HK1104082A - Method and system for wavelength-dependent imaging and detection using a hybrid filter - Google Patents

Description

Wavelength dependent imaging and detection method and system using hybrid filters

Technical Field

Embodiments in accordance with the present invention relate generally to the field of imaging. More particularly, embodiments in accordance with the present invention relate to wavelength dependent imaging and detection methods and systems utilizing hybrid filters.

Background

A number of applications focus on detecting or imaging objects. Detecting an object can determine the presence or absence of the object, while imaging results in an image of the object. Depending on the application, objects can be imaged or detected in daylight and/or in darkness.

Wavelength-dependent imaging is a technique for imaging or detecting an object and generally involves detecting one or more specific wavelengths that are reflected by or transmitted through the object. In some applications, only sunlight or ambient lighting is required, while in other applications, auxiliary lighting is required. Light passes through the atmosphere at a number of different wavelengths, including visible and non-visible wavelengths. Thus, the wavelengths of interest are not visible wavelengths.

FIG. 1 is a diagram of the spectra of solar emission, light emitting diodes and lasers. As can be seen, the spectrum 100 of the laser is very narrow, while the spectrum 102 of the Light Emitting Diode (LED) is broad compared to the spectrum of the laser. The solar emission has a very broad spectrum 104 compared to LEDs and lasers. The simultaneous presence of broad-spectrum solar radiation during the day can complicate the detection of light emitted from an eye-safe LED or laser and reflected by an object considerably. Solar radiation dominates the detection system and in comparison may cause less relatively weak scattering from the eye-safe light source.

In addition, the object being detected may not remain stationary during successive measurements. For example, if a person is an object, the person may shift position or move during the time the measurement is taken. If measurements made at different wavelengths are performed at different times, the movement of the object during successive measurements can distort the measurements and render them useless.

Disclosure of Invention

In accordance with the present invention, wavelength-dependent imaging and detection methods and systems are provided that utilize hybrid filters. The object to be imaged or detected is illuminated by a single broadband light source or multiple light sources emitting light of different wavelengths. The light is detected by a detector comprising a light detection sensor covered by a hybrid filter. The hybrid filter includes a multiband narrowband filter mounted over a patterned filter layer. The light impinges on a narrow band filter that passes light at or near the multiple wavelengths of interest while blocking light at all other wavelengths. The patterned filter layer alternately passes light of one particular wavelength while blocking light of other wavelengths of interest. This allows the sensor to determine the intensity of light at the wavelength of interest simultaneously or alternately. Filters may also be installed over the light source to narrow the spectrum of the light source.

Drawings

The invention will be better understood by reference to the following detailed description of embodiments in accordance with the invention when read in conjunction with the accompanying drawings.

FIG. 1 is a spectrum of solar emission, light emitting diodes and lasers;

FIG. 2 is a diagram of a system for pupil detection using a hybrid filter in an embodiment in accordance with the invention;

FIG. 3a illustrates an image generated using an on-axis light source in accordance with the system shown in FIG. 2;

FIG. 3b depicts an image generated using an off-axis light source in accordance with the system shown in FIG. 2;

FIG. 3c illustrates an image resulting from the difference between the image of FIG. 3a and the image of FIG. 3 b;

FIG. 4 depicts a sensor in one embodiment in accordance with the invention;

FIG. 5 is a cross-sectional view of a probe according to one embodiment of the invention;

FIG. 6 depicts spectra of the polymer filter and the narrowband filter shown in FIG. 5;

FIG. 7a illustrates a first method of fabricating a dual spike filter in an embodiment in accordance with the invention;

FIG. 7b depicts the spectrum of the dual spike filter shown in FIG. 7 a;

FIG. 8a illustrates a second method for fabricating a dual spike filter in an embodiment in accordance with the invention;

FIG. 8b depicts the spectrum of the dual spike filter shown in FIG. 8 a;

FIG. 9 is a diagram of a light source and a narrowband filter in an embodiment in accordance with the invention;

FIG. 10 illustrates the spectrum of the light source and the combination of the light source and the narrowband filter shown in FIG. 9;

