JP2010079022A - Optical scanning module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of deterioration of reading performance due to generation of spot disturbance in a scanning laser beam for reading derived from superposition of the main peak and the sub peak of an output laser beam after generation of diffraction by shading of the laser beam at the aperture end part in the case of setting the laser beam width with the output aperture in an optical scanning module. <P>SOLUTION: The optical scanning module obtains information by receiving a reflected optical wave after scanning an object with a laser beam shaped without overlapping onto the output aperture end part utilizing the inclination of the laser beam output optical axis as the central axis, while an angle θ1 formed between the scanning surface of a scanning laser beam output from a semiconductor laser and the semiconductor laser active surface in the laser beam is adjusted in a range of 0<θ1<90 degrees. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical scanning module that is mounted on an electronic apparatus and scans a laser beam for reading information.

  In general, there is known a barcode reader that irradiates a barcode symbol printed on an article or tag so as to scan a laser beam and reads information described from reflected light (returned light). As a light source of this device, for example, a semiconductor laser diode is used, and an optical scanning module that scans emitted laser light (light beam) and obtains luminance value information of an object from the return light is widely used. Here, a barcode is cited as an object to be read, but other information such as shadow information of a car or a person, a sample observed with a laser scanning microscope, or the like may be used.

  As such an optical scanning module, for example, there is an apparatus proposed in Patent Document 1. Japanese Patent Application Laid-Open No. H10-228561 discloses a device that emits laser light so as to scan using a plate spring and a scanning mirror, and can read a barcode with the return light. This optical scanning module integrates a light source, a photodetector, a scanning mirror, etc., so that the barcode scanning function can be easily added by mounting this optical scanning module on any device. It has become.

  In general, laser light is known to easily interfere. In the case where an optical scanning module is configured using a laser element as a light source, when the laser light hits the emission aperture, the laser light is diffracted due to scuffing. This diffraction generates a phenomenon in which a sub peak (diffraction peak) is superimposed on the main peak of the emitted laser light. This is observed as spot disturbance, and an optical scanning module having such a disordered spot significantly reduces product performance such as reading performance.

  Such performance degradation due to spot disturbance can be actually detected. For example, when the chart is scanned using the above spot and the reflected light is detected by a photodetector, the spot and its disturbance can be evaluated as a noise component superimposed on the signal component of the electric signal. In the following description, the noise resulting from diffraction caused by the scoring in the emission optical system is referred to as diffraction noise.

As a prior art for improving such diffraction noise, for example, Patent Document 2 has been proposed. Patent Document 2 discloses a diffraction noise removal circuit that captures reflected and scattered light of scanning light with a photodetector and performs peak detection using a differentiation circuit. By using a differentiating circuit, it is possible to detect a minute change in reflectance of a printed matter or the like as a peak, and it is possible to improve reading even when the distance of the barcode is greatly changed. An attempt is made to reduce diffraction noise by adding an electric circuit in order to reduce the above-described diffraction noise.
US Patent No. US 6,360,949 Japanese Patent No. 3447928 US Patent No. US 7,004,391

  When diffraction noise as shown in Patent Document 2 described above is input, the electric circuit works to determine and reduce this waveform as diffraction noise. Accordingly, if the input is of a level assumed in advance, it functions properly.

  However, when barcodes provided on various articles are subject to reading under various reading conditions, such as barcode reading devices, patterns such as the input level and width vary even with patterns based on standards. To do. That is, in Patent Document 2, if a true signal having a pattern similar to diffraction noise is input, it may be determined as a false signal. If an erroneous determination is made, inherently unnecessary signal processing is performed, so that incorrect information is generated and output. That is, when the input signal fluctuates due to external factors, when the signal is captured by the preceding optical system and processed by the subsequent digital circuit or the like, the authenticity of the received information is In principle, it is difficult to discriminate only from the input pattern information.

  This can be understood from the viewpoint of the amount of information. In other words, the amount of information handled by the subsequent digital circuit has an upper limit with an integer value. For example, the number of bits of luminance value data of the analog / digital conversion circuit is about 8 to 10 bits, and the amount of information is a sampling number times the number of bits.

  In this case, the digital circuit cannot theoretically obtain more information (signal amount) than is acquired. Under such restrictions, if intentional processing such as digital processing for noise reduction is added to information that has been digitized once, the upper limit (signal amount) of the information amount will not increase, but information that will be lost The amount comes out. Then, the total performance may be deteriorated. For example, if smoothing processing (averaging processing) is performed for noise removal, a fine signal having a high frequency is lost. Or, a false signal is given. It works if the desired diffraction noise occurs, but the true signal with the higher signal frequency will also be lost.

 Therefore, when viewed from the total balance, the reading performance often decreases. In a later stage with an upper limit on the amount of information, it is not possible to obtain a greater amount of information (signal amount) than the limited amount of information. In general, the more the information is processed from the preceding stage to the latter stage, the more significant information amount and signal-to-noise ratio are deteriorated. Adding digital processing does not improve the signal component from the viewpoint of the signal-to-noise ratio, which is equivalent to adding noise, and often degrades performance.

  Therefore, the present invention has an object to provide an optical scanning module that improves diffraction noise during analog signal processing when optically captured information is converted into an analog signal by photoelectric conversion and digital processing is performed later. To do.

  According to the present invention, it is possible to provide an optical scanning module that improves diffraction noise during analog signal processing when optically captured information is converted into an analog signal by photoelectric conversion and digital processing is performed later. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
With reference to FIG. 1A thru | or FIG. 1C, the optical scanning module which concerns on the 1st Embodiment of this invention is demonstrated. FIG. 1A is a perspective view showing an external configuration of the optical scanning module according to the first embodiment. FIG. 1B is a diagram illustrating the configuration of the optical scanning module in a state where the upper lid is removed. FIG. 1C is a diagram conceptually showing an optical system in the optical scanning module.

First, the outline and appearance of the optical scanning module will be described.
The external dimensions realized in the optical scanning module 1 are about 20 mm × 15 mm × 10 mm. Of course, the numerical values of these external dimensions are only examples, and can be realized with numerical values below these. Moreover, if it is a certain range, an external dimension can also be changed according to the mounting space of an electronic device.

  An optical scanning module 1 shown in FIG. 1A includes a housing 2 serving as an exterior having a strength capable of withstanding an impact such as dropping. The housing 2 includes a base member 2a for mounting each component and a substrate unit 2b serving as an upper lid. The substrate unit 2b is fixed to a plurality of support members 2c planted on the base member 2a by screws 2d. In addition, as a fixing method, a hook and a stopper may be respectively formed and fixed by fitting or fixing with an adhesive may be used.

  The optical scanning module 1 has, for example, a fixing screw hole formed on the lower surface of the base member 2a so that it can be mounted on various electronic devices as one unit of an optical reading function.

  A connector 31 and a control unit 32 are provided on the board unit 2b. The control unit 32 includes a circuit board on which a control circuit, a signal processing circuit, and the like for performing driving and signal processing of each unit and constituent parts described later are formed.

  The connector 31 is connected to an external device such as a computer (not shown) via a cable. For example, the computer supplies a power supply voltage to the optical scanning module to drive and control the optical scanning module 1. For example, in accordance with an instruction (command) of a computer of the mounted electronic device, barcode reading is started, the scanning mirror is swung, and the scanned laser light (scanning light) is irradiated. When a barcode is placed on the scanning light, the barcode is read. In the following description, the surface of the housing 2 that faces the direction in which laser light is irradiated and the reflected light of the laser light is received is referred to as a scanning aperture surface.

