JP2010182057A - Optical information reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information reading device suppressing the failure of recognition due to blur without deteriorating a reading speed. <P>SOLUTION: Reflected rays from a QR code are condensed on the light reception face of a light receiving sensor by changing the focal distance of a fluid lens functioning as a focal distance changing means. Then, when blurring quantity (blurring degree) is calculated from the luminance value of the finder pattern of the QR code, a voltage to be applied to the fluid lens is determined so that the blurring quantity can be reduced. Then, the focal distance is changed by the fluid lens according to the determined application voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical information reader.

  2. Description of the Related Art Conventionally, an imaging apparatus shown in Patent Document 1 below is known as a technique related to an optical information reading apparatus. In this imaging apparatus, when a feature point is extracted at the time of QR code reading, a high-frequency component is extracted by applying a band-pass filter to the feature point mark portion, and the integration value is taken to evaluate the integration value as a focus condition evaluation value. I will ask for it. Then, when the evaluation value continuously obtained while sequentially changing the digital filter to be used detects the maximum value, the blurred restoration image is read, and the focal point of this image is corrected and restored, and restored. The recognition rate is improved by performing predetermined image processing on the image signal.

JP 2007-206738 A

  By the way, the extraction of the frequency components necessary for applying the digital filter described above is greatly influenced by the pixel allocation (pixel allocation amount of one cell) in principle. Therefore, when the number of pixels of the image sensor used increases to 350,000, 1 million, 3 million, for example, the theoretically possible combinations of pixel allocation amounts become enormous (for example, a certain QR code is imaged to the full screen). Pixel allocation (frequency component) when compared with the near-point image to the farthest-point image that can be read), resulting in an increase in processing time due to an increase in the number of digital filter types used after extraction of the frequency component. is there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical information reading apparatus capable of suppressing recognition failure due to blur without reducing the reading speed. There is.

  In order to achieve the above object, in the optical information reading device according to claim 1, a two-dimensional code composed of a plurality of light cells and a plurality of dark cells, the light cells and In an optical information reading apparatus capable of reading a two-dimensional code including a specific pattern in which the dark color cells are arranged in a predetermined order, the focal length capable of collecting the reflected light from the two-dimensional code and changing the focal length A receiving unit that receives the reflected light collected by the focal length changing unit, a decoding unit that performs a decoding process based on a light reception result by the light receiving unit, and a light reception result by the light receiving unit. The degree of blur is calculated from the specific pattern detection means for detecting the specific pattern and the brightness value of the specific pattern detected by the specific pattern detection means. And a focal length determination unit that determines a target focal length based on the blur condition calculated by the blur condition calculation unit. The focal length change unit is determined by the focal length determination unit. The focal length is changed based on the target focal length.

  According to a second aspect of the present invention, in the optical information reading apparatus according to the first aspect, the specific pattern is a position detection pattern for detecting a position of the two-dimensional code.

  According to a third aspect of the present invention, in the optical information reading apparatus according to the first aspect, the specific pattern includes a timing pattern in which the light color cells and the dark color cells are alternately arranged, and an outer edge portion of the two-dimensional code. And a quiet zone composed only of the light-colored cells.

  According to a fourth aspect of the present invention, in the optical information reading device according to any one of the first to third aspects, the blur condition calculating unit calculates the blur condition from a luminance gradient in the specific pattern. And

  According to a fifth aspect of the present invention, in the optical information reading device according to any one of the first to fourth aspects, the focal length changing means is a liquid lens whose focal length can be changed according to an applied voltage. It is characterized by being.

  In the first aspect of the invention, the reflected light from the two-dimensional code is condensed on the light receiving means by changing the focal distance by the focal length changing means. When the blur condition is calculated from the brightness value of the specific pattern by the blur condition calculator, the target focal distance is determined by the focal distance determiner based on the blur condition. Then, the focal length is changed by the focal length changing means based on the target focal length thus determined.

Thus, since the focal length is changed by the focal length changing means based on the target focal length determined according to the degree of blur, the focal length can be changed so as to suppress blur. For this reason, the recognition failure resulting from blurring can be suppressed. In particular, since the degree of blur is calculated from the luminance value of the specific pattern, it is possible to speed up the process of determining the target focal length as compared to the case where the degree of blur is calculated from the luminance value of the entire region.
Accordingly, it is possible to suppress recognition failure due to blur without reducing the reading speed.