FIG. 11 is a diagram of a second system for pupil detection using a narrowband filter with respective light sources and a hybrid filter with a sensor in an embodiment in accordance with the invention;

FIG. 12 is a diagram of a device that may be used for pupil detection in an embodiment in accordance with the invention;

FIG. 13 is a diagram of detecting transmission through an object using a hybrid filter in another embodiment of the invention;

FIG. 14 depicts spectra of a polymer filter and a triple band narrowband filter in an embodiment in accordance with the invention;

FIG. 15 depicts a sensor according to the embodiment shown in FIG. 14;

FIG. 16 depicts spectra for a polymer filter and a quad-band narrowband filter in an embodiment in accordance with the invention;

FIG. 17 depicts a sensor according to the embodiment shown in FIG. 16.

Detailed Description

The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the following claims and the principles and features described herein. It should be understood that the figures referred to in this description are not drawn to scale.

Embodiments in accordance with the present invention relate to wavelength-dependent imaging and detection methods and systems utilizing hybrid filters. The technique of pupil detection is included in the detailed description of one such system that utilizes a hybrid filter in accordance with the present invention. However, the hybrid filter according to the invention may be used in a variety of applications where wavelength dependent detection and/or imaging of objects or scenery is desired. For example, a hybrid filter according to the present invention may be used to detect movement along a seismic fault, or to detect the presence, attention, or location of a person or subject. In addition, the hybrid filters according to the present invention may be used in biometric applications, such as systems that identify individuals using their eyes or facial features.

Referring now to the drawings and in particular to fig. 2, there is shown a diagram of a pupil detection system utilizing a hybrid filter in an embodiment in accordance with the invention. The system includes a detector 200 and two light sources 202, 204. The system may optionally incorporate a controller or processor (not shown) in other embodiments according to the invention.

In the embodiment of FIG. 2, light sources 202, 204 are shown on opposite sides of detector 200. In other embodiments in accordance with the invention, the light sources 202, 204 may be located on the same side of the detector 200. In other embodiments in accordance with the invention, the light sources 202, 204 may also be replaced by a single broadband light source emitting two or more different wavelengths. One example of such a broadband light source is the sun.

In this embodiment of pupil detection, two images are obtained with respect to the face and/or eyes of the subject 206 using the detector 200. One image is obtained using the light source 202 near or on the axis 208 ("on-axis") of the detector 200. The second image is obtained with the light source 204 at a greater angle away from the axis 208 of the detector 200 ("off-axis"). When the eyes of the subject 206 are open, the difference between the images will highlight the pupils of the eyes. This is because specular reflections from the retina are detected only in the on-axis image. Diffuse reflections from other facial and environmental features are largely cancelled out, leaving the pupil as the dominant feature in the differential image. When the pupil is not detected in the differential image, this can be used to infer that the subject's 206 eyes are closed.

In this embodiment in accordance with the invention, the amount of time that the subject's 206 eyes are open or closed may be monitored against a threshold. If the threshold is not met (e.g., the percentage of time the eyes are open is below the threshold), an alarm or some other action may be taken to alert the subject 206. Other measures, such as frequency or duration of blinking, may be used in other embodiments in accordance with the invention.

The differential reflectivity of the retina of the subject 206 depends on the angle 210 between the light source 202 and the axis 208 of the detector 200 and the angle 212 between the light source 204 and the axis 208. Generally, a smaller angle 210 will increase the retinal reflex. As used herein, "retinal reflection" refers to the intensity (brightness) reflected by the back of the eye of subject 206 and detected at detector 200. "retinal reflection" is also intended to include reflections from other tissues (other than or in addition to the retina) at the back of the eye. Thus, the angle 210 is selected such that the light source 202 is on or near the axis 208. In this embodiment in accordance with the invention, angle 210 is an angle approaching zero to two degrees.