With reference to FIG. 1B, FIG. 1C, and FIG. 2, the structure of the optical scanning module 1 is demonstrated.
On the base member 2a, a light source unit 3, a folding mirror 5, an optical scanning device 4, and a light detection unit 6 are mounted as main components.

The light source unit 3 includes a laser diode (LD) 11 that emits laser light, a collimator lens 12, and an emission aperture 13. Here, the collimator lens 12 collimates the laser light emitted from the laser diode 11, and the emission aperture 13 narrows down the light beam cross section of the collimated laser light to generate a desired shape and spot size. The LD 11, the collimator lens 12, and the emission aperture 13 are appropriately arranged and distanced according to the reading specification (design), and are accommodated as a unit in an accommodating portion (not shown).
The laser light emitted from the light source unit 3 is deflected by reflection by the folding mirror 5 and travels toward the optical scanning device 4.

  In the optical scanning device 4, the scanning mirror 21, the bearing portion 23, and the driving portion 22 are integrally joined by resin molding, and the optical scanning device 4 is rotatable about a rotation shaft 24 planted on the base member 2 a. Yes. The front surface of the scanning mirror 21 is formed with a condensing mirror 21a having an aspheric surface and curved in a concave shape, and a flat and rectangular output mirror 21b is provided at the approximate center thereof. The exit mirror 21b and the condensing mirror 21a are integrally formed by resin molding, and the shape and orientation are preliminarily set so that the captured light is directed to the photodetector even when the scanning angle (scanning angle) varies. Is properly designed. The exit mirror 21b and the condensing mirror 21a of the resin-molded scanning mirror 21 are formed on a mirror surface on which a gold thin film is deposited by vacuum deposition. This mirror surface is manufactured so that the vertical reflectance with respect to the wavelength of the laser beam is about 90%.

The scanning mirror 21 is swung in the scanning direction described later by the rotation of the bearing portion 23.

  The drive unit 22 includes a drive coil 25, a leaf spring 26, a support spring holding member 27, and a magnet 29 disposed on the yoke 28. In the present embodiment, the driving coil 25 is fixed to the scanning mirror 21 side, the magnet 29 is fixed to the base member 2a side, and electromagnetic force is generated by applying a predetermined driving pulse to the driving coil 25 from the control unit 32. This is a so-called moving coil drive motor that swings the scanning mirror 21. On the other hand, a so-called moving magnet system in which the magnet 29 and the drive coil 25 are arranged opposite to each other may be used.

  The light detection unit 6 is mounted on the base member 2 a and includes a band pass filter 15, a light receiving opening 16, and a light detector 17. Among these, the band pass filter 15 allows the light in the vicinity of the wavelength of the light source to pass through the captured reflected and scattered light, but blocks the other light. The intensity of the reflected / scattered light incident on the photodetector 17 corresponds to a change in the reflectance of the object in scanning, and corresponds to external information in the scanning plane region.

Here, the concept of the scanning light and the scanning surface in the optical scanning module of the present embodiment will be described with reference to FIG.
First, the laser light emitted from the light source unit 3 is reflected by the oscillating scanning mirror 21 and emitted from the scanning aperture surface (FIG. 1A). As the scanning mirror 21 swings, the laser light is reciprocated and scanned in a substantially plane. Hereinafter, a virtual surface formed along with the movement of the scanning light is referred to as a scanning surface B. In FIG. 2, the scanning plane B is a plane on which two vectors of the direction of the scanning light and the scanning direction extend. That is, the laser beam reflected and emitted from the emission mirror surface 21b passes through the scanning aperture surface provided in the housing 2 shown in FIG. 1A and is emitted to the outside. The angle of the scanning mirror 21 when the optical axis fluctuation (scanning surface B) of the laser beam reflected by the exit mirror surface 21b coincides with the perpendicular of the scanning aperture surface is used as a reference (scanning angle 0 °). A mechanical rotation angle of the scanning mirror from the reference is defined as a scanning angle (swing angle) θ.

  In this state, when the user puts the barcode in a region crossing the scanning surface, the scanning light crosses the barcode, and reflected scattered light is generated. The reflected scattered light is taken in from the scanning aperture as return light, and the barcode information is read. The read information is output from the connector and subjected to various processes in an external computer or the like. For example, based on barcode data, articles are individually recognized, and slips / accounting processes are executed in accordance with preset sorting conditions.

Next, FIG. 3 is a block diagram showing a circuit configuration arranged along the signal flow of the optical scanning module 1.
The board unit 2b is fixed to the upper part of the base member 2a of the optical scanning module 1 with screws. A connector 31, a light detection unit 6, and a control unit 32 are mounted on the substrate unit 2b. The control unit 32 includes a CPU (not shown) that performs arithmetic processing and determination / control, a current / voltage conversion circuit 41, an amplification circuit 43, a differentiation circuit 44, an analog / digital (A / D) conversion circuit, and the like. 45, a digital signal processor (DSP) 46 and a decoding circuit 47. Note that the emission optical system 40 includes the light source unit 3 and the folding mirror 5.

  First, the user operates an external computer (not shown) to send a start command for starting scanning of the barcode to the optical scanning module 1 through the connector. Upon receiving this start command, the control unit 32 applies a drive voltage to the drive coil 25 and rotates the scanning mirror 21 to reciprocate periodically by the interaction with the magnet 29.

  Further, a drive voltage is supplied to the laser diode 11 and laser light is emitted. The laser beam is reflected by the emitting mirror 21b at the center of the oscillating scanning mirror 21 via the collimator lens 12, the folding mirror 5, and the like, and is applied to the scanning object scanning object from the scanning aperture surface so as to scan. Is done.

  The light reflected and scattered by the scanning object such as a barcode enters the condensing mirror 21a of the scanning mirror 21 from the scanning aperture surface while spreading in the opposite direction to the emitted light. The reflected scattered light (returned light) is collected by the condenser mirror surface 21 a, passes through the bandpass filter 15, and then is taken into the photodetector 17.

  In the photodetector 17, the photocurrent (optical signal) output from the photoelectric conversion photodetector 17 is converted into a voltage of an appropriate level via the current / voltage conversion circuit 41 and the amplification circuit 43, and differentiated. It is input to the circuit 44. The output signal of the differentiation circuit 44 is converted into a 10-bit digital signal via the A / D conversion circuit 45 and then taken into a digital signal processor (DSP) 46. The DSP 46 performs binarization processing on the input signal. The binarized signal corresponds to the reflectance and shadow information of the scanned object. The binarized signal is further sent to the decoding circuit 47.

  The decoding circuit 47 accumulates the binarized signal and compares the accumulated pattern with the barcode pattern based on a predetermined barcode specification or the like to decode the barcode information. . The decoded barcode information is output to the external computer 48 or the like via the connector 31.

  Next, the optical system of the optical scanning module 1 will be described in detail with reference to FIG. 1C.

  A laser diode (LD) 11 which is a light emitting element of the light source unit 3 emits laser light having a wavelength of 650 nm. In the light source unit 3, the light emitted from the LD 11 passes through the collimator lens 12 to become substantially parallel light, and further passes through the emission aperture 13 to be shaped into a desired spot shape.

  The collimator lens 12 is a glass lens having a diameter of about 3.0 mm and a focal length f1 of about 3.0 mm, and its position is adjusted so that the performance near the reading distance guaranteed by the product is optimized.

