 1245, tunnel junction layer 1347 may be similar to tunnel junction layer 1247, and tunnel junction layer 1350 may be similar to tunnel junction layer 1250.

The semiconductor technology envisioned can also be used in the fabrication of laser diodes. An exemplary laser is shown in fig. 7. Laser 1600 includes contact 1605, which may comprise any conductive material, such as gold-chromium alloy. The contact layer 1605 has a thickness from about 0.5 microns to about 2.0 microns.

Substrate 1610 comprises indium phosphide, preferably at about 5 to about 10e18/cm³Is n-doped. The thickness of substrate 1610 is from about 250 to about 600 microns.

The optional epitaxial indium phosphide layer 1615 is preferably at about 0.24e19/cm³To about 1e19/cm³Is n-doped. The epitaxial layer 615 has a thickness from about 10nm to about 500 nm.

The lattice InP1-yAsy layer 1620 is similar to the lattice InP1-yAsy buffer portion shown in FIG. 2. The cushioning portion 1620 is preferably at about 1 to about 9e18/cm³Is n-doped.

Layers 1625 and 1630 form waveguide 1627. Layer 1625 includes InGaAsP (In1-xGAxAszP 1-z). Layer 1630 similarly includes In1-xGAxAszP 1-z. Layers 1625 and 1630 are both lattice matched to the top of layer 1620. In other words, layers 1625 and 1630 include about 0 to about 0.3 mole fraction gallium and 0 to about 0.8 mole fraction arsenic. Layer 1625 is about 0.5 to about 2 microns thick and is about 1-9e18/cm³Is n-doped. Layer 1630 is about 500 to about 1,500nm thick and is about 0.5 to 1e18/cm³Is n-doped.

Confinement layer 1635, dot layer 1640, and confinement layer 1645 are similar to the dot and confinement layers described above with respect to other embodiments. For example, confinement layer 1635 is similar to confinement layer 1040, and dot layer 1640 is similar to dot layer 1050 shown in FIG. 3. In one or more embodiments, the number of dot layers used within the dot area of the laser device exceeds 5 dot layers, optionally exceeds 7 dot layers, and optionally exceeds 9 dot layers (e.g., cycles). Confinement layers 1635 and 1645 may have a thickness from about 125 to about 500nm and are lattice matched to the waveguide. Layers 1635, 1640, and 1645 are preferably undoped (i.e., they are intrinsic).

Layers 1650 and 1655 form waveguide 1653. In a similar manner to layers 1625 and 1630, layers 1650 and 1655 include In1-xGAxAszP1-z, which is lattice matched to the top of buffer 1620. Layer 1650 is about 500 to about 1,500nm, which is at about 0.5 to about 1e18/cm³Is p-doped. Layer 655 is about 1 to about 2 microns thick and is at about 1 to about 9e18/cm³Is p-doped.

In one embodiment, layer 1660 is a buffer layer, similar to buffer layer 1620. That is, the molar fraction of arsenic decreases with each step of increasing distance from the quantum dot. Layer 1660 is preferably at 1-9e18/cm³Is p-doped.

Layer 1665 comprises indium phosphide (InP). The thickness of layer 1665 is about 200 to about 500nm thick, and preferably from about 1 to about 4e19/cm³Is p-doped.

Layer 1670 is a contact layer, similar to the other contact layers described in the embodiments above.

In other embodiments, layers 1660, 1665, and 1670 may be similar to other configurations described with respect to other embodiments. For example, these layers may be similar to layers 1145, 1150, and 1155 shown in fig. 4. Alternatively, layers similar to 1245, 1247, 1250, and 1255 shown in FIG. 5 may be used in place of layers 1660, 1665, and 1670. Various modifications and alterations that do not depart from the scope and spirit of these device embodiments will become apparent to those skilled in the art.

It will be appreciated, of course, that in one form, the invention incorporates RED elements as described above. However, it should be appreciated that various other device technologies may be used. For example, experimental mid-IR LEDs operating in the 1.6-5.0 micron range are known, but are not in line with commercial reality. Further, various semiconductor lasers and laser diodes with appropriate modifications may be used. Of course, other implementation techniques may be developed to efficiently produce limited bandwidth illumination with favorable wavelengths.

In order to practice the invention for a particular application, it will generally be necessary to deploy many suitable devices in order to have sufficient illumination amplitude. Further, in one form, these devices will be RED devices. In most heating applications of the present invention, such devices will typically be deployed in some high density x y array or multiple x y arrays, some of which take the form of a custom arrangement of individual RED devices. The array can range from a single device to more commonly hundreds, thousands, or infinite number of device arrays, depending on the type and size of device used, the output required, and the wavelength required for a particular implementation of the invention. RED devices are often mounted on circuit boards having at least one heat dissipation capability if no dedicated heat dissipation is required. RED devices will typically be mounted on such circuit boards in a very high density/close proximity deployment. It is possible to maximize density in situations where high power applications are required, with recent innovations in die mounting and circuit board construction. For example, such techniques for use with flip chips are advantageous for such uses. While the efficiency of RED devices favors this unique class of diode devices, most electrical energy input is directly converted into localized heat. This waste heat must be conducted away from the semiconductor junction to prevent individual devices from overheating and burning out. For the highest density arrays, it may similarly use flip chip and chip-on-board packaging techniques with active and/or passive cooling. For practical and positioning flexibility purposes, multiple circuit boards will often be used. The x by y array may also include a mix of RED devices that represent infrared radiation at two different selected wavelengths, for example, in the range of at least 1 micron to 5 microns.

