JP2006293596A - Code reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the performance of a code reader for creating the image data of digital codes and decoding the image data. <P>SOLUTION: An optical image (input image Fg) of a digital code transmitted through an imaging lens 41 is projected onto a prism P. The prism P branches the optical path of the input image Fg in the directions of arrows Va and Vb. The input image Fg branching in the direction of the arrow Va is projected onto a close lens 43a while the input image Fg branching in the direction of the arrow Vb is projected onto a far lens 43b. The input image Fga transmitted through the close lens 43a is decoded after being converted into image data by a first image sensor Sa. The input image Fgb transmitted through the far lens 43b is decoded after being converted into image data by a second image sensor Sb. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a code reading device that generates digital code image data and decodes the image data.

  Conventionally, barcodes (one-dimensional codes) in which various information is encoded by arranging bars with different thicknesses and intervals are known. However, due to the lack of information amount of one-dimensional codes, points and lines Two-dimensional codes that encode more information than a complicated combination of length and width have been devised and widely used (hereinafter, the one-dimensional code and the two-dimensional code are collectively referred to as “digital code”).

  In addition, code readers that generate and decode digital code image data to read information encoded by the digital code have become widespread. The code reading device decodes (decodes) image data generated by photoelectrically converting an optical image of a digital code transmitted through a lens by an image sensor.

As an example of such a code reading device, there is known a code reading device that irradiates spot light so that a focal point is formed at the center position of the reading range of the image sensor at the focal length of the lens (Patent Document 1 and 2).
JP-A-08-180128 Japanese Patent Laid-Open No. 08-253529

  FIG. 34A is an example of a block diagram of a conventional code reading device 100. Here, a specific operation example of the code reading apparatus 100 will be briefly described with reference to the time chart of FIG.

  First, a CPU (Central Processing Unit) 10 stores an exposure value based on a shutter speed and an aperture value of the image sensor 70 as an exposure setting value 33 in a RAM (Random Access Memory) 30. Then, the CPU 10 performs exposure by controlling the image sensor 70 based on the exposure setting value 33. This exposure is performed while the vertical synchronization signal Vsync generated inside the image sensor 70 is L (Low). Therefore, as shown in FIG. 34B, exposure is performed with the exposure setting value 33 “A” in the period A 1, and image data obtained by the exposure is output to the data buffer 53. In addition, the image sensor 70 outputs a vertical synchronization signal Vsync to the timing controller 51.

  The timing controller 51 accumulates and stores the image data (input image) input from the image sensor 70 for each line in the data buffer 53 while the vertical synchronization signal Vsync is L. Therefore, the input image A1 exposed by the image sensor 70 during the period A1 is accumulated for each line in the data buffer 53 and transferred to the RAM 30 during the period A2. The CPU 10 decodes the frame image 31 of the input image A1 and calculates so that the exposure setting value 33 becomes an appropriate value based on the exposure amount of the input image A1. Then, the exposure setting value 33 is updated to “B” and exposure is performed again.

  While the input image A1-1 exposed in the period A2 is transferred to the RAM 30, that is, during the period B1, the image sensor 70 performs exposure with the exposure setting value 33 “B”. Since the image sensor 70 performs exposure twice with the same exposure setting value 33 of “A” as shown in FIG. 34B, the input image A1-1 is image data substantially equivalent to the input image A. It becomes.

  Therefore, the decoder of the CPU 10 decodes every other frame image 31 that is sequentially updated with the input images A1, B1, C1,. If this decoding fails, that is, if the exposure setting value 33 is not appropriate, as shown in FIG. 35, the optimum exposure setting value range under a certain environment (hereinafter, this range is referred to as “optimum exposure range”). .) The exposure setting value 33 is calculated and updated until R100 is reached.

  By the way, for example, the size of the cell of the two-dimensional code varies depending on the code format, the information amount, and the like. However, since the code reading devices of Patent Documents 1 and 2 use one single-focus lens, the digital code must be read within the range of the focal length that can be read by the lens. The distance between the digital code and the lens 71 must be adjusted so that the spot light is irradiated upward.

  If an autofocus function that automatically adjusts the focus by combining a plurality of lenses as in a general camera is adopted, the user does not need to adjust manually. However, the balance adjustment of the combination of the single focus lenses in the autofocus function is very fine and takes time, and the realization cost increases.

  In addition, for example, by providing a single focus lens for each of the near and far, it is possible to read both the close digital code and the far digital code, but in this case, depending on the position of each lens, The composition of the digital code captured by each lens will be different. For this reason, even when one lens can capture the entire image of the digital code, the other lens may be missing.

  Further, for example, when the digital code is read in an indoor dark place, the exposure amount of the image sensor depends on the environment in which the user uses the code reading device so that clear image data cannot be obtained due to insufficient exposure amount. Will fluctuate, making decoding difficult.

  For this reason, the initial exposure setting value 33 is sequentially calculated and updated so as to reach the optimum exposure range R100 in the usage environment of the code reading apparatus. As shown in FIG. When the optimum exposure range R200 is far from the value, it takes time for the exposure setting value 33 to reach the optimum exposure range R200.

  For this reason, in order to speed up the time to reach the optimum exposure range and speed up the reading of the digital code, the settings of the exposure setting value 33, the illumination LED 73, etc. must be changed according to the user's usage environment. The operation is complicated and requires specialized knowledge.

  Further, as shown in FIG. 34B, the frame image 31 is sequentially updated by transferring the image data generated by the image sensor 70 to the RAM 30 as needed. However, since the ratio that the transferred image data occupies on the system bus 90, that is, the occupancy ratio increases, the processing performance load of the entire code reading apparatus 100 increases, and further, the power consumption increases. End up. For this reason, for example, when a code reading device is applied to a handy terminal or the like having a large amount of data communication, the occupation rate of the system bus 90 further increases, resulting in a further decrease in processing performance.

  An object of the present invention is to improve the performance of a code reading device.

  According to the first aspect of the present invention, there is provided a spectroscopic unit that branches an optical path that propagates an optical image of a digital code into a plurality of optical paths, and a plurality of optical paths that have different focal points and are arranged in the branched optical paths, respectively. A lens, an image generating unit that converts an optical image of each digital code that has passed through the plurality of lenses into an electrical signal, and generates a plurality of image data of the digital code; and a decoding that decodes the plurality of image data Means.

  According to a fifth aspect of the present invention, there is provided a switching means for switching a plurality of exposure modes, a setting means for setting an exposure condition in accordance with the exposure mode switched by the switching means, and a digital signal according to the exposure condition set by the setting means. An image generating unit that exposes an optical image of the code to generate image data of the digital code, and a decoding unit that decodes the image data generated by the image generating unit.

  The invention according to claim 9 is an exposure value storage means for storing a plurality of exposure values, an initial setting means for setting a plurality of different initial values as a plurality of exposure values stored in the exposure value storage means, and the exposure An exposure unit that exposes an optical image of a digital code based on each of a plurality of exposure values stored by the value storage unit, and a plurality of exposure values stored by the exposure value storage unit based on the result of exposure by the exposure unit Exposure value updating means for individually updating the exposure value, and repetitive control for repeating a series of processes by the exposure means and the exposure value updating means until the exposure value updated by the exposure value updating means reaches an optimum exposure range. Means.

  The invention according to claim 13 is a history recording means for recording a history of optimum exposure values, an average calculating means for calculating an average value of optimum exposure values recorded by the history recording means, and a calculation means calculated by the calculating means. An image generating unit that performs exposure of an optical image of a digital code based on an average value of exposure values and generates image data of the digital code, and a decoding unit that decodes image data generated by the image generating unit It is characterized by providing.

  According to a fourteenth aspect of the present invention, storage means for storing digital code image data, image generation means for generating and outputting digital code image data, signal generation means for generating a transfer permission signal, and signal generation A transfer means for transferring the image data output from the image generation means to the storage means, and a decode means for decoding the image data stored by the storage means in accordance with a transfer permission signal generated by the means. Features.

  According to the first aspect of the present invention, since the decoding means can individually decode the image data of the digital code obtained by projecting at different focal points by branching the optical image of the digital code, The reading device can read a wide range of digital codes from close digital codes to distant digital codes, and an optical image of one digital code is projected to each of a plurality of lenses. The composition will not be misaligned.

  According to the second aspect of the present invention, it is possible to improve the probability of successful decoding, that is, the decoding rate, by sequentially decoding the digital code image data that has passed through lenses with different focal points.

  According to the third aspect of the present invention, by providing the storage means for storing the image data generated by the image generation means, the free space in the system memory of the code reading device increases, and the load on the device can be reduced.

  According to the fourth aspect of the present invention, even if the digital code is not focused on the lens, it is possible to increase the contrast of the image data of the digital code by combining with the combining means, so that the decoding rate is improved. Can be planned.

  According to the invention described in claim 5, since exposure is performed by setting exposure conditions according to the switched exposure mode, it is not necessary to make fine settings of exposure values such as shutter speed and aperture value. Does not require technical knowledge.

  According to the sixth aspect of the present invention, the user can switch the exposure mode according to the usage environment of the code reading device.

  According to the seventh aspect of the invention, it is possible to automatically switch to an appropriate exposure mode by switching the exposure mode when decoding fails.

  According to the eighth aspect of the present invention, the exposure mode can be switched in accordance with the illuminance of outside light, that is, the usage environment of the code reader.

  According to the ninth aspect of the present invention, the exposure is performed based on the plurality of exposure values of the exposure value storage means storing the plurality of different initial values, and the exposure value is repeatedly updated. The time required to reach the exposure range can be shortened.