In general, the magnitude of angle 212 is selected such that only low retinal reflections from light source 204 will be detected at detector 200. The iris (surrounding the pupil) blocks this signal and therefore pupil size under different illumination conditions should be taken into account when selecting the size of angle 212. In this embodiment in accordance with the invention, angle 210 is in the range of approximately three to fifteen degrees. In other embodiments in accordance with the invention, the size of the angles 210, 212 may be different. For example, the characteristics of a particular subject may determine the size of the angle 21, 212.

In this embodiment in accordance with the invention, the light sources 202, 204 emit light that produces substantially equal image intensity (brightness). In this embodiment in accordance with the invention, the light sources 202, 204 emit light of different wavelengths. Even though the light sources 202, 204 may be any wavelength, the wavelength may be selected in this embodiment so that the light does not disturb the subject and the iris of the eye does not contract in response to the light. The selected wavelength should be in a range that makes the detector 200 responsive. In this embodiment in accordance with the invention, the light sources 202, 204 may be implemented as multi-mode lasers or Light Emitting Diodes (LEDs) having infrared or near infrared wavelengths. Each light source 202, 204 may be implemented as one or more light sources, with each such device being positioned at substantially the same angle to the axis 208.

Figure 3a illustrates an image generated using an on-axis light source in accordance with the system shown in figure 2. The image shows an open eye. The eye has a bright pupil due to the intense retinal reflection produced by the on-axis light source 202. If the eye is already closed or nearly closed, a bright pupil will not be detected or imaged.

FIG. 3b depicts an image generated using an off-axis light source in accordance with the system shown in FIG. 2. The image in fig. 3b may be taken simultaneously with the image in fig. 3a, or in interleaved frames (continuous or discontinuous) of the image in fig. 3 a. The image of fig. 3b illustrates a normal black pupil. If the eye is already closed or nearly closed, the normal pupil will not be detected or imaged.

Fig. 3c illustrates an image resulting from the difference between the image of fig. 3a and the image of fig. 3 b. By taking the difference between the images of fig. 3a and fig. 3b, a relatively bright spot 300 is left on the relatively dark background 302 when the eye is open. There may be other traces of ocular features left on the background 302. However, typically, the bright spot 300 will stand out compared to the background 302. When the eye is closed or nearly closed, no bright spots 300 will appear in the differential image.

Fig. 3a-3c illustrate one eye of the subject 206. Those skilled in the art will appreciate that both eyes may also be monitored. It will also be appreciated that the same effect will be achieved if the image includes other features of the subject 206 (such as other facial features) as well as environmental features of the subject 206. These features will cancel each other out to a large extent in a similar manner to that just described, leaving a bright spot 300 when the eye is open (or two bright spots, one for each eye) or no bright spot when the eye is closed or nearly closed.

Referring now to fig. 4, a sensor in one embodiment in accordance with the invention is shown. In this embodiment, sensor 400 is incorporated into detector 200 (FIG. 2) and is configured as a Complementary Metal Oxide (CMOS) imaging sensor. However, in other embodiments in accordance with the invention, sensor 400 may be implemented using other types of imaging devices, such as a charge-coupled device (CCD) imager.

A patterned filter layer is formed over sensor 400 using two different filters shaped into a checkerboard pattern. The two filters are determined by the wavelengths used by the light sources 202, 204. For example, in this embodiment in accordance with the invention, sensor 400 includes a region (identified as 1) that includes filter material for selecting wavelengths used by light source 202, while other regions (identified as 2) include filter material for selecting wavelengths used by light source 204.

In the embodiment of fig. 4, the patterned filter layer is deposited as a separate sensor layer 400, for example on top of an underlying layer, while still in wafer form, using conventional deposition and lithography processes. In another embodiment in accordance with the invention, a patterned filter layer may be created as a separate element between the sensor 400 and the incident light. In addition, the filter pattern may be configured in a form different from the checkerboard pattern. For example, the patterned filter layer may be made in an interlaced, striped, or asymmetric configuration (e.g., 3 pixel by 2 pixel shape). The patterned filter layer may also incorporate other functions, such as a color imager.

Various types of filter materials may be used for the patterned filter layer. In this embodiment according to the invention the filter material comprises a polymer doped with a pigment or dye. In other embodiments according to the invention, the filter material may comprise absorption filters, reflection filters and interference filters made of semiconductors, other inorganic materials or organic materials.

