JP4391367B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads image information of a reading object such as a coin or medal.

Conventionally, as a technology in such a field, there is JP-A-2002-259977. The device described in this publication is an image reading device that is incorporated in a vending machine and reads information such as graphics stamped on coins. This vending machine is provided with a guide frame for guiding the coins inserted into the coin slot and a stopper for locking the coins in the guide frame. The image reading apparatus is an apparatus for imaging a coin locked by a stopper in a stationary state and outputting image data, and includes a CMOS image sensor as an imaging element.
Japanese Patent Laid-Open No. 2002-259977

  However, in a device that reads an image of a coin while conveying the coin at a high speed, when such a CMOS image sensor is used as an imaging device, there is a problem that stable image data cannot be obtained. And if it is going to acquire the image data of the imaging object which moves at high speed with a CMOS image sensor, the problem that a complicated structure will be needed will generate | occur | produce.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus capable of obtaining stable image data by a CMOS image sensor with a simple configuration when imaging a reading object to be conveyed.

  An image reading apparatus according to the present invention is an image reading apparatus that reads an image of a surface of a reading object conveyed on a predetermined conveying path, and illuminates an illumination unit that irradiates the reading object conveyed to an imaging position on the conveying path. A CMOS image sensor that receives the reflected light reflected by the reading object and images the reading object; and a CMOS image sensor that is disposed between the illumination unit and the CMOS image sensor and reflects the reflected light reflected by the reading object. An imaging lens that forms an image on the image sensor, a detection unit that detects that the reading object has reached the reset position upstream of the imaging position in the transport direction, and that the reading object has reached the imaging position, and reading When the detection unit detects that the object has reached the reset position, reset means for resetting the drive timing of the CMOS image sensor, and the reading object reaches the imaging position. When the detection unit detects this, the illumination control means for turning on the illumination unit, and the CMOS image sensor is approximately an integral multiple of one frame from when the reading object reaches the reset position until it reaches the imaging position. And clock control means for controlling the operating clock frequency of the CMOS image sensor so as to output image data.

  In the CMOS image sensor, unstable image data is output until one frame after the drive timing is reset. The present inventors paid attention to the fact that this makes it difficult to quickly capture images with a CMOS image sensor, and as a result, a stable image of the read object being conveyed cannot be obtained. According to the image reading apparatus of the present invention, when the reading object reaches the reset position, the driving timing of the CMOS image sensor is reset, and then the illumination object moves when the reading object moves and reaches the imaging position. The image is taken by the CMOS image sensor by lighting the part. From this reset to imaging, that is, before the reading object reaches the imaging position, image data for at least about one frame is discharged from the CMOS image sensor. Most or all of the image data is discharged. Since the reading object is imaged after the unstable data is discharged, stable image data of the reading object at the time of reaching the imaging position can be obtained. In addition, by performing imaging at the time when a time that is substantially an integral multiple of one frame has elapsed after resetting, it is possible to match the imaging timing with the set timing in driving the CMOS image sensor. As a result, a stable overall image of the read object to be conveyed can be contained in one frame.

  The image reading apparatus of the present invention further includes a conveyance speed detection unit that detects a conveyance speed of the object to be read, and the clock control unit conveys the operation clock frequency of the CMOS image sensor detected by the conveyance speed detection unit. It is preferred to control the operating clock frequency to be proportional to the speed.

  According to this image reading apparatus, the operation clock frequency of the CMOS image sensor is controlled, and the time that the reading object moves from the reset position to the imaging position is proportional to the speed at which the CMOS image sensor discharges image data. become. Therefore, the CMOS image sensor can always discharge the same amount of image data from the reset of the drive timing of the CMOS image sensor to the time when imaging is performed, regardless of the conveyance speed. As a result, the CMOS image sensor can always image the reading object at the same timing.

  In the image reading apparatus of the present invention, the detection unit performs arrival detection for detecting that the reading object has reached the reset position and passage detection for detecting that the reading object has reached the imaging position. It is preferable. In this way, it is possible to detect that the reading object has reached the reset position and that the reading object has reached the imaging position using the same detection unit. Can be achieved.