  According to the tenth aspect of the present invention, the time until the exposure value reaches the optimum exposure range is stabilized by setting the maximum value and the minimum value of the exposure value that can be exposed by the exposure means as the initial values. For example, when the optimum exposure range is high, the optimum exposure range can be reached at a high speed depending on the use environment, such as the exposure value set with the maximum value reaching the optimum exposure range earlier. Can do.

  According to the eleventh aspect of the present invention, the exposure value when the exposure value updated by the exposure value updating means reaches the optimum exposure range is set to the initial value. Thus, the optimum exposure range can be reached at a higher speed.

  According to the invention of claim 12, by setting the average value of the history of the optimum exposure value as the initial value, the time until the exposure value reaches the optimum exposure range is matched with the use environment of the code reading device. You can expedite.

  According to the thirteenth aspect of the present invention, the digital code can be exposed with the average value of the optimum exposure value history, that is, with an appropriate exposure value that matches the operating environment of the code reader.

  According to the fourteenth aspect of the present invention, since the image data output from the image generation means is transferred to the storage means in accordance with the transfer permission signal, the data amount of the transfer data in the code reading device can be reduced. It is possible to reduce the overall load and reduce power consumption.

  According to the fifteenth aspect of the present invention, since the transfer permission signal is generated by the synchronization signal and the request signal, the image generation unit transfers the image data for a predetermined period in accordance with the timing at which the image data is output. Can do.

  Hereinafter, embodiments of the code reading device of the present invention will be described in detail with reference to FIGS. The code reading device decodes image data of a digital code generated by exposure and imaging with an image sensor, so that information encoded by the digital code (for example, product management information such as price and serial number, URL, E-mail address, etc.).

  Digital code formats include one-dimensional code (barcode) JAN (Japan Article Number), code 39, ITF (Interleaved Two of Five), etc., and two-dimensional code QR (Quick Response) code (QR code is ( DENSO WAVE INCORPORATED), PDF417 (PDF417 is a registered trademark of Symbol Technology Inc.), DataMatrix code (DataMatrix code is a registered trademark of Datamatrix Inc.), Maxi code (Maxi code is a registered trademark of USP), etc. The CPU performs decoding adapted to the code format on the image data generated by the image sensor.

  This code reading apparatus is applied to, for example, a bar code reader or bar code scanner of a POS (Point of Sales) system, but the application example is not limited to this, for example, a handy terminal, a mobile phone, a PDA (Personal) Digital Assistant) can be applied to various electronic devices as appropriate.

[First Embodiment]
First, a first embodiment of the code reading device 1 will be described with reference to FIGS. FIG. 1 is a block diagram illustrating an example of a functional configuration of the code reading device 1. As shown in FIG. 1, the code reading device 1 is configured by connecting a CPU 10, a ROM 20, a RAM 30, and a dedicated ASIC 50 to a system bus 90.

  The CPU 10 performs processing based on a program stored in the ROM 20 and performs overall control of the code reading device 1 by inputting instructions to each functional unit and inputting / outputting data. The CPU 10 functions as a decoder that decodes the frame image 31.

  The frame image 31 is digital code image data generated by the first image sensor Sa and the second image sensor Sb. When the digital image is a one-dimensional code as a result of binarizing the frame image 31, the CPU 10 calculates the length and width of the barcode and the interval between adjacent bars, and based on the calculation result Information is restored, and if the digital code is a two-dimensional code, decoding (restoration) is performed based on the arrangement pattern of black and white data cells. In addition, error correction is performed on the information obtained by decoding using a check digit included in the digital code of the frame image 31. Note that the decoding function of the CPU 10 may be realized in hardware by an electronic circuit separate from the CPU 10.

  The ROM 20 stores an initial program for performing various initial settings, hardware inspections, and the like, and a program for realizing various functions related to the operation of the code reading device 1.

  The RAM 30 is a storage area that temporarily stores data related to execution of various programs executed by the CPU 10. According to FIG. 1, the RAM 30 stores the frame image 31 described above.

  The dedicated ASIC 50 is an LSI (Large Scale Integration) uniquely designed and manufactured for the code reading device 1, and controls the exposure of each of the first image sensor Sa and the second image sensor Sb included in the lens unit 40. The image data generated by the image sensors Sa and Sb is transferred to the RAM 30.

  FIG. 2 shows a configuration example of the lens unit 40. The lens unit 40 includes a photographing lens 41, a prism P, a proximity lens 43a, a far lens 43b, a first image sensor Sa, and a second image sensor Sb.

  The prism P is composed of, for example, a half prism, a pentaprism, or the like, and branches the optical path of the input image Fg transmitted through the photographing lens 41 in the directions of arrows Va and Vb in FIG. The input image Fg branched by the prism P is projected to the proximity lens 43a and the far lens 43b.

  The proximity lens 43a and the far lens 43b are single focus lenses having different focal points, and have the reading depth characteristic and the resolution characteristic shown in FIG. The reading depth characteristic is a characteristic of a distance (depth) from a lens capable of reading a digital code to the digital code, that is, a focal length supported by the lens.

  As shown in FIG. 3A, the read depth characteristic of the proximity lens 43a is approximately 30 to 350 mm. This indicates that a digital code whose distance from the proximity lens 43a is about 30 to 350 mm can be clearly read without being out of focus. The reading depth characteristic of the far lens 43b is approximately 130 to 630 mm.

  The resolution characteristic is the characteristic of the bar or cell size of the digital code that can be read and identified. As shown in FIG. 3B, the resolution characteristic of the proximity lens 43a is approximately 0.08 to 0.38 mm, and the far lens 43b is approximately 0.25 to 1.2 mm.

  For example, when the length of one side of the cell of the two-dimensional code is 0.8 to 0.38 mm, the cell of the digital code transmitted through the proximity lens 43a can be identified, and 0.25 to 1 .2 mm indicates that the cell of the digital code transmitted through the distant lens 43b can be identified. In this way, the input image Fg captured by the photographing lens 41 is projected onto the proximity lens 43a and the far lens 43b having different characteristics.

  The first image sensor Sa and the second image sensor Sb are configured to include a CMOS (Complementary Metal Oxide Semiconductor) sensor and a CCD (Charge Coupled Device) imaging element, and expose an optical image of a digital code, that is, an input image Fg. By scanning, the input image Fg is optically read (photoelectrically converted) to generate image data.

  The first image sensor Sa generates image data of the input image Fga transmitted through the proximity lens 43a, and the second image sensor Sb generates image data of the input image Fgb transmitted through the far lens 43b. Therefore, the reading depth characteristic of the entire lens unit 40 is approximately 30 to 630 mm, which is obtained by combining the reading depth characteristics of the proximity lens 43a and the far lens 43b as shown in FIG. As shown in (b), the combined resolution characteristics of the proximity lens 43a and the distance lens 43b are approximately 0.08 to 1.2 mm.

  Each image sensor includes an oscillation circuit such as a crystal oscillator, and internally generates a pixel clock signal PCLK, a horizontal synchronization signal Hsync, and a vertical synchronization signal Vsync, and based on these signals, Control scanning by pixel, line by line and frame by frame. The pixel clock signal PCLK is a clock signal that controls scanning for each pixel (for example, 8-bit data). The horizontal synchronization signal Hsync is a synchronization signal that controls scanning for each line, and the vertical synchronization signal Vsync is a synchronization signal that controls scanning for each frame.

  The image sensor exposes and scans the input optical image based on the pixel clock signal PCLK, generates image data in units of pixels, and outputs the image data to the dedicated ASIC 50. Then, while the horizontal synchronization signal Hsync is H (High), one line is scanned by scanning one pixel at a time in the horizontal direction based on the pixel clock signal PCLK. Shift to During this L period, invalid data (dummy data) is output. Therefore, the dedicated ASIC 50 can acquire only valid image data in units of lines by acquiring data in synchronization with the horizontal synchronization signal Hsync.

  The image sensor outputs image data for one frame obtained by scanning based on the pixel clock signal PCLK and the horizontal synchronization signal Hsync to the dedicated ASIC 50 while the vertical synchronization signal Vsync is L, Invalid data is output to. Therefore, the dedicated ASIC 50 can acquire only valid image data in units of frames by acquiring data in synchronization with the vertical synchronization signal Vsync.

  Each of the first image sensor Sa and the second image sensor Sb outputs the generated pixel clock signal PCLK, horizontal synchronization signal Hsync, and vertical synchronization signal Vsync to the selector 61 of the dedicated ASIC 50.

  As shown in FIG. 1, the dedicated ASIC 50 includes a timing controller 51, a data buffer 53, a DMA 55 that directly accesses the RAM 30 to read / write data, an AE (Auto Exposure) calculator 57, an image sensor controller 59, and a selector 61. It is configured with.

  The selector 61 alternately selects the input image Fga input from the first image sensor Sa and the input image Fgb input from the second image sensor Sb, and outputs them to the data buffer 53.

  More specifically, a rectangular wave select signal 61a having a period as shown in FIG. 4 is generated based on the vertical synchronization signal Vsync output from the first image sensor Sa and the second image sensor Sb. When the select signal 61 a is H, the image data of the input image Fga input from the first image sensor Sa is output to the data buffer 53. At this time, the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync input from the first image sensor Sa are output to the timing controller 51.

  On the other hand, when the select signal 61a is L, the image data of the input image Fgb input from the second image sensor Sa is stored in the data buffer 53, and the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync are transmitted to the timing controller 51. Output to.

  The timing controller 51 is a circuit unit that controls accumulation (buffering) of image data input to the data buffer 53 based on the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync input from the selector 61. is there.