  According to the second aspect of the present invention, since the specific pattern is a position detection pattern for detecting the position of the two-dimensional code, it is easy to recognize the specific pattern, so that the degree of blur can be reliably calculated.

  In the invention of claim 3, the specific pattern is composed of a timing pattern in which light cells and dark cells are alternately arranged, and a quiet zone which is an outer edge portion of the two-dimensional code and is composed only of light cells. Therefore, the specific pattern can be easily recognized as in the second aspect of the invention, so that the degree of blur can be reliably calculated.

  As in the invention of claim 4, the blur condition calculating means may calculate the blur condition from the luminance gradient in the specific pattern.

  In the invention of claim 5, since the focal length changing means is a liquid lens whose focal length can be changed according to the applied voltage, the focal length is changed only by changing the applied voltage. Can be easily adjusted. Moreover, since there are few drive parts, such as a motor, durability can be improved.

It is a block diagram which shows the electric constitution of the information code reader which concerns on this embodiment. It is a graph which shows the relationship between the applied voltage value applied to a liquid lens, and a focal distance. It is a flowchart which illustrates the flow of a focal distance adjustment process. 4A is a diagram showing a QR code in a non-blurred state, and FIG. 4B is a graph showing each luminance value of the finder pattern on the measurement line in FIG. 4A. FIG. 5A is a diagram showing the QR code in a blurred state, and FIG. 5B is a graph showing each luminance value of the finder pattern on the measurement line in FIG. 5A. FIG. 6A is a chart showing the relationship between the applied voltage value applied to the liquid lens in increments of 1V and the focal length, and FIG. 6B is an application applied to the liquid lens in increments of 0.1V. It is a graph which shows the relationship between a voltage value and a focal distance. FIG. 7A is a diagram illustrating a QR code in a blurred state, and FIG. 7B is a graph illustrating the timing pattern and the brightness values of the quiet zone on the measurement line in FIG. 7A. .

  Hereinafter, an embodiment in which an optical information reader of the present invention is applied to an information code reader will be described with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of the information code reader 20 according to the present embodiment. FIG. 2 is a chart showing the relationship between the applied voltage value applied to the liquid lens 27 and the focal length.

  As shown in FIG. 1, the information code reader 20 mainly includes an optical system such as an illumination light source 21, a light receiving sensor 23, a liquid lens 27, a memory 35, a control circuit 40, an operation switch 42, a liquid crystal display 46, and the like. A microcomputer (hereinafter referred to as “microcomputer”) system and a power supply system such as a power switch 41 and a battery 49 are included. These are mounted on a printed wiring board (not shown) or housed in a housing (not shown).

  The optical illumination light source 21 functions as an illumination light source capable of emitting illumination light Lf, and includes, for example, a red LED and a diffusing lens, a condensing lens, and the like provided on the emission side of the LED. . In the present embodiment, illumination light sources 21 are provided on both sides of the light receiving sensor 23, and configured to irradiate the illumination light Lf toward the reading object R through a reading port of a housing (not shown). . The reading object R corresponds to a display medium such as a packaging container, packaging paper, or a label, for example, and a QR code Q is printed on the surface as a two-dimensional code.

  The light receiving sensor 23 is configured to receive the reflected light Lr irradiated and reflected on the reading object R or the QR code Q. For example, the light receiving sensor 23 includes two light receiving elements which are solid-state imaging elements such as a C-MOS and a CCD. An area sensor arranged in a dimension corresponds to this. The light receiving sensor 23 is mounted on a printed wiring board (not shown) so that incident light incident through the liquid lens 27 can be received by the light receiving surface 23a. The light receiving sensor 23 corresponds to an example of a “light receiving unit” recited in the claims.

  The liquid lens 27 functions as an imaging optical system capable of condensing incident light incident from the outside via the reading port and forming an image on the light receiving surface 23a of the light receiving sensor 23. In the present embodiment, the illumination light Lf emitted from the illumination light source 21 is reflected by the QR code Q, and the reflected light Lr incident on the reading port is collected, whereby the QR code Q is reflected on the light receiving surface 23a of the light receiving sensor 23. The code image can be formed. In particular, as shown in FIG. 2, the liquid lens 27 is configured such that its focal length can be changed according to an applied voltage applied from a drive circuit (not shown) of the control circuit 40. The liquid lens 27 corresponds to an example of “focal length changing means” recited in the claims.