  According to the image reading apparatus of the present invention, stable image data obtained by a CMOS image sensor can be obtained with a simple configuration when imaging a reading object to be conveyed.

  Hereinafter, a preferred embodiment of an image reading apparatus according to the present invention will be described in detail with reference to the drawings. The image reading device 1 according to the present embodiment is a device that reads a pattern on the surface of a coin in order to determine whether or not the coin is true or false. For example, the image reading device 1 is incorporated in an ATM or the like.

  As shown in FIGS. 1 and 2, the image reading apparatus 1 includes a rectangular parallelepiped housing 10 made of resin, and a circular opening window 11 is provided on the top surface of the housing 10. In addition, a transparent plate 12 made of sapphire glass or the like is fitted into the opening window 11, and the 500 yen coin (reading object) 20 is placed on the reading surface 12 b that is made to coincide with the upper surface (outer surface) of the transparent plate 12. Is imaged at the imaging position 12c. And the conveying apparatus 30 for conveying the coin 20 to the transparent board 12 above the housing | casing 10 is provided.

  The transport device 30 transports an endless belt 31 extending in the transport direction A of the coin 20, a pair of pulleys 32 and 33 for circulatingly driving the endless belt 31, and a top surface of the image reading device 1. And a transfer table 34 extending in the direction A. Therefore, the pulley 33 is rotated by a motor (not shown) to drive the endless belt 31, and the coin 20 is moved on the conveyance path B formed between the image reading device 1 and the conveyance table 34 and the endless belt 31. Can be transported. An encoder (conveying speed detecting means) 53 is connected to the pulley 33 of the conveying device 30, and the encoder 53 generates a pulse signal having a frequency corresponding to the number of rotations of the pulley 33. That is, the frequency of the pulse signal generated by the encoder 53 corresponds to the conveying speed of the coin 20 on the conveying path B. The pulse signal generated here is sent to a coin detection circuit 59 described later.

  An illumination unit 14 is provided in the housing 10 at a position close to the lower surface (inner surface) of the transparent plate 12. The illumination unit 14 is annularly arranged around the imaging position 12c of the transparent plate 12, and a plurality of light sources 15 (for example, surface mount type LEDs or lead type LEDs) that emit illumination light toward the outside, An annular reflecting mirror 16 is disposed around each light source 15 and reflects the irradiation light from each light source 15 toward the coin 20 on the transparent plate 12. Indirect illumination is achieved by such an illumination unit 14. That is, the light emitted from the light source 15 is once reflected by the reflecting mirror 16 and then illuminates the coin 20 from the back side.

  Further, a CMOS image sensor 37 for capturing an image of the surface of the coin 20 is provided inside the housing 10, and reflected light reflected by the coin 20 is provided between the CMOS image sensor 37 and the illumination unit 14. Is formed on the CMOS image sensor 37. Therefore, the light reflected by the coin 20 is collected on the CMOS image sensor 37 by the imaging lens 36, and an image of the coin 20 can be formed on the CMOS image sensor 37.

  The CMOS image sensor 37 accumulates charges in the pixels on the light receiving surface in accordance with the image of the coin 20 imaged by the imaging lens 36, converts the accumulated charges into image data, and outputs the image data to a processing circuit 57 described later. This is an image sensor to output. The number of pixels in the vertical direction of the CMOS image sensor 37 is 503, and the image of the surface of the coin 20 to be imaged is composed of 503 scanning lines per frame. Further, since the number of operation clocks in the horizontal direction of the CMOS image sensor 37 is 762 clocks, 762 pixels are included per scanning line. The CMOS image sensor 37 is always driven during the operation of the apparatus 1 and continuously sends image data to the processing circuit 57. However, at the moment when the coin 20 being conveyed reaches the imaging position 12c, illumination is performed. Light is emitted from the unit 14 for a very short time, and a still image capturing a moment of the coin 20 being conveyed is captured.