  The data buffer 53 is a circuit unit that temporarily stores image data of an input image read by the image sensor and then outputs the data to the DMA 55. Referring to FIG. 1, the data buffer 53 includes a buffer selector BS, a first line buffer LBa, and a second line buffer LBb. The buffer selector BS is a circuit unit that selectively selects and switches a line buffer that stores the image data input via the selector 61.

  Here, the operation of the timing controller 51 and the data buffer 53 will be briefly described as follows. First, the buffer selector BS outputs image data for each pixel input via the selector 61 to the first line buffer LBa and the AE calculator 57 based on the control of the timing controller 51.

  Then, after the buffer selector BS outputs the image data for one line to the first line buffer LBa, the output destination is switched to the second line buffer LBb based on the control of the timing controller 51, and the next one line is output. Output image data. While the image data is stored in the second line buffer LBb, the image data for one line stored in the first line buffer LBa is transferred to the RAM 30 via the DMA 55 and written in the data area of the frame image 31. It is. Next, when the buffer selector BS switches the output to the first line buffer LBa, the image data stored in the second line buffer LBb is written to the RAM 30 via the DMA 55.

  As described above, the image data for each line is stored in the first line buffer LBa and the second line buffer LBb. In the data area of the frame image 31 of the RAM 30, the image data of the input image generated by the image sensor is 1. As a result, the image data for one frame is stored as the frame image 31.

  The selector 61 alternately selects the first image sensor Sa and the second image sensor Sb every other frame, so that the frame image 31 is an image of the input image Fga read by the first image sensor Sa. The data and the image data of the input image Fgb read by the second image sensor Sb are alternately updated.

  The AE calculator 57 is a circuit unit that calculates an exposure value (shutter speed and aperture value) so that the exposure amount of the image data input from the buffer selector BS is appropriate exposure. The image sensor controller 59 is configured by an I2C interface or the like, and outputs the exposure value calculated by the AE calculator 57 to the first image sensor Sa and the second image sensor Sb via the selector 61, and the exposure of each image sensor. Change the setting value. At this time, the selector 61 outputs the exposure value to the image sensor selected based on the select signal 61a. This exposure value is reflected in the exposure / scanning of the input image of the frame to be exposed / scanned next to the image sensor.

  Next, a specific operation of the code reading device 1 will be described using the time chart of FIG. In the figure, the input image is read first from the first image sensor Sa. However, the input image may be read from the second image sensor Sb. For example, the distance between the digital code and the lens unit 40 is 400 mm. In the case of the code reading device 1 that is used apart from the above, it may be performed from the second image sensor Sb, and the order can be appropriately changed.

  First, the first image sensor Sa performs exposure while the vertical synchronization signal Vsync is L, and sequentially reads the input images A1, A1-1, A2, A2-1,. As described above, since the exposure setting is updated every two frames, the input image A1 and the input image A1-1 are substantially the same image data, and the input image A2 and the input image A2-1 are substantially the same. The second image sensor Sb also sequentially reads the input images B1, B1-1, B2,... Based on the vertical synchronization signal Vsync.

  The selector 61 selects the first image sensor Sa while the select signal 61 a is H, and transfers the input image data to the RAM 30 via the data buffer 53 and the DMA 55. Therefore, the image data of the input image A1 read by the first image sensor Sa starting exposure at time t1 is transferred to the RAM 30 and stored as the frame image 31 at time t3 after the end of reading.

  At time t5, the select signal 61a becomes L, and the image data of the input image B1 read by the second image sensor Sa is transferred to the RAM 30. Therefore, as shown in FIG. 4, the frame image 31 of the RAM 30 is an input image read by the first image sensor Sa and the second image sensor Sb such as the input images A1, B1, A2, B2,. Are alternately updated with the image data. Further, the input image A <b> 1-1 and the input image B <b> 1-1 obtained by exposure without changing the exposure setting value are not transferred to the RAM 30.

  The CPU 10 sequentially decodes the frame images 31 that are updated in the order of the input images A1, B1, A2,..., And decodes / acquires information encoded by the digital code of the frame images 31.

  As described above, according to the first embodiment, the input image Fg transmitted through the photographing lens 41 can be projected onto the proximity lens 43a and the far lens 43b having different focal points through the prism P. The digital code image data input to each of the first image sensor Sa and the second image sensor Sb is the same, and the composition does not deviate.

  In addition, since it is possible to capture the input image with two lenses without providing a drive unit such as an adjustment mechanism for adjusting the focal point, failure due to external factors such as dropping, vibration, and impact can be reduced. Power consumption is also reduced.

  Further, since the frame image 31 is updated alternately between the input image Fga that has passed through the proximity lens 43a and the input image Fgb that has passed through the far lens 43b, it is possible to sequentially decode the frame images 31 having different image quality. Therefore, unlike the conventional code reading apparatus 100, the idle time until the next decoding is not wasted, and the decoding efficiency can be improved.

  Further, since the input images Fga and Fgb transmitted through the proximity lens 43a and the far lens 43b are respectively decoded, the apparent reading depth characteristic and resolution characteristic of the entire code reading device 1 are widened. In addition, since it is not necessary to provide an autofocus for focusing, an input image can be read at high speed.

  The lens unit 40 is not limited to the configuration example of FIG. 2 described above, and can be changed as appropriate. Next, a modification when the configuration of the lens unit 40 is changed will be described with reference to FIGS. In the following description, the same components as those of the code reading device 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[First Modification of First Embodiment]
FIG. 5A is a diagram illustrating an example of the configuration of the lens unit 40a according to the first modification. Referring to FIG. 5A, the lens unit 40a includes a photographing lens 41, a prism P1, a proximity lens 43a, a far lens 43b, a middle lens 43c, and first to third image sensors Sa to Sc. Composed.

  The prism P1 is constituted by, for example, a dichroic prism or the like, and branches the optical path of the input image Fg transmitted through the photographing lens 41 in three directions as shown in FIG. The mid-range lens 43c is a lens having a focal point different from that of the proximity lens 43a and the distant lens 43b, and the third image sensor Sc reads the input image Fgc transmitted through the mid-range lens 43c.

  For example, by configuring the lens unit 401 with a proximity lens 43a having a reading depth characteristic of about 30 to 350 mm, a middle lens 43c of about 300 mm to 650 mm, and a far lens 43b of about 600 to 900 mm, The entire reading depth characteristic can be widened to about 30 to 900 mm.

  Further, by adopting a high-performance lens having a narrow reading depth characteristic of each lens, the performance of the lens unit 40 can be expected to be improved, and the same effect can be obtained with respect to the resolution characteristic. As shown in FIG. 5B, as the lens unit 40b, the proximity lens 43a, the far lens 43b, the middle lens 43c, and the prism P2 may be integrally formed.

[Second Modification of First Embodiment]
FIG. 6 is a diagram illustrating an example of the configuration of the lens unit 40c in the second modification. According to FIG. 6, the lens unit 40c is configured to include a photographing lens 41, a reflection mirror M, a proximity lens 43a, a far lens 43b, and first and second image sensors Sa and Sb. It is formed in a hollow T-shape.

  The reflection mirror M is configured to be able to vibrate and rotate left and right around the rotation axis Pb1 by a step motor or the like, for example, and reflects the input image Fg transmitted through the photographing lens 41 in the directions of the arrows Vc and Vd. The image Fg is projected onto the proximity lens 43a and the far lens 43b.

  More specifically, first, in order to reflect the input image Fg in the direction of the arrow Vc, the reflection mirror M is temporarily stopped as shown in FIG. 6 at an angle such that the incident angle of the input image Fg is 45 degrees. . Then, the reflecting mirror M indicated by the solid line in FIG. 6 is rotated 90 degrees clockwise to the reflecting mirror M indicated by the wavy line, and is temporarily stopped. As a result, the input image Fg is reflected in the direction of the arrow Vd and input to the far lens 43b.

  Next, the input mirror Fg is reflected in the direction of the arrow Vc by rotating the reflecting mirror M indicated by the wavy line 90 degrees counterclockwise and stopping. In this way, by repeating the clockwise and counterclockwise 90 degree rotations of the reflecting mirror M, the input image Fg is alternately projected onto the proximity lens 43a and the far lens 43b. By shortening the rotation cycle, the input image Fg can be read at high speed.

  As described above, according to the second modification, the input image Fg is alternately projected onto the proximity lens 43a and the far lens 43b by rotating the reflection mirror M at a predetermined period. For this reason, since the output of the image data of the first image sensor Sa and the second image sensor Sb is also alternate, it is not necessary to provide the selector 61 of the first embodiment for selecting the image data. Therefore, the circuit configuration of the dedicated ASIC 50 can be reduced in size and simplified.

  Although the spectroscopic means is realized by a prism or a reflecting mirror, a publicly known technique can be appropriately adopted as the realizing method. For example, the optical path of the input image Fg transmitted through the photographing lens 41 is branched using an optical fiber. It is good as well.

[Third Modification of First Embodiment]
Next, FIG. 7A shows a configuration example of the lens unit 40d in the third modification. According to FIG. 7A, the lens unit 40d is configured to include a photographing lens 41, a slide unit SU, and an image sensor 45.

  As shown in FIG. 7A, the slide unit SU is divided vertically, and is provided with a proximity lens 43a on the upper side and a far lens 43b on the lower side. The slide unit SU slides up and down (vibrates) at a predetermined cycle, so that the input image Fg transmitted through the photographing lens 41 is alternately projected onto the proximity lens 43a and the far lens 43b. Therefore, the input image Fg transmitted through the proximity lens 43a and the input image Fg transmitted through the far lens 43b are alternately input to the image sensor 45.

