JP2007156643A - Optical inspection equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical inspection equipment for stably detecting an object by uniformly detecting the reflecting characteristics of a reading object for every wavelength region. <P>SOLUTION: A color discrimination device 1 is configured to irradiate a coin A with illumination rays of light L1 to be emitted from a white LED 4, and to discriminate the color of the coin A based on reflected rays of light L2 reflected from the detection range R of the coin A. In this case, this device is provided with a reflector 6 installed on the optical path of the illumination rays of light L1 wherein a reflection surface 6a and a reflection surface 6b for reflecting the illumination rays of light L1 toward the detection range R are respectively formed like almost planes and a photo-diode array 9 for receiving the reflected rays of light L2 reflected from the detection range R of the illumination rays of light L1 reflected by the reflector 6 for each of a plurality of wavelength regions. Then, the reflection surface 6a and the reflection surface 6b are installed so as to be in contact with each other on a straight line B1 almost vertically crossing the optical axis C1 of the illumination rays of light L1, and so that one surface can be inclined at the optical axis C1 side to the other surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical inspection apparatus that performs inspections such as discrimination and identification of a reading object based on reflected light reflected from the reading object.

Conventionally, as a technique in such a field, there is a coin discriminating apparatus described in Patent Document 1 below. The coin discriminating apparatus described in this publication sequentially irradiates a coin with two types of light having different wavelengths, detects light reflected from the coin with a light receiving element, and compares the output from the light receiving element. Determine the true or false of. In this coin discriminating apparatus, light is irradiated to a coin from two light sources such as LEDs having different emission wavelengths, and reflected light from the coin is received by a light receiving element via a lens.
JP 2001-216550 A

  However, in the coin discriminating apparatus described above, reflected light generated by directly irradiating coins with illumination light having different wavelengths is received by the light receiving element at different timings, and the output signal from the light receiving element obtained as a result is received. Therefore, the intensity distribution of the illumination light in the coin differs depending on the position and orientation of the coin, and the intensity distribution of the reflected light also varies. As a result, the irradiation condition of the illumination light for each different wavelength region varies, and it is difficult to stably detect the object.

  Therefore, the present invention has been made in view of such problems, and an optical inspection apparatus capable of stably detecting an object by uniformly detecting the reflection characteristics of the object to be read for each wavelength region. The purpose is to provide.

  In order to solve the above problems, the optical inspection apparatus of the present invention irradiates the reading object with illumination light emitted from the illumination light source, and reads based on the reflected light reflected from the predetermined detection range of the reading object. In an optical inspection apparatus that inspects an object, a first reflection surface and a second reflection surface that are provided on an optical path of illumination light and reflect the illumination light toward a predetermined detection range are each formed in a substantially planar shape. And a light receiving element that receives, for each of a plurality of wavelength regions, reflected light reflected from a predetermined detection range among illumination light reflected by the reflecting plate, and includes a first reflecting surface and a second reflecting surface. The reflection surface is characterized in that it is in contact with a straight line that intersects the optical axis of the illumination light substantially perpendicularly, and one surface is inclined to the optical axis side with respect to the other surface.

  In such an optical inspection apparatus, the illumination light from the illumination light source is reflected by a reflecting plate having two reflecting surfaces provided on the optical axis of the illumination light source, so that the luminous flux of the illumination light is reflected. The reflected light which is divided into two by the plane including the optical axis and is irradiated toward the predetermined detection range of the reading object, and reflected from the detection range of the reading object is received by the light receiving element for each of a plurality of wavelength regions. Received light. At this time, since one of the two reflecting surfaces of the reflecting plate is inclined toward the optical axis side with respect to the other, the difference in illuminance of the illumination light within the detection range can be reduced. Thereby, the irradiation condition of the illumination light at the time of inspection of each wavelength region is matched, and variation in the received light signal intensity of the reflected light due to the difference in the position of the light receiving surface of each wavelength region in the light receiving element can be prevented. Stable detection of the reading object is possible.

  The first reflecting surface and the second reflecting surface are preferably provided so as to reflect the light component on the optical axis of the illumination light toward the peripheral edge within the predetermined detection range. With such a configuration, the portion with a large amount of the luminous flux of the illumination light is reflected toward the peripheral edge of the detection range, so that the illuminance of the illumination light can be made more uniform over the detection range.