For most applications, RED devices will be advantageously deployed in arrays of various sizes, some of which may be three-dimensional or non-planar in nature, in order to better illuminate a particular type of target. This is done for at least the following reasons:

1. in order to provide sufficient output power by combining the outputs of a plurality of devices.

2. Illumination may be appropriate in order to provide sufficient "spreading" of the output over a larger surface than a single device.

3. To provide the programmability of an array of RED devices can bring functionality to an application.

4. To allow for mixing into an array device, the array device is tuned to different specified wavelengths for many functional reasons described in this document.

5. To facilitate matching the "geometry" of the output to the specific application requirements.

6. In order to facilitate matching the installation position, the radiation angle and the economy of the device to the requirements of the application.

7. To facilitate synchronization of the output with the moving object or another "output action".

8. To coordinate the drive groups of the devices with a common control circuit.

9. In order to employ a multi-stage heating technique.

Diodes are manufactured in this manner by reducing the size of the junction to minimize cost because of their typical end use. Therefore, less semiconductor wafer area is required (which is directly related to cost). The end use of RED devices often requires radiant energy output in the form of substantially more photons. It is theorized that REDs can be fabricated using innovative ways of forming larger photon-generating blanket junction regions. In this way, it will be possible to produce RED devices capable of maintaining much higher mid-infrared, radiant outputs. If such devices can be used, the absolute number of RED devices required to practice the present invention can be reduced. However, given the high power output associated with many applications of the present invention, it may not be necessary or practical to reduce the number of devices to a single device. The present invention may be practiced with a single device for low power applications, single wavelength applications, or if RED devices with sufficient output capabilities can be manufactured.

Similarly, it is possible to fabricate an array of RED devices as an integrated circuit. In such embodiments, the RED is arranged within the boundaries of a monolithic silicon or other suitable substrate, but with a plurality of junctions that act as photon-converting radiation spots on the chip. Which may be similar to other integrated circuit packages that use a ball grid array for electrical connections. Such device packages may then be used as an array, facilitating the electrical connections required to connect to and be controlled by the control system. Also, one design parameter is the control of junction temperature, which should not be allowed to reach about 100 to 105 ℃ under current chemistries, otherwise damage will begin to occur. It is anticipated that future chemical compounds may have increased heat resistance, but the heat must always remain below the critical damage range of the device being used. They may further be deployed singly or multiply on a circuit board, or they may be arranged into higher-level arrays of devices, depending on the application and economics.

In designing the optimal configuration for deploying a RED device into an illumination array, the designer must consider the entire range of variables, regardless of the device's form factor. Some variables that should be considered in view of the target application include packaging, ease of deployment, cost, electrical connections, control over programmable considerations, cooling, deployment environment, power transfer, power supply, string voltage, string geometry, illumination requirements, safety, and many other factors that will be appreciated by those skilled in the art.

All of the raw materials used to make the product are associated with specific absorption and transmission characteristics at various wavelengths within the electromagnetic spectrum. Each material also has characteristic infrared reflection and emission characteristics, but we will not spend time discussing these because the practice of the invention depends to a greater extent on absorption/transmission characteristics. The percent absorption at any given wavelength can be measured and plotted for any particular material. Next, as will be explained and illustrated in more detail later in this document, the percent absorption over a wide range of wavelengths can be shown graphically. Since each type of material has characteristic absorption or transmission properties at different wavelengths, it would be highly beneficial to optimize the optimal thermal process, knowing these material properties. It will be appreciated that if a particular material is highly transmissive in a particular range of wavelengths, it will be very inefficient to attempt to heat the material in that wavelength range. Conversely, if the material is too absorptive at a particular wavelength, then applying radiant heating will result in heating of the material surface.

It is well known in the art for many years that various materials have specific absorption or transmission characteristics at various wavelengths. However, because high power infrared sources, which can be specified at a particular wavelength or combination of wavelengths, are not available, it has not been possible in the past to fully optimize many existing heating or processing operations. Since it is impractical to deliver infrared radiation of a particular wavelength to a product, many manufacturers are unaware of the wavelength most needed to heat or treat their particular product.

This phenomenon is illustrated by the example of the plastics industry. Referring to fig. 9 and 10, by looking at the transmission curve of polyethylene terephthalate (PET resin material, as known in the industry) with which plastic beverage containers are stretch blow molded, it can be observed that the PET material has a high degree of absorption in the long wavelength region and a high degree of transmission in the visible and near infrared wavelength regions. Its transmission varies greatly between 1 and 5 microns. Its transmission not only varies greatly within this range, but sometimes frequently, abruptly and often to a considerable extent within 0.1 microns.

For example, at 2.9 microns, PET has very strong absorption. This means that if 2.9 micron infrared radiation is introduced into PET, it will be almost completely absorbed by the material surface or outer skin. This wavelength can be used if only the outer surface of the material needs to be heated. Because PET is a very poor thermal conductor (has a low thermal conductivity) and because it is more desirable in stretch blow molding operations to heat the PET material deeply from the inside and uniformly throughout its volume, which in practice is a poor wavelength to heat PET properly.

Looking at another case, the PET material is highly transmissive at 1.0 micron (1000 nm). This means that a large percentage of the radiation at this wavelength (which would affect the surface of the PET) will be transmitted through the PET and will exit therefrom without transferring any preferential heating and will therefore be largely wasted. It is important to note that the transmission of electromagnetic energy decreases exponentially as a function of the thickness of all dielectric materials, since the material thickness has a substantial effect on the selection of the optimal wavelength for a given material.