  As described above, according to the third modification, the proximity lens 43a and the far lens 43b are slid, so that the optical lens of the input image Fg is not branched and the proximity lens 43a and the far lens are provided to one image sensor 45. It is possible to project an input image Fg transmitted through each of the lenses 43b for use. For this reason, it is not necessary to provide a plurality of image sensors 45.

[Fourth Modification of First Embodiment]
Next, FIG. 7B shows a configuration example of the lens unit 40e in the fourth modification. According to FIG. 7B, the lens unit 40 e is configured to include a photographing lens 41, a turntable 47, and an image sensor 45.

  The rotating disk 47 is formed in a thin disk shape and has a first lens 49a (proximity lens 43a), a second lens 49b (distance lens 43b), a third lens 49c, and a fourth lens 49d each having a different focal point. Are arranged around the rotation axis Pb3. The turntable 47 is configured to be rotatable about a rotation axis Pb3. For this reason, the input image Fg transmitted through the photographing lens 41 is transmitted in the order of the first lens 49a, the second lens 49b, the third lens 49c, and the fourth lens 49d in accordance with the rotation period of the turntable 47, and the image. Projected to the sensor 45.

  As described above, according to the fourth modification, a plurality of lenses can be disposed on the turntable 47, so that the reading depth characteristics and resolution characteristics of the lens unit 40e can be further widened. As in one modification, the focal point of each lens can be narrowed to increase the accuracy of the lens unit 40e. Further, similarly to the third modification, it is not necessary to branch the optical path of the input image Fg, so that it is not necessary to provide a plurality of image sensors.

  Next, fifth and sixth modifications will be described with reference to FIGS. The code reading device 1 according to the first embodiment sequentially acquires the digital code image data generated in each of the first image sensor Sa and the second image sensor Sb by the selector 61. The code reading devices 1a and 1b according to the sixth modification acquire the image data individually through independent paths. In the following description, the same components as those of the code reading device 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Fifth Modification of First Embodiment]
FIG. 8 is a block diagram of a code reading device 1a according to the fifth modification. According to FIG. 8, the code reading device 1 a is configured by connecting a CPU 10, a ROM 20, a RAM 30 and a dedicated ASIC 50 a to a system bus 90. The dedicated ASIC 50a includes a first system block 50a, a second system block 50b, a DMA 55, an AE calculator 57, and an image sensor controller 59.

  The first system block 50a is a processing system for storing the image data generated by the first image sensor Sa in the first frame memory FMa, and the second system block 50b is generated by the second image sensor Sb. This is a processing system for storing image data in the second frame memory FMb. The first frame memory FMa and the second frame memory FMb are storage areas configured by a RAM, a flash memory, or the like.

  The first system block 50a includes a timing controller 51a, a data buffer 53a, and a memory controller MCa. Based on the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync input from the first image sensor Sa, the timing controller 51a stores image data in a data buffer 53a for a predetermined amount of data (for example, for one line). ) Accumulate.

  The memory controller MCa controls the writing of data to the first frame memory FMa and the access from the CPU 10 to the first frame memory FMa. More specifically, while image data for one frame is being input to the data buffer 53a, the image data is stored in the first frame memory FMa. When the storage of the image data for one frame in the first frame memory FMa is completed, access to the first frame memory FMa from the CPU 10 is permitted, and during that time, writing to the first frame memory FMa is not performed. Thereby, the CPU 10 decodes the image data of the digital code read by the first image sensor Sa.

  Further, the data buffer 53a outputs the image data input from the first image sensor Sa to the AE calculator 57. The AE calculator 57 recalculates the exposure value from the image data, and outputs the exposure value as the exposure setting value to the first image sensor Sa via the image sensor controller 59.

The second system block 50b includes a timing controller 51b, a data buffer 53b, and a memory controller MCb. Note that the processing of the second system block 50b is the same as that of the first system block 50a, and thus the description thereof is omitted.

  As described above, according to the fifth modification, the image data of digital codes generated by the first image sensor Sa and the second image sensor Sb are stored in the first frame memory FMa and the second frame memory FMb, respectively. For this reason, since the empty area of RAM30 used as a system memory of the code reader 1a increases, the load of the code reader 1a can be reduced. Note that such a code reading device 1a is suitably applied to a handy terminal or the like that performs high-load processing such as a wireless communication function.

[Sixth Modification of First Embodiment]
FIG. 9 shows a block diagram of a code reading device 1b according to a sixth modification. According to FIG. 9, the code reading device 1 b is configured by connecting a CPU 10, a ROM 20, a RAM 30, and a dedicated ASIC 50 b to a system bus 90.

  The dedicated ASIC 50b includes a first system block 52a, a second system block 52b, a DMA 55, an AE calculator 57, an image sensor controller 59, a memory controller MC, and an image composition processor 82.

  The first system block 52a is a processing system for outputting the image data generated by the first image sensor Sa line by line to the image composition processor 82, and the second system block 50b is generated by the second image sensor Sb. This is a processing system for outputting the processed image data to the image composition processor 82 line by line.

  The first system block 52a includes a timing controller 51c, a buffer selector BSa, a first line buffer LB1a, and a second line buffer LB2a. The timing controller 51c controls selection of the line buffer of the buffer selector BSa and output of image data based on the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync input from the first image sensor Sa. .

  The buffer selector BSa alternately outputs image data in units of pixels input from the first image sensor Sa to the first line buffer LB1a and the second line buffer LB1b line by line. At this time, the timing controller 51c alternately switches the output destination of the image data between the first line buffer LB1a and the second line buffer LB2a based on the vertical synchronization signal Vsync. The first line buffer LB1a and the second line buffer LB2a sequentially store image data for each line, and the image data is output to the image composition processor 82.

  The second system block 52b includes a timing controller 52d, a buffer selector BSb, a first line buffer LB1b, and a second line buffer LB2b. Since the processing of the second system block 52b is the same as that of the first system block 52a, description thereof is omitted.

  The image synthesis processor 82 is a circuit unit that synthesizes image data input from the first system block 52a and the second system block 52b. From the first system block 52a and the second system block 52b, image data for each line is output by the selection of the line buffers of the buffer selectors BSa and BSb. The image synthesizing processor 82 synthesizes the image data for each line by performing image processing, and stores it in the frame memory FM via the memory controller MC.

  The frame memory FM is a storage area configured by a RAM, a flash memory, or the like. Similarly to the memory controllers MCa and MCb in FIG. 8, the memory controller MC performs data writing to the frame memory FM and control of access from the CPU 10 to the frame memory FM. The AE calculator 57 recalculates the exposure value from the image data synthesized by the image synthesis processor 82, and changes the exposure setting value of the first image sensor Sa and the second image sensor Sb.

  For example, as shown in FIG. 10A, when the focus of the proximity lens 43a is about 50 to 300 mm and the distance lens 43b is about 400 to 1000 mm, the point Pt where the distance from the lens unit 40 is 350 mm. It is assumed that the digital code in is read. In this case, it becomes difficult for each of the proximity lens 43a and the far lens 43b to focus on the digital code at the point Pt.

  For this reason, the input image Fg that has passed through the proximity lens 43a and the input image Fgb that has passed through the far lens 43b are out of focus as shown in FIG. Therefore, when the image composition processor 82 synthesizes the input images Fga and Fgb, a clear composite image Fgs as shown in FIG. 10B is obtained.

  As described above, according to the sixth modification, the image data generated by the first image sensor Sa and the second image sensor Sb are combined, and the exposure value is recalculated and decoded using the combined image data. For this reason, even if the digital code is read in a state where the near lens 43a and the far lens 43b are out of focus, the decoding rate can be increased by increasing the contrast of the digital code. Further, it is possible to read a digital code at a position out of focus of the proximity lens 43a and the far lens 43b.

[Second Embodiment]
Next, a second embodiment of the code reading device 2 to which the present invention is applied will be described with reference to FIGS. In the following description, the same components as those of the conventional code reading device 100 are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 11 is a block diagram illustrating an example of a functional configuration of the code reading device 2. As shown in FIG. 11, the code reading device 2 has a configuration in which the code reading device 100 shown in FIG. 34A further includes a mode setting switch SW.

  The mode setting switch SW is a switch configured by, for example, a dip switch for setting / switching the exposure mode of the code reading device 2. The mode setting switch SW outputs a mode value for identifying the set exposure mode to the CPU 10.

  The exposure mode is a combination of an exposure setting and an LED setting that are determined in advance according to the exposure environment of the code reading device 2, and as shown in FIG. 12A, a default mode, an outdoor mode, a window mode, an indoor mode. There are five types: mode and warehouse mode. The exposure setting includes a maximum exposure value and a frame rate, and the LED setting includes luminance.

  FIG. 12B is a diagram showing the relationship between the frame rate, which is the number of frames that the image sensor 70 exposes per unit time, and the ambient illuminance. Using this relationship, the exposure setting in the exposure mode and the LED Define settings.

  For example, when the frame rate is 10 fps (frame per second), the ambient illuminance at which digital code image data can be clearly acquired is about 150 to 600 Lux, and the frame rate is increased, that is, the exposure time is shortened (shutter speed). ), The ambient illuminance increases as shown in FIG. 12B because it is necessary to expose a necessary amount of light within a short time.

  From such a relationship between the frame rate and the ambient illuminance, for example, when exposure is performed in a dark environment in a warehouse, it is sufficient to increase the brightness of the LED by increasing the exposure time by lowering the frame rate. The warehouse mode exposure setting and LED setting are determined so that the exposure amount can be obtained.

