JP2013118006A - Code reading device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a code reading device capable of efficiently and securely focusing on a code symbol to be read to read the symbol.SOLUTION: The code reading device includes a variable focus lens, focus driving means, imaging means, light emitting means for emitting a laser beam, and control means for performing operation control and code symbol reading. The control means includes: first focus means for performing focus adjustment by repeatedly performing focus setting based upon coordinates of a bright point formed by the beam within a first execution time; second focus means for performing focus adjustment based upon levels of contrast respectively calculated while changing a focus position within a second execution time; counting means for counting the numbers of times of execution of the focus adjustment performed by the first and second focus means, respectively; and focus adjustment time setting means for setting the first and second execution times so that they decrease as the numbers of times of execution of the focus adjustment increase, respectively.

Description

  The present invention relates to a code reader that reads a barcode or a two-dimensional code.

  2. Description of the Related Art Conventionally, code readers that acquire information by decoding symbols such as one-dimensional barcodes and two-dimensional codes are known. This code reader is equipped with a two-dimensional imager device that optically images a symbol and acquires data by decoding (decoding) the symbol using the captured image data.

  When the code is read by the code reader, it is necessary to perform a focus process for matching the focal position of the lens optical system used for imaging with the symbol to be read. This focus processing includes a method of changing the distance from the lens to the reading target using a fixed focus lens and a method of changing the focal position of the lens using a variable focus lens. As a lens using a fixed focus lens, for example, in Patent Document 1, a bar code symbol to be read or a moving direction of a bar code reader is instructed by changing a generation pattern of light emission or beep sound. A technique in which a user places a barcode symbol and a barcode reader at an appropriate relative position is shown.

  On the other hand, in a bar code reader using a variable focus lens, the focus position is adjusted by autofocus. One autofocus method is to irradiate a spotter beam with a laser beam at a predetermined angle with respect to the optical axis of the lens, and then read it according to the position of the spotter beam image (bright spot) formed on the code surface. There is a laser focus method (for example, Patent Document 2) that adjusts the focus of a lens by measuring a distance to an object. As another method of autofocusing, symbols to be read are captured one after another while sequentially changing the focal position, and a focus image is obtained based on characteristic values (for example, image contrast values) in each imaging data. There is a method (contrast focus method or the like) in which the focus position is identified by searching for and the focus of the lens is adjusted. The focus processing by the laser focus method can be executed in a shorter time compared to the focus processing by the contrast focus method, but the contrast focus method has a feature that the accuracy of autofocus is higher.

  Therefore, there is a bar code reader equipped with an autofocus function using both the laser focus method and the contrast focus method. In such a barcode reader, focus processing and decoding processing are repeatedly performed for a predetermined time period until decoding by any autofocus method is successful. In such a focus process, the focal position is determined asymptotically asymptotically. Therefore, a technique is used in which the code data reading speed is increased by reducing the unnecessary focus time by gradually shortening the predetermined focus time each time the focus processing is repeated.

JP 2001-184552 A Japanese Patent Laid-Open No. 05-217013

  However, as described above, there is a difference in time required for focus processing between the laser focus method and the contrast focus method. Therefore, there is a problem that efficient decoding is not performed if the predetermined focus time is uniformly reduced every time the focus processing is performed.

  An object of the present invention is to provide a code reading apparatus capable of reading a symbol efficiently and surely focusing on a code symbol to be read.

In order to achieve the above object, the present invention
A variable focus lens,
Focus drive means for adjusting the focal position of the variable focus lens;
Imaging means for acquiring image data in the imaging direction by the variable focus lens;
A light emitting means for emitting a laser beam in the imaging direction;
Control means for controlling operations of the focus driving means, the imaging means, and the light emitting means, and reading code symbols included in the acquired image data;
With
The control means includes
Focus is performed by repeatedly performing focus setting within the first execution time based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the emitted laser beam. First focusing means for adjusting;
Focus adjustment is performed by changing the focus position within a second execution time and moving the focus position based on the magnitude of contrast calculated for each of the image data acquired for each changed focus position. Second focusing means to perform,
Counting means for counting the number of executions of focus adjustment by the first focus means and focus adjustment by the second focus means;
The first execution time is set to be shortened from a predetermined first initial setting time so that the first execution time becomes shorter as the number of executions of focus adjustment by the first focus means increases, and the second A focus adjustment time setting means for setting the second execution time to be shortened from a predetermined second initial setting time so that the second execution time is shortened as the number of times of focus adjustment by the focus means increases;
A code reading device comprising:

  According to the present invention, there is an effect that the code reading apparatus can read the symbol with a focus on the code symbol to be read efficiently and surely.

It is a front view which shows the whole structure of the code reader of embodiment of this invention. It is a block diagram which shows the internal structure of a code reader. It is a top view of an imager module and an imager controller. It is a figure explaining a mode when a symbol is placed in the 1st position and the 2nd position far from the 1st position. It is a figure which shows the frame image which imaged the symbol placed in the 1st position and the 2nd position. It is a figure which shows the change of the contrast value at the time of changing the frame image which imaged the symbol set | placed on the 2nd position when there is a focus position in the 1st position and the 2nd position, and the focus position. It is a figure which shows typically the time distribution in the reading operation | movement of a barcode symbol. It is a flowchart which shows the control procedure of a decoding process. It is a flowchart which shows the control procedure of the decoding process using a laser focus method. It is a flowchart which shows the control procedure of the decoding process using the contrast focus method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing an overall structure of a code reading device according to an embodiment of the present invention.
The code reader 1 (computer) of this embodiment is a portable device having a function of reading symbols such as a one-dimensional barcode and a two-dimensional code.