  The emission aperture 13 is a rectangular opening, and the width A1x in the scanning direction is 0.7 mm. And the light of this width A1x or more is blocked | interrupted because outgoing light passes. Thereby, the emitted light is shaped. The width A1x of the opening is set in advance so that a desired object reading area is optimized like a bar code having a bar space width of 5 mil or 13 mil. The laser light that has passed through the emission aperture 13 is incident and reflected by the folding mirror 5 and is incident on the emission mirror 21 b disposed substantially at the center of the scanning mirror 21.

  The laser beam reflected by the exit mirror 21b makes a reciprocating motion (scanning light) in the scanning plane described above. The scanning light is formed in a spot shape and moves so as to cross over an object such as a barcode, and generates reflected scattered light corresponding to the reflectance of the object.

  This reflected and scattered light enters the condensing mirror 21a. The condensing mirror 21a has a concave surface with a focal length f2 of about 10 mm, and is fixed to the output mirror 21b with a predetermined angle in advance.

  The reflected and scattered light incident on the condensing mirror 21 a is condensed near the detection surface of the photodetector 17 via the bandpass filter 15. The band pass filter 15 has a structure in which a dielectric multilayer film is deposited on both sides of a transparent glass plate. The light in the vicinity of 650 nm which is the wavelength of the light source has a vertical transmittance of about 90%, but the multilayer film has a thickness of about 5% to 1% or less so that the other light transmittance is about 5% to 1% or less. It has been adjusted.

  Therefore, the band-pass filter 15 captures the reflected and scattered light of the laser light, but blocks other light. The reflected scattered light that has passed through the bandpass filter 15 enters the photodetector 17 and is converted into a photocurrent.

  Therefore, when the barcode object is arranged so as to block the scanning surface, optical information of the area is acquired by the electric circuit, and various processes such as automatic recognition of the object are possible.

Next, the LD 11 and other emission optical systems will be described.
FIG. 4 shows the appearance of the laser diode 11. In the LD 11, a laser chip (not shown) for light emission is disposed inside the package, and a plurality of pins 11b for power supply and the like are provided on the back surface. The laser chip is formed by semiconductor bonding and has an active surface. Laser light is emitted along the active surface.

  FIG. 5 is a view of the LD 11 as seen from the back. As shown in the figure, the three pins 11b of the LD 11 are arranged corresponding to the direction of the active surface. A plurality of notches 11c1, 11c2, and 11c3 are provided on the outer periphery of the LD 11. When a predetermined voltage is applied to these pins 11b, laser light is generated from the active surface.

FIG. 6 is a diagram showing how laser light is emitted from the active surface.
This is a conceptual diagram showing a so-called far field pattern. As illustrated, the laser light travels with a certain spread angle in the emission direction. Since the semiconductor structure differs between a direction horizontal to the active surface and a direction perpendicular to the active surface, the spread angles in the horizontal direction and the vertical direction are generally different from each other. Therefore, the spread angle in the direction along the active surface is θ //, and the spread angle in the direction perpendicular to the active surface is θ⊥. Further, the spread angle is defined by the full width at half maximum. That is, it is defined by a full angle giving a half value with respect to the light intensity peak at substantially the center. For example, in the case of a 650 nm visible light semiconductor laser, the divergence angles are usually about θ // = 8 degrees and θ⊥ = 30 degrees. Referring to FIG. 6, the spot directly irradiated from the laser beam is generally an ellipse having a major axis and a minor axis that are orthogonal to each other. The short axis is substantially parallel to the active surface, and the long axis is substantially orthogonal to the active surface.

Next, the angle θ1 between the active surface and the scanning surface will be described.
FIG. 7 is a view showing a state in which the LD 11 is temporarily assembled in the housing 2 described above. In the following description, an angle formed by the two surfaces of the active surface and the scanning surface is defined as an angle θ1. In the state shown in FIG. 7, the angle θ1 is about 90 degrees. In this case, the direction of the scanning plane angle and the direction of θ⊥ in FIG. 6 are substantially parallel, and the light spread angle of the light source is about 30 degrees as shown in FIG. It will be arranged in.

 FIG. 8 shows the arrangement when the emission optical system is viewed from the direction above the scanning surface in the state of FIG. The light emitted from the LD 11 with a divergence angle of approximately 30 degrees passes through the collimator lens 12 to become substantially parallel light, and further passes through the emission aperture 13 so that the width in the scanning direction is shaped to 0.7 mm. Is done. Accordingly, the beam width in the scanning direction of the outgoing beam is 0.7 mm, partly shielded immediately after passing through the outgoing aperture 13.

Here, the definition of the spot shape, the line image distribution function, and the beam diameter will be described.
FIG. 9 shows the shape of the spot of the laser beam emitted from the emission aperture 13 in the arrangement of FIG. 8, and is called a line image distribution function. In a scanning optical system, a one-dimensional change in light intensity in the scanning direction often correlates with product performance such as resolution.

  Therefore, first, the emitted light is projected onto a plane perpendicular to the emitting direction to obtain the two-dimensional light intensity (point spread function) of the spot. Next, the light intensity is integrated (integrated) on the assumption that it is projected in one linear direction such as the scanning direction. Thereby, a one-dimensional light intensity distribution in the scanning direction can be obtained. Such a light intensity distribution is called a line image distribution function and is often used in performance evaluation and the like because it often correlates with an actual measurement value by a measuring instrument using a slit or the like and a product performance of a scanning optical system.

  Further, in this line image distribution function, the beam diameter is 1 / e ^ 2 = 13.5% with respect to the maximum value of light intensity (e is the base of natural logarithm, and e = 2.71828... ) Is often specified in full width. The beam diameter shown in FIG. 9 is about 250 μm.

[Beam waist, focus adjustment]
Further, FIG. 9 shows a line image distribution function at the beam waist.

  In the present embodiment, the optical scanning module 1 performs fine adjustment (focus adjustment) of the collimator lens 12 so that the beam diameter described above becomes the sharpest at a distance of 150 mm from the emission aperture 13. Actually, the adjustment distance of the beam waist is determined according to the distance at which the barcode reading is to be optimized based on the product specifications.

  For the spot shape shown in FIG. 9 and the like, the light exiting the exit aperture 13 is incident / reflected on the next folding mirror 5 and the scanning mirror 21. However, for these two mirrors, the optical system is designed in advance so that the cross-sectional shape in the scanning direction is a plane. Therefore, the shape of the beam spot in the scanning direction is not affected even through these two mirrors.

Further, the following Airy equation will be described in order to estimate the spot at the beam waist as related to the spot diameter of the emitted laser beam. Generally, the following formula (1) is established.

  Here, Ra is called the Airy radius, and represents the first dark ring in the point spread function (the position darkened when the spot is observed) by the radius. F1 is an effective F number on the observing side. This equation is valid only in the vicinity of the beam waist.

  Although it has been described that the beam diameter described above is often 1 / e ^ 2 of the peak value due to the convenience of measurement and the like, the equation (1) indicates the radius of the dark ring, and the definition of the beam diameter is as follows. Is different. Furthermore, the Airy disk is defined in terms of a point spread function, but the beam diameter described above is defined in the line spread function, and is different from the equation (1).

  Because of this difference, in general, the beam diameter of 1 / e ^ 2 does not completely match the Airy diameter (twice the Airy radius). When evaluated with a barcode scanner or the like, the beam diameter of 1 / e ^ 2 is usually slightly smaller than the Airy diameter.

However, since Airy's equation and beam diameter are correlated as a trend, it is convenient for grasping design guidelines and adjustment directions. For later explanation, equation (1) is rewritten using the parameters of the optical scanning module explained so far.