  Next, a configuration outline of the microcomputer system will be described. The microcomputer system includes an amplification circuit 31, an A / D conversion circuit 33, a memory 35, an address generation circuit 36, a synchronization signal generation circuit 38, a control circuit 40, an operation switch 42, an LED 43, a buzzer 44, a liquid crystal display 46, and a communication interface 48. Etc. As the name suggests, this microcomputer system is composed mainly of a control circuit 40 and a memory 35 that can function as a microcomputer (information processing device). The microcomputer system captures an image signal of the QR code Q captured by the optical system described above. It can perform signal processing in terms of hardware and software. The control circuit 40 also performs control related to the entire system of the information code reader 20.

  An image signal (analog signal) output from the light receiving sensor 23 of the optical system is input to the amplification circuit 31 and amplified by a predetermined gain, and then input to the A / D conversion circuit 33. Converted into a digital signal. When the digitized image signal, that is, image data (image information) is input to the memory 35, it is stored in the image data storage area. The synchronization signal generation circuit 38 is configured to generate a synchronization signal for the light receiving sensor 23 and the address generation circuit 36. The address generation circuit 36 is based on the synchronization signal supplied from the synchronization signal generation circuit 38. Thus, the storage address of the image data stored in the memory 35 can be generated.

  The memory 35 is a semiconductor memory device, and corresponds to, for example, a RAM (DRAM, SRAM, etc.) or a ROM (EPROM, EEPROM, etc.). In addition to the above-described image data storage area, the RAM of the memory 35 is configured to be able to secure a work area and a reading condition table used by the control circuit 40 in each processing such as arithmetic operation and logical operation. . In addition, the ROM stores in advance a predetermined program that can execute a reading process, an evaluation process, and the like, which will be described later, and a system program that can control each piece of hardware such as the illumination light source 21 and the light receiving sensor 23.

  The control circuit 40 is a microcomputer capable of controlling the entire information code reader 20 and includes a CPU, a system bus, an input / output interface, and the like. The control circuit 40 can constitute an information processing apparatus together with the memory 35 and has an information processing function. The control circuit 40 is configured to be connectable to various input / output devices (peripheral devices) via a built-in input / output interface. In the present embodiment, the power switch 41, the operation switch 42, the LED 43, A buzzer 44, a liquid crystal display 46, a communication interface 48, and the like are connected. The control circuit 40 is connected to the liquid lens 27 via the drive circuit described above.

  Thereby, for example, monitoring and management of the power switch 41 and the operation switch 42, turning on / off the LED 43 functioning as an indicator, turning on / off the buzzer 44 capable of generating a beep sound and an alarm sound, and further reading the QR code Screen control of the liquid crystal display 46 capable of displaying the code content by Q, communication control of the communication interface 48 enabling serial communication with an external device, and the like are enabled. The focal length of the liquid lens 27 can be adjusted by driving the drive circuit. The external device connected to the communication interface 48 includes a host computer HST corresponding to the host system of the information code reader 20 and the like.

  The power supply system includes a power switch 41, a battery 49, and the like. When the power switch 41 managed by the control circuit 40 is turned on and off, the conduction of the drive voltage supplied from the battery 49 to each device and each circuit described above is established. Or shut off is controlled. The battery 49 is a secondary battery that can generate a predetermined DC voltage, and corresponds to, for example, a lithium ion battery. Further, the battery 49 may be configured to receive power supply from an external device such as the host computer HST connected via the communication interface 48 without using the battery 49. In this case, the battery 49 is unnecessary.

  By configuring the information code reader 20 in this way, for example, when the power switch 41 is turned on and a predetermined self-diagnosis process or the like is normally completed and the QR code Q can be read, the illumination light Lf is emitted. The input of the operation switch 42 (for example, a trigger switch) is given. As a result, when the operator presses the trigger switch to turn it on, the control circuit 40 outputs a light emission signal to the illumination light source 21 based on the synchronization signal, so that the illumination light source 21 that has received the light emission signal turns on the LED. Light is emitted to irradiate illumination light Lf.

  Then, the illumination light Lf irradiated to the QR code Q is reflected, and the reflected light Lr enters the liquid lens 27 through the reading port, so that the light receiving surface 23a of the light receiving sensor 23 has a focal length as described later. An image of the QR code Q, that is, a code image is formed by the adjusted liquid lens 27. Thereby, each light receiving element which comprises the light-receiving surface 23a is exposed, and the signal according to the light reception amount is output from each light receiving element, respectively. The signal output from each light receiving element constitutes the image data of the QR code Q. The image data is binarized and then encoded as QR code Q by performing a predetermined decoding process. Character data etc. will be deciphered. The decrypted contents can be displayed on the liquid crystal display 46 or outputted to the host computer HST via the communication interface 48. The control circuit 40 corresponds to an example of “decoding means” recited in the claims.