It will be appreciated that although PET thermoplastic materials are used here as an example, the principles described apply to a wide range of different types of materials used in different industries and to different types of processes. As a very different example, a glue or adhesive lamination system is illustrative. In this example, it is assumed that the parent material to be glued has a very high transmission at the chosen infrared wavelength. The heat-curable glue to be used may have a very large absorption at the same wavelength. By irradiating the gluing/laminating sandwich with this particular advantageous wavelength, the process is further optimized because the glue is heated instead of the adjacent parent material. By selectively selecting the interaction of these wavelengths, the optimum point will be found in a wide variety of different types of processing or heating applications within the industry.

In the past, the ability to produce relatively high infrared radiation densities at specific wavelengths was not applicable at all in the industry. Therefore, most manufacturers have not considered this optimization because this type of heating or treatment optimization is not available. It is anticipated that the availability of such wavelength specific infrared radiation power will fully open new methods and processes. The present invention will make such new processes practical and will provide implementation techniques with great flexibility for a wide range of applications. It is anticipated that initial exploitation of the invention will be in industry, and it will also be recognized that there will be many applications in business, medical, consumer and other fields.

It is anticipated that the present invention will be very useful as a substitute for the wide band quartz infrared heating bulbs or other conventional heating devices that are currently in widespread use. Such quartz bulbs are used in a variety of situations including heating sheets of plastic material in preparation for thermoforming operations. Not only can the present invention be used as a replacement for the existing functionality of quartz infrared lamps or other conventional heating devices, but it is also contemplated to add a great deal of additional functionality.

In contrast, the present invention may generate radiant energy in a continuous or pulsed manner. Because the basic RED device of the present invention has a very fast response time in microseconds, it can have a higher energy efficiency to turn on energy when needed or when the target component is within the target area and to turn off energy when the component is no longer within the target area.

The additional functionality of being able to energize the infrared source in pulses can result in considerable improvement in the overall energy efficiency of many radiant heating applications. For example, by appropriately modulating the activation time of individual or arrayed infrared Radiation Emitting Devices (REDs), it is possible to track individual targets as they move past a large infrared array source. In other words, the infrared emitting device closest to the target device will be the device that is energized. As the target component or area moves upward, the "excitation wave" may pass down the array.

In the case of a heated material to be thermoformed, it may be necessary to apply more heat input to areas that are more strongly shaped than areas that are more moderately shaped or not shaped at all. By properly designing the configuration of the infrared emitter array, not only can all devices not be energized at the same time, but it is possible to energize them in a very strategic manner to correspond to the shape of the area to be heated. For example, for a continuously moving production line, it may be desirable to program a specially shaped region having a desired thermal profile that can be programmably moved in a motion synchronized with the target region to be heated. Consider the picture frame shaped area shown in figure 17 that needs to be heated. In this case, an array of devices (402) that may have similar picture frame shapes at the desired radiation intensity will be programmably moved down the array, synchronized with the motion of the target thermoformed sheet (401). By using an encoder to track the movement of the product, such as (401) thermoformed sheets, well known electronic synchronization techniques can be used to turn on the correct device at the desired intensity according to instructions of a programmable controller or computer. The devices within the array can be turned on by the control system in either a "continuous" mode or a "pulsed" mode to achieve their desired output intensity. Both modes can modulate the intensity as a function of time to the most desirable output conditions. This control may be of groups of devices, or may be of individual RED devices. For certain applications, fine control of individual RED devices may not be required. In this case, the RED devices can be connected in strings in the most desirable geometry. These strings or groups of strings may then be programmably controlled according to application-specified requirements. In practice, it will sometimes be required to drive RED devices in groups or strings in order to achieve the most convenient voltage and reduce the cost of individual device control.

The string or array of RED may be controlled by supplying current only in an open loop configuration, or more complex control may be used. The fact-intensive evaluation for any particular application will specify the appropriate amount and level of infrared radiation control. The control circuit may continuously monitor and modulate the input current, voltage or specific output due to the complex or precise control required. Monitoring of the most desirable radiation output or result may be performed by directly measuring the output of the infrared array or some parameter associated with the target object of infrared radiation. This can be performed by a range of different techniques, from incorporation of simple thermocouples or pyrometers to more advanced techniques, which take the form of, for example, infrared cameras. Those skilled in the art will be able to recommend specific closed loop monitoring techniques that are economically sensible and reasonable for a particular application of the present invention.

Direct and indirect monitoring methods may be incorporated. For example, if a particular material is heated in order to reach a formable temperature range, it may be desirable to measure the force required to form the material and use that data as at least part of the feedback to the modulation of the infrared radiation array. There may be many other direct or indirect feedback means to facilitate optimization and control of the output of the present invention.

It should be clearly understood that the shape, intensity and activation time of the radiant heat sources of the present invention described herein are highly programmable and can accept a very high level of programmable customization. In the industry, custom shapes or configurations of heating sources are often designed and constructed for specific components in order to direct heating to the correct location on the component. With the flexible programmability of the present invention, a single programmable heating panel can be made to serve as a flexible alternative to an almost unlimited number of custom-constructed panels. There is a wide range of infrared ovens and processing systems in the industry. Such ovens are useful for various types and types of cured coatings, slurries, and many other uses. It can also be used in a number of different laminate lines for heating molten materials together, or for curing glues, adhesives, surface treatments, coatings or other various layers that may be added to the laminate "sandwich".