  Here, f0 is the beam waist distance (focus adjustment distance), A1x is the exit aperture diameter in the scanning direction, and λ1 is the wavelength of light. In this case, f0 = 150 mm, A1x = 0.7 mm, and λ1 = 0.650 um.

Further, since the beam diameter described above is defined by the full width, both sides are doubled to correspond. Substituting the above numerical values into equation (2) yields the following.

  Equation 3 shows a dark ring of the point spread function. On the other hand, the beam diameter of the line image distribution function shown in FIG. 9 is around 250 μm. Although there is a difference of about 20-30% due to the difference in definition and the beam diameter of 1 / e ^ 2 before the dark ring, there is no big contradiction when viewed as an order.

[Spot shape at a position away from the beam waist]
FIG. 9 is a line image distribution function in the vicinity of the beam waist whose distance from the exit aperture is 150 mm. On the other hand, FIG. 10 shows an example in which only the distance of the object from the exit aperture is changed in the same arrangement of the optical system as in FIG.

  FIG. 10 is an example of a line image distribution function (beam diameter) when the distance from the emission aperture 13 is 50 mm. Thus, the shape of the beam diameter is broken in the region closer to the exit aperture than the shape of the spot at the beam waist. As shown in the figure, the high-order sub-peak becomes prominent and is known as Fresnel diffraction.

  Furthermore, the beam diameter shown in FIG. 10 is larger than the beam diameter at the beam waist. This is because the width of the emission aperture in the scanning direction is set to 0.7 mm in FIG. The Airy's equation mentioned above is an equation that stands near the beam waist, so it cannot be applied in the current situation. When away from the beam waist, the beam diameter behaves so as to approach the aperture diameter according to the distance. This can also be inferred from geometric optics.

[Signal processing of scanning optical system]
Next, FIG. 11 shows an example of a chart for evaluation, and signals obtained from the scanning optical system will be described. In practice, a bar code or the like is used, but this chart is used to simplify the explanation.

  In this chart, there are only two bars and the bar width is 13 mils. It is defined as 1 mil = 25.4 mm / 1000, and the bar width is 330.2 um. Such a chart is arranged so as to face the scanning surface at a position where the distance from the emission aperture 13 is about 150 mm.

  When the laser beam spot is moved on the chart, the signal shown in FIG. 12 is obtained from the photodetector. This signal is a waveform after the photocurrent detected by the photodetector is processed in the current / voltage conversion circuit 42 and the amplification circuit 43. The horizontal axis represents time and corresponds to the movement of the spot of the scanning light. The vertical axis represents the voltage value scaled by the maximum value. Here, the scanning frequency of the scanning mirror 21 is designed to be 50 Hz, and the maximum value of the scanning angle is 45 degrees.

  FIG. 12 shows the variation of the voltage value corresponding to the change in the reflectance of the scanning object. This optical signal is passed through the differentiation circuit 44 described above. FIG. 13 is a conceptual diagram showing the main part of the differentiation circuit 44. Here, the cutoff frequency is set to 50 kHz. Other details are omitted. FIG. 14 is a differential signal output from the differentiating circuit 44. The horizontal axis is time. The vertical axis is the voltage value, and the scale is the maximum value.

  As described above, a peak occurs corresponding to the edge of the chart that is the object. Therefore, if the position of this peak is detected and the time interval is converted into a width value and output, the pattern of the original chart (FIG. 11) that is the scanning object can be reproduced on the electric circuit.

  Specifically, the differential waveform shown in FIG. 14 is sampled at predetermined time intervals by the DSP 46 mounted on the board unit 2b after analog / digital conversion. The sampled data is compared with a preset threshold value, and when the threshold value is exceeded, the maximum absolute value is detected. That is, the peak value is detected.

  When this peak value is detected, it is determined that the point is an edge, and a binary value corresponding to black and white is assigned to each edge. By repeating this for the sampled signal, binarization processing is performed. The binarized signal corresponds to the luminance value pattern of the scanning object (chart). The binarized signal is further transferred to the decoding circuit 47.

  The decoding circuit 47 first stores the binarized signal acquired corresponding to the scanning in a memory in the circuit. The pattern stored in the memory is repeatedly compared for matching / mismatching of patterns based on various bar code standards.

If the patterns match in this comparison, the barcode check digit is calculated to check whether there is a problem in reading. As a result, when the barcode can be recognized as an appropriate barcode, the barcode data is transmitted to the outside and the initial state is restored. For example, when an alphanumeric character is read, this character information is transferred to an external computer via a connector by serial communication, and the process is completed. If it is not recognized as an appropriate barcode, the data stored in the memory is discarded and the initial state is restored. [Diffraction noise occurs]
Next, the diffraction noise will be described in more detail.
As described above, the spot shape changes when the distance from the exit aperture 13 to the object is changed. For example, the distance from the emission aperture 13 is changed from 150 mm to 50 mm by changing the position of the object.

  By this movement, the spot shape becomes as shown in FIG. As described above, a plurality of diffraction peaks (sub-peaks) are generated in this spot due to the diffraction phenomenon of laser light. Therefore, the chart shown in FIG. 11 is scanned with the spots shown in FIG. As a result, the waveform of the optical signal shown in FIG. 15 is obtained. Compared to the waveform shown in FIG. 12 described above, the inclination of the optical signal is gentle because it is far from the distance of the beam waist.

  FIG. 16 shows a differentiated waveform of the output signal obtained by passing this optical signal through the differentiating circuit 44. Thus, the same shape as the spot obtained in FIG. 10 appears again in the differential waveform. This means that the beam spot is applied to the chart and the reflected and scattered light in that region is taken in, which corresponds to the integration calculation of the convolution of the beam spot and the chart. Passing the scanning waveform through the differentiating circuit 44 is equivalent to performing differentiation after performing integration, so that the spot shape of the original beam appears.

  Therefore, it can be seen that a plurality of sub-peaks are generated in the differential waveform corresponding to the sub-peak (high-order diffracted light) described in FIG. This means that higher-order diffracted light in the optical system behaves equivalently to noise in the electric circuit. In this case, the above-described peak detection does not function properly. This is because, in addition to the original main peak (signal component), a large number of sub-peaks (noise components) are overwritten and appear, making it difficult to determine the true / false of the peak.

  In the above-described example, the description has been made using a simple chart as shown in FIG. 11, but actually, the print density of the chart is further increased, and each line (or dot) has a further variation in thickness and density. It becomes a considerable number. For example, the above chart shows an example of 13 mil, but in the case of a 5 mil chart, the true signal becomes finer and overlaps with the noise component. Accordingly, it is increasingly difficult to judge whether the waveform is true or not.

  As a phenomenon, if the barcode distance is increased from the beam waist, the signal component decreases and the noise becomes relatively large. become unable.

[Signal to noise ratio]
The signal-to-noise ratio is a ratio of signal components to noise components. For example, as described above, if the differential signal is to be evaluated, it may be evaluated as the ratio of the peak voltage of the signal to the peak voltage of noise. Alternatively, if the optical system is an evaluation target, the area ratio may be used on the assumption that the area of the main peak and the sub peak corresponds to the signal amount in the above-described line image distribution function. Furthermore, if a digital signal is to be evaluated, the noise and the signal may be evaluated with gradation values and the ratio may be used. Alternatively, if software processing is to be evaluated, for example, the superiority or inferiority of each processing method may be evaluated from the amount of change in signal amplitude and noise before and after smoothing processing.