  Next, focal length adjustment processing using the information code reader 20 will be described with reference to FIGS. FIG. 3 is a flowchart illustrating the flow of the focal length adjustment process. This focal length adjustment process is executed by the control circuit 40 in accordance with a program stored in the memory 35.

Further, FIG. 4 (A) is a diagram showing a QR code Q in the state not blurred, FIG. 4 (B), each luminance value of the finder pattern FP on the measurement line L ₁ shown in FIG. 4 (A) It is a graph to show. 5 (A) is a diagram showing the QR code Q of blurred and state, and FIG. 5 (B) is a graph showing the respective luminance values of the finder pattern FP on the measurement line L ₁ shown in FIG. 5 (A) It is. In FIGS. 4B and 5B, the vertical axis indicates the luminance value, and the numerical value is high for light colors and low for dark colors.

  When the focal length adjustment process is started, first, an image acquisition process is performed in step S101 of FIG. This image acquisition process is a process of generating image data of QR code Q based on the light reception result by the light receiving sensor 23 and storing it in the memory 35 when the process is performed. The flow of generating the image data of the QR code Q and storing it in the memory 35 is as described above.

  Next, decoding processing is performed in step S103. In this process, the decoding process described above is performed on the image data acquired in step S101. When it is determined that the decoding process has been performed normally and the QR code Q has been successfully decoded (Yes in S105), the focal length adjustment process is terminated without adjusting the focal length of the liquid lens 27.

  On the other hand, if the image data acquired in S101 is blurred or the like, and it is determined in step S105 that the decoding process has failed, a timing process is performed in step S107. In this process, an elapsed time t from when it is determined that the decoding process has failed by a timing device (not shown) such as a clock device included in the control circuit 40 is counted.

  Next, in step S109, a specific pattern detection process is performed. In this process, a process for detecting a finder pattern FP, which is a pattern for detecting the position of the QR code as the specific pattern, is performed from the image data acquired in step S101. The detection process of the QR code position detection pattern is well known and will not be described in detail. However, as a summary, a part where the arrangement of light cells and dark cells is a specific ratio (1: 1: 3: 1: 1) is used. Processing is performed to detect. The finder pattern FP corresponds to an example of “specific pattern” recited in the claims, and the control circuit 40 corresponds to an example of “specific pattern detection means” recited in the claims.

  In step S111, it is determined whether or not the finder pattern FP is detected. If the image data acquired in S101 is blurred and the finder pattern FP is not normally detected (No in S111), step S111 is performed. In S113, it is determined whether or not the elapsed time t is greater than or equal to the allowable maximum processing time ta.

  If it is determined in step S113 that the elapsed time t is less than the allowable maximum processing time ta (No in S113), a focal length changing process is performed in step S115. In this process, the liquid lens 27 is adjusted to change its focal length in accordance with the voltage applied by the drive circuit of the control circuit 40. Specifically, for example, 1V is applied to the liquid lens 27 as an initial voltage, and the voltage changed to, for example, 2V is applied to the liquid lens 27 by this focal length changing process. That is, by determining the voltage to 2V, the focal length corresponding to this applied voltage is determined.

  In step S101, the reflected light Lr through the liquid lens 27 having the focal length changed in S115 is received by the light receiving sensor 23, whereby image data based on the light reception result is acquired. On the other hand, the processing after step S103 described above is performed. In the focal length changing process in step S115, the changed voltage is applied to the liquid lens 27 until it is determined Yes in any one of steps S105, S111, and S113. The applied voltage changed in this way is stored in the memory 35 by the applied voltage storing process in step S117.

When the finder pattern FP is normally detected in step S111 described above (Yes in S111), blur amount calculation processing is performed in step S119. In this process, calculated as the blur amount F = Y-X from the difference between the amplitudes X and amplitude Y of the predetermined position in each of luminance values constituting a finder pattern FP at the upper measuring line L _1. The blur amount may be calculated from the difference between the luminance value of one light cell constituting the finder pattern FP and the luminance value of another light cell different from the one light cell, or the finder pattern FP. The amount of blur may be calculated from the difference between the luminance value of one dark cell constituting the dark cell and the luminance value of another dark cell different from this one dark cell.