Other ovens may be used for a variety of drying applications. For example, in the two-piece beverage can industry, it is common to spray a coating into the interior of the beverage can and then continuously transport it "en bloc" through a long curing oven by a conveyor. The uncured interior coating has the appearance of a white paint when applied, but becomes nearly transparent after curing. In these various drying and curing applications carried out by the present invention, it will be possible to select the wavelength or combination of wavelengths that are most easily and appropriately absorbed by the material to be dried, treated or cured. In some applications, the absence of wavelengths may be more important than the presence of wavelengths for improved processing. Unwanted wavelengths may adversely affect the material by drying, heating, changing the grain structure or many other deleterious results that can be avoided in a more optimized process by the present invention.

It is often desirable to increase the temperature of the object to be cured or dried without substantially affecting the substrate or the parent material. It is likely that the parent material may be damaged by such treatment. It is further desirable not to introduce heat into the parent material while still introducing heat into the target. The present invention facilitates this type of selective heating.

Looking now at another field of application of the invention, the medical industry has been experimenting with a wide range of visible and near infrared radiation treatments. It is also theorized that electromagnetic energy of a particular wavelength stimulates and promotes healing. It is also hypothesized that radiation with specific wavelengths may stimulate the production of kinases, hormones, antibodies and other chemicals within the body, and stimulate activity in inert organs. It is not necessary to examine any of the specific details or processing methods or the advantages of such assumptions within the scope of the present invention. However, the present invention may provide a solid state, wavelength selectable and programmable mid-infrared radiation source that may be useful with a variety of such medical devices.

However, the medical industry has in the past not had a practical method for producing high power, wavelength specific illumination in the mid-IR wavelength band. The present invention will allow such narrowband wavelength specific infrared radiation and it can be achieved with a weak, lightweight, safe and convenient form factor that is easily used for medical applications.

For medical treatment, there are some very important advantages to being able to select a particular wavelength or combination of wavelengths for irradiation. Organic substances also have characteristic transmission/absorption spectra curves as in industrially manufactured materials. Animal, plant or human tissue exhibits a specific absorption/transmission window, which can be exploited.

A very high percentage of the human body is essentially composed of the water element, and therefore the transmission/absorption curve of water may be a good starting point for rough estimation of a large amount of human tissue. Through extensive research it is possible to derive accurate curves for all types of tissues in humans, animals and plants step by step. It is also possible to derive the relationship between the various types of healing or stimulation that may be obtained from an organ or tissue and correlate the relationship with the transmission/absorption curve. By careful selection of the wavelength or combination of wavelengths, it will be possible to develop treatments that can have a positive effect on a wide range of diseases and ailments.

Some of the tissues or organs to be treated are very close to the surface, while others are located deep inside the body. Such deeper regions may not be accessible with non-invasive techniques due to the absorptive characteristics of human tissue. Some form of invasive technique may have to be used in order to bring the illumination source close to the target tissue. The illumination array of the present invention can be designed to be of an appropriate size and/or shape for use in a variety of invasive or non-invasive treatments. While treatment techniques, devices and configurations are beyond the scope of this discussion, the present invention is the first technique to make solid-state, wavelength-selective radiation available in the mid-infrared wavelength band. Which may be configured for a variety of instruments and treatment types. Due to its highly flexible form factor and programmable nature, it can be configured for a specific body size and weight to produce the appropriate angles, intensities and wavelengths for conventional treatment.

Infrared radiation is being used in an increasing number of medical applications, from the treatment of hemorrhoids to dermatology. One example of infrared therapy currently performed with broadband infrared sources is known as infrared coagulation therapy. In addition, infrared lamp therapy is sometimes used to treat diabetic peripheral neuropathy. Currently, broadband infrared lamps are also commonly used to treat elbow inflammation and other similar ailments. The ability to generate specific wavelengths of radiation incorporated with the present invention, as well as the ability to generate pulsed radiation of the present invention, can provide substantial improvements in these treatments. It may also provide better patient tolerance and comfort. The invention also facilitates the manufacture of medical devices that can be powered with intrinsically safe voltages.

It may be that the pulses of radiant energy are a key aspect associated with many medical treatment applications. Continuous irradiation may cause overheating of the tissue, and the fact may prove that pulsed irradiation provides sufficient stimulation without the deleterious effects of overheating, discomfort or tissue damage. The device/array may be pulsed at very high rates (on times in microseconds or faster) to provide another useful characteristic. It is expected that radiation pulses of very high intensity may be tolerated if they are activated at a very short duty cycle, since with such a short pulse time there will be no time for overheating of the semiconductor junction to occur. This will allow for greater total instantaneous intensity, which may help to penetrate more tissue.

It may also prove important that the frequency of the pulses occur. It is known in the art that irradiation of a particular frequency to a human may have a healing or deleterious effect. For example, certain amplitude modulation frequencies or frequency combinations of visible light may cause humans to become nausea, and other amplitude modulation frequencies or frequency combinations may cause seizures. As further medical research proceeds, it may in fact be determined that the pulse frequency, waveform shape, or frequency combination, along with the selected wavelength or wavelength combination, have a substantial effect on the success of various radiation treatments. It is likely that many medical devices that will use the present invention are not yet known or appreciated because the present invention is not yet available to researchers or practitioners.

Another application of the invention is in the preparation process or preparation of food. Of course, humans have historically used a variety of different types of ovens or heating systems in preparing food products. Since most of them are well known, it is not necessary to describe the full scope of such ovens and heating systems within the scope of this patent application. Virtually all cooking technologies utilize various types of broadband heating sources, except for the obvious exclusion of microwave cooking utilizing non-infrared/non-heat source cooking technologies. The infrared heating sources and elements used in such ovens are broadband sources. It does not produce infrared energy of a particular wavelength that is most advantageous for a particular cooking condition or product being cooked.