  Further, a light emitting element (for example, LED) 38 that emits light toward the transparent plate 12 is provided below the transparent plate 12, and the light emitting element 38 is interposed above the transparent plate 12 via the transparent plate 12. A light receiving element (for example, a photodiode) 39 that receives light emitted from the light emitting element 38 is provided at the facing position. By the cooperation of the light emitting element 38 and the light receiving element 39, a coin arrival sensor 41 for determining whether or not the coin 20 exists on the transport path B is configured. When the coin 20 does not exist at the coin arrival position 40, the light receiving element 39 receives light from the light emitting element 38, and a light reception signal is sent to a coin detection circuit 59 described later. On the other hand, when the coin 20 is present at the coin arrival position 40, the light from the light emitting element 38 is blocked and the light reception signal is interrupted. The coin arrival position 40 is set on the upstream side of the transparent plate 12 on the transport path B, and the coin 20 is positioned at the imaging position 12c at the moment when the transported coin 20 passes through the coin arrival position 40. It is set to be. Although details will be described later, by using such a coin arrival sensor 41, it is possible to detect the arrival of the coin 20 at the coin arrival position 40 and the passage of the coin 20 through the coin arrival position 40.

  As shown in FIG. 3, the image reading apparatus 1 is a timing generator that generates an operation clock signal for image reading processing, a horizontal sync signal (HD signal) and a vertical sync signal (VD signal) of a television system. 55. The operation clock, HD signal, and VD signal generated by the timing generator 55 are sent to the CMOS image sensor 37 and the processing circuit 57, and the CMOS image sensor 37 operates at the clock frequency of the sent operation clock signal while imaging. Is output to the processing circuit 57 as 8-bit data. Corresponding to the pixel configuration of the CMOS image sensor 37 described above, the VD signal is set every 503 periods of the HD signal, and image data for one frame is output from the CMOS image sensor 37 in one period of the VD signal.

  The processing circuit 57 processes the image data input from the CMOS image sensor 37 in response to a trigger signal (described later) sent from the coin detection circuit 59. In such a processing circuit 57, for example, image processing such as binarization and feature extraction is performed. At this time, the processing circuit 57 operates at the clock frequency of the operation clock signal sent from the timing generator 55, and processes the image data input from the CMOS image sensor 37 based on the HD signal and the VD signal. The processed data is sent to a subsequent processing unit (not shown) to be used for coin discrimination and authenticity determination.

  When the light reception signal from the coin arrival sensor 41 is interrupted, the coin detection circuit 59 sends a first trigger signal to the timing generator 55 and the processing circuit 57. This corresponds to a state in which the coin 20 conveyed on the conveyance path B has arrived at the coin arrival position 40. When the light reception signal is received again after the light reception signal is interrupted, the coin detection circuit 59 sends a second trigger signal to the timing generator 55 and the processing circuit 57. This corresponds to a state in which the coin 20 that has arrived at the coin arrival position 40 has passed through the coin arrival position 40. As described above, the coin detection circuit 59 and the coin arrival sensor 41 detect that the coin 20 has arrived at the coin arrival position 40 and detect that the coin has passed the coin arrival position 40.

  Here, the operation timing of each part necessary for imaging the coin 20 conveyed at high speed by such an image reading apparatus 1 will be described.

  In such an image reading apparatus 1, in order to capture the coin 20 conveyed at high speed on the conveyance path B as a still image, the illumination unit 14 is turned on at the moment when the coin 20 has just reached the imaging position 12 c on the conveyance path B. It is necessary to take an image for a very short time. For this purpose, it is necessary to match the lighting timing of the illumination unit 14 with the timing of passage detection by the coin arrival sensor 41.

  Further, at the time of this imaging, it is necessary to substantially match the imaging timing with the timing of setting the VD signal of the CMOS image sensor 37 in order to fit the entire image of the coin 20 in one frame of image data. In order to realize this, it is conceivable to reset the HD signal and the VD signal by resetting the drive timing of the CMOS image sensor 37 at the moment of imaging. However, due to the nature of the CMOS image sensor, unstable image data is output within one frame after reset.