FIG. 5 is a cross-sectional view of a probe in accordance with an embodiment of the present invention. In this figure, only a part of the detector is shown. The probe 200 includes: the sensor 400, comprised of pixels 500, 502, 504, 506, includes a patterned filter layer 508 having two alternating filter regions 510, 512, a glass cover 514, and a dual-band narrowband filter 516. In this embodiment in accordance with the invention, the sensor 400 is configured as a CMOS imager and the patterned filter layer 508 is configured as two polymers 510, 512 doped with pigments or dyes. Each region in the patterned filter layer 508 (e.g., a square in a checkerboard pattern) overlies a pixel in the CMOS imager.

When light is irradiated onto the upper surface of the narrowband filter 516, the wavelength is different from the wavelength (λ) of the light source 202₁) And the wavelength (λ) of the light source 204₂) Is filtered out or blocked when passing through the narrowband filter 516. Thus, in this embodiment, the visible wavelength λ_VISLight of and different from lambda₁And λ₂Wavelength (λ) of_n) Is filtered out and has a wavelength lambda₁And λ₂Or nearby light is transmitted through the narrowband filter 516. Thus, only the wavelength is λ₁And λ₂Or nearby light, passes through the glass cover 514. Thereafter, the polymer 510 transmits light having a wavelength λ₁While blocking light of wavelength lambda₂Of (2) is detected. As a result, pixels 500 and 504 receive only wavelengths λ₁Thereby generating an image acquired with the on-axis light source 202.

The polymer 512 transmits light with wavelength lambda₂While blocking light of wavelength lambda₁Such that pixels 502 and 506 receive only light having a wavelength lambda₂Of (2) is detected. In this manner, an image acquired with the off-axis light source 204 is generated. In this embodiment according to the invention, the shorter wavelength λ₁Associated with the coaxial light source 202, and a longer wavelength λ₂Associated with the off-axis light source 204And (4) connecting. However, in other embodiments according to the invention, the shorter wavelength λ₁Longer wavelength λ that may be associated with off-axis light source 204₂May be associated with the coaxial light source 202.

In this embodiment in accordance with the invention, narrowband filter 516 is a thin film bulk dielectric stack filter. Dielectric stack filters are designed to have specific spectral properties. In this embodiment in accordance with the invention, the dielectric stack filter is formed as a dual spike filter. The narrowband filter 516 (i.e., dielectric stack filter) is designed to have a wavelength at λ₁A sum of peaks at λ₂Another peak at (c).

In this embodiment in accordance with the invention, the narrowband filter 516 and the patterned filter layer 508 form a hybrid filter. Fig. 6 depicts spectra for the polymer filter and the narrowband filter of fig. 5. As shown in FIG. 6, the hybrid filter (combination of polymer filters 510, 512 and narrowband filter 516) effectively filters out the light-rejecting wavelengths (λ)₁And λ₂) Or all light other than nearby light. The narrowband filter 516 transmits the wavelength of interest (λ)₁And λ₂) Or a narrow range of nearby light while blocking the transmission of other wavelengths of light. Thus, only the wavelength is λ₁And λ₂Or nearby light, impinges on the polymer filters 510, 512 in the patterned filter layer 508. The patterned filter layer 508 is then used to distinguish λ₁And λ₂. Wavelength lambda₁A transmission filter 510 (unfiltered light 512), and a wavelength λ₂Pass through a filter 512 (unfiltered 510).

Those skilled in the art will appreciate that the patterned filter layer 508 provides a mechanism for selecting channels at pixel spatial resolution. In this embodiment in accordance with the invention, channel one is associated with the on-axis image and channel two is associated with the off-axis image. In other embodiments according to the invention, channel one may be associated with the off-axis image and channel two with the on-axis image.