  According to the present invention, the object can be stably detected by uniformly detecting the reflection characteristic of the object to be read for each wavelength region.

  Hereinafter, preferred embodiments of a color discrimination device according to the present invention will be described in detail with reference to the drawings.

  A color discrimination device 1 shown in FIG. 1A is an optical inspection device that discriminates the color of a coin (reading object) conveyed to a predetermined imaging position. For example, a coin such as a bank ATM is conveyed and processed. It is built in the device. Note that the coins referred to here include not only coins in a narrow sense used as currency but also coins used for gaming and the like.

  The color discrimination device 1 has a box-shaped housing 2, and a white LED (lighting light source) 4 has an optical axis C 1 of the substrate 3 inside the substrate 3 that forms one end surface of the housing 2. It is arranged so as to be substantially perpendicular to the inner surface and face the inner side. A window portion 5 made of a transparent material is fixed to the other end surface of the housing 2, and the coin A can be transported in a direction parallel to the outer surface of the window portion 5 outside the window portion 5. On the optical path of the illumination light L1 emitted from the white LED 4 between the window portion 5 inside the housing 2 and the white LED 4, the illumination light L1 falls within a predetermined detection range R of the coin A outside the window portion 5. A reflecting plate 6 for reflecting the light toward the screen is installed. The reflecting plate 6 has two planar reflecting surfaces having different inclination angles with respect to the optical axis C1 of the white LED 4, and plays a role of uniformly reflecting the illumination light L1 toward the detection range R.

  Further, in the housing 2, a condenser lens that collects the reflected light L <b> 2 reflected from the detection range R of the coin A toward the inside of the housing 2 out of the illumination light L <b> 1 reflected by the reflecting plate 6. The part 8 is arranged to face the window part 5. Here, since the condensing lens part 8 is provided in the position which can condense the reflected light from the detection range R, the reflected light which generate | occur | produced by the diffuse reflection of the illumination light L1 resulting from the uneven | corrugated shape in the surface of the coin A L2 enters the condenser lens unit 8. Between the condensing lens portion 8 and the substrate 3, a photodiode array (light receiving element) 9 that receives the reflected light L <b> 2 is provided, and the optical axis C <b> 2 of the condensing lens portion 8 is the center of the light receiving surface of the photodiode array 9. It is fixed so as to coincide with the perpendicular line passing through.

  Hereinafter, the configuration of the reflecting plate 6 and the reflection state of the illumination light L1 by the reflecting plate 6 will be described with reference to FIGS.

As shown in FIG. 2A, the reflecting plate 6 is formed in a V-shaped cross section so that the two reflecting surfaces 6a and 6b are in contact with each other with a straight line B1 perpendicularly intersecting the optical axis C1 of the white LED 4 as a boundary line. ing. The reflecting surface 6a, 6b are inclined angle theta ₁ is about 31 degrees with respect to the optical axis C1 of the reflection surface 6a, inclination angle theta ₂ with respect to the optical axis C1 of the reflecting surface 6b is approximately 143 degrees, one surface and the other It arrange | positions so that it may incline to the optical axis C1 side with respect to a surface. Note that the distance between the optical axis C2 of the condenser lens 8 and the optical axis C1 of the white LED 4 is about 8 mm, the distance between the plane including the detection range R of the coin A and the boundary line B1 is about 3 mm, and the diameter of the detection range R. Is about 4 mm. In such a reflection surface 6a, the component of the illumination light L1 incident along the optical axis C1 is reflected toward the peripheral edge E1 of the detection range R near the optical axis C1. Further, as the incident position of the illumination light L1 on the reflecting surface 6a moves away from the boundary line B1, the reflection position of the component of the illumination light L1 shifts toward the center of the detection range R and further to the peripheral edge E2 on the opposite side. To do. Thereby, since the light quantity of the illumination light L1 is so strong that it is near the optical axis C1, the relative illumination intensity on the coin A corresponding to each component of the illumination light L1 reflected by the reflective surface 6a has a peak in the peripheral part E1, The distribution decreases monotonously toward the peripheral edge E2 (FIG. 2B).