  Therefore, in the image reading apparatus 1, by resetting the driving timing of the CMOS image sensor 37 prior to imaging, imaging is performed after unstable image data within one frame after resetting is sufficiently discharged. I have to. Specifically, as shown in FIG. 4, first, when the light reception signal from the coin arrival sensor 41 (FIG. 4 (a)) is interrupted, a first trigger signal is generated from the coin detection circuit 59 to generate timing. The clock signal, HD signal (FIG. 4B) and VD signal (FIG. 4C) generated by the device 55 are reset. Thereafter, the light reception signal from the coin arrival sensor 41 is received again, and when the second trigger signal is issued from the coin detection circuit 59, a lighting signal (FIG. 4 (d)) is sent from the timing generator 55 to the illumination unit 14. The illumination unit 14 is lit for a very short time. Then, when the CMOS image sensor 37 receives light from the illumination unit 14, a still image of the coin 20 is captured, and image data output from the CMOS image sensor 37 (FIG. 4E) is performed.

  By such control, when the coin 20 arrives at a position (hereinafter referred to as “reset position”) 12r where the leading edge of the coin 20 coincides with the coin arrival position 40, the drive timing of the CMOS image sensor 37 is reset in advance. Will be done. Thereafter, when the coin 20 arrives at a position where the trailing edge of the coin 20 coincides with the coin arrival position 40 (that is, when the coin 20 has just reached the imaging position 12c), the illumination unit 14 is turned on and the coin is turned on. Twenty images are taken.

  Furthermore, most of the image data up to one frame after reset needs to be reliably discharged from the CMOS image sensor 37 while the coin 20 moves from the reset position 12r to the imaging position 12c. And the timing of setting the VD signal of the CMOS image sensor 37 should be substantially matched. For this reason, the frequency of the clock signal generated by the timing generator 55 is associated with the transport speed of the coin 20 on the transport path B, and the operation clock frequency of the CMOS image sensor 37 is synchronized with the transport speed of the coin 20. Control is performed in proportion to each other. In the image reading apparatus 1, while the coin 20 moves from the reset position 12 r to the imaging position 12 c, the CMOS image sensor 37 has approximately one frame (here, slightly more than one frame) of image data. The frequency of the clock signal is controlled so as to be output and discharged.

  Specifically, in order to perform such control, the image reading apparatus 1 includes a clock control unit 60 including a PLL circuit 61. The clock control unit 60 has a function of controlling the frequency of the clock signal generated by the timing generator 55 based on the pulse signal from the encoder 53. The PLL circuit 61 has a phase comparator 61 a and a VCO oscillator 61 b, and the encoder 53 is connected to the timing generator 55 via the PLL circuit 61. In the phase comparator 61a of the PLL circuit 61, the phase of the pulse signal from the encoder 53 and the clock signal from the counter 55a in the timing generator 55 are compared, and the phase difference between the two is reduced to the VCO oscillator 61b. Output voltage is controlled. The VCO oscillator 61b oscillates at a frequency corresponding to the output voltage, and determines the frequency of the clock signal generated by the timing generator 55. With such a configuration, the clock signal generated by the timing generator 55 can be synchronized with the pulse signal from the encoder 53, and as a result, the operation clock frequency of the CMOS image sensor 37 is set to a coin on the transport path B. It can be controlled to be in proportion to the conveyance speed of 20.

  As a result of the above control, in the image reading apparatus 1, before the coin 20 reaches the imaging position 12c, all unstable image data within one frame after reset is discharged, and the second frame is set by setting the VD signal. Starts to output. Immediately after that, when the coin 20 reaches the imaging position 12c and imaging is performed, the entire image of the coin 20 is stored in the image data of the second frame and output. As described above, since the image pickup of the coin 20 is performed after discharging unstable data within one frame, stable image data of the coin 20 at the time when the image pickup position 12c is reached can be obtained. Further, after the reset of the VD signal, almost one frame time has elapsed, and imaging is performed immediately after the start of the second frame. Therefore, a stable whole image of the coin 20 is displayed in the image data of the second frame. It can be stored and sent to the processing circuit 57.

  Moreover, in this image reading apparatus 1, the coin arrival sensor 41 has a function of a sensor that detects that the coin 20 has reached the reset position 12r and a sensor that detects that the coin 20 has reached the imaging position 12c. The parts are shared.