  The code reading device 1 includes a case 2 as a housing. The code reading device 1 includes a trigger key 12 </ b> A, various keys 12 </ b> B, and a display unit 14 on the front surface of the case 2. The code reading device 1 includes a trigger key 12 </ b> C on the side surface of the case 2. In addition, the code reading device 1 includes an imager module 21 at the tip of the case 2.

  The trigger keys 12 </ b> A and 12 </ b> C are trigger keys that receive an input of a symbol reading operation start command by the imager module 21. The various keys 12B include input keys such as numbers and characters, function keys, and the like, and accept input operations of various information. The display unit 14 displays information such as menus and statuses related to input operations, and information such as statuses and decoding results when a symbol reading operation using the imager module 21 is executed.

  FIG. 2 is a block diagram showing an internal configuration of the code reading device 1.

  The code reading device 1 includes a CPU (Central Processing Unit) 11 as a control means (first focus means, second focus means, counting means, focus adjustment time setting means), an operation unit 12, and a RAM (Random Access Memory). 13, a display unit 14, a storage unit 15, a communication unit 16, an imager controller 19, an imager module 21, a power supply unit 22, and a laser drive power supply 23.

  The units other than the imager module 21 and the power supply unit 22 of the code reading device 1 are connected to each other via a bus 24. The imager module 21 includes an imaging element 211 as an imaging unit, a variable focus lens 212, a focus mechanism 213 as a focus driving unit that drives the variable focus lens 212 to adjust a focus, an aimer 214 as a light emitting unit, And illumination 215 as a lighting means.

  The CPU 11 controls each unit of the code reading device 1. The CPU 11 reads out various programs from the storage unit 15 and expands them in the RAM 13, and executes various processes in cooperation with the programs expanded in the RAM 13.

  The operation unit 12 has a key group such as various keys 12B and trigger keys 12A and 12C, receives a pressing operation of each key of the key group, converts the operation information into an input signal, and outputs the input signal to the CPU 11.

  The RAM 13 is a volatile semiconductor memory and provides a working memory space to the CPU 11. The RAM 13 is used for temporary storage of various data and for expansion when executing various programs.

  The display unit 14 includes an LCD (Liquid Crystal Display), an EL (Electro-Luminescent) display, and the like, and displays various types of information according to display information input from the CPU 11.

  The storage unit 15 is a readable / writable nonvolatile memory, for example, a flash memory. The storage unit 15 stores various programs and setting data in advance. Alternatively, the storage unit 15 may be an EEPROM (Electrically Erasable and Programmable Read Only Memory) or a hard disk. Alternatively, in a dedicated code reader, a ROM (Read Only Memory) may be used. The program stored in the storage unit 15 includes a program 15a for controlling the operation of the focus mechanism 213 to focus on the symbol and performing a decoding process. The CPU 11 expands this program in the RAM 13 and will be described later. The decoding control processing shown in the processing flow is executed.

  The communication unit 16 includes a communication antenna, a signal processing unit, a modulation unit, a demodulation unit, and the like, and performs wireless communication with an access point. An access point is a device that relays communication. That is, the code reading device 1 communicates with an external device such as a server device connected to the access point via the access point by the communication unit 16. The communication unit 16 processes a signal of transmission information with a signal processing unit, modulates the signal with a modulation unit, and wirelessly transmits the transmission information as a radio wave from the communication antenna to the access point. In addition, the communication unit 16 receives radio waves transmitted from the access point through the communication antenna, demodulates them by the demodulation unit, and performs signal processing on the signals by the signal processing unit to obtain reception information.

  Moreover, the communication part 16 is good also as a radio | wireless communication part which carries out radio | wireless communication with a server apparatus via a base station by a mobile telephone communication system. The communication unit 16 may be a cradle on which the code reading device 1 is placed or a wired communication unit that performs wired communication with the server device via a communication cable.

  The imager controller 19 controls the operation of each part of the imager module 21 and controls transmission / reception of data between the imager module 21 and other parts of the code reader 1. The imager controller 19 is configured by a semiconductor circuit such as an ASIC (Application Specific Integrated Circuit).

  The imager controller 19 synchronizes with the image data from the image sensor 211, the frame synchronization signal synchronized with the output timing of one frame of the captured image data, the line synchronization signal synchronized with the output timing of one line of the image data, and the image data. And a clock signal for input. The imager controller 19 monitors the transfer timing of the image data to the RAM 13 based on the frame synchronization signal, line synchronization signal, and clock signal. The imager controller 19 has a DMA (Direct Memory Access) transfer function for transferring image data input from the image sensor 211 to the imager controller 19 directly to the RAM 13 without using the CPU 11.

  The imager controller 19 controls the operation of the focus mechanism 213 in accordance with the monitoring status of the image data transfer timing, thereby changing the focal position of the variable focus lens 212 in real time.

  The imager module 21 is a module that images the symbol of the subject by adjusting the focal position of the variable focus lens 212. The imaging element 211 is a CMOS (Complementary Metal Oxide Semiconductor) image sensor, although not limited thereto. The image sensor 211 captures (acquires) image data by photoelectrically converting a subject image incident via an optical system including the variable focus lens 212 and converting it into an electrical signal.

  The image sensor 211 outputs the image data of the line designated by the image area designation signal input from the imager controller 19 to the imager controller 19 as line data line by line. Further, the image sensor 211 outputs a frame synchronization signal, a line synchronization signal, and a clock signal to the imager controller 19. The variable focus lens 212 is a liquid lens, for example, and is an optical element that constitutes a part of the optical system of the imager module 21. This liquid lens has a configuration in which the focal position can be changed at high speed in accordance with the voltage applied to the focus mechanism 213.