[Adjustment method of signal to noise ratio]
Next, a method for adjusting the signal-to-noise ratio in the optical scanning module of this embodiment will be described. FIGS. 17A to 17C show a state in which the angle θ1 is gradually changed from the state of 90 degrees to approach 0 degrees as described above. The arrangement of the laser diode 11 shown in FIG. 7 described above corresponds to FIG. 17A and is in a state of θ1 = 90 degrees. As described above, at this time, the spread angle of the laser light is about 30 degrees, and the end portion of the emitted light is shielded by the exit aperture 13. As a result, diffraction occurs in the edge portion, and sub-peaks are generated on both sides of the spot as shown in FIG.

  Therefore, the laser diode 11 shown in FIG. 7 is rotated around the emission axis to adjust the angle θ1 to 0 degree. That is, the laser light is brought into the state shown in FIGS. 17 (a) to 17 (c).

  As described in FIG. 6, the spread angle of the laser beam is different between the direction of the active surface and the direction orthogonal thereto, and therefore, when the angle θ1 is changed, the spread angle of the light in the scanning direction is continuously and arbitrarily changed. Can be made. When the angle θ1 = 0 degrees, the spread angle in the scanning direction is about 8 degrees, and the light is concentrated on the center of the emission axis when viewed from the upper part of the scanning surface. Therefore, when the angle θ1 is brought close to 0 degree, it is possible to reduce the scatter of light due to the emission aperture. Due to this decrease, the outgoing light is concentrated around the outgoing axis, and the intensity of the light near the end of the outgoing aperture is weakened. As a result, the intensity of the diffraction peak is reduced.

  Therefore, when the distance from the emission aperture 13 is 50 mm, the higher-order diffraction peaks as shown in FIG. 10 decrease and only the central main peak increases. This corresponds to the fact that the originally emitted light has a Gaussian light intensity as shown in FIG. However, in this case, the beam diameter at the beam waist increases. That is, as illustrated in FIG. 17C, the width of the outgoing light is narrower than the width A1x of the outgoing aperture. Compared to FIG. 17A, the width of the light passing through the emission aperture is about 1/3.

  This corresponds to the fact that the substantial width of the outgoing light at the position of the outgoing aperture is narrowed. In other words, returning to the above-described equation (2), when the angle θ1 is decreased from 90 degrees to 0 degrees, the effective emission aperture width A1x is reduced to about ３ times. Therefore, from the equation (2), it is estimated that the beam diameter in the vicinity of the beam waist increases about three times. In this case, as the beam diameter increases, the differential waveform becomes gentle and the height (voltage) of the main peak decreases. This degrades the peak detection function. In particular, the reading of high-density barcodes such as 5 mils is greatly degraded. Therefore, while measuring the differential waveform, the angle θ1 is gradually decreased from 90 degrees to search for an angle that does not deteriorate the beam diameter at the beam waist distance, that is, the peak that does not lower the peak of the differential waveform.

  As described above, a value that minimizes the angle θ1 is searched for within a range in which the beam diameter at the beam waist is substantially maintained. The result is shown in FIG. As can be seen from FIG. 17B, FIG. 17B is almost the same as FIG. 17A from the viewpoint of the width of the outgoing beam. Therefore, according to the equation (2), a very sharp beam diameter can be obtained in the vicinity of the beam waist as in FIG.

  Therefore, it is possible to satisfactorily read a high-density bar code such as 5 mil. Compared with FIG. 17C, a sharper beam diameter can be obtained with the arrangement of FIG. 17B. On the other hand, as shown in FIG. 17B, from the viewpoint of the amount of light spilled at the exit aperture, FIG. 17B is less squeezed than FIG. 17A. Rather, it can be seen that the state is close to FIG.

  Therefore, according to the arrangement of FIG. 17B, the differential waveform in the vicinity of the emission aperture is closer to FIG. 14 than FIG. This corresponds to the fact that the amount of scoring is reduced, and the differential waveform originally in the state shown in FIG. 16 approaches the shape shown in FIG. This adjustment makes it possible to remove and reduce diffraction noise while improving the signal amplitude.

  With the adjustment described above, the diffraction diameter described above can be reduced in the vicinity of the beam waist, while adjusting the beam diameter sufficiently sharply and away from the beam waist. it can.

  From the viewpoint of the signal-to-noise ratio, it is possible to find a position where the signal component is good and the noise component is minimized. As a result, product performance is significantly improved over the entire reading area. That is, since the diffraction noise shown in FIG. 16 is eliminated or reduced, the subsequent electrical circuit and software function more accurately and efficiently.

  As described above, in the prior art suggested in Patent Document 2 and the like, there is an upper limit in improving the signal component. For example, as in a smoothing process (averaging process) by software, there is a tendency that a signal peak is generally lost at the same time as noise removal is attempted.

  The present embodiment uses a phenomenon different from the disclosed matter, and there is an adjustment state in which the signal component is improved even though the noise component is reduced. Therefore, the performance can be remarkably improved by adjusting the angle formed at the position where the signal to noise ratio is good.

  FIG. 10 shows an example in which the distance between the object and the exit aperture 13 is short, but this adjustment improves diffraction noise even when these distances are near the beam waist or farther away. Can do. For example, FIG. 9 shows a spot shape at the beam waist. Specifically, it can be seen that the above-described diffraction phenomenon occurs in the beam waist, and higher-order diffracted light is generated. Such sub-peaks are also improved at the same time because the above-described adjustment improves the squeezing caused by the exit aperture 13.

  Therefore, adjustment of the angle θ1 in the laser diode 11 improves not only the Fresnel diffraction near the emission aperture 13 but also the so-called Fraunhofer diffraction near the beam waist and far away. Since the signal-to-noise ratio is improved over the entire reading area, subsequent processing such as peak detection functions more appropriately, and product performance is improved.

  FIG. 18 shows an example of the arrangement of the laser diodes 11 after the adjustment of the angle θ1. In this example, the optimum adjustment angle of the angle θ1 is about 45 degrees. This is the position (angle) at which the position where the signal to noise ratio is maximized is found while looking at the waveform of the differentiation circuit 44.

The procedure of a simple adjustment method will be described below.
First, a commercially available beam diameter measuring device is disposed in the vicinity of the beam waist, and laser light is emitted in a state where scanning driving of the optical scanning module 1 is stopped. At this time, the beam diameter measuring device continuously detects the beam by continuously driving it, and displays the measured value of the beam diameter on the monitor.

  Next, the beam diameter is roughly adjusted to an allowable range (for example, 260 μm or less). Next, the angle θ1 is sequentially decreased every several degrees from 90 degrees to 0 degrees, and the setting measurement is repeated. If a position where θ1 is minimum within an allowable range is found, the angle θ1 is fixed. By such a procedure, it is possible to find a position where the beam diameter is sufficiently sharp and the amount of squealing is minimized.

  This angle θ1 is uniquely determined when a laser diode is selected by determining a collimator lens or the like. Therefore, the angle θ1 may be fixed during mass production as long as the optimum angle is found by the above procedure during product development. That is, when the optimum angle θ1 is found in a trial production or the like, a convex part is provided on the mass production housing member, and it is assembled so as to coincide with the notch on the back part of the laser diode. Thereby, the adjustment work of the angle θ1 during mass production can be simplified and simplified.

In this case, for example, assembly and adjustment procedures in mass production are as follows. First, a collimator lens is incorporated in a housing member, and then a laser diode is attached to the housing and fixed by so-called caulking. Here, the angle θ1 is specified.

  Next, a voltage is applied to the pin of the laser diode 11 and the position of the collimator lens 12 is finely adjusted while observing the spot diameter of the laser beam that has passed through the collimator lens 12. When the focus adjustment is performed so that the beam waist is at a desired distance, the position of the collimator lens 12 is bonded and fixed to complete the assembly / adjustment operation.