In this embodiment according to the invention, the sensor 400 is located on a carrier (not shown in the figure). The glass cover 514 generally protects the sensor 400 from damage and particle contamination (e.g., dust). In another embodiment in accordance with the invention, the hybrid filter includes a patterned filter layer 508, a glass cover 514, and a narrowband filter 516. In this embodiment, the glass cover 514 is formed as a colored glass filter and is included as a substrate for a dielectric stack filter (i.e., the narrowband filter 516). Colored glass filters are designed to have certain spectral properties and are doped with pigments or dyes. Schott optical glass company, Mainz, germany, is a company that manufactures colored glass that can be used for colored glass filters.

Referring now to fig. 7a, a first method of fabricating a dual spike filter in an embodiment in accordance with the invention is shown. As discussed in connection with the embodiment of fig. 5, the narrowband filter 516 is a dielectric stack filter formed as a dual spike filter. The dielectric stack filters may comprise any combination of filter types. The desired spectral properties of the complete dielectric stack filter determine which type of filter is included in the stack.

For example, a dual spike filter can be fabricated by combining the two filters 700, 702. The filter wavelength of the band-stop filter 700 is between λ₁And λ₂Light of wavelengths in the vicinity of the bandpass filter 702 while passing light of wavelengths near and between λ₁And λ₂In between. The combination of the two filters 700, 702 transmits light in the shaded area while blocking light of all other wavelengths. Fig. 7b depicts the spectrum of the dual spike filter shown in fig. 7 a. As can be seen, only the wavelength λ of interest₁(Peak 704) and λ₂(peak 706) or near light is transmitted through the combination filter.

Referring now to fig. 8a, a second method of fabricating a dual spike filter in an embodiment in accordance with the invention is shown. By combining the upper cut filter 800, the lower cut filter 802, and the band-stop filter 804, a device can be manufacturedA dual spike filter. The combination of the three filters transmits light in the shaded area while blocking light of all other wavelengths. Fig. 8b depicts the spectrum of the dual spike filter shown in fig. 8 a. As can be seen, only the wavelength λ of interest₁(Peak 806) and λ₂(Peak 808) or near light is transmitted through the combination filter.

In some applications, such as pupil detection, it may be more desirable to utilize an LED as the light source rather than a laser. The use of LEDs in eye detection is generally safer than lasers. LEDs also have lower coherence than lasers, which eliminates speckle. In addition, more objects are illuminated by the LEDs because the LEDs have a wider divergence. Finally, LEDs are generally cheaper than lasers.

Narrow band light sources can be created with LEDs by placing a narrow band filter in front of or on top of the LED light source to narrow the spectrum of the LED. FIG. 9 is an illustration of a light source and a narrowband filter in an embodiment in accordance with the invention. Light source 900 is a Light Emitting Diode (LED) and narrowband filter 902 is a single spike dielectric stack filter in the embodiment of fig. 9. However, in other embodiments in accordance with the invention, the narrowband filter 902 may be configured as other types of filters. In addition, the dielectric stack filter may be fabricated as or include a colored glass filter. Other light sources, such as white light sources, may be used for other light sources according to the invention

In the examples.

Referring now to fig. 10, there is shown an illustration of the spectrum of a light source and the combination of the light source and narrowband filter shown in fig. 9. As can be seen, the spectrum (1000) of light source 900 itself is broader than the spectrum (1002) of the combination of light source 900 and narrowband filter 902. As previously discussed, a narrowband light source may be constructed using the broader spectrum light source 900 by forming or placing a narrowband filter 902 on top of or in front of the broader spectrum light source.

Fig. 11 is a diagram of a second system for pupil detection using a narrowband filter with respective light sources and a hybrid filter with a sensor in an embodiment in accordance with the invention. The same reference numerals have been used for those elements that function as described in connection with the previous figures. The detector 200 includes a sensor 400, a patterned filter layer 508, a glass cover 514, and a narrowband filter 516. The lens 1100 captures the light reflected by the subject 206 and focuses it on the top surface of the narrowband filter 516 in the detector 200.