  The focus mechanism 213 is a drive unit that adjusts the focal position of the variable focus lens 212. When the variable focus lens 212 is a liquid lens, the focus mechanism 213 is an electric circuit including an electrode for applying a voltage to a predetermined portion of the liquid lens. When a solid lens such as glass or plastic is used as the variable focus lens 212, a voice coil motor is used for the focus mechanism 213, for example.

  The aimer 214 measures a distance measurement index between the imager module 21 and the symbol that is a subject, and a laser beam as a spot light (target light) serving as a reference for matching the imaging direction of the imager module 21 and the subject direction. A laser diode (LD) that emits light. The illumination 215 is composed of a light source such as an LED (Light Emitting Diode), for example, and emits irradiation light for brightly illuminating the subject and the surrounding area.

  The power supply unit 22 is composed of a secondary battery or the like, and supplies power to each unit of the code reading device 1. The laser drive power supply 23 supplies power when driving the aimer 214 to emit spot light. The laser drive power source 23 is disposed on the main board together with the imager controller 19.

Next, the arrangement of each part of the imager module 21 will be described in detail with reference to FIG.
FIG. 3 is a plan view of the imager module 21.

  In the imager module 21, the optical system 212 </ b> A including the variable focus lens 212 is arranged so as to be able to image the outside of the imager module 21. In addition, the image sensor 211 is disposed perpendicular to the optical axis of the optical system 212A. The aimer 214 and the illumination 215 are arranged in parallel with the optical system 212A and the focus mechanism 213. The aimer 214 is arranged such that the emitted laser beam is included in an angle of view that can be captured by the imager module 21 (the optical system 212A and the image sensor 211) within a focal length that can be changed with respect to the optical system 212A. . In the present embodiment, the laser beam is emitted in a direction parallel to the optical axis of the optical system 212A. Also, the illumination 215 is arranged so that the fan-shaped light is included in an angle of view that can be photographed by the imager module 21 (the optical system 212A and the image sensor 211) within a focal length that can be changed for the optical system 212A. Yes.

  Next, a focus adjustment method of the optical system 212A will be described.

  FIG. 4 is a diagram illustrating a state where a symbol is placed at a first position and a second position far from the first position. FIG. 5 is a diagram illustrating a frame image obtained by imaging the symbols placed at the first position and the second position.

In FIG. 4, when a plane on which the one-dimensional barcode symbol 41 is displayed is arranged at the first position D1, as shown in FIG. 5A, an image Q1 of the symbol 41 in the frame image q1. Is obtained. At this time, when laser light is emitted from the aimer 214, the laser light reaches the surface of the symbol 41 to form a bright spot. In the example of FIG. 5A, a bright spot E1 is formed near the right end of the image Q1 of the symbol 41.
The barcode symbol 41 is not particularly limited, and is, for example, printed on white paper.

  On the other hand, in FIG. 4, when the plane on which the symbol 41 is displayed is arranged at the second position D2 that is farther from the imager module 21 than the first position D1, as shown in FIG. The area occupied by the image Q2 of the symbol 41 in the frame image q2 is relatively smaller than the area occupied by the image Q1 of the symbol 41 in the frame image q1. At this time, when the laser beam is emitted from the aimer 214 and irradiated near the right end of the symbol 41, the position of the bright spot E2 formed in the frame image q2 is compared with the position of the bright spot E1 in the frame image q1. The position is closer to the center of the frame image q2.

  That is, in the frame image, the imaging area of the same subject (code symbol) acquired by the optical system 212 </ b> A and the imaging device 211 becomes small in inverse proportion to the square of the distance from the imager module 21. In the frame image, the distance from the center of the frame image to the bright spot position formed by the laser beam becomes smaller in inverse proportion to the distance from the imager module 21 to the symbol 41, and gradually approaches the center of the frame image. . Therefore, the distance from the imager module 21 to the symbol 41, that is, the focal position to be set by the imager module 21 can be obtained from the position (coordinates) of the bright spot in the frame image.

  In the laser focus method, based on the above-described principle, the aimer 214 is turned on to acquire a frame image, the coordinates of the bright spot in the frame image are identified, and the focal position is calculated based on the coordinates of the bright spot. At this time, if the position of the bright spot of the laser beam and the focus position of the variable focus lens 212 do not match, the image of the bright spot becomes unclear. In such a case, the coordinates of the center of the bright part can be obtained by obtaining the center of gravity position of the detected bright part.

  FIG. 6 is a diagram illustrating a frame image obtained by capturing the symbol placed at the second position when the focal position of the variable focus lens is at the first position and the second position.

  When the symbol 41 of the one-dimensional barcode is placed at the position D2 in FIG. 4, the imaging data obtained when the focal position of the imager module 21 overlaps the position D2 is the clearest, and the focal position is at the position D2. On the other hand, if it is shifted back and forth, the obtained imaging data becomes unclear. For example, as shown in FIG. 6A, when the focal position of the imager module 21 is at the position D1, the focal position is closer to the imager module 21 than the position D2 of the symbol 41. The barcode image Q3 in the frame image q3 to be displayed is unclear as a whole. As a result, in the predetermined area F3 including the barcode image Q3, the contrast is small between the space portion that is the bright portion and the bar portion that is the dark portion in the barcode symbol. On the other hand, as shown in FIG. 6B, when the focal position overlaps with the position D2, the outline of the barcode image Q4 in the obtained frame image q4 becomes clear and the bright part and the dark part are separated. The contrast increases in a predetermined area F4 including the image Q4.

  In the contrast focus method, using the above-mentioned features, frame image data is acquired while changing the focus position, the contrast value is calculated for each frame image, and the focus position where the contrast value is maximized is selected. Determine the focal position for the code symbol.