  By adjusting the focus after adjusting the angle θ1, the beam diameter at the beam waist or the like can be adjusted accurately, the signal-to-noise ratio can be maximized, and the variation in adjustment can be reduced. Thereby, the adjustment of the signal-to-noise ratio can be simplified, and the optical scanning module 1 having the optimum performance can be mass-produced.

Alternatively, the laser diode 11 may be fixed by press-fitting or adhesion instead of being fixed to the housing 2 by caulking. Or you may fix by screwing. If it is fixed by screwing, the number of parts increases, but the angle θ1 can be readjusted or adjusted individually, and the signal-to-noise ratio can be further improved.

  Note that the optimum adjustment value for the angle θ1 in the first embodiment is fixed at about 45 degrees, but according to the standard of the laser diode 11, the values of θ // and θ の are about several tens of percent. There is a range. For example, θ // = 8 ± 2 degrees and θ⊥ = 30 ± 5 degrees, which are different depending on the manufacturing process and semiconductor material of each manufacturer.

  Furthermore, the change in the signal-to-noise ratio when the angle θ1 is changed is continuous and has a certain allowable range. Accordingly, the angle θ1 in the first embodiment is preferably around 45 degrees, but has an allowable range of about several tens of degrees. Actually, the angle θ1 may be in the range of 0 degrees to 90 degrees, but preferably in the range of about 10 degrees to 80 degrees. Furthermore, it is better if each of the optical scanning modules is finely adjusted individually so that the signal-to-noise ratio is optimized. In any case, as long as the angle θ1 is adjusted to such a range, the scoring can be eliminated and the performance of the optical scanning module is improved. That is, diffraction noise can be reduced while sharpening the spot.

  Further, according to the present embodiment, even if the type of the laser diode 11 is changed and the spread angle is changed, it can be easily optimized by adjusting the formed angle. Even in the adjustment, the effect can be easily verified by observing the differential waveform.

  In the prior art described in Patent Document 2 and the like described above, the shape of diffraction noise changes when the type or lot of the laser diode changes and the spread angle of the laser light changes. As a result, if the performance variation of parts exceeds the specification or setting range of the electrical circuit or software, it cannot be stated that malfunction will not occur, so it will be necessary to verify the operation again, and readjust and re-adjust parameters. Design needs may arise.

In the first embodiment, various parameters have been described. However, they can be expressed as follows. First, the spread angle in the scanning plane direction of the laser diode is defined as θ2. As described above, θ2 is variable in the range of θ // to θ⊥, that is, in the range of 8 degrees to 30 degrees. Next, the angle θ3 is defined as follows.

  Here, A1x is the width of the emission aperture in the scanning direction, and f1 is the focal length of the collimator lens. tan-1x is synonymous with Atanx and is an inverse function of tanx. Substituting the values of the focal length f1 = 3.0 mm and the emission aperture interval A1x = 0.7 mm in the scanning direction, θ3 = about 13 degrees can be obtained. θ3 is in the middle of the range of θ2. Accordingly, when the aforementioned angle θ1 is set to around 45 degrees, the spread angle θ2 can be set to approximately θ3 or less. Thereby, in the example of the first embodiment, the signal-to-noise ratio can be improved as compared with the case where θ1 = 0 degrees and 90 degrees. Further, by adjusting the above-described angle θ1, the above-described θ2 can be continuously changed and finely adjusted to θ2 at which the signal-to-noise ratio is maximized. Actually, since the above-mentioned divergence angle is defined by the full width at half maximum, there is light that spreads beyond this angle. Therefore, there is a certain range. Specifically, if θ2 is about the same as θ3 or less than θ3, it functions sufficiently. If this is expressed using θ1, the angle θ1 may be in the range of 0 to 90 degrees, but is preferably in the range of 10 to 80 degrees. Or, in other words, using the focal length f1, the exit aperture width A1x, etc., it can also be expressed as follows.

  In the above-described θ3 and θ2, either the focal length f1, the spread angle θ2, the width A1x, or the direction of the light source may be adjusted so that θ3≈θ2 or θ2 ≦ θ3. . In this case, as described above, the signal component and the noise component are optimized, and the performance of the optical scanning module can be improved.

  In addition, as described above, if it is desired to specify a more precise angle θ1, the adjustment procedure using the differentiation circuit 44 described above can be adjusted and verified by an experimental method, so fine adjustment can be performed while changing parameters. Repeat it. For example, when it is desired to further improve the performance of the optical scanning module, the angle θ1 may be finely adjusted for each optical scanning module. In this case, individual signal-to-noise ratio variations due to component processing tolerances and laser diode performance variations can be canceled and optimized by each adjustment. Therefore, the guaranteed performance, product specifications, etc. can be further improved.

Next, a second embodiment will be described.
FIG. 19 shows an optical system according to the second embodiment. Other components such as electric circuits and machine parts are the same as those in the first embodiment, and description thereof is omitted here. Also in the optical system of the present embodiment, the same members as those shown in FIG. 1C are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 19, the angle θ1 has already been adjusted by the above-described procedure, and is set to 45 degrees, for example. FIG. 19 conceptually shows the result of ray tracing, but the spread angle of the laser beam viewed from the upper part of the scanning surface is narrowed by adjusting θ1. In the first embodiment described above, after adjustment, the squeezing caused by the emission aperture 13 is reduced. That is, if the angle formed is adjusted, the width of the outgoing beam is substantially optimized, and the outgoing aperture 13 is not necessarily provided. Therefore, in the second embodiment, the emission aperture 13 is removed from the configuration of the first embodiment, and the shaping of the laser beam by the emission optical system is performed only by the collimator lens 12.

  As described above, the beam diameter in the vicinity of the beam waist can be sufficiently sharpened in the vicinity where the beam has passed through the collimator lens 12 because the beam width is appropriately adjusted. Therefore, even if the simplified configuration is obtained by removing the emission aperture, no distortion occurs and a suitable signal component can be obtained.

  In the present embodiment, the differential signal is greatly improved in diffraction noise and the performance of the optical scanning module is remarkably improved as compared with the prior art in which the sub-peak occurs in the differential signal. Although adjustment of the angle θ1 is required, the exit aperture is not necessary due to the adjustment work. Therefore, the design is simplified, the effect that the number of parts and the space can be reduced, and the product performance can be further improved.

Next, a third embodiment will be described.
In the first and second embodiments described above, the differentiation circuit and the like formed on the circuit board are provided on the board unit 2b.

  In the third embodiment, as shown in FIG. 20, the above-described photodetector 52 and differentiation circuit 51 are attached as adjustment jigs only during adjustment, and are removed after adjustment is completed. On the base member 2a, the light source unit 3, the folding mirror 5, the optical scanning device 4, and the light detection unit 6 are mounted.

  The laser diode 11 of the light source unit 3 is mounted at a predetermined position on the base member 2a, and the aforementioned angle θ1 is adjusted. At the time of this adjustment, in the adjustment and evaluation of the signal to noise ratio, a chart is arranged at a desired distance and laser light is scanned. Separately, an adjustment jig having a photodetector 52 and a differentiation circuit 51 is disposed in the vicinity of the scanning plane.

  In this arrangement, the reflected and scattered light of the scanning light is acquired by the photodetector 52. Based on the acquired signal waveform, the differential waveform can be evaluated and confirmed as described above.