  11, the ROM 20 stores a code reading program 21, and the RAM 30 stores a frame image 31, an exposure setting value 33, a maximum exposure value 35, a frame rate 37, an LED luminance 39, and a mode value 32. Is remembered. The code reading program 21 is a program for realizing the code reading process shown in FIGS.

  The exposure setting value 33 is an exposure value when the image sensor 70 actually performs exposure. Every time exposure is performed, the CPU 10 calculates and updates the exposure value so that the exposure amount is appropriate. The mode value 32 is a mode value output from the mode setting switch SW, and “0” is stored in the initial state.

  The maximum exposure value 35, the frame rate 37, and the LED luminance 39 are set by the CPU 10 according to the exposure mode set by the user, as shown in FIG. In the initial state, the exposure mode is set to the default mode, and “100” is stored in the maximum exposure value 35, “30” is stored in the frame rate 37, and “100” is stored in the LED luminance 39.

  The CPU 10 performs exposure by controlling the image sensor 70 based on the exposure setting value 33 and the LED luminance 39. In addition, an oscillation circuit such as a crystal oscillator is provided, and clocking is performed based on a clock signal output from the oscillation circuit.

  Next, a specific operation of the code reading device 2 will be described with reference to the flowcharts of FIGS. The CPU 10 reads the code reading program 21 stored in the ROM 20 to start the code reading process shown in FIG. 13 and start measuring the elapsed time.

  First, in the code reading process shown in FIG. 13, the CPU 10 captures the state of the mode setting switch SW (step S1), and starts the exposure mode setting process shown in detail in FIG. 14 (step S3). The mode value 32 of the exposure mode thus obtained is acquired (step S31).

  When it is determined that the acquired mode value 32 is “1”, that is, the outdoor mode is set (step S33; Yes), the process proceeds to step S41, where the maximum exposure value 35 is “100” and the frame rate 37. “30” and “50” in the LED luminance 39 are stored. Then, after execution of step S41, the exposure mode setting process is terminated, and the process proceeds to step S5 of the code reading process shown in FIG.

  If it is determined that the mode value 32 is “2”, that is, the window-side mode is set (step S35; Yes), the process proceeds to step S43, where the maximum exposure value 35 is “200” and the frame rate 37 is “30”. "50" is stored in the LED luminance 39. Then, after the execution of step S43, the exposure mode setting process is terminated, and the process proceeds to step S5 of the code reading process shown in FIG.

  When it is determined that the mode value 32 is “3”, that is, the indoor mode is set (step S37; Yes), the process proceeds to step S45, where the maximum exposure value 35 is “200” and the frame rate 37 is “20”. "," 100 "is stored in the LED luminance 39. Then, after the execution of step S45, the exposure mode setting process is terminated, and the process proceeds to step S5 of the code reading process shown in FIG.

  If it is determined that the mode value 32 is “4”, that is, the warehouse mode is set (step S39; Yes), the process proceeds to step S47, where the maximum exposure value 35 is “250” and the frame rate 37 is “10”. "," 100 "is stored in the LED luminance 39. Then, after execution of step S47, the exposure mode setting process is terminated, and the process proceeds to step S5 of the code reading process shown in FIG.

  When it is determined that the mode value 32 is not any of “1” to “4”, that is, the default mode is maintained (step S39; No), the maximum exposure value 35, the frame rate 37, and the LED luminance 39 are set. The exposure mode setting process is terminated without storing, and the process proceeds to step S5 of the code reading process shown in FIG.

  Returning to the code reading process of FIG. 13, the CPU 10 sets an initial value to the exposure setting value 33 based on the frame rate 37 (step S <b> 5), and controls the image sensor 70 with the exposure setting value 33 and the LED luminance 39. The input image is exposed (image capture) (step S7). Then, after the image data read by the exposure is transferred to the RAM 30 via the data buffer 53 and the DMA 55 (step S9), the frame image 31 is decoded (step S11).

  As a result of decoding, when it is determined that the information encoded by the digital code can be acquired and the decoding is successful (step S13; Yes), the CPU 10 determines that the code reading process is completed but has failed. If it is determined (step S13; No), it is determined whether or not the elapsed time being timed has exceeded 5 seconds, for example, and timed out (step S15).

  When the CPU 10 determines that the time-out has occurred (step S15; No), the code reading process is terminated, but when it is determined that the time-out has not occurred (step S14; Yes); the exposure amount is optimal from the frame image 31. The exposure value is recalculated so that the exposure setting value 33 is updated (step S17).

  When the maximum exposure value 35 is exceeded by recalculation of the exposure value, the maximum exposure value 35 is set as the exposure setting value 33 to limit the exposure amount so as not to exceed a certain amount. After setting the calculated exposure value as the exposure setting value 33, the CPU 10 repeats the processes of steps S7 to S17 until the determination conditions of steps S13 and S15 are satisfied.

  As described above, according to the second embodiment, the exposure mode is provided for each exposure setting and LED setting determined in advance according to the environment in which the code reading device 2 is used, and the maximum exposure is set according to the exposure mode set by the user. A value 35, a frame rate 37, and an LED luminance 39 are set. For this reason, high-contrast image data can be obtained by appropriately setting the exposure mode according to the use environment of the user's code reader 2 such as in a warehouse or indoors.

  Further, by selecting the exposure mode with the mode setting switch SW, the exposure setting and the LED setting of the code reading device 2 are automatically selected, so that the user does not need to change the setting such as the exposure setting and the LED setting. It does not require specialized knowledge.

  Although the code reading device 2 in the second embodiment sets the exposure mode based on the user's operation of the mode setting switch SW, the setting method is not limited to this and can be changed as appropriate.

  Next, a modified example of the code reading device 2 will be described with reference to FIGS. In the following description, the same components as those of the code reading device 2 of the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Further, in the code reading process in the modified example, the same processing steps as those in the flowcharts shown in FIGS. 13 and 14 are denoted by the same step numbers, and the description thereof is omitted.

[First Modification of Second Embodiment]
First, a first modification of the code reading device 2 will be described. The code reading device 2 in the first modification has a configuration in which the mode switch SW is deleted from the code reading device 1 shown in FIG.

  FIG. 15A is a flowchart for explaining the code reading process in the first modification. First, the CPU 10 stores an initial value set in advance as the exposure setting value 33 and performs the initial setting (step S2), and then starts the exposure mode setting process shown in FIG. Since the mode value 32 is “0” in the initial state, the CPU 10 does not set the maximum exposure value 35, the frame rate 37, and the LED luminance 39 in the exposure mode setting process, and maintains the default mode.

  Then, after performing exposure, data transfer and decoding of the input image (steps S5 to S11), if it is determined that the decoding has failed and is not timed out (step S13 → S15; No), the exposure value is recalculated. (Step S17), and the exposure mode switching process (see FIG. 15B) is started.

  The CPU 10 determines that the exposure setting value 33 is greater than or equal to the maximum exposure value 35 (step S41; Yes), and further determines that the mode value 32 is smaller than 4 (step S43; Yes), the mode value 32 is set. The mode value 32 is updated by adding 1. That is, when the exposure setting value 33 reaches the maximum exposure value 35 and there is an exposure mode whose mode value is higher than the current exposure mode, the mode value 32 is changed to the mode value of the next exposure mode, and exposure is performed. In the mode setting process (step S3), the maximum exposure value 35, the frame rate 37, and the LED luminance 39 are set.

  Therefore, the exposure mode is changed from the default mode (mode value = 0) in the initial state to the outdoor mode (mode value = 1), the window mode (mode value = 2), the indoor mode (mode value = 3), and the warehouse mode ( The mode value is switched in order of 4) until the decoding is successful.

  As described above, according to the first modified example, the exposure modes are automatically switched sequentially, and an appropriate exposure mode is selected and set. Therefore, the user does not have to perform an exposure mode setting operation.

[Second Modification of Second Embodiment]
Next, a second modification of the code reading device 2a will be described with reference to FIGS. The code reading device 2a is obtained by further adding an illuminance sensor 80 to the code reading device 2 shown in FIG. The illuminance sensor 80 is a circuit unit that detects the illuminance of external light from the main body of the code reading device 2a and outputs a detection signal corresponding to the detected illuminance to the CPU 10.

  Further, according to FIG. 16, the RAM 30 stores a frame image 31, an exposure setting value 33, a maximum exposure value 35, a frame rate 37, an LED luminance 39, and an illuminance 34. The CPU 10 acquires illuminance based on the detection signal output from the illuminance sensor 80 and stores it in the RAM 30.

  FIG. 17 is a flowchart for explaining a code reading process in the second modification. After acquiring the illuminance 34 from the detection signal output from the illuminance sensor 80 and storing it (step S1-1), the CPU 10 starts the exposure mode setting process shown in FIG. 18 (step S3-1).

  In the exposure mode setting process in the second modification, the exposure mode is set based on the acquired illuminance 34. That is, first, when the illuminance 34 is 8000 Lux or more (step S51; Yes), the CPU 10 sets the maximum exposure value 35, the frame rate 37, and the LED luminance 39 as the outdoor mode (step S41).

  When the illuminance 34 is between 1500 and 7999 Lux (step S53; Yes), it is set as the window mode (step S42), and when it is between 750 and 1449 Lux (step S55; Yes), it is set as the indoor mode. (Step S45) If it is 749 Lux or less (Step S55; No), the warehouse mode is set (Step S47).