  Specifically, as shown in FIG. 4A, when the finder pattern FP is not blurred, the difference between the amplitude X and the amplitude Y becomes small as shown in FIG. The amount F becomes smaller. On the other hand, as shown in FIG. 5A, when the finder pattern FP is blurred, the difference between the amplitude X and the amplitude Y becomes large as shown in FIG. growing. At this stage, since it is determined No in Step S105 and then Yes in Step S111, the finder pattern FP is blurred as shown in FIG. Is getting bigger. At this stage, a voltage of 2 V is applied to the liquid lens 27, and the blur amount F is calculated as 10, for example, in step S119. The control circuit 40 corresponds to an example of the “blur condition calculation unit” described in the claims.

  Next, in step S <b> 121, an applied voltage and blur amount storing process is performed, and the applied voltage and the blur amount F corresponding to the applied voltage are stored in the memory 35. If it is determined in step S123 that the elapsed time t is less than the allowable maximum processing time ta (No in S123), a focal length changing process is performed in step S125. In this process, the voltage changed in increments of 1V is applied to the liquid lens 27 until the blur amount F increases. When the blur amount F increases, a voltage that is changed in increments of 0.1 V is applied. That is, by determining the voltage to a predetermined value, the focal length corresponding to the applied voltage is determined. The control circuit 40 corresponds to an example of “focal length determination means” described in the claims.

FIG. 6A is a chart showing the relationship between the applied voltage value applied to the liquid lens in increments of 1V and the focal length, and FIG. 6B is an application applied to the liquid lens in increments of 0.1V. It is a graph which shows the relationship between a voltage value and a focal distance.
Specifically, the voltage changed from 2V to 3V in step S125 is applied to the liquid lens 27. As a result, the image data is acquired in step S101 by the liquid lens 27 whose focal length has been changed, and the blur amount F is calculated as, for example, 6 again in step S119 (see FIG. 6A).

  Since the blur amount F is reduced, the voltage changed from 3 V to 4 V in step S125 is applied to the liquid lens 27. Thus, the image data is acquired in step S101 by the liquid lens 27 whose focal length has been changed, and the blur amount F is calculated as 10 again in step S119, for example.

  Since the blur amount F is increased, a voltage changed in steps of 0.1V between 2V and 3V is applied to the liquid lens 27 in step S125. Thus, when a voltage is applied to the liquid lens 27 in increments of 0.1V, as shown in FIG. 6B, the case where a voltage of 2.7V is applied to the liquid lens 27 is most blurred in increments of 0.1V. It can be seen that the amount F becomes smaller.

  In this way, since the image data becomes clear by changing the applied voltage applied to the liquid lens 27 so as to reduce the blur amount F, it is determined in step S105 that the QR code Q has been successfully decoded. Then, the focal length adjustment process ends. On the other hand, when the elapsed time t is equal to or greater than the allowable maximum processing time ta, it is determined Yes in step S113 or S123, and the focal length adjustment process is terminated.

  As described above, in the information code reader 20 according to the present embodiment, the reflected light Lr from the QR code Q is changed by the liquid lens 27 functioning as the focal length changing means, and the light receiving surface of the light receiving sensor 23 is changed. It is condensed on 23a. When the blur amount F (blurring degree) is calculated from the brightness value of the finder pattern FP of the QR code Q, the voltage applied to the liquid lens 27 is determined so as to reduce the blur amount F. The focal length is changed by the liquid lens 27 in accordance with the applied voltage determined in this way.

Thus, since the focal length is changed by the liquid lens 27 according to the applied voltage determined according to the blur amount F, the focal length can be changed so as to suppress the blur. For this reason, the recognition failure resulting from blurring can be suppressed. In particular, since the blur amount F is calculated from the brightness value of the finder pattern FP, which is a specific pattern, the process for determining the applied voltage is accelerated compared to the case where the blur amount F is calculated from the brightness values of the entire region. Can be planned.
Accordingly, it is possible to suppress recognition failure due to blur without reducing the reading speed.

  In the information code reader 20 according to the present embodiment, the finder pattern FP, which is a specific pattern, is a position detection pattern for detecting the position of the two-dimensional code, and therefore it is easy to recognize the specific pattern. The amount F (the degree of blur) can be calculated reliably.

  Furthermore, in the information code reader 20 according to the present embodiment, the liquid lens 27 is employed as the focal length changing means, and the focal length is changed only by changing the voltage applied to the liquid lens 27. Therefore, the focal length is changed. Can be easily adjusted. Moreover, since there are few drive parts, such as a motor, durability can be improved.