Light source 202 includes a narrowband filter 902a and light source 204 includes a narrowband filter 902 b. Narrowband filters 902a, 902b have been fabricated to create filters with spectral properties appropriate for light sources 202, 204, respectively. As discussed previously, the narrowband filters 902a, 902b allow the system to utilize light sources with a wider spectrum, but utilizing light sources with a narrower spectrum may be safer and cheaper. In other embodiments in accordance with the invention, different types of filters may be used with the light sources 202, 204. Examples of different filter types include, but are not limited to, a lower cut filter and an upper cut filter.

An on-axis image is captured by detector 200 with light source 202 and an off-axis image is captured by detector 200 with light source 204. In this embodiment in accordance with the invention, the hybrid filter includes a patterned filter layer 508 and a narrowband filter 516. The hybrid filter blocks all light having a wavelength different from the wavelengths of the light sources 202, 204. Thus, the sensor 400 only detects light at the wavelength of the light sources 202, 204.

Referring now to fig. 12, shown is a diagram of a device that may be used for pupil detection in an embodiment in accordance with the invention. The apparatus 1200 includes a detector 200, a number of on-axis light sources 202, and a number of off-axis light sources 204. In this embodiment in accordance with the invention, each of the coaxial light sources 202 is positioned at substantially the same angle to the axis of the detector 200. Likewise, each off-axis light source 204 is positioned at substantially the same angle to the axis of the detector 200.

An on-axis image is captured by detector 200 using light source 202 and an off-axis image is captured by detector 200 using light source 204. In this embodiment in accordance with the invention, the light sources 202, 204 are shown packaged in the same apparatus 1200 as the detector 200. In other embodiments in accordance with the invention, the light source 204 may be located within a housing that is isolated from the light source 202 and the detector 200. In addition, the light source 202 may be located within a housing that is isolated from the detector 200 by placing a beam splitter between the detector and the object.

FIG. 13 is a diagram of detecting transmission through an object using a hybrid filter in another embodiment of the invention. The same reference numerals have been used for those elements that function as described in connection with the previous figures. The detector 200 includes a sensor 400, a patterned filter layer 508, a glass cover 514, and a narrowband filter 516.

The broadband light source 1300 transmits light to a transparent object 1302. Broadband light source 1300 transmits multiple wavelengths of light, two of which are to be detected by detector 200. In other embodiments in accordance with the invention, broadband light source 1300 may be replaced by two light sources that emit light at different wavelengths.

The lens 1100 captures the light transmitted through the transparent object 1300 and focuses it on the top surface of the narrowband filter 516. One image is captured by the detector 200 with light of one wavelength transmitted, while a second image is captured by the detector 200 with light of another wavelength transmitted.

In this embodiment in accordance with the invention, the hybrid filter includes a patterned filter layer 508 and a narrowband filter 516. The hybrid filter blocks all light at wavelengths other than the two wavelengths of interest, allowing the sensor 400 to detect only light at the two wavelengths.

Although two wavelengths λ have been detected by reference₁And λ₂The hybrid filter is described, but in other embodiments according to the invention, the hybrid filter may be used to detect more than two wavelengths of interest. Fig. 14 depicts spectra of a polymer filter and a triple band narrowband filter in an embodiment in accordance with the invention. In this embodiment, the hybrid filter detects three wavelengths of interest λ₁、λ₂And λ₃Of (2) is detected. Wavelength lambda₁And λ₃Spectra 1400 and 1402 of (a) represent two signals to be used by the imaging system, respectively. Detected wavelength lambda₂Is used to determine the amount of light received by the imaging system outside the two wavelengths of interest. Detected wavelength lambda₂The amount of light of (a) may be used as a reference amount of light detectable by the imaging system.

In this embodiment in accordance with the invention, the triple band narrowband filter transmits wavelengths of interest (λ)₁、λ₂And λ₃) Or nearby light, while blocking the transmission of all other wavelengths of light. Then, the polymer filter in the patterned filter layer distinguishes the received wavelength λ₁、λ₂And λ₃Of (2) is detected. FIG. 15 depicts a sensor according to the embodiment shown in FIG. 14. A patterned filter layer is formed over the sensor 1500 using three different filters. For example, in one embodiment in accordance with the invention, sensor 1500 may include a tri-band filter version of the red-green-blue colors. In the figure, red corresponds to region 1, green corresponds to region 2 and blue corresponds to region 3. In this embodiment, there may be twice as many other colors as green, since human perception of brightness depends more strongly on the green range.