  As described above, according to the second modification, since the exposure mode is set based on the illuminance detected by the illuminance sensor 80, the exposure mode suitable for the environmental illuminance in which the code reading device 2a is used is immediately selected. Can be set.

  In addition to setting the exposure mode based on the illuminance sensor 80, for example, an ultraviolet sensor that detects ultraviolet rays is provided, and the outdoor mode is set when the ultraviolet rays detected by the ultraviolet sensor exceed a predetermined amount. However, if it is less than the predetermined amount, the indoor mode may be set.

  The type of exposure mode is not limited to that shown in FIG. 12A, and for example, the exposure mode may be set based on the color of recording paper on which a digital code is recorded. The recording paper on which the digital code is recorded includes, for example, white paper such as a price tag and colored paper such as corrugated cardboard.

  As shown in FIG. 19A, the frame image 31 of the barcode C1 recorded on the white recording paper has a clear contrast as shown in FIG. Easy to read. However, as shown in FIG. 20A, the frame image 31 of the barcode C3 recorded on the corrugated paper becomes difficult to read as shown in FIG.

  Therefore, a cardboard mode is provided in advance as an exposure mode, and the cardboard mode mode value is “5”, the maximum exposure value is “200”, the frame rate is “30”, and the LED luminance is “100”. Then, by setting the exposure mode to the cardboard mode, the contrast of the frame image 31 is increased as shown in FIG. 20C, and the barcode C3 can be read.

  The setting to the cardboard mode may be switched according to the user operation of the mode setting switch SW, or the color of the recording paper is determined from the frame image 31 obtained by once exposure. It may be performed according to the color.

  Note that the exposure mode shown in FIG. 12 and the cardboard mode may be combined, thereby improving the decoding rate when reading the digital code recorded on the cardboard indoors or in a warehouse such as a factory. . In addition to the color of the recording paper, as an exposure mode based on the material of the recording paper, for example, a vinyl mode in which the frame rate is set high so as to suppress the reflected light from vinyl may be provided.

[Third Embodiment]
Next, a third embodiment of the code reading apparatus to which the present invention is applied will be described with reference to FIGS. In the code reading device 3 according to the third embodiment, the same components as those of the code reading device 100 shown in FIG.

  FIG. 21A is a block diagram illustrating an example of a functional configuration of the code reading device 3 according to the third embodiment. As shown in FIG. 21, the code reading device 3 has a configuration in which the RAM 30 of the code reading device 100 shown in FIG.

  The flash memory 300 is a non-volatile storage area in which data can be read and written. According to FIG. 21A, a frame image 310 that is image data read by the image sensor 70, a first exposure setting value 320, The second exposure setting value 330 and the optimum exposure value 350 are stored.

  As described above, the conventional code reading device 100 performs exposure by updating the exposure setting value every other frame, but the code reading device 3 of the third embodiment has two exposure setting values, that is, the first exposure value. Exposure is performed while alternately updating the exposure setting value 320 and the second exposure setting value 330. The optimum exposure value 350 is one of the first exposure setting value 320 and the second exposure setting value 330 that has reached the optimum exposure range R3 during the previous exposure.

  Here, the basic operation of the code reading device 3 will be described with reference to the time chart of FIG. First, the CPU 10 sets different initial values such as a first initial value v1 for the first exposure setting value 320 and a second initial value v2 for the second exposure setting value 330.

  Then, the first frame exposure while the vertical synchronization signal Vsync is L is performed with the first exposure setting value 320 set to the first initial value v1. Next, the second frame exposure is performed with the second exposure setting value 330 set to the second initial value v2.

  During the exposure of the second frame, the CPU 10 transfers the image data DT1 obtained by the exposure of the first frame to the flash memory 300 and stores it as the frame image 310. Then, an exposure value is calculated based on the image data DT1, and the exposure value (calculated value AE1) is stored as the second exposure setting value 330.

  When the exposure for the second frame is completed, the image data DT2 obtained by the exposure is transferred to the flash memory 300, and the exposure for the third frame is performed. The exposure for the third frame is performed with the first exposure setting value 310 set to the calculated value AE1. Then, during the exposure of the third frame, the CPU 10 transfers the image data DT2 obtained by the exposure of the second frame to the flash memory 300, calculates the exposure value based on the image data DT2, and calculates the calculated value. AE2 is calculated. The exposure of the fourth frame is performed with this calculated value AE2 (second exposure setting value 330).

  In this way, the exposure of the odd-numbered frame is performed with the first exposure setting value 320, and the first exposure setting value 320 is sequentially calculated and updated. Further, even-numbered frames are exposed with the second exposure setting value 330, and the second exposure setting value 330 is sequentially updated. Then, this series of processing is repeated until the exposure setting value reaches the optimum exposure range R3, and exposure is performed alternately with the two exposure setting values. As a result, image data exposed with different exposure setting values can be obtained sequentially for each frame, so that it is possible to reduce the waste of decoding every other frame as in the prior art and to perform efficient decoding.

  Next, a setting method of the first initial value v1 and the second initial value v2, and a transition example of the first exposure setting value 320 and the second exposure setting value 330 that are sequentially calculated and updated after the setting will be described.

  22A and 22B show the maximum value max (for example, 255) within the range of exposure values that can be exposed by the image sensor 70 (hereinafter this range is referred to as “exposure range”). It is a figure which shows the example of a transition of the 1st exposure setting value 320 and the 2nd exposure setting value 330 when the minimum value min (for example, 0) is set as the 2nd initial value v2 as the initial value v1.

  Here, it is assumed that the optimum exposure range R3 under a certain environment where the code reading device 3 is used is around the center value c in the exposure possible range R1, as shown in FIG. The first exposure setting value 320 is calculated at odd numbers such as the first frame, the third frame, and the fifth frame, and the optimal exposure range is calculated values AE1, AE3, AE5,... In order from the first initial value v1. Approaching R3.

  On the other hand, the second exposure setting value 330 is calculated as an even number such as the second frame, the fourth frame, the sixth frame, and the calculated values AE2, AE4, AE6,... Sequentially from the second initial value v2. , And approaches the optimum exposure range R3. As a result, the first exposure setting value 320 reaches the optimum exposure range R3 at the calculated value AE9 of the eleventh frame, and at this time, a frame image 310 with high contrast is obtained.

  On the other hand, as shown in FIG. 22B, when the optimum exposure range R3 is shifted from the center value c to the minimum value side, the optimum exposure is performed on the sixth frame in which the second exposure setting value 330 is calculated as the calculated value AE3. Reach within range R3. Thus, when the optimum exposure range R3 deviates from the center of the exposure possible range R3, the second exposure set value 330 is within the optimum exposure range R3 faster than the transition example shown in FIG. Can be reached. Although illustration is omitted, when the optimum exposure range R3 is shifted from the center of the exposure possible range R3 to the maximum value side, the first exposure set value 320 similarly reaches the optimum exposure range R3 early as well. .

  In FIGS. 23A and 23B, the optimum exposure value 350 stored in the flash memory 300 is set as the first initial value v1, and the exposure setting value obtained by subtracting the optimum exposure value 350 from the maximum value max is set as the second initial value. It is a figure which shows the example of a transition of the 1st exposure setting value 320 and the 2nd exposure setting value 330 at the time of setting as value v2.

  As shown in FIGS. 23A and 23B, the initial value v1 and the initial value v2 have a line-symmetric positional relationship with respect to the center value c of the exposure possible range R1, and the optimum exposure value 350 is as shown in FIG. ), The calculated value AE3 reached within the optimum exposure range R3. For this reason, when the apparatus is used in an environment equivalent to the code reading apparatus 3 used in FIG. 22B, the first initial value v1 set as the first exposure setting value 320 is the same as that in FIG. As shown in a), since it is already within the optimum exposure range R3, it is not necessary to recalculate the first exposure setting value 320 and the second exposure setting value 330.

  On the other hand, when the optimum exposure range R3 is above the center value c as shown in FIG. 23B, the calculated value AE2 of the second exposure setting value 330 calculated in the fourth frame is within the optimum exposure range R3. To reach. In this way, by setting the exposure setting value that has reached the optimum exposure range R3 at the time of past exposure, that is, the optimum exposure value 350, as an initial value, even when the usage environment of the code reader 3 changes, It quickly stabilizes within the optimum exposure range R3.

  FIG. 24A shows the first exposure in the case where the maximum value max is set as the first initial value v1, and a value obtained by adding an offset to the first initial value v1 is set as the second initial value v2. It is a figure which shows the example of a transition of the setting value 320 and the 2nd exposure setting value 330. FIG.

  Since the second initial value v2 is closer to the center value c than the first initial value v1, the second exposure setting value 330 reaches the optimum exposure range R3 earlier than the first exposure setting value 320. When the optimum exposure range R3 is between the first initial value v1 and the second initial value v2, the first exposure setting value 320 reaches the optimum exposure range R3 earlier.

  The same effect can be obtained by setting the minimum value min as the first initial value v1 and setting the offset value with respect to the first initial value v1 as the second initial value v2. Of course.

  In FIG. 24B, a third exposure setting value 340 is provided in addition to the first exposure setting value 320 and the second exposure setting value 330, the maximum value max being the first initial value v1, and the minimum value being the second initial value v2. It is a figure which shows the example of a transition of these exposure setting values at the time of setting the center value c to the 3rd initial value v3 which is the initial value of min and the 3rd exposure setting value 340.

  In this case, the CPU 10 sets the first exposure setting value 320 in the “3n−2 (n is a natural number)” frame, the second exposure setting value 330 in the “3n−1” frame, and the first exposure setting value 330 in the “3n” frame. Control is performed so that exposure is performed at three exposure setting values 340, and each exposure setting value is recalculated for each exposure.