In addition, this invention is not limited to the said embodiment, You may actualize as follows, and even in that case, an effect | action and effect equivalent to the said embodiment are acquired.
(1) FIG. 7 (A) is a diagram showing the QR code Q of blurred and state, FIG. 7 (B), the timing pattern TP and quiet zone QZ on the measurement line _{L 2} shown in FIG. 7 (A) It is a graph which shows each luminance value.
In out-of-focus-amount calculating process in step S119 described above is not limited to calculating blur amount F from the luminance values of the finder pattern FP of on measurement line L _1, bright cells and dark cells in the above measurement line L ₂ The blur amount F is calculated from the difference between the brightness value of the light cell in the timing pattern TP in which are alternately arranged and the brightness value of the quiet zone QZ that is the outer edge of the QR code Q and is composed only of the light cell. May be.

  Specifically, as shown in FIG. 7A, when the QR code Q is blurred, as shown in FIG. 7B, the brightness value of the light cell in the timing pattern TP and the quiet zone Since the difference from the luminance value of QZ is increased, the blur amount F is increased. Even in this way, the blur amount F can be reliably calculated.

(2) The information code reader 20 according to the present embodiment is not limited to suppressing the recognition failure due to blur by performing the focal length adjustment process on the QR code Q, but also includes the timing pattern TP and the quiet zone QZ. A recognition failure due to blur may be suppressed by performing a focal length adjustment process on a two-dimensional code in which, for example, Data Matrix code is defined.

(3) The blur amount F is not limited to being calculated as the blur amount F = Y−X from the difference between the amplitude X and the amplitude Y at a predetermined position in each luminance value constituting the finder pattern FP. You may calculate from a brightness | luminance gradient.

(4) In steps S115 and S125, the applied voltage is not limited to changing in increments of 1V, the applied voltage may be changed in increments of 0.1V, and the increment width is adjusted according to the blur amount F or the like. Also good.

(5) The liquid lens 27 is not limited to condensing the reflected light Lr from the QR code Q on the light receiving surface 23a of the light receiving sensor 23 by changing its focal length. For example, focal length changing means that can change the focal length with a motor or the like may be employed.

(6) In steps S113 and 123, when the elapsed time t is determined to be equal to or greater than the allowable maximum processing time ta, it is determined that the determination is Yes and the focal length adjustment processing is not terminated. If it is not determined that the decoding is successful even if the application voltages of all the patterns having the set step width are applied to the liquid lens 27, the determination may be Yes and the focal length adjustment process may be terminated.

20. Information code reader (optical information reader)
23. Light receiving sensor (light receiving means)
27 ... Liquid lens (focal length changing means)
40... Control circuit (decoding means, specific pattern detection means, blur condition calculation means, focal length determination means)
F ... Bokeh amount (blur condition)
FP ... Finder pattern (specific pattern)
TP ... Timing pattern (specific pattern)
Q ... QR code (two-dimensional code)
QZ ... Quiet Zone (specific pattern)
X, Y ... amplitude

Claims (5)

Optical information capable of reading a two-dimensional code composed of a plurality of light-colored cells and a plurality of dark-colored cells and including a specific pattern in which the light-colored cells and the dark-colored cells are arranged in a predetermined order In the reading device,
A focal length changing means capable of collecting the reflected light from the two-dimensional code and changing the focal length;
A light receiving means for receiving the reflected light collected by the focal length changing means;
Decoding means for performing decoding processing based on a light reception result by the light receiving means;
Specific pattern detecting means for detecting the specific pattern based on a light reception result by the light receiving means;
A blur condition calculating means for calculating a blur condition from a luminance value of the specific pattern detected by the specific pattern detecting means;
A focal length determination means for determining a target focal distance based on the blur condition calculated by the blur condition calculation means;
With
The optical distance reading unit changes the focal length based on the target focal length determined by the focal length determination unit.   The optical information reading apparatus according to claim 1, wherein the specific pattern is a position detection pattern for detecting a position of the two-dimensional code.   The specific pattern includes a timing pattern in which the light cells and the dark cells are alternately arranged, and a quiet zone that is an outer edge portion of the two-dimensional code and includes only the light cells. The optical information reader according to claim 1.   The optical information reading apparatus according to claim 1, wherein the blur condition calculating unit calculates the blur condition from a luminance gradient in the specific pattern.   The optical information reading apparatus according to claim 1, wherein the focal length changing unit is a liquid lens that can change the focal length in accordance with an applied voltage.

Images