  Thus, by attaching the photodetector 52 and the differentiation circuit 51 only at the time of adjustment, the signal-to-noise ratio can be easily optimized and verified. For example, the adjustment jig is configured so that the optical scanning module can be easily electrically connected to a connector or the like, and the positional relationship with the photodetector 52 is established simply by placing the optical scanning module at a specified position. When mass-producing the optical scanning module, it is possible to continuously perform the adjustment operation by sequentially replacing the adjustment jig while the adjustment jig is in operation. This is effective when it is desired to greatly improve production efficiency.

  As described above, according to the present embodiment, the signal-to-noise ratio can be improved without adding complicated electrical circuits or software processing. Thereby, performance such as reading can be remarkably improved. Furthermore, since noise (diffraction noise) is reduced, it is not necessary to complicate binarization processing and decoding processing, and signal processing can be speeded up. Further, since the signal processing becomes efficient without the addition of an electric circuit, the processing period is shortened. Therefore, power consumption can be improved. The number of parts can also be reduced.

  The optical scanning module in each embodiment described above can be mounted on any electronic device. For example, barcode reader, laser printer, laser scanning microscope, laser projector, information input device, information output device, image forming device, precision medical device, portable information terminal, inter-vehicle sensor, security sensor, three-dimensional scanner, wireless device , Handheld devices, automobiles, ships, aircraft, semiconductor manufacturing equipment, card recognition equipment, vending machines, etc.

  Moreover, the optical scanning module of each embodiment is suitable for reading all barcodes. For example, suitable for reading barcodes such as JAN, EAN, UPC, Code39, ITF (Interleaved 2 of 5), Codabar, Code128, UCC / EAN128, BooklandEAN, MSI Plessey, Code93, Reduced Spaced Symbology (RSS), PDF417, etc. . It is also suitable for applications that read special patterns such as combinations of line drawings, dots, line segments, symbols, and engraved uneven shapes. Further, the optical scanning module of the present invention can be easily applied to object detection and the like by rewriting software installed in the decoding circuit. For example, it can be used for recognition of a car or a person. Since it is possible to detect the moving object and the presence / absence of the moving object, the security device may be configured by using the scanning light as infrared light. In addition, a three-dimensional scanner for reading a three-dimensional shape may be configured using the optical scanning module of the present invention, and a human body or the like may be a scanning target. In addition, according to the present invention, since the spot shape is improved over a wide distance range, it is suitable for highly accurate detection of a wide range of moving objects and the like. Further, an example of scanning a screen or a wall surface as a high-definition laser projector may be used.

  According to the present invention, the diffraction noise and the signal to noise ratio can be improved satisfactorily. However, it goes without saying that other noise and optical system improvements may be used in combination. For example, an optical gain correction filter described in Patent Document 3 may be mounted as the above-described bandpass filter. This optical gain correction filter is a multilayer film component that the amount of light increases or decreases when the incident angle changes. By installing this component, performance can be further improved, such as reducing the drop in the amount of peripheral light due to scanning, etc. .

  In addition, the laser light of the present embodiment has a wavelength of 650 nm, but is not limited. For example, a wavelength near 400 nm may be used, or infrared light of 800 nm or more may be used. In such a case, the transmission wavelength of the bandpass filter described above may be changed.

Furthermore, according to this embodiment, a sharp beam spot with little diffraction noise can be generated. Therefore, it is also suitable as a scanning optical system for laser printers, laser scanning microscopes, laser projectors, and three-dimensional scanners. In this case, the resolution and depth can be improved, and a higher definition output can be obtained.
As described above, according to the present invention, the following effects can be obtained.

  1. Diffraction noise can be reduced in the previous stage of the scanning optical system. Thereby, the performance of the optical scanning module can be improved.

  2. While reducing diffraction noise, the signal component can be adjusted well and the signal-to-noise ratio can be improved. Thereby, an optical scanning module with excellent performance can be provided.

  3. Adjustment that maximizes the signal-to-noise ratio can be realized. As a result, it is possible to optimize the reading performance without the need for complicated adjustment of an electric circuit or the like.

  4). By reducing diffraction noise while maintaining good signal components, complicated circuits and processing can be eliminated. Thereby, electrical parts and complicated processing can be reduced, and binarization processing, decoding processing, and software processing can be speeded up. Power consumption can also be reduced.

  5. An object of the present invention is to provide an optical scanning module having an excellent signal-to-noise ratio by obtaining a good signal component while reducing diffraction noise. In general, there is a conflicting relationship that signal components are also degraded when noise is reduced. However, the present invention provides an optical scanning module suitable from the viewpoint of the signal-to-noise ratio. Specifically, the sub-peak (high-order diffracted light) is reduced while maintaining and improving the sharpness and spot width of the main peak (zero-order diffracted light) of the laser beam spot. Thereby, the signal-to-noise ratio is improved, and the operation area of the optical scanning module is improved.

  6). A method for adjusting a signal-to-noise ratio in an optical scanning module can be provided. That is, in the above-described prior art, when there are contradictory characteristics of noise component reduction and signal component improvement, an infinite number of combinations of electric circuit constants and software parameters are examined, and malfunctions due to false signals are detected. It was necessary to verify that it did not happen. This debugging and finding the optimal balance point has been a very complicated task. In general, there is often a conflicting relationship that signal components are also degraded when trying to reduce noise, and it is often difficult to find an optimal adjustment.

  However, the present invention provides a method for adjusting a signal-to-noise ratio that can reduce diffraction noise while improving signal components.

  7). The object is to reduce complex electric circuits and processing by reducing diffraction noise while improving good signal components. Electric parts and complicated processing can be reduced, and binarization processing, decoding processing, and software processing can be accelerated. Power consumption can also be reduced.

[Appendix]
The present invention includes the following inventions.

(1) a semiconductor laser that emits diffused light;
A collimator lens for collimating diffused light from a semiconductor laser;
A scanning unit that reflects the parallel light toward the reading object and scans the parallel light to reciprocate in a predetermined direction;
A photodetector that receives reflected light from the object to be read; and
The chassis on which they are placed,
In an optical scanning module having
When the scanning direction relative to the optical axis of the parallel light scanned by the scanning unit corresponds to the optical axis of the diffused light emitted from the semiconductor laser, when viewed from the optical axis of the diffused light Θ1 is in the range of 0 ° <θ1 <90 °, where θ1 is an angle formed between the scanning direction of the laser beam and the in-plane direction of the active layer of the semiconductor laser as viewed from the optical axis of the diffused light. And a semiconductor laser mounted on the chassis.
(2) The optical scanning module according to (1), wherein the θ1 is adjusted in a range of 10 degrees <θ1 <80 degrees.
(3) a semiconductor laser that emits diffused light having an elliptical cross section;
A collimator lens for collimating diffused light from a semiconductor laser;
A scanning unit that reflects the parallel light toward the reading object and scans the parallel light to reciprocate in a predetermined direction;
A photodetector that receives reflected light from the object to be read; and
The chassis on which they are placed,
In an optical scanning module having
When the scanning direction relative to the optical axis of the parallel light scanned by the scanning unit corresponds to the optical axis of the diffused light emitted from the semiconductor laser, when viewed from the optical axis of the diffused light Θ1 is in the range of 0 degree <θ1 <90 degrees, where θ1 is an angle formed by the scanning direction of the diffused light and the direction of the major axis of the elliptical cross section of the diffused light when viewed from the optical axis of the diffused light An optical scanning module, wherein a semiconductor laser is mounted on a chassis.
(4) The optical scanning module according to (3), wherein the θ1 is adjusted in a range of 10 degrees <θ1 <80 degrees.
(5) a semiconductor laser that emits diffused light;
A collimator lens for collimating diffused light from a semiconductor laser;
A scanning unit that reflects the parallel light toward the reading object and scans the parallel light so as to reciprocate within a predetermined scanning plane;
A photodetector that receives reflected light from the object to be read; and
The chassis on which they are placed,
In an optical scanning module having
When the direction of the scanning surface relative to the optical axis of the parallel light to be scanned corresponds to the optical axis of the diffused light emitted from the semiconductor laser, the direction of the scanning surface viewed from the optical axis of the diffused light and the diffusion When the angle formed with the in-plane direction of the active layer of the semiconductor laser when viewed from the optical axis of the light is θ1, the semiconductor laser is mounted on the chassis so that θ1 is in the range of 0 ° <θ1 <90 °. An optical scanning module characterized by being placed.
(6) The optical scanning module according to (5), wherein θ1 is adjusted in a range of 10 degrees <θ1 <80 degrees.
(7) a semiconductor laser that emits diffused light;
A collimator lens for collimating diffused light from a semiconductor laser;
An opening that shapes the cross-sectional shape of the parallel light;
A scanning unit that reflects the parallel light toward the reading object and scans the parallel light to reciprocate in a predetermined direction;
A photodetector that receives reflected light from the object to be read; and
A differentiating circuit for differentiating the received light signal of the photodetector;
The chassis on which they are placed,
In an optical scanning module having
When the scanning direction relative to the optical axis of the parallel light scanned by the scanning unit corresponds to the optical axis of the diffused light emitted from the semiconductor laser, when viewed from the optical axis of the diffused light When the angle formed by the scanning direction of the laser beam and the in-plane direction of the active layer of the semiconductor laser when viewed from the optical axis of the diffused light is θ1, the diffraction noise generated by shaping is reduced in the output of the differentiation circuit. The optical scanning module is characterized in that the θ1 is adjusted so as to increase the signal-to-noise ratio.
(8) The optical scanning module according to (7), wherein θ1 is adjusted in a range of 10 degrees <θ1 <80 degrees.