  In FIG. 24B, the third exposure setting value 340 reaches the optimum exposure range R3 at the sixth frame. If the optimum exposure range R3 is on the maximum value max side, the first exposure set value 320 reaches the optimum exposure range R3 earlier, and if it is on the minimum value min side, the second exposure set value 330 is reached. Reaches the optimum exposure range R3 earlier. Thus, by providing a plurality of exposure setting values, the probability of reaching the optimum exposure range R3 early can be improved.

  25 (a) and 25 (b) show an average value of the first exposure setting value 320 and the second exposure setting value 330 by setting the maximum value max to the first initial value v1 and the minimum value min to the second initial value v2. It is a figure which shows the example of a transition at the time of updating each exposure setting value.

  As in FIG. 22A, the CPU 10 calculates a calculated value AE1 of the first exposure setting value 320 from the frame image 310 obtained by exposure at the first frame, and sets the calculated value AE1 at the third frame. Based on the exposure. Further, a calculated value AE2 of the second exposure setting value 330 is calculated from the frame image 310 obtained in the second frame, and exposure based on the calculated value AE2 is performed in the fourth frame.

  After updating the first exposure setting value 320 and the second exposure setting value 330, the CPU 10 calculates an average value AE10 of the updated first exposure setting value 320 and second exposure setting value 330. The calculated average value AV1 is set as the first exposure setting value 320, and exposure for the fifth frame is performed. Further, an average value AV2 between the first exposure setting value 320 set to the average value AV1 and the second exposure setting value 330 is calculated. After the calculated average value AV2 is set as the second exposure setting value 330, the sixth frame exposure is performed.

  In this way, by calculating the average value of the first exposure setting value 320 and the second exposure setting value 330 as needed, and setting the calculated average value to each exposure setting value, for example, FIG. As described above, when the optimum exposure range R3 is near the center value c, the first exposure setting value 320 reaches the optimum exposure range R3 in the fifth frame. As shown in FIG. 25B, when the optimum exposure range R3 is below the center value c, the second exposure setting value 330 can reach the optimum exposure range R3 at the sixth frame.

  In FIG. 23, the previous optimum exposure value 350 is set as an initial value. However, the optimum exposure value 350 for a certain period such as one day, one week, or one month is stored in the flash memory 300, An average value of the optimum exposure values may be calculated, and the average value may be set as an initial value of the exposure setting value.

  FIG. 26A is a diagram showing a history of optimum exposure values 350 accumulated for one month when the code reading device 3 is used in a relatively stable environment. In this case, the average value AV3 of the history of the optimum exposure value 350 is calculated, and the average value AV10 is set to the first initial value v1 of the first exposure setting value 320, so that the exposure setting value can be set at a higher speed. It can be stabilized within the optimum exposure range R3.

  FIG. 26B is an example of a history of the optimum exposure value 350 when the use environment of the code reading device 3 has changed significantly. When the difference between the maximum optimum exposure value (maximum exposure value Max) in the history for one month and the minimum optimum exposure value (minimum exposure value Min) exceeds a predetermined value (for example, 50) Is determined that there is a variation in the usage environment of the code reading device 3, and two average values are calculated as follows.

  First, the maximum exposure value Max and the minimum exposure value Min are extracted from the history of optimum exposure values. Then, the average of the maximum exposure value Max and the minimum exposure value Min is calculated, and the history of the optimum exposure value is divided into two with the average as the threshold BL. Then, an average value AV11 of one optimal exposure value divided into two and an average value AV12 of the other optimal exposure value are calculated, and these average values are respectively set as a first initial value v1 and a second initial value v2. .

  FIG. 27 is a diagram showing a transition example of the first exposure setting value 320 and the second exposure setting value 330 when the average value AV11 is set as the first initial value v1 and the average value AV12 is set as the second initial value v2. is there.

  For example, the optimum exposure range R3 is on the minimum value min side with the center value c as shown in FIG. 27A, and the first exposure setting value 320 is already included in the optimum exposure range R3. Therefore, it is not necessary to calculate the exposure setting value. When the optimum exposure range R3 is on the maximum value max side with the center value c as shown in FIG. 27B, the calculated value AE2 of the second exposure setting value 330 calculated in the fourth frame is the optimum exposure. Reach within range R3.

  For this reason, even when the usage environment of the code reader 3 varies, the average value AV11 or AV12 closer to the optimum exposure range R3 reaches the optimum exposure range R3 earlier. In this way, by setting the average value in the history of the past optimum exposure value 350 as the initial value, the optimum exposure range R3 can be reached at a higher speed even if the usage environment of the code reader 3 varies. it can.

  As described above, according to the third embodiment, a plurality of initial values of exposure setting values are set with different values, and the exposure setting values starting with these initial values are sequentially calculated and updated. Thereby, even if the use environment of the code reader 3 changes, the time until the exposure setting value reaches the optimum exposure range can be shortened.

[Fourth Embodiment]
Next, a fourth embodiment of the code reading device to which the present invention is applied will be described with reference to FIGS. In the code reading device 4 according to the fourth embodiment, the same components as those of the conventional code reading device 1 shown in FIG.

  FIG. 28 is a block diagram illustrating an example of a functional configuration of the code reading device 4 according to the fourth embodiment. As shown in FIG. 28, the code reading device 4 has a configuration in which the dedicated ASIC 50 of the code reading device 1 shown in FIG. 1 is replaced with the dedicated ASIC 50 e of FIG. 28 and the lens unit 40 is replaced with an image sensor 70.

  The dedicated ASIC 50e includes a timing controller 51e, a data buffer 53, and a DMA 55. The timing controller 51e is configured to include the transfer control circuit 510 shown in FIG. 29A, and based on the pixel clock signal PCLK, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync output from the image sensor 70, the buffer selector BS. The data transfer for each line to the first line buffer LBa and the second line buffer LBb is controlled.

  The transfer control circuit 510 is a circuit that controls the data transfer of the buffer selector BS to the first line buffer LBa and the second line buffer LBb by generating a transfer permission signal TE and outputting it to the buffer selector BS. It is composed of D flip-flops.

  Further, the timing controller 51 e internally generates a frame start request signal FSR based on the control of the CPU 10 and outputs it to the transfer control circuit 510. More specifically, the CPU 10 issues a frame image transfer start request to the timing controller 51e to the timing controller 51e at an arbitrary timing. The timing controller 51e generates a frame start request signal FSR that holds 1 (H) for a certain period in response to a request from the CPU 10 and outputs the frame start request signal FSR to the transfer control circuit 510.

  29A shows an example of a circuit configuration of the transfer control circuit 510, FIG. 29B shows a relationship between signals input to and output from the transfer control circuit 510, and FIG. 30 explains an operation example of the transfer control circuit 510. It is a time chart for doing. Here, a specific operation example of the transfer control circuit 510 will be described with reference to FIGS.

  The transfer control circuit 510 generates a transfer permission signal TE as shown in FIG. 29A based on the frame start request signal FSR and the vertical synchronization signal Vsync generated by the timing controller 51e.

  That is, when the frame start request signal FSR becomes 1 (H) at time t11, an image data transfer request is output. After that, when the vertical synchronization signal Vsync switches from H to L at time t15, the transfer permission signal TE. Rises to 1 (H).

  Then, after the frame start request signal FSR is switched to 0 (L) (time t19), when the vertical synchronization signal Vsync is switched from H to L at time t21, the transfer permission signal TE returns to 0 (L).

  The transfer control circuit 510 outputs the transfer permission signal TE to the buffer selector BS. When the transfer permission signal TE is 1 (H), the transfer control circuit 510 transmits the image data to the first line buffer LBa and the second line buffer LBb. Allow transfer.

  Next, a specific operation of the code reading device 4 will be described with reference to FIG. First, the CPU 10 outputs an imager transfer control signal TC as shown in FIG. 31 to the image sensor 70, thereby outputting the vertical synchronization signal Vsync and the output of the image data generated by the image sensor 70 to the dedicated ASIC 50e. Let it begin. While the imager transfer control signal TC is H, image data transfer is started and each circuit unit operates. During L, data transfer is not performed, so that the standby state is set.

  At this time, image data (input image) is transferred to the dedicated ASIC 50e while the vertical synchronization signal Vsync output from the image sensor 70 is L. For example, as shown in FIG. 31, an imager transfer control signal Input images C1, C2, and C3 are sequentially transferred in synchronization with a vertical synchronization signal Vsync that oscillates three times while TC is H.

  Then, the timing controller 51e obtains one input image C2 among the input images sequentially transferred from the image sensor 70 by outputting the transfer permission signal TE generated as described above to the buffer selector BS. The data is transferred to the RAM 30. The CPU 10 decodes the frame image 31 of the transferred input image C2.

  As described above, according to the fourth embodiment, by providing the transfer control circuit 510 in the timing controller 51e and generating the transfer permission signal TE, the frame start request signal among the input images sequentially transferred from the image sensor 70. An input image while data transfer is requested by the FSR is acquired and transferred to the RAM 30. For this reason, it is possible to reduce the occupation ratio that the input image occupies the system bus 90. Accordingly, the circuit of the code reading device 4 is not always activated for processing of the input image, so that the load on the device can be reduced and further power saving can be expected.

  In the fourth embodiment, the transfer permission signal TE is generated based on the vertical synchronization signal Vsync. However, the transfer permission signal TE may be generated based on the horizontal synchronization signal Hsync. In this case, a line data transfer control circuit 512 shown in FIG. 32 is provided inside the timing controller 51e.