  The method for calculating the contrast value is not particularly limited. For example, an MRD value (Minimum Reflectance Difference) is used. This MRD value is obtained by the difference between the minimum reflectance of the space portion that is the bright portion and the maximum reflectance of the bar portion that is the dark portion. The contrast value is calculated by extracting the data of the regions F3 and F4 in FIGS. 6A and 6B from the frame image data. These areas F3 and F4 are set, for example, near the center of the frame images q3 and q4 so as to reduce the ratio occupied by areas other than the barcode images Q3 and Q4. The settings of the areas F3 and F4 do not necessarily include the entire barcode images Q3 and Q4.

  FIG. 6C shows an example of a change pattern of contrast values when the focus position of the variable focus lens 212 is changed in order by the focus mechanism 213 in the imager module 21.

  When a frame image is acquired while changing the focal position back and forth, and the contrast value of the area set in each frame image is obtained in order, a barcode image of a size that can be distinguished in the area set in the frame image Is present, the obtained contrast value shows a maximum value (maximum value) on the way. The focal position showing the maximum value is expected to be the position closest to the position where the barcode symbol is placed. Therefore, the barcode symbol is decoded using the imaging data obtained by aligning the focal position of the variable focus lens 212 with the focal position showing the maximum contrast value and imaging.

  Next, the procedure of the focus adjustment operation and the barcode reading operation in the code reading device 1 of the present embodiment will be described.

  FIG. 7 is a diagram schematically showing time distribution in the barcode reading operation.

In the barcode reading operation of the present embodiment (hereinafter referred to as decoding process), focus adjustment by the laser focus method, frame image acquisition, symbol decoding (hereinafter collectively referred to as laser focus process), contrast The symbol image is successfully decoded by alternately executing focus adjustment by the focus method, frame image acquisition, and symbol decoding (hereinafter collectively referred to as contrast focus processing) for each independently set execution time. Repeat until.
The same processing is performed even when reading a two-dimensional code other than the one-dimensional barcode.

First, according to the first laser focus process, the focus position of the variable focus lens 212 is changed to the set position while the aimer 214 is turned on, and a frame image at the changed focus position is acquired. When the bright spot formed by the beam of the aimer 214 is searched from the acquired frame image and the bright spot is recognized, the focal position is calculated based on the coordinates in the frame image, and the variable focus lens The focal position 212 is adjusted to this calculated value (laser focus (focus setting)).
Here, the calculation of the focal position is performed by storing table data indicating the correspondence between the coordinates of the bright spot and the focal position in the storage unit 15 in advance. Or it is good also as making it calculate based on numerical formula.

  Next, an image is captured by capturing the image with the aimer 214 turned off at this focal position (capture). Then, the symbols included in the captured image are decoded (decode). As a method of recognizing a symbol from image data at the time of decoding, various conventionally known techniques can be used. When symbol decoding fails, focus adjustment is performed by repeating these series of processing within the set execution time (T0 × S0) (first execution time, first initial setting time). Here, the constant T0 is a predetermined unit time for laser focus (for example, an average required time for a series of processes of laser focus, capture, and decode), and the predetermined number S0 is a set laser focus process. An integer indicating the maximum number of executions of.

If the decoding by the first laser focus process fails, the barcode reading operation by the contrast process is performed next. According to the contrast focus processing, first, the focal position of the variable focus lens 212 is changed within a predetermined range over a set execution time (T1 × S1) (second execution time, second initial setting time). While acquiring the frame image.
Here, the predetermined range for changing the focal position is determined before and after the focal position when the focal position is obtained by the laser focus in the immediately preceding laser focusing process, and the focal position is obtained. If not, it is determined based on the initial setting data stored in the storage unit 15 in advance.
The constant T1 is a unit time for focus adjustment in a predetermined contrast focus process (for example, a time required when a focus position change with a predetermined maximum number of steps is performed in one focus adjustment). The predetermined number S1 is an integer indicating the set maximum number of executions of the contrast focus processing. Next, with respect to the acquired frame image, a contrast value is calculated from data in a predetermined region in each frame image, and the focal position of the variable focus lens 212 is moved to the focal position of the frame image where the maximum contrast value is obtained. By doing so, focus adjustment is performed (contrast focus).

  Then, imaging is performed at the focal position (capture), and symbols included in the acquired frame image are decoded (decode).

  When the symbol decoding by the first contrast focus processing fails, the second laser focus processing is performed. The contents of the second laser focus process differ from the contents of the first laser focus process in the following two points. (1) When the maximum contrast value is obtained in the contrast focus process, the detection of the bright spot position and the calculation of the focus position by the emission of the aimer 214 are started at the focus position where the contrast value is obtained. (2) The execution time for performing the laser focus process is changed to T0 × (S0-1).

That is, in the second and subsequent laser focus processing, only the limited range is searched using the focus position data obtained by the laser focus processing and / or the contrast focus processing performed before the processing. The focus position is obtained again in a shorter execution time.
In this way, after the laser focus processing has been performed S0 times while the execution time Ta (first execution time) in the Nth laser focus processing is shortened to T0 × (S0−N + 1), the symbol still remains If the decoding is not successful, the laser focus process times out. In the laser focus process, for example, the number of executions of a process loop of laser focus, capture, and decoding repeated within a single process is reduced by shortening the predetermined time.