As described above for other materials, plant and animal products have specific absorption spectra profiles. These specific absorption curves relate to how absorbent or transmissive a particular food product has at a particular wavelength. By selecting a particular wavelength or a number of carefully selected wavelengths for illuminating the subject food, the desired cooking characteristics can be modified or optimized. The most efficient use of radiant energy may reduce heating or cooking costs.

For example, if it is most desirable to heat or brown the exterior surface of a particular food product, the present invention will allow for the selection of wavelengths for which the particular food product is highly absorptive. The result will be that when illuminated at the selected wavelength, the infrared energy is fully absorbed in close proximity to the surface, thus allowing the desired heating and/or browning action to occur just at the surface. Conversely, if it is desired not to heat the surface but to begin cooking the food from a very deep interior of the food, it is possible to select a wavelength or combination of selected wavelengths at which the particular food has a much higher transmittance so that the desired cooking result can be achieved. Thus, the radiant energy will be gradually absorbed as it penetrates to the desired depth.

It is important to note that for an electromagnetic wave traveling through a non-metallic material, the intensity of this wave i (t) decreases as a function of the distance traveled t as described by:

I(t)＝Io(e-αt)

in this equation, Io is the initial intensity of the light beam, and α is the specific absorption coefficient of the material. As time t increases, the beam intensity undergoes an exponential decay, which results from the absorption of the radiant energy in the original beam by the host material. For this reason, the use of infrared radiant heating to achieve optimal cooking results can necessarily result in complex interactions between the thickness of the food item, the intensity of the applied infrared radiation, the wavelength of the irradiation, and the material absorption coefficient.

By mixing RED elements that illuminate at different wavelengths, the cooking results can be further optimized. In such a multi-wavelength array, one element type will be selected at a wavelength where the radiant energy absorption is low, thus allowing deep heating penetration to occur. The second element type will be selected to be more radiation energy absorbing and thus contribute to the surface heating that occurs. After the array is completed, a third RED element type is envisioned, chosen to be at a wavelength intermediate these two extremes in absorption. By controlling the relative radiation output levels of the 3 types of RED emitters contained in such an array, important characteristics of the prepared food item will be optimized.

By connecting the color sensor, temperature sensor and possibly visual sensor to the control system, the loop can be closed and the desired cooking result can be further optimized. In such environments, the exact parameters that may be in question can be checked and the control system allowed to respond by sending illumination at the appropriate wavelength, intensity and direction that will be most needed. By using and integrating a visual sensor it will be possible to actually observe the position and size of the food product to be cooked and then to optimize the output of the oven accordingly as described above. When used in conjunction with a humidity sensor, it will be possible to respond with a combination that can maintain a desired humidity level. Thus, it is possible to understand how the present invention "intelligence" in conjunction with appropriate sensors and controllers would actually help to promote future smart ovens. Of course, it is possible to combine the present invention with conventional cooking techniques (including convection oven and microwave oven capabilities) to obtain the best combination of each of these technical achievements. The intelligent control system can be designed to optimally optimize the combination of the present technology with conventional cooking techniques.

By selecting wavelengths that will be absorbed by one food but not highly absorbed by another, it is also possible to have a very selective amount of heating that occurs in a pan of mixed food. It can thus be appreciated that by varying the combination and arrangement and intensity of the various wavelengths that can be selected, one can achieve a wide range of specifically designed cooking results.

With any one application of the present invention, various lenses or beam directing devices may be used to achieve the desired directionality of the illumination energy. This can take the form of a number of different embodiments, from individually lensing the RED device to a microlens array mounted adjacent to the device. The beam directing means chosen must be appropriately selected to function at the wavelength of radiation being directed or directed. By utilizing well-known diffraction, refraction, and reflection techniques, energy from different portions of an array of RED devices can be directed in desired directions. By programmably controlling the particular device that is turned on, and by modulating its intensity, a wide range of illumination selectivity is possible. Functionality can be further improved by selecting a steady state or pulse mode, and by further programming which devices are pulsed at which time.

While the present disclosure discusses the application of radiant energy primarily in the 1.0 to 3.5 micron range, it should be apparent to those skilled in the art that similar material heating effects can be achieved at other operating wavelengths, including longer wavelengths in the infrared, or shorter wavelengths down to the visible region. The spirit of the present invention includes the use of direct electron to photon solid state emitters for radiant heating purposes, where it is envisioned that the emitters may operate from visible light to far infrared. For certain types of applications, it may be desirable to combine other wavelength selectable devices that illuminate at other wavelengths outside the mid-infrared range into the present invention.

Fig. 8 gives a diagrammatic indication of a single RED assembly 10. RED 10 includes a stack 20. The stack 20 may take on a variety of configurations, such as a semiconductor layer stack and similar stacks described in connection with fig. 1-7. In at least one form, contact 40 (e.g., corresponding to contacts 1105, 1205, and 1305) of RED 10 is fabricated onto stack 20 by line 80. When a current 60 is caused to flow through the bond wire 80 and the stack 20, photons 70 having a characteristic energy or wavelength consistent with the configuration of the stack 20 are emitted.

Since many of the semiconductor experience known in the manufacture of LEDs is applicable to RED, it is useful to mention similar techniques that may contribute to the development of new RED devices. Over the years since the introduction of LEDs into the general market, there has been a great improvement in the energy conversion efficiency (light energy output/electric energy input) of LEDs. Energy conversion efficiencies above 10% have been achieved in commercially available LEDs operating in the visible and IR only portions of the spectrum. The present invention contemplates the use of the new RED operating somewhere in the 1 micron to 3.5 micron range as the primary infrared heating element in various heating systems. The present application describes particular embodiments in a blow molding system.