Referring now to fig. 16, shown is the spectra of a polymer filter and a quad-band narrowband filter in an embodiment in accordance with the invention. In this embodiment, the hybrid filter detects four wavelengths of interest λ₁、λ₂、λ₃And λ₄Of (2) is detected. Wavelength lambda₁And λ₃Spectra 1600 and 1602 of (a) represent two signals to be used by the imaging system, respectively. Detected wavelength lambda₂And λ₄Is used as a reference to determine the amount of light received by the imaging system that is outside the two wavelengths of interest.

In this embodiment in accordance with the invention, a quad-band narrowband filter transmits wavelengths of interest (λ)₁、λ₂、λ₃And λ₄) Or nearby light, while blocking the transmission of all other wavelengths of light. Then, the polymer filter in the patterned filter layer distinguishes the received wavelength λ₁、λ₂、λ₃And λ₄Of (2) is detected. FIG. 17 depicts a sensor according to the embodiment shown in FIG. 16. A patterned filter layer is formed over the sensor 1700 using four different filters. For example, in this embodiment in accordance with the invention, sensor 1700 may include rows of filters 1 and 2 interleaved with rows of filters 3 and 4. The detection wavelength of the optical filters 1 and 2 is lambda₁And λ₂While the filters 3 and 4 detect the light of wavelength lambda₃And λ₄Of (2) is detected.

In other embodiments according to the invention, the hybrid filter may detect any number of wavelengths of interest. For example, an n-band narrowband filter will transmit light at or near the wavelength of interest. The regions within the patterned filter layer will alternately block at least one of the wavelengths of interest (and up to (n-1)). For systems that utilize a patterned filter layer having regions that transmit two or more wavelengths of interest, mathematical calculations (e.g., linear algebra) may be performed in order to determine the amount of light received for each wavelength of interest.

Claims (10)

1. An imaging system, comprising:

a source (900) that emits light of a plurality of wavelengths of interest to an object (206);

a hybrid filter that receives light from the object (206) and distinguishes light received at or near a plurality of wavelengths of interest while blocking light received at all other wavelengths; and

a light detection sensor (400) located below the hybrid filter and detecting an amount of light received at or near the plurality of wavelengths of interest.

2. The imaging system of claim 1, wherein the hybrid filter comprises a first filter layer (516) and a patterned filter layer (508) located below the first filter layer (516), wherein the first filter layer (516) passes light at or near a plurality of wavelengths of interest and blocks light at all other wavelengths, and wherein the patterned filter layer (508) comprises regions that transmit light received at or near one wavelength of interest and block light received at or near the other wavelengths of interest.

3. The imaging system of claim 2, wherein the first filter layer (516) comprises a dielectric stack filter.

4. The imaging system of claim 3, wherein the dielectric stack filter comprises a colored glass filter.

5. The imaging system of claim 2, 3 or 4, wherein the patterned filter layer (508) is comprised of one of a patterned dye-doped polymer, a patterned pigment-doped polymer, a patterned interference filter, a patterned reflective filter, or a patterned absorptive filter.

6. The imaging system of claim 1, 2, 3, 4, or 5, further comprising at least one filter (902) overlaid over the source (900) to narrow a spectrum of the source (900).

7. The imaging system of claim 6, wherein the at least one filter (902) comprises a dielectric stack filter.

8. The imaging system of claim 7, wherein the dielectric stack filter comprises a colored glass filter.

9. A wavelength dependent detection method, comprising:

receiving light from an object (206), wherein the light comprises light propagating at two or more wavelengths of interest;

distinguishing between light received at or near the wavelength of interest while blocking light received at all other wavelengths;

the amount of light received at or near the wavelength of interest is detected.

10. The method of claim 9, wherein detecting the amount of light received at or near the wavelength of interest comprises simultaneously detecting the amount of light received at or near the wavelength of interest, or alternately detecting the amount of light received at or near the wavelength of interest.