The second and subsequent contrast focus processes are performed in the same manner. That is, in the M-th contrast focus process, contrast values are obtained at a plurality of focus positions set within a predetermined range before and after the focus position most recently obtained in the laser focus process or the contrast focus process. The symbol is decoded by selecting the focal position where the contrast value is maximized. In addition, the execution time Tb (second execution time) set for focus adjustment in the Mth contrast focus processing is T1 × (S1−M + 1).
If the code has not been successfully decoded after the S1 contrast focus process, the contrast focus process times out. In contrast focus processing, when the predetermined time is shortened, for example, the number of steps of the focal position to be changed by one focus adjustment is reduced.

  As described above, the number of executions of the laser focus process and the number of executions of the contrast focus process are managed independently. Even if one of the focus processes times out, the other focus process is continued until the other focus process times out. On the other hand, if the symbol has been successfully decoded by any focus processing, the decoding processing ends at that point.

Next, a procedure of control processing executed by the CPU 11 for the barcode reading operation will be described.
FIG. 8 is a flowchart showing the control procedure of the decoding process.

  The decoding control process executed by the CPU 11 is started after the CPU 11 expands the program 15 a read from the storage unit 15 on the RAM 13 based on an input signal based on an operation on the operation unit 12 by the user.

First, the CPU 11 sets an initial value for laser focus processing and an initial value for contrast focus processing (step S11). Specifically, as an initial value for focus adjustment by the laser focus method, the CPU 11 performs focus adjustment in the maximum number of executions S0 of the laser focus processing, the number of executions N = 0, and the first laser focus processing. Set the initial focus position. Further, as an initial value for the contrast focus process, the CPU 11 changes the maximum number of executions of the contrast focus process S1, the number of executions M = 0, and the change of the focus position when the focus adjustment is performed in the first contrast focus process. Set the number of steps and step interval.
Note that the maximum number of executions S0 and S1 need not be the same.

  Next, the CPU 11 determines whether or not the remaining number of times of laser focus processing (S0-N) is “0”. If it is determined that the remaining number of times (S0-N) is “0”, the processing of the CPU 11 proceeds to step S17. If it is determined that the remaining number of times (S0-N) is not “0”, the processing of the CPU 11 proceeds to step S13.

  When the process of the CPU 11 proceeds to step S13, the CPU 11 sets the execution time Ta = T0 × (S0−N) of the laser focus process. Subsequently, the CPU 11 executes a control process (laser focus control process) of the laser focus process (step S14). The processing content of step S14 will be described in detail later. Then, the CPU 11 determines whether or not the barcode symbol has been successfully decoded (step S15). If it is determined that the decoding is successful, the processing of the CPU 11 proceeds to step S30. When it is determined that the decoding has not been successful, the CPU 11 adds 1 to the number of executions N of the laser focus process (step S16). Then, the process of the CPU 11 proceeds to step S17.

  When the process of the CPU 11 proceeds to the step S17 following the branch process of the step S12 or the process of the step S16, the CPU 11 determines whether or not the remaining number of contrast focus processes (S1-M) is “0”. To do. If it is determined that the remaining number of times (S1-M) is “0”, the processing of the CPU 11 proceeds to step S22. If it is determined that the remaining number of times (S1-M) is not “0”, the CPU 11 sets the focus adjustment execution time Tb = T1 × (S1-M) in the contrast focus process (step S18). Then, the CPU 11 executes control processing for contrast focus processing (contrast focus control processing) (step S19). The processing content of step S19 will be described in detail later.

  Next, the CPU 11 determines whether or not the barcode symbol has been successfully decoded by the contrast focus process (step S20). If it is determined that the decoding is successful, the processing of the CPU 11 proceeds to step S30. If it is determined that the decoding has not been successful, the CPU 11 adds 1 to the number M of executions of the contrast focus process (step S21). And the process of CPU11 transfers to step S22.

  When the process proceeds to the process of step S22 after the branch process of step S17 or the process of step S21, the CPU 11 determines that the remaining number of times of laser focus processing (S0-N) and the remaining number of times of contrast focus processing (S1-M). It is determined whether or not both are “0”. If it is determined that both are “0”, the processing of the CPU 11 proceeds to step S31. If it is determined that at least one of them is not “0”, the process of the CPU 11 returns to step S12, and the CPU 11 performs a control process related to the second and subsequent laser focus processes.

  When the process proceeds to the process of step S30 by the branch process of step S15 or the branch process of step S20, the CPU 11 outputs successful decoded data (step S30). Then, the decoding control process ends.

  When the process proceeds to step S31 in the branch process of step S22, the CPU 11 outputs a signal indicating that the decoding has failed. Then, the decoding process ends.

  FIG. 9 is a flowchart showing the control procedure of the laser focus process called in step S14.

  When the laser focus control process is started, the CPU 11 first sends a command to the laser drive power source 23 and the imager controller 19 to turn on the aimer 214 (step S41). At this time, the CPU 11 starts counting the elapsed time from the start of the laser focus control process. The CPU 11 sends a command to the imager controller 19 to operate the focus mechanism 213, and moves the focal position of the variable focus lens 212 to the set position (step S42).

  The CPU 11 sends a command to the imager controller 19 to cause the image pickup device 211 to pick up an image, and directly transfers image pickup data sent from the image pickup device 211 to the imager controller 19 to the RAM 13 by DMA (step S43). At this time, as data to be transferred to the RAM 13, only data in a range in which bright spots due to light emission of the aimer 214 can appear may be selected from the imaging data. Then, the CPU 11 sends a command to the laser drive power source 23 and the imager controller 19 to turn off the aimer 214 (step S44).

  Then, the CPU 11 analyzes the imaging data transferred to the RAM 13 and determines whether or not a bright spot due to light emission of the aimer 214 is detected in the data (step S45). If it is determined that the bright spot due to the light emission of the aimer 214 has not been detected, the process branches to “NO”, and the process of the CPU 11 proceeds to step S54.