Fig. 9 and 10 show the relative percentage of IR energy transmitted in a 10mil thick portion of PET as a function of wavelength. The presence of a band of strong absorption (a band of wavelengths with low or no transmission) is evident at several wavelengths including 2.3 microns, 2.8 microns and 3.4 microns within the quartz transmission range (up to 3.5 microns). The basic principle associated with the present invention is to use RED elements designed and selected to operate at selected wavelengths in the range of 1 micron to 3.5 microns as the primary heating elements within the thermal conditioning portion of the blow molding machine.

11a, 11b and 11c show an example collection of individual RED emitters 10 packaged together into a suitable RED heater element 100. In the present embodiment of the invention, the RED 10 is physically mounted such that the N-doped region is directly attached to the cathode bus bar 120. Ideally, the cathode bus bar 120 is made of a material that is both a good electrical and a good thermal conductor, such as copper or gold. The respective regions of the RED 10 are connected to the anode bus bar 110 via bonding wires 80. Ideally, the anode bus bar will have the same thermal and electrical characteristics as the cathode bus bar. An input voltage is externally generated across the 2 bus bars, which causes a current (I) to flow within RED 10, resulting in emission of IR photons or radiant energy, such as shown at 170. Reflectors 130 are used in the preferred embodiment to direct radiant energy in a preferred direction away from the RED heater element 100. The smaller physical extent of the RED 10 makes it easier to direct the radiant energy 170 emitted in a preferred direction. This statement is equally applicable to the case of much larger coiled filaments; the relationship between the physical size of the emitter and the ability to direct the resulting radiant flux using conventional lensing means is well known in the art.

The heat sink 140 is used to conduct waste heat generated in the process of forming the IR radiant energy 170 away from the RED heater element 100. The heat sink 140 may be constructed using various components known in the industry. These components include passive heat dissipation, active heat dissipation using convective air cooling, and active heat dissipation using water or liquid cooling. Liquid cooling, for example by means of a liquid jacket, has the following advantages: a large amount of heat can be conducted away, which is generated by electrical energy not converted into radiation photons. This heat can be conducted to an outdoor location or to another area where heat is needed through a liquid medium. Air conditioning/cooling energy can be greatly reduced if heat is conducted away from the plant or to another location.

Further, the bulb 150 is optimally used in the present embodiment of the present invention. The primary function of the light bulb 150 as applied herein is to protect the RED 10 and bond wires 80 from damage. The bulb 150 is preferably constructed from quartz because quartz has a transmission range extending from visible light to 3.5 microns. However, other optical materials may be used, including glasses having transmission ranges extending beyond the wavelengths of operation of the RED 10.

Fig. 12a and 12b depict one deployment of the RED heater element 100 in a blow molding machine. In this system, preforms 240 enter the thermal monitoring and conditioning system 210 via the conveyance system 220. The preforms 240 may enter the thermal monitoring and control system 210 at room temperature after having been previously injection molded at some time earlier. Alternatively, the preform 240 may come directly from the injection molding process, as is done in a single stage injection molding blow molding system. Alternatively, the preform may be made by one of several other processes. Regardless of the form and timing of preform manufacture, preforms 240 entered in this manner will contain varying amounts of latent heat therein.

Once provided by the conveyance system 220, the preforms 240 are conveyed through the thermal monitoring and control system 210 via a conveyor 250, such conveyors being well known in the industry. As the preform 240 travels through the thermal monitoring and control system 210, it is subjected to radiant IR energy 170 emitted by a series of RED heater elements 100. The IR energy 170 emitted by these RED heater elements 100 is directly absorbed by preforms 240 that are prepared to enter the blow-molding system 230. It should be appreciated that the energy may be continuous or pulsed, which is a function of supply or drive current and/or other design objectives. A control system, such as control system 280, controls this functionality in one form. Alternatively, the control system is operated to pulse the system at a current level substantially greater than the recommended steady state current level in order to achieve a higher instantaneous emission intensity in pulsed operation, and to respond to input signals from the associated sensor capability to determine the timing of pulsed operation.

In a preferred embodiment of a blow molding machine using the methods and components described herein, it is also preferred to deploy a convective cooling system 260. This system removes waste heat from the air and mechanical equipment in the vicinity of the preforms 240 being processed. This can also be done using conduction cooling means. It is known in the art that heating the preform by convection and/or conduction is detrimental to the overall thermal conditioning process. This is because PET is a very poor conductor of heat and heating the outer edges of the preform can result in uneven heating, overcooling in the center and overheating at the outside.

Also included in the preferred system embodiment are a temperature sensor 270 and a temperature control system 280, wherein the temperature sensor 270 may take the form of a smart sensor or camera capable of monitoring a target in at least one aspect beyond the capabilities of a single point temperature measurement sensor. These aspects of the preferred blow-molding machine design are particularly applicable to the attributes of a one-stage blow-molding system. In a one-stage blow molding system, preforms 240 enter the thermal monitoring and conditioning system 210 in a state containing latent heat energy obtained during the injection molding stage. By monitoring the temperature, and thus the heat content, of the incoming preforms 240 (or in specific sub-portions of such preforms), the temperature monitoring and control system 280 may generate preform-specific (or sub-portion-specific) heating requirements, and then communicate these requirements in the form of drive signals to the individual RED heater elements 100. The solid state nature of the RED emitter 10 and the associated fast response time make it particularly suitable for allowing the power supply current or turn-on time to be modulated as a function of time or preform movement. Further, it will be appreciated that the sub-sections of the RED array may be controlled.