  Further, according to the image reading apparatus 1, the operation clock frequency of the CMOS image sensor 37 is controlled, the time for the coin 20 to move from the reset position 12r to the imaging position 12c, and the speed at which the CMOS image sensor 37 discharges image data. Is proportional. Therefore, the CMOS image sensor 37 can always discharge the same amount of image data from the reset of the drive timing of the CMOS image sensor 37 until imaging is performed, regardless of the conveyance speed. As a result, the CMOS image sensor 37 can always capture the coin 20 at the same timing, so that the entire image of the coin 20 can be always contained within one frame.

  Here, while the coin 20 moves from the reset position 12r to the imaging position 12c, the amount of image data output by the CMOS image sensor 37 is set slightly larger than one frame, but slightly larger than one frame. You may set so that it may decrease. In this case, when the unstable image data within one frame after the reset is almost discharged, the coin 20 reaches the imaging position 12c and imaging is performed. Then, the output of the second frame starts with the subsequent setting of the VD signal, and the entire image of the coin 20 is stored in the image data of the second frame and output.

  The amount of image data is not limited to approximately one frame, and may be set to be an integer multiple of one frame. Even with this setting, the image capturing timing and the VD signal set timing can be substantially matched, so the same effect can be obtained. Also, in the case of reading a 500-yen coin having the maximum diameter among the coins, for example, the period of the HD signal of the CMOS image sensor 37 is 63.5 μs, and the period of the VD signal is 503H (that is, 1 frame = 503H). In this case, it is preferable that the number of image lines discharged by the CMOS image sensor 37 while the 500-yen coin 20 moves from the reset position 12r to the imaging position 12c is 1 frame + 9H ± 24H.

1 is a perspective view showing an embodiment of an image reading apparatus according to the present invention. It is sectional drawing of the image reading apparatus shown in FIG. FIG. 2 is a block diagram illustrating a configuration of the image reading apparatus illustrated in FIG. 1. 3 is a timing chart illustrating an operation of the image reading apparatus illustrated in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image reader, 12r ... Reset position, 12c ... Imaging position, 14 ... Illumination part, 20 ... Coin (reading object), 36 ... Imaging lens, 37 ... CMOS image sensor, 38 ... Light emitting element, 39 ... Light reception Element 41 ... Coin arrival sensor (detection unit) 53 ... Encoder (conveyance speed detection means) 55a ... Counter 55 ... Timing generator 59 ... Coin detection circuit 60 ... Clock control unit (clock control means) 61 ... PLL circuit, 61a ... phase comparator, 61b ... VCO oscillator, B ... transport path.

Claims (3)

In an image reading apparatus that reads an image of the surface of a reading object conveyed along a predetermined conveyance path,
An illumination unit that irradiates illumination light to the reading object conveyed to the imaging position on the conveyance path;
A CMOS image sensor that receives reflected light reflected by the reading object and images the reading object;
An imaging lens that is disposed between the illumination unit and the CMOS image sensor and forms an image on the CMOS image sensor of reflected light reflected by the reading object;
A detection unit that detects that the reading object has reached a reset position upstream in the transport direction from the imaging position and that the reading object has reached the imaging position;
Reset means for resetting the driving timing of the CMOS image sensor when the detection unit detects that the reading object has reached the reset position;
Illumination control means for turning on the illumination unit when the detection unit detects that the reading object has reached the imaging position;
The operation clock of the CMOS image sensor so that the CMOS image sensor outputs image data of almost an integral multiple of one frame from when the reading object reaches the reset position to the imaging position. An image reading apparatus comprising: clock control means for controlling the frequency. Further comprising a conveyance speed detecting means for detecting a conveyance speed of the reading object;
The clock control unit controls the operation clock frequency so that the operation clock frequency of the CMOS image sensor is proportional to and proportional to the transport speed detected by the transport speed detection unit. The image reading apparatus according to claim 1. The detector is
Arrival detection for detecting that the reading object has reached the reset position;
The image reading apparatus according to claim 1, wherein passage detection is performed to detect that the reading object has reached the imaging position.

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