  If it is determined that a bright spot due to the emission of the aimer 214 has been detected, the process branches to “YES”, and the CPU 11 identifies the coordinates of the bright spot in the frame image (step S46). Then, the CPU 11 calculates a focal position based on the coordinates of the bright spot (step S47).

  Next, the CPU 11 sends a command to the imager controller 19 to operate the focus mechanism 213 to drive the focal position of the variable focus lens 212 to the calculated position. Specifically, the CPU 11 causes the focus mechanism 213 to apply an applied voltage corresponding to the calculated focus position based on a correspondence table between the focus position stored in the storage unit 15 and the applied voltage to the focus mechanism 213. (Step S48).

  The CPU 11 sends a command to the imager controller 19 to first turn on the illumination 215 (step S49). Subsequently, the CPU 11 causes the image pickup device 211 to pick up an image and sends image data sent from the image pickup device 211 to the imager controller 19 to the RAM 13. DMA transfer is performed (step S50). Then, the CPU 11 sends a command to the imager controller 19 to turn off the illumination 215 (step S51).

  Then, the CPU 11 decodes the captured barcode symbol based on the imaging data transferred to the RAM 13 (step S52). The CPU 11 determines whether the decoding has succeeded (step S53). If it is determined that the process is successful, the process of the CPU 11 returns to the decode control process. On the other hand, if it is determined that the operation has not been successful, the CPU 11 further determines whether or not the set execution time Ta has elapsed (step S54). If it is determined that the execution time Ta has elapsed, the CPU 11 ends the laser focus control process and returns to the decode control process. If it is determined that the execution time Ta has not elapsed, the process of the CPU 11 returns to step S41 and repeats the laser focus control process.

  FIG. 10 is a flowchart showing the control procedure of the contrast focus process called in step S19.

  When the contrast focus control process is started, the CPU 11 first sets the change range of the focus position by the variable focus lens 212 and the number of change steps (step S61). Specifically, the CPU 11 can change the applied voltage range that can be changed based on the applied voltage corresponding to the central focal position calculated most recently by the focus process and the focus control execution time Tb in the contrast focus control process. And the number of change steps is set.

  The CPU 11 sends a command to the imager controller 19 to turn on the illumination 215 (step S62). Subsequently, the CPU 11 sends a command to the imager controller 19 to operate the focus mechanism 213 and change the focal position of the variable focus lens 212 (step S63).

  The CPU 11 sends a command to the imager controller 19 to cause the image pickup device 211 to pick up an image, and causes the image pickup data sent from the image pickup device 211 to the imager controller 19 to be DMA-transferred to the RAM 13 (step S64). Then, the CPU 11 calculates a contrast value in a predetermined area of the imaging data transferred to the RAM 13 (step S65).

  Next, the CPU 11 determines whether or not all applied voltage steps set in the process of step S61 have been set and imaged (step S66). If it is determined that imaging has not yet been performed for all applied voltage steps in the set range, the process returns to step S63, and the CPU 11 repeats the processes of steps S63 to S66 using the applied voltage of the next step. On the other hand, if it is determined that imaging has been performed at all applied voltage steps, the processing of the CPU 11 proceeds to step S67.

  The CPU 11 selects the focal position indicating the maximum value from the contrast values in the imaging data of each calculated focal position, sends a command to the imager controller 19, and focuses the variable focal lens 212 to the selected focal position. Is moved (step S67). Subsequently, the CPU 11 sends a command to the imager controller 19 to cause the image pickup device 211 to pick up an image and cause the image pickup data to be DMA-transferred to the RAM 13 (step S68). Further, the CPU 11 sends a command to the imager controller 19 to turn off the illumination 215 (step S69).

  Then, the CPU 11 decodes the barcode symbol based on the imaging data fetched into the RAM 13 (step S70). When decoding of the symbols is completed, the CPU 11 ends the contrast focus control process and returns to the decode control process.

As described above, according to the code reader 1 of the above embodiment,
Focus adjustment is performed by repeatedly performing focus setting within the execution time Ta based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the laser light beam emitted from the aimer 214 And the focus mechanism 213 is operated within the execution time Tb to change the focal position, and the contrast value is calculated for each image data acquired for each changed focal position, and the maximum (maximum) In combination with the contrast focus method for adjusting the focus by moving the focus position of the variable focus lens 212 to the focus position showing the contrast value, the number of executions of the laser focus process and the contrast focus process is counted independently, Execution times Ta and Tb as the number of executions increases Since each of the configurations is shortened, the focus adjustment can be executed in a shorter time during the second and subsequent focus adjustments, and the laser focus process and the contrast focus process that are greatly different in execution time are independent of each other. Since the execution time of the initial setting is determined and the execution time is shortened independently, even when performing highly accurate contrast processing for the second time or later, processing is performed in a shorter time than necessary due to the influence of the laser focus processing. On the contrary, it is possible to focus on the code symbol efficiently and reliably without setting an unnecessarily long execution time for the laser focusing process.

  Further, according to the laser focus process, the focus position can be adjusted asymptotically by alternately repeating the focus adjustment by the laser focus and the reading of the code symbol. Further, the laser focus process can be terminated when the symbol is successfully read.

  If the code symbol cannot be read successfully, the laser focus process and the contrast focus process are alternately performed, so that the focal position can be efficiently obtained while compensating for the disadvantages of both, and the code symbol can be read. it can.

  In addition, by adjusting the number of continuous executions of the laser focus processing and contrast focus processing as appropriate, the advantages of the laser focus processing that can obtain a certain degree of accuracy in a short time, and finally the focus adjustment with high accuracy can be achieved. The code symbol can be reliably read by taking advantage of the contrast focus processing that can be performed.