FIG. 1A is a diagram showing an external configuration of an optical scanning module according to the first embodiment of the present invention. FIG. 1B is a diagram illustrating an internal configuration of the optical scanning module according to the first embodiment. FIG. 1C is a diagram illustrating an arrangement configuration of main optical systems of the optical scanning module according to the first embodiment. FIG. 2 is a diagram for explaining the scanning light, the scanning direction, and the scanning surface of the optical scanning module according to the first embodiment. FIG. 3 is a block diagram showing an electrical configuration of the optical scanning module according to the first embodiment. FIG. 4 is a diagram showing an external configuration of the laser diode. FIG. 5 is a diagram for explaining the orientation of the pins and the active surface viewed from the laser diode mounting side. FIG. 6 is a diagram for explaining optical characteristics of laser light in a laser diode. FIG. 7 is a view showing an assembled state of the laser diode to the housing. FIG. 8 is a diagram for explaining the relationship between the spread of laser light and the optical part in the laser diode. FIG. 9 is a diagram for explaining the spot shape of the laser light in an arrangement at a predetermined distance from the emission aperture. FIG. 10 is a diagram for explaining the spot shape of the laser light in an arrangement close to the emission aperture. FIG. 11 is a diagram illustrating an example of a chart for evaluation. 12 is a diagram showing a waveform of a detection signal detected from the chart shown in FIG. 11 using the laser beam in FIG. FIG. 13 is a diagram illustrating a circuit configuration of a main part of the differentiation circuit. FIG. 14 is a diagram illustrating a waveform of an output signal from the differentiating circuit to which the detection signal in FIG. 12 is input. 15 is a diagram showing a waveform of a detection signal detected from the chart shown in FIG. 11 using the laser beam in FIG. FIG. 16 is a diagram illustrating a waveform of an output signal from the differentiating circuit to which the detection signal in FIG. 15 is input. FIGS. 17A to 17C are diagrams showing the width of the laser diode viewed from above when the angle formed by the scanning surface and the active surface is changed. FIG. 18 is a diagram for explaining the adjustment of the scanning surface and the active surface in the laser diode. FIG. 19 is a diagram illustrating an arrangement configuration of main optical systems of the optical scanning module according to the second embodiment. FIG. 20 is a diagram for explaining an optical scanning module according to the third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical scanning module, 2 ... Housing, 2a ... Base member, 2b ... Substrate unit, 3 ... Light source unit, 4 ... Optical scanning device, 5 ... Folding mirror, 6 ... Photodetection unit, 11 ... Laser diode (LD), DESCRIPTION OF SYMBOLS 12 ... Collimator lens, 13 ... Output aperture, 15 ... Band pass filter, 16 ... Light-receiving opening part, 17 ... Photodetector, 21 ... Scanning mirror, 21a ... Condensing mirror, 21b ... Output mirror, 22 ... Drive part, 23 DESCRIPTION OF SYMBOLS ... Bearing part, 25 ... Drive coil, 26 ... Leaf spring, 27 ... Support spring holding member, 28 ... Yoke, 29 ... Magnet, 31 ... Connector, 32 ... Control part.

Claims (5)

A light source having an active surface and emitting laser light;
An emission optical system for shaping the laser light emitted from the light source;
A scanning unit that scans the shaped laser beam in a scanning plane;
A photodetector for receiving reflected and scattered light of the scanned laser light;
In an optical scanning module having
When the angle θ1 between the scanning surface around the optical axis of the laser beam when viewing the outgoing optical axis from the light source and the active surface when viewing the outgoing optical axis from the semiconductor laser, the θ1 is An optical scanning module which is adjusted in a range of 0 to 90 degrees.   2. The optical scanning module according to claim 1, wherein the θ1 is adjusted in a range of 10 degrees <θ1 <80 degrees. A light source having an active surface and emitting laser light;
An emission optical system for shaping the laser light emitted from the light source;
A scanning unit that scans the shaped laser beam in a scanning plane;
A photodetector for receiving reflected and scattered light of the scanned laser light;
A differentiating circuit for differentiating and outputting a signal from the photodetector;
In an optical scanning module having
When the angle θ1 between the scanning surface around the optical axis of the laser beam when the outgoing optical axis is viewed from the light source and the active surface when the outgoing optical axis is viewed from the semiconductor laser, the differential circuit The optical scanning module is characterized in that, in the output, the θ1 is adjusted in a direction to reduce the diffraction noise of the laser beam generated by the shaping and increase the signal-to-noise ratio. A light source having an active surface and emitting laser light;
An emission optical system for shaping the laser light emitted from the light source;
A scanning unit that scans the shaped laser beam in a scanning plane;
In an optical scanning module having
When the angle θ1 between the scanning surface around the optical axis of the laser beam when viewing the outgoing optical axis from the light source and the active surface when viewing the outgoing optical axis from the semiconductor laser,
When an optical detector for receiving reflected and scattered light of the scanned laser light and a differential circuit for differentially processing and outputting a signal from the optical detector are provided, in the output from the differential circuit The optical scanning module is characterized in that the θ1 is adjusted so as to reduce the diffraction noise of the laser light generated by the shaping or to increase the signal-to-noise ratio. A light source that emits laser light having an elliptical cross section;
An emission optical system for shaping the laser light emitted from the light source;
A scanning unit that scans the shaped laser beam in a scanning plane;
A photodetector for receiving reflected and scattered light of the scanned laser light;
In an optical scanning module having
The angle θ1 is adjusted in the range of 0 ° <θ1 <90 °, where θ1 is an angle between the scanning plane around the optical axis of the laser beam and the minor axis of the elliptical cross section of the laser beam. An optical scanning module.

Images