  On the other hand, as shown in FIG. 3A, the component of the illumination light L1 incident along the optical axis C1 is reflected toward the peripheral edge E2 of the detection range R on the reflection surface 6b. Further, as the incident position of the illumination light L1 on the reflection surface 6b moves away from the boundary line B1, the reflection position of the component of the illumination light L1 shifts toward the center of the detection range R and further toward the peripheral edge E1 on the opposite side. To do. As a result, the relative illuminance on the coin A corresponding to the component of the illumination light L1 reflected by the reflecting surface 6b has a peak at the peripheral edge E2 and decreases monotonously toward the opposite peripheral edge E1. (FIG. 3B). As a result, as shown in FIG. 4, the relative illuminance distribution G1 on the coin A corresponding to all components of the illumination light L1 is compared with the illuminance distribution G2 when the illumination light L1 is directly irradiated onto the detection range R. Thus, the distribution is almost uniform over the detection range R.

  Next, the configuration of the photodiode array 9 will be described.

  As shown in FIG. 1B, which is a plan view of the photodiode array 9 in FIG. 1A viewed from the light receiving surface side, the photodiode array 9 simultaneously receives red light, green light, and blue light. Thus, this is a matrix type photodiode array that outputs a voltage signal corresponding to each intensity. More specifically, the light receiving surface 10 of the photodiode array 9 has 16 photodiodes 11a having spectral sensitivity characteristics in a red light region (for example, 590 nm to 720 nm), and a green light region (for example, 480 nm to 600 nm). Sixteen photodiodes 11b having spectral sensitivity characteristics, sixteen photodiodes 11c having spectral sensitivity characteristics in a blue light region (for example, 400 nm to 540 nm), and sixteen photodiodes 11d having sensitivity in the entire visible light region. Are arranged two-dimensionally in 8 × 8 so that photodiodes having different spectral sensitivity characteristics are adjacent to each other. These photodiodes 11a, 11b, and 11c have the highest light receiving sensitivity at wavelengths of 600 to 620 nm, 530 to 540 nm, and 460 to 470 nm, respectively. In this photodiode array 9, 16 photodiodes 11a, 11b, and 11c are connected in parallel, so that the current generated by receiving the reflected light L2 is changed into three types of photodiodes 11a, 11b, After being output every 11c, it is converted into three voltage signals corresponding to the intensities of the red light component, green light component, and blue light component of the reflected light L2, and then output.

FIG. 5 is a diagram illustrating a circuit configuration of a control circuit mounted on the substrate 3 of the color discrimination device 1. As shown in the figure, a drive voltage is applied between both ends of the white LED 4 via a transistor 12 connected in series to the white LED 4. The transistor 12 is turned on the drive voltage to be applied across the white LED4 in accordance with the control signal S ₁ input to the base terminal - by turning off, to control the emission of white LED4.

In the photodiode array 9, a transimpedance amplifier (current-voltage conversion circuit) 13b that converts a current generated by receiving the green light component of the reflected light L2 into a voltage is connected to both ends of the 16 photodiodes 11b. Yes. The transimpedance amplifier 13b converts the current generated by the photodiode 11b into an output voltage signal _Vb at a conversion rate determined by a feedback resistor, and outputs the output voltage signal _Vb . Similarly, a transimpedance amplifier 13c and a transimpedance amplifier 13a are connected to the 16 photodiodes 11c and the 16 photodiodes 11a, respectively. Transimpedance amplifier 13c, 13a, respectively, the photodiodes 11c, the output voltage signal _{V c} the current generated by 11a, and converts the output voltage signal _{V a} and outputs. Furthermore, low-pass filters 14b, 14c, and 14a for removing high-frequency noise from the output voltage signals V _b , V _c , and V _a are connected to the outputs of the transimpedance amplifiers 13b, 13c, and 13a, respectively.