  In addition, the image data acquired by the image sensor 211 is transferred to the RAM 13 and the code symbol is read by the CPU 11, thereby simplifying the configuration of the imager controller 19 and direct DMA transfer from the image sensor 211 to the RAM 13. As a result, the reading process can be advanced promptly.

  In particular, since only the data necessary for focus adjustment and code symbol reading is transferred from the image sensor 211 to the RAM 13, the data transfer time can be further shortened to speed up the reading process.

  Also, when focus adjustment is repeated multiple times, the focus is determined based on the previous focus setting and focus adjustment results, and laser focus processing and contrast focus processing are performed, so asymptotically and efficiently improving the focus position accuracy. I can go.

  Further, by using a liquid lens as the variable focus lens 212, it is possible to move to a large number of focus positions at high speed only by changing the applied voltage, particularly when performing the contrast focus processing.

  Further, since the illumination for illuminating the code symbol of the subject is provided, the code symbol can be reliably read without being affected even in a dark place or a shadow portion.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, the CPU 11 detects the bright spot of the aimer 214 based on the imaging data DMA-transferred to the RAM 13, identifies the focal position based on the bright spot coordinates, calculates the contrast value, and decodes the barcode. However, the imager controller 19 may mount these processing functions on the ASIC board so that they can be operated in hardware.

  In the above embodiment, in the contrast focus control process, the illumination 215 is turned on after obtaining the maximum contrast value, and the image data at the focal position is obtained again. It is also possible to perform decoding using each image data in parallel.

  In the above-described embodiment, the laser focus process and the contrast focus process are alternately performed. However, the shift to the other focus process is performed after the deviation or one of them is continuously performed a plurality of times. It's also good. Further, the order of the laser focus process and the contrast focus process may be reversed.

  In the above embodiment, it is determined whether or not the set execution time has elapsed after the series of focus adjustment processes in the laser focus process and the contrast focus process has been completed, and whether or not the same process is to be repeated is determined. However, if the execution time has elapsed due to an interrupt signal, etc., it may be terminated halfway, or if the next iteration is performed before the execution time elapses, the execution time may be exceeded. The presence or absence of repetition may be determined.

  In the above embodiment, the time including all of the focus adjustment, capture, and decoding is set as the execution time for the laser focus process, and only the focus adjustment time is set as the execution time in the contrast focus process. In the laser focus processing, only the focus adjustment time can be set as the execution time, and the time required for capture and decoding may be included as the execution time of the contrast focus processing.

  In the above embodiment, the focus adjustment execution times Ta and Tb are shortened in a linear function, but the execution time can be shortened with an arbitrary pattern such as a quadratic function or an exponential function.

  Moreover, although the solid lens using a liquid lens, glass, etc. was mentioned as an example as a variable focus lens in the said embodiment, it is not limited to these. For example, a variable focus lens using KTN (potassium niobate tantalate, KTa1-xNbxO3), which is a kind of “electro-optic crystal” whose refractive index changes depending on the applied voltage, can also be used.

  Moreover, although the example which used the memory | storage part 15 (for example, flash memory, EEPROM, hard disk, ROM) as a computer-readable medium of the program concerning this invention was disclosed in the said embodiment, it is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also applied to the present invention as a medium for providing program data according to the present invention via a communication line.

In the above embodiment, the decoding process is terminated when the code symbol is successfully read. However, when the reading accuracy is low, the reading accuracy is exceeded or the reading is performed twice. It is also possible to continue the decoding process until successful.
In addition, specific details such as the numerical values and the control order shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and equivalents thereof.
The invention described in the scope of claims attached to the application of this application will be added below. The item numbers of the claims described in the appendix are as set forth in the claims attached to the application of this application.