The temperature control system 280 used to perform such output control may be implemented as an industrial PC, as embedded logic, or as an industrial Programmable Logic Controller (PLC), all of which are well known in the art for their nature and operation. The control system (e.g., as shown at 280) can be configured in a variety of ways to meet the goals herein. However, as some examples, the system may control the on/off state, current flow, and position of the activation device for each wavelength in the RED array.

Fig. 13-16 illustrate a method according to the present invention. It should be understood that these methods may be implemented using appropriate software and hardware combinations and techniques. For example, the mentioned hardware elements may be controlled by software routines stored and executed by temperature control system 280.

Referring now to FIG. 13, a preferred method 300 of heat treating thermoplastic preforms is shown, wherein the basic steps of operation are outlined. The preforms 240 are conveyed through the thermal monitoring and control system 210 via the conveyor 250 (step 305). Of course, it should be understood that for all embodiments showing a transport, a simple means with or without a transport may be used to position the item to be exposed. The preform 240 is irradiated using the RED heater element 100 contained within the thermal monitoring and control system 210 (step 310). The convective cooling system 260 is used to remove waste heat from the air and mechanical components within the thermal monitoring and control system 210 (step 315).

Another method 301 of processing thermoplastic preforms is outlined in fig. 14. In method 301, the process of irradiating preform 240 using RED heater element 100 is replaced with step 320 (step 310). During step 320 of method 301, the preforms 240 are pulsed in synchronization with their movement through the thermal monitoring and conditioning system 210. This synchronized pulsed irradiation provides a substantial amount of additional energy efficiency, since the RED device closest to the preform is the RED device that is turned on only at any given instant. In one form, the maximum output of pulse energy is timed synchronously with the transmission of the individual targets.

Yet another method 302 of processing thermoplastic preforms is outlined in FIG. 15. In this method 302, the temperature of the incoming preform 240 is measured using the temperature sensor 270. This is done to measure the latent heat energy of the preform 240 as the preform 240 enters the system (step 325). The preforms 240 are then conveyed through the thermal monitoring and control system 210 via the conveyor 250 (step 305). The temperature control system 280 uses the temperature information supplied by the temperature sensor 270 to generate a preferred control signal to be applied to the RED heater element 100 (step 330). Next, a preferred control signal is passed from the temperature control system 280 to the RED heater element 100 (step 335). Next, the preform 240 is irradiated using the RED heater element 100 contained within the thermal monitoring and control system 210 (step 310). Next, the convective cooling system 260 is used to remove waste heat from the air and mechanical components within the thermal monitoring and control system 210 (step 315).

Yet another method 303 of processing thermoplastic preforms is outlined in FIG. 16. In method 303, the process of irradiating preform 240 using RED heating element 100 is replaced with step 320 (step 310). During step 320 of method 303, the preforms 240 are pulsed in synchronization with their movement through the thermal monitoring and conditioning system 210.

The above description merely provides a disclosure of particular embodiments of the invention and is not intended to limit the invention to these particular embodiments. Likewise, the invention is not limited to the above described applications or embodiments only. This disclosure is broadly directed to many applications of the present invention and specifically to one application embodiment. It should be recognized that those skilled in the art may devise alternative applications and specific embodiments that are within the scope of the present invention.

Claims (41)

1. A system for non-contact thermal treatment of a plastic target component prior to a molding or processing operation, comprising:

means (220, 250) operable to position a plastic target assembly (240) at a location where radiant heating is applied; and

a thermal monitoring and control portion (210) in which the plastic component is positioned for exposure, the thermal monitoring and control portion comprising one or more semiconductor-based narrow wavelength band radiant heating elements (10, 100, 1000, 1030, 1050, 1100, 1200, 1300, 1600) operable to emit radiant energy within a narrow wavelength band matching absorption characteristics required by the plastic target component via a direct current-to-photon conversion process.

2. The system as recited in claim 1, wherein the member operable to position is a transfer member (250) operable to transfer the plastic target assembly.

3. The system of claim 1, wherein a supply current continuously flows into the semiconductor-based narrow wavelength band radiant heating element, thereby enabling continuous radiant energy output.

4. The system of claim 1, wherein the semiconductor-based narrow wavelength band radiant heating element is operable to emit radiant energy in a pulsed mode with the time of maximum output timed in synchronization with the transmission of individual molded target components through the thermal monitoring and control portion.

5. The system of claim 1, further comprising at least one of a convective cooling device or a conductive cooling device (260) configured to remove waste heat from air and mechanical components within the thermal monitoring and control portion.

6. The system of claim 1, further comprising a temperature sensor (270) configured to measure a temperature of individual target components prior to their entry into the thermal monitoring and control portion, whereby latent heat content may be determined.

7. The system as recited in claim 6, wherein a temperature control system (280) is employed to generate control signals for application to the semiconductor-based narrow wavelength band radiant heating element based upon a target component temperature.

8. The system of claim 7, wherein temperatures of sub-portions of the target component are measured and used to generate control signals to apply semiconductor-based narrow wavelength band radiant heating to sub-portions of target component.

9. The system of claim 1, wherein the semiconductor-based narrow wavelength band radiant heating element is operable to emit radiant energy having a wavelength in a range of 1 to 3.5 microns.

10. The system of claim 1, wherein the semiconductor-based narrow wavelength band radiant heating element is operable to emit radiant energy within at least one narrow wavelength range specifically tuned according to heating requirements of a particular target component application.