A comparator 24 composed of three differential amplifiers 15, 16, and 17 is connected to the output side of these low-pass filters 14b, 14c, and 14a. The non-inverting input terminal 18 of the differential amplifier 15 is connected to the output of the transimpedance amplifier 13b through the low-pass filter 14b, and the inverting input terminal 19 of the differential amplifier 15 is output from the trans-impedance amplifier 13c through the low-pass filter 14c. Connected with. Differential amplifier 15, amplifies the level of the output voltage signal V _b in which the level of the output voltage signal V _c is a reference voltage signal as a reference in the positive direction of the amplification factor (the non-inverting amplifier) to output as a comparison signal V ₁ To do. On the other hand, the non-inverting input terminal 20 of the differential amplifier 16 is connected to the output of the transimpedance amplifier 13c via the low pass filter 14c, and the inverting input terminal 21 of the differential amplifier 16 is connected to the transimpedance amplifier 13a via the low pass filter 14a. Connected with the output of. Differential amplifier 16 outputs the level of the output voltage signal V _a in which the level of the output voltage signal V _c is a reference voltage signal and the reference amplifier (inverting amplifier) to a comparison signal V ₂ in the negative direction of the amplification factor .

Further, the inverting input terminal 22 of the differential amplifier 17 is connected to the output of the differential amplifier 15, and the non-inverting input terminal 23 is connected to the output of the differential amplifier 16. Differential amplifier 17 outputs a comparison signal V ₃ amplifies the difference between the comparison signal V ₂ and the comparison signal V _1. Here, the connection of the differential amplifiers 15 and 16 to the differential amplifier 17 may be reversed.

Comparison signal V ₃ outputted from the differential amplifier 17 is inputted to the signal processing section 25, the color of the coin A based on the comparison signal V ₃ in the signal processing unit 25 is determined, and the determination result is output to the outside . Specifically, the signal processing unit 25 compares the time variation of the level of the comparison signal V ₃ and the plurality of signal data stored in advance, the level difference to identify the signal data is within a predetermined error range Thus, the color of the coin A is determined. The signal processing unit 25, when the level difference between the comparison signal V ₃ and the pre-held signal data is not within the predetermined error range, to determine the discrepancies between the color of a particular type of coin of the coin A You can also Here, the signal processing unit 25 may be provided in the housing 2 of the color discrimination device 1 or may be provided outside the housing 2.

  Hereinafter, the operation of the color discrimination device 1 will be described.

First, when the coin A reaches the detection range R is conveyed in parallel to the outer surface of the window portion 5, emission of white LED4 is initiated by the control signals S ₁ from the outside, the illumination light L1 toward the reflecting plate 6 irradiated Then, the light is separated into two light components by the two reflecting surfaces 6 a and 6 b of the reflecting plate 6 and reflected toward the detection range R of the coin A. Thus, the reflected light L2 is generated from the detection range R toward the condenser lens unit 8 by the illumination light L1 incident on the entire detection range R of the coin A, and the reflected light L2 is collected by the condenser lens unit 8. The light is incident on the light receiving surface 10 of the photodiode array.

On the other hand, the output corresponding to each intensity | strength of the red light component of the reflected light L2, the green light component, and the blue light component by light reception of the reflected light L2 of the photodiode 11a, 11b, 11c which comprises the light-receiving surface 10. Voltage signals V _a , V _b , and V _c are output. Next, after the high frequency noise is removed from the output voltage signals V _a , V _b and V _c , the level of the output voltage signal V _b is non-inverted and amplified by the differential amplifier 15 based on the level of the output voltage signal V _c. At the same time the output is, the level of the output voltage signal V _a relative to the level of the output voltage signal V _c by differential amplifier 16 is output is inverted and amplified. Moreover, the difference between the output voltages of the differential amplifier 16 of the differential amplifier 15 is amplified, and is output as a comparison signal V _3. In this case, the comparison signal V ₃ is output continuously until the coin A passes a detecting range R. After that, the signal data that has been previously held by the signal processing unit 25 and the comparison signal V ₃ is compared, the color of the coin A is determined.