  The line data transfer control circuit 512 is a circuit unit that generates the line data transfer permission signal LTE from the transfer permission signal TE, the vertical synchronization signal Vsync, and the horizontal synchronization signal Hsync, and includes, for example, an AND circuit. That is, when the transfer permission signal TE is 1 (H), the vertical synchronization signal Vsync is 0 (L), and the horizontal synchronization signal Hsync is 1 (H), the line data transfer permission signal LTE that holds 1 (H) is set. Generate.

  The line data transfer control circuit 512 outputs the line data transfer permission signal LTE to the buffer selector BS, and when the line data transfer permission signal LTE is 1 (H), the first line buffer LBa and the second line buffer. Transfer of image data to LBb is permitted.

  Therefore, as shown in FIG. 33, while the transfer permission signal TE is 1 (H) and the vertical synchronization signal Vsync is L, the line data transfer permission signal LTE also rises every time the horizontal synchronization signal Hsync rises. While the line data transfer permission signal LTE is H, the input images C202, C204, C206,... For each line are transferred via the first line buffer LBa and the second line buffer LBb. It will be done.

  For this reason, the line-unit input image C110 of the input image C1 input before time t31 (see FIGS. 32 and 32) is not transferred to the RAM 30. Accordingly, the data transfer of the input image to the RAM 30 can be controlled more finely.

  In the second to fourth embodiments, the CPU 10 realizes recalculation of the exposure setting value, change of the exposure setting of the image sensor 70, and the like in software, but the code reading device 1 of the first embodiment. As described above, the AE calculator 57 and the image sensor controller 59 may be provided and realized in hardware.

The block diagram which shows an example of a function structure of the code reader in 1st Embodiment. FIG. 3 is a diagram illustrating a configuration example of a lens unit in the first embodiment. The figure which shows an example of the reading depth characteristic and resolution characteristic of a lens unit. The time chart for demonstrating the operation example of the code reader in 1st Embodiment. The figure which shows the structural example of the lens unit in the 1st modification of 1st Embodiment. The figure which shows the structural example of the lens unit in the 2nd modification of 1st Embodiment. The figure which shows the structural example of the lens unit (a) in the 3rd modification of 1st Embodiment, and the lens unit (b) in a 4th modification. The block diagram which shows an example of a function structure of the code reader in the 5th modification of 1st Embodiment. The block diagram which shows an example of a function structure of the code reader in the 6th modification of 1st Embodiment. The figure for demonstrating the specific operation example of the code reader in the 6th modification of 1st Embodiment. The block diagram which shows an example of a function structure of the code reader in 2nd Embodiment. The figure for demonstrating exposure mode. The flowchart for demonstrating the code reading process in 2nd Embodiment. 9 is a flowchart for explaining exposure mode setting processing in the second embodiment. The flowchart for demonstrating the code reading process (a) in the 1st modification of 2nd Embodiment, and exposure mode setting process (b). The block diagram which shows an example of a function structure of the code reader in the 2nd modification of 2nd Embodiment. The flowchart for demonstrating the code reading process in the 3rd modification of 2nd Embodiment. 15 is a flowchart for explaining exposure mode setting processing in a third modification of the second embodiment. The figure for demonstrating the reading example of the digital code recorded on the recording paper of white background. The figure for demonstrating the reading example of the digital code recorded on the cardboard. The block diagram (a) which shows an example of a function structure of the code reader in 3rd Embodiment, The time chart (b) for demonstrating operation | movement of a code reader. The 1st figure which shows the example of a transition of a 1st exposure setting value and a 2nd exposure setting value. The 2nd figure which shows the example of a transition of a 1st exposure setting value and a 2nd exposure setting value. The 3rd figure which shows the example of a transition of a 1st exposure setting value and a 2nd exposure setting value. FIG. 14 is a fourth diagram showing an example of transition between the first exposure setting value and the second exposure setting value. The figure which shows an example of the log | history of an optimal exposure value. FIG. 10 is a fifth diagram illustrating a transition example of the first exposure setting value and the second exposure setting value. The block diagram which shows an example of a function structure of the code reader in 4th Embodiment. The figure for demonstrating the relationship between the circuit structure of a transfer control circuit, and the signal input / output. 4 is a time chart for explaining an operation example of a transfer control circuit. The time chart for demonstrating the operation example of the code reader in 4th Embodiment. The figure which shows an example of the circuit structure of a line data transfer control circuit. The time chart for demonstrating the operation example of the code reader in the modification of 4th Embodiment. The block diagram (a) which shows an example of a function structure of the conventional code reader, and the time chart (b) for demonstrating an operation example. The figure which shows the example of a transition of the exposure setting value of the conventional code reader.

Explanation of symbols

1 Code reader 10 CPU (decoding means, setting means, determination means, initial setting means, exposure value updating means, repetition control means, average calculation means)
20 ROM
30 RAM
31 Frame image 40 Lens unit 41 Shooting lens P Prism (spectral means)
43a Proximity lens 43b Distant lens Sa First image sensor (image generating means)
Sb second image sensor (image generating means)
Vsync Vertical sync signal Hsync Horizontal sync signal 50 Dedicated ASIC
51 Timing controller (request signal generating means)
53 Data buffer (transfer means)
BS buffer selector (transfer means)
LBa first line buffer
LBb second line buffer 55 DMA
57 AE calculator 59 Image sensor controller 61 Selector 82 Image composition processor (composition means)
FM frame memory (storage means)
SW mode setting switch (switching means)
70 Image sensor (exposure means, synchronization signal generation means)
80 Illuminance sensor 300 Flash memory (history recording means)
320 1st exposure setting value (exposure value storage means)
330 Second exposure setting value (exposure value storage means)
350 Optimal exposure value (optimum value storage means)
510 Transfer control circuit (signal generating means)

Claims (15)

A spectroscopic means for branching an optical path propagating an optical image of the digital code into a plurality of optical paths;
A plurality of lenses having different focal points and arranged in each of the branched optical paths;
An image generating means for converting an optical image of each digital code that has passed through the plurality of lenses into an electrical signal and generating a plurality of image data of the digital code;
Decoding means for decoding the plurality of image data;
A code reading device comprising: The decoding means includes
2. The code reading apparatus according to claim 1, wherein the plurality of image data generated by the image generation means are sequentially decoded. A storage means for individually storing a plurality of image data generated by the image generation means;
3. The code reading device according to claim 1, wherein the decoding unit reads and decodes the image data stored in the storage unit. And further comprising a combining means for combining a plurality of image data generated by the image generating means,
The code reading device according to claim 1, wherein the decoding unit decodes the image data combined by the combining unit. Switching means for switching between a plurality of exposure modes;
Setting means for setting exposure conditions according to the exposure mode switched by the switching means;
Image generating means for exposing the optical image of the digital code under the exposure conditions set by the setting means to generate image data of the digital code;
Decoding means for decoding the image data generated by the image generation means;
A code reading device comprising:   6. The code reading apparatus according to claim 5, wherein the switching unit switches the plurality of exposure modes based on a user operation. A determination means for determining success or failure of decoding by the decoding means;
6. The code reading apparatus according to claim 5, wherein the switching unit switches the exposure mode when the determination unit determines that the decoding has failed. It further comprises illuminance detection means for detecting the illuminance of outside light,
6. The code reading device according to claim 5, wherein the switching unit switches the exposure mode based on the illuminance detected by the illuminance detection unit. Exposure value storage means for storing a plurality of exposure values;
Initial setting means for setting a plurality of different initial values as a plurality of exposure values stored in the exposure value storage means;
Exposure means for exposing an optical image of a digital code based on each of a plurality of exposure values stored by the exposure value storage means;
Exposure value updating means for individually updating a plurality of exposure values stored by the exposure value storage means based on the result of exposure by the exposure means;
Repetitive control means for repeating a series of processes by the exposure means and the exposure value update means until the exposure value updated by the exposure value update means reaches an optimum exposure range;
A code reading device comprising:   10. The code reading apparatus according to claim 9, wherein the initial setting means sets the maximum and minimum exposure values that can be exposed by the exposure means as the initial values. An optimum value storing means for storing an exposure value when the exposure value updated by the exposure value updating means reaches an optimum exposure range as an optimum exposure value;
The code reading device according to claim 9, wherein the initial setting unit sets the optimum exposure value as the initial value. A history recording means for recording a history of the optimum exposure value;
An average calculating means for calculating an average value of the optimum exposure values recorded by the history recording means,
12. The code reading device according to claim 11, wherein the initial setting unit sets the average value calculated by the average calculation unit as the initial value. A history recording means for recording a history of optimum exposure values;
An average calculating means for calculating an average value of the optimum exposure values recorded by the history recording means;
Image generating means for performing exposure of an optical image of a digital code based on an average value of exposure values calculated by the calculating means, and generating image data of the digital code;
Decoding means for decoding the image data generated by the image generation means;
A code reading device comprising: Storage means for storing digital code image data;
Image generation means for generating and outputting digital code image data;
Signal generating means for generating a transfer permission signal;
Transfer means for transferring image data output from the image generation means to the storage means in accordance with a transfer permission signal generated by the signal generation means;
Decoding means for decoding the image data stored by the storage means;
A code reading device comprising: The image generation means includes synchronization signal generation means for generating a synchronization signal for controlling the output of the image data,
Request signal generating means for generating a request signal for requesting the image data generated by the image generating means for a certain period of time;
15. The code reading device according to claim 14, wherein the signal generating unit generates a transfer permission signal based on the synchronization signal and the request signal.

Images