11. The system of claim 1, wherein the plastic target component comprises at least one of a PET preform or a PET bottle.

12. The system of claim 1, further comprising:

a mounting arrangement that positions the at least one semiconductor-based narrow wavelength band element to direct illumination therefrom toward the target component; and

supply means for supplying current to the at least one semiconductor-based narrow wavelength band element whereby a direct current-to-photon radiation conversion process occurs.

13. The system of claim 12, wherein the at least one semiconductor-based narrowband element is in the form of an x y array of individual semiconductor-based narrowband devices.

14. The system of claim 12, wherein the at least one semiconductor-based narrowband element takes the form of a custom arrangement of individual semiconductor-based narrowband devices.

15. The system of claim 13, wherein the array takes the form of an x y array of on-board chips of individual semiconductor-based narrow wavelength band devices mounted directly in a chip-on-board configuration.

16. The system of claim 13, wherein the circuit board on which the semiconductor-based narrowband device is mounted is selected to be operable to conduct heat away from the semiconductor-based narrowband device.

17. The system of claim 16, wherein the circuit board on which the semiconductor-based narrowband device is mounted has a heat sink associated therewith for conducting heat away from the semiconductor-based narrowband device and the circuit board.

18. The system of claim 16, wherein means for conducting heat away comprises a liquid heat exchange jacket operable to move the heat away from the system a greater distance.

19. The system of claim 13, wherein the x y array of individual semiconductor-based narrow wavelength band devices comprises at least some semiconductor-based narrow wavelength band devices operable to generate infrared radiation of more than one selected narrow wavelength band ranging from 1 micron to 5 microns.

20. The system of claim 13, wherein the x y array comprises a mixture of semiconductor-based narrow wavelength band devices representing infrared radiation in at least two different selected narrow wavelength bands, at least one band ranging from 1 micron to 5 microns.

21. The system of claim 13, further comprising a control system configured to separately control at least one of an on/off state, current flow, and position of an activation device arm for each wavelength represented in the array.

22. The system of claim 13, further comprising a control system configured to individually control sub-portions of the array for at least one of a location and an output intensity within the array.

23. The system of claim 12, further comprising a control system configured to supply a power drive current to facilitate a pulsed mode of operation.

24. The system of claim 23, wherein the control system is operable to pulse the system at a current level substantially greater than a recommended steady state current level to achieve a higher instantaneous emission intensity in pulsed operation, and to determine the timing of the pulsed operation in response to an input signal from an associated sensor capability.

25. The system of claim 24, wherein the control system further comprises the ability to synchronize the pulsed operation with a moving target.

26. The system of claim 12, wherein the at least one semiconductor-based narrowband element comprises an array of a plurality of semiconductor-based narrowband devices configured in a substantially non-planar configured arrangement.

27. The system of claim 26, wherein the semiconductor-based narrow wavelength band device is deployed on a plurality of circuit boards configured in a three-dimensional arrangement, thereby enabling better illumination of a particular type of target.

28. The system of claim 20, wherein the array further comprises a semiconductor-based narrow wavelength band device operable to generate wavelengths ranging outside of a1 to 5 micron range.

29. The system of claim 12, wherein the means for providing an electrical current is a programmable control system operable to control an illumination output of at least one aspect of the system.

30. The system of claim 29, wherein the programmable control system comprises at least one input from a temperature sensor and is operable to vary at least one output parameter as a function of the at least one temperature sensor input.

31. The system of claim 30, wherein the programmable control system further comprises a smart sensor input to monitor other parameters about the target in order to provide data for modifying at least one aspect of the system illumination output.

32. The system of claim 31, wherein the smart sensor comprises a camera system.

33. The system of claim 30, wherein the temperature sensor comprises a thermal infrared camera operable to monitor the target in at least one aspect other than an aspect monitorable by a single point temperature measurement sensor.

34. A method of heat injection applied to a target, the method comprising:

positioning (305) the target for exposure to at least one semiconductor-based narrow wavelength band radiation emitting device;

selectively supplying current to the at least one semiconductor-based narrow wavelength band radiation emitting device; and selectively injecting (310), by the semiconductor-based narrow wavelength band radiation emitting device, heat of at least one selected narrow wavelength band into the target based on the selected supply current, the selected narrow wavelength band matching an absorption characteristic required by the target.

35. The method of claim 34, wherein the at least one semiconductor-based narrow wavelength band radiation emitting device operates in a pulsed mode.

36. The method of claim 34, further comprising measuring a temperature of the target, and controlling the selective supply of current based on the temperature.

37. The method of claim 34, wherein the target is a series of thermoplastic preforms being processed prior to a stretch blow molding operation, the method further comprising the steps of:

transporting (305) the series of preforms through a thermal monitoring and control portion of a blow molding machine; and

removing (315) waste heat from air and mechanical components of the thermal monitoring and control portion of the blow-molding machine using a cooling system.

38. The method of claim 37, wherein the semiconductor-based narrow wavelength band radiant heating element is operated in a pulsed mode synchronized to the transport of individual preforms.

39. The method of claim 37, further comprising the step of:

measuring (325) the temperature of the incoming preforms before they are fed into said thermal monitoring and control section to estimate the latent heat content;

generating (330) a control signal to apply to the semiconductor-based narrow wavelength band radiant heating element based on the temperature of the incoming preform; and

these control signals are passed (335) to the semiconductor-based narrow wavelength band radiant heating element.

40. The method of claim 37, further comprising measuring a temperature of a sub-portion of a target component and generating a control signal to apply semiconductor-based narrow wavelength band radiant heating to the sub-portion.

41. The method of claim 39, wherein the semiconductor-based narrow wavelength band radiant heating elements are operated in a pulsed mode synchronized to the transport of individual preforms.