According to the color discriminating apparatus 1 described above, the illumination light L1 from the white LED 4 is reflected by the reflecting plate 6 having the two reflecting surfaces 6a and 6b provided on the optical axis C1 of the white LED 4, The light beam of the illumination light L1 is divided into two by a plane including the optical axis C1, and each is irradiated toward the detection range R of the coin A, and the reflected light L2 reflected from the detection range R is a plurality of wavelength regions. The light is received by the photodiode array 9. At this time, since one of the two reflecting surfaces 6a and 6b of the reflecting plate 6 is inclined toward the optical axis C1 with respect to the other, the difference in illuminance of the illumination light L1 within the detection range R can be reduced. . Thereby, the irradiation conditions of the illumination light L1 at the time of inspection of each wavelength region coincide with each other, and the light reception signal V of the reflected light L2 due to the difference in the positions of the light receiving surfaces of the photodiodes 11a, 11b, and 11c constituting the photodiode array 9 _Since fluctuations in the intensity of _{a 1} , V _b , and V _c can be prevented, the coin A can be detected stably. This effect is particularly noticeable in the case of a detection object having many uneven surfaces such as coins. In particular, the reflecting surfaces 6a and 6b are provided so as to reflect the light component along the optical axis C1 of the illumination light L1 toward the peripheral edges E1 and E2 in the detection range R, respectively. Since the portion with a large amount of light flux is reflected toward the peripheral edge of the detection range R, the illuminance of the illumination light L1 can be made more uniform over the detection range R.

  In addition, this invention is not limited to embodiment mentioned above. For example, the configuration of the light receiving element that receives the reflected light L2 is not limited to a specific configuration. FIG. 6A is a partially cutaway view of a color discriminating apparatus 31 which is a modification of the present invention, and FIG. 6B is a plan view seen from the light receiving surface side of the color sensor 39 in FIG. . As shown in these drawings, the color discrimination device 31 is provided with a 3ch type color sensor (light receiving element) 39 instead of the photodiode array 9. The color sensor 39 has a circular light receiving surface 40, and photodiodes 41 a, 41 b, 41 c having fan-shaped light receiving surfaces are arranged on the light receiving surface 40 so as to divide the light receiving surface 40 into three. . These photodiodes 41a, 41b, and 41c have the same spectral sensitivity characteristics as the photodiodes 11a, 11b, and 11c, respectively. The color sensor 39 is disposed so as to face the window portion 5 so that a perpendicular passing through the center portion of the light receiving surface 40 substantially coincides with the optical axis C2 of the condenser lens portion 8. Further, a diffusion sheet 42 is disposed in the vicinity of the light receiving surface 40 between the detection range R of the coin A and the color sensor 39 so as to be parallel to the light receiving surface 40. The diffusion sheet 42 diffuses the reflected light L <b> 2 incident from the detection range R of the coin A through the condenser lens unit 8 toward the light receiving surface 40 of the color sensor 39.

  The configuration of the control circuit of such a color discriminating device 31 is that the transimpedance amplifiers 13a, 13b, and 13c are connected to the photodiodes 41a, 41b, and 41c in the color sensor 39 as shown in FIG. Except for this, it is the same as the color discriminating apparatus 1.

8 to 11 show examples of signals output from the color discrimination device 31. FIG. These figures show the results when two types of coins are conveyed four times each. FIGS. 8A to 8C are graphs showing temporal changes in the output voltage signals V _c , V _b , and V _a output from the transimpedance amplifiers 13 c, 13 b, and 13 a when the coin A is detected. 9 (a) to 9 (c) are graphs showing temporal changes in the output voltage signals V _c , V _b , and V _a when detecting different types of coins from the coin A, and FIG. graph, Figure 11 shows the time change of the comparison signal V ₃ outputted from the differential amplifier 17 to the output voltage signal shown in FIG. 8 is outputted from the differential amplifier 17 to the output voltage signal shown in FIG. 9 is a graph showing temporal changes of the comparison signal V ₃ has. The comparison signal V ₃ is input to the signal processing section 25, the color of the coin A is determined on the basis of the signal processing unit 25 in the comparison signal V _3. As can be seen from these results, even when the same coin is detected a plurality of times, stable output voltage signals V _c , V _b , V _a and comparison signal V ₃ are obtained for each color component. Yes.

In the color discrimination device 31 having the above-described configuration, the illumination light L1 is irradiated to the detection range R of the coin A via the reflection plate 6, and the reflected light L2 from the detection range R generated as a result is the 3ch type. The light is diffused toward the light receiving surface 40 of the color sensor 39 and received by the color sensor 39 in which photodiodes having three types of spectral sensitivity characteristics are divided and arranged. As described above, the light receiving signals V _a , V _b , and V _c of the reflected light L2 due to the difference in the positions of the light receiving surfaces of the photodiodes 41a, 41b, and 41c constituting the color sensor 39 are obtained by the cooperation of the reflecting plate 6 and the diffusion sheet 42. Since the fluctuation of the strength of the coin A can be prevented, the coin A can be stably detected.

In the differential amplifiers 15 and 16 of the color discrimination devices 1 and 31, any one of the output voltage signals V _a , V _b , and V _c is input to the inverting input terminal 19 and the non-inverting input terminal 20 as a reference voltage signal. _{Alternatively} , any of the output voltage signals V _a , V _b , and V _c other than the reference voltage signal may be input to the non-inverting input terminal 18 and the inverting input terminal 21. That is, the comparison signals V ₁ and V ₂ may be generated based on any of the three output voltage signals V _a , V _b and V _c from the light receiving element.

  Further, the reading object may be a card such as a credit card other than a coin, an IC card, or a printed material.

(A) is a partially broken view showing a preferred embodiment of the color discrimination device according to the present invention, and (b) is a plan view of the photodiode array of (a) as viewed from the light receiving surface side. (A) is a figure explaining the reflection state of the illumination light by one reflective surface of a reflecting plate, (b) is the position distribution of relative illumination in the detection range of the coin regarding the light component reflected by one reflective surface. It is a graph to show. (A) is a figure explaining the reflection state of the illumination light by the other reflective surface of a reflecting plate, (b) is the position distribution of the relative illumination intensity in the detection range of the coin regarding the light component reflected by the other reflective surface. It is a graph to show. It is a graph which shows the position distribution of the whole relative illumination intensity in the detection range of a coin. It is a figure which shows the structure of the control circuit of the color discrimination device of Fig.1 (a). (A) is a partially broken view showing a color discriminating apparatus according to a modification of the present invention, and (b) is a plan view of the color sensor of (a) as viewed from the light receiving surface side. It is a figure which shows the structure of the control circuit of the color discrimination device of Fig.6 (a). FIG. 7 is a graph showing a time change of an output voltage signal output from a transimpedance amplifier when a coin is detected a plurality of times in the color discrimination device of FIG. FIG. 7 is a graph showing a time change of an output voltage signal output from a transimpedance amplifier when another type of coin is detected a plurality of times in the color discrimination device of FIG. It is a graph which shows the time change of the comparison signal output with respect to the output voltage signal shown in FIG. It is a graph which shows the time change of the comparison signal output with respect to the output voltage signal shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,31 ... Color discrimination apparatus (optical inspection apparatus), 4 ... White LED (light source for illumination), 6 ... Reflecting plate, 6a, 6b ... Reflecting surface, 9 ... Photodiode array (light receiving element), 39 ... Color sensor ( (Light receiving element), A ... coin (reading object), B1 ... boundary line, C1 ... optical axis, E1, E2 ... peripheral edge, L1 ... illumination light, L2 ... reflected light, R ... detection range.

Claims (2)

In an optical inspection apparatus that irradiates a reading object with illumination light emitted from an illumination light source and inspects the reading object based on reflected light reflected from a predetermined detection range of the reading object.
A reflection plate provided on the optical path of the illumination light, the first reflection surface and the second reflection surface each reflecting the illumination light toward the predetermined detection range;
A light receiving element that receives the reflected light reflected from the predetermined detection range of the illumination light reflected by the reflecting plate for each of a plurality of wavelength regions;
The first reflective surface and the second reflective surface are in contact with each other on a straight line that intersects the optical axis of the illumination light substantially perpendicularly, and one surface is inclined toward the optical axis with respect to the other surface. Provided to
An optical inspection device. Each of the first reflection surface and the second reflection surface is provided so as to reflect a light component on the optical axis of the illumination light toward a peripheral edge within the predetermined detection range.
An optical inspection device.

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