[Appendix]
<Claim 1>
A variable focus lens,
Focus drive means for adjusting the focal position of the variable focus lens;
Imaging means for acquiring image data in the imaging direction by the variable focus lens;
A light emitting means for emitting a laser beam in the imaging direction;
Control means for controlling operations of the focus driving means, the imaging means, and the light emitting means, and reading code symbols included in the acquired image data;
With
The control means includes
Focus is performed by repeatedly performing focus setting within the first execution time based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the emitted laser beam. First focusing means for adjusting;
Focus adjustment is performed by changing the focus position within a second execution time and moving the focus position based on the magnitude of contrast calculated for each of the image data acquired for each changed focus position. Second focusing means to perform,
Counting means for counting the number of executions of focus adjustment by the first focus means and focus adjustment by the second focus means;
The first execution time is set to be shortened from a predetermined first initial setting time so that the first execution time becomes shorter as the number of executions of focus adjustment by the first focus means increases, and the second A focus adjustment time setting means for setting the second execution time to be shortened from a predetermined second initial setting time so that the second execution time is shortened as the number of times of focus adjustment by the focus means increases;
A code reading device comprising:
<Claim 2>
The control means includes
If the code symbol included in the image data acquired based on the focus setting is not successfully read by the imaging unit, the first execution time until the total execution time of the focus setting reaches the first execution time. The code reading apparatus according to claim 1, wherein the focus setting by the focus unit and the reading of the code symbol included in the image data acquired based on the focus setting are repeated.
<Claim 3>
The control means includes
If the reading of the code symbol based on the focus adjustment by the first focus means is not successful within the first execution time, the code symbol is read based on the focus adjustment by the second focus means;
The code symbol is read by the first focus means when reading of the code symbol based on focus adjustment by the second focus means is not successful within the second execution time. Item 3. The code reader according to item 1 or 2.
<Claim 4>
The control means includes
If the code symbol reading based on the focus adjustment by the first focus means does not succeed in the predetermined number of continuous executions, the code symbol is read based on the focus adjustment by the second focus means,
If the code symbol reading based on the focus adjustment by the second focus means does not succeed the predetermined number of consecutive executions, the code symbol is read based on the focus adjustment by the first focus means. The code reader according to claim 1, wherein
<Claim 5>
Storage means for storing image data acquired by the imaging means;
The code according to any one of claims 1 to 4, wherein the control means stores the acquired image data in the storage means, and reads a code symbol included in the image data. Reader.
<Claim 6>
The control means causes the storage means to store only image data of a predetermined part of the imaging range by the imaging means,
The code reading apparatus according to claim 5, wherein the first focus unit and the second focus unit perform focus adjustment based on the image data in the partial range.
<Claim 7>
When the focus position of the movement destination has already been obtained by the focus setting or the focus adjustment by the second focus means, the first focus means determines the focus position of the variable focus lens at the nearest movement destination. The focus setting is performed by causing the imaging unit to acquire image data in a state in which the laser light beam is emitted from the light emitting unit after being adjusted to a focal position. The code reader according to item.
<Claim 8>
The second focus means, when the focus position of the movement destination has already been obtained by the focus adjustment by the first focus means or the focus adjustment by the second focus means, the second focus means starts from the focus position of the movement destination. 8. The focus adjustment is performed by causing the imaging unit to acquire image data of an imaging target for each focal position that is changed back and forth within two execution times. 8. Code reader.
<Claim 9>
The variable focus lens is a liquid lens,
The said 2nd focus means changes the said focus position by applying a voltage to the said variable focus lens with a predetermined voltage interval by the said focus drive means. The any one of Claims 1-8 characterized by the above-mentioned. The code reader according to claim 1.
<Claim 10>
Illuminating means for illuminating the imaging direction,
The code reading unit according to any one of claims 1 to 9, wherein the control unit turns on the illumination unit during focus adjustment by the second focusing unit and when reading the code symbol. apparatus.
<Claim 11>
A variable focus lens, focus drive means for adjusting the focal position of the variable focus lens, imaging means for acquiring image data in the imaging direction by the variable focus lens, and light emission for emitting a laser light beam in the imaging direction And a computer used for the code reader,
A program that controls operations of the focus driving unit, the imaging unit, and the light emitting unit, and functions as a control unit that reads a code symbol included in acquired image data.
The control means includes
Focus is performed by repeatedly performing focus setting within the first execution time based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the emitted laser beam. First focusing means for adjusting;
Focus adjustment is performed by changing the focus position within a second execution time and moving the focus position based on the magnitude of contrast calculated for each of the image data acquired for each changed focus position. Second focusing means to perform,
Counting means for counting the number of executions of focus adjustment by the first focus means and focus adjustment by the second focus means;
The first execution time is set to be shortened from a predetermined first initial setting time so that the first execution time becomes shorter as the number of executions of focus adjustment by the first focus means increases, and the second A focus adjustment time setting means for setting the second execution time to be shortened from a predetermined second initial setting time so that the second execution time is shortened as the number of times of focus adjustment by the focus means increases;
A program comprising:

1 Code Reader 2 Case 11 CPU
12 Operation unit 12A, 12C Trigger key 12B Various keys 13 RAM
DESCRIPTION OF SYMBOLS 14 Display part 15 Memory | storage part 15a Program 16 Communication part 19 Imager controller 21 Imager module 211 Image pick-up element 212 Variable focus lens 212A Optical system 213 Focus mechanism 214 Aimer 215 Illumination 22 Power supply part 23 Laser drive power supply 24 Bus

Claims (11)

A variable focus lens,
Focus drive means for adjusting the focal position of the variable focus lens;
Imaging means for acquiring image data in the imaging direction by the variable focus lens;
A light emitting means for emitting a laser beam in the imaging direction;
Control means for controlling operations of the focus driving means, the imaging means, and the light emitting means, and reading code symbols included in the acquired image data;
With
The control means includes
Focus is performed by repeatedly performing focus setting within the first execution time based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the emitted laser beam. First focusing means for adjusting;
Focus adjustment is performed by changing the focus position within a second execution time and moving the focus position based on the magnitude of contrast calculated for each of the image data acquired for each changed focus position. Second focusing means to perform,
Counting means for counting the number of executions of focus adjustment by the first focus means and focus adjustment by the second focus means;
The first execution time is set to be shortened from a predetermined first initial setting time so that the first execution time becomes shorter as the number of executions of focus adjustment by the first focus means increases, and the second A focus adjustment time setting means for setting the second execution time to be shortened from a predetermined second initial setting time so that the second execution time is shortened as the number of times of focus adjustment by the focus means increases;
A code reading device comprising: The control means includes
If the code symbol included in the image data acquired based on the focus setting is not successfully read by the imaging unit, the first execution time until the total execution time of the focus setting reaches the first execution time. The code reading apparatus according to claim 1, wherein the focus setting by the focus unit and the reading of the code symbol included in the image data acquired based on the focus setting are repeated. The control means includes
If the reading of the code symbol based on the focus adjustment by the first focus means is not successful within the first execution time, the code symbol is read based on the focus adjustment by the second focus means;
The code symbol is read by the first focus means when reading of the code symbol based on focus adjustment by the second focus means is not successful within the second execution time. Item 3. The code reader according to item 1 or 2. The control means includes
If the code symbol reading based on the focus adjustment by the first focus means does not succeed in the predetermined number of continuous executions, the code symbol is read based on the focus adjustment by the second focus means,
If the code symbol reading based on the focus adjustment by the second focus means does not succeed the predetermined number of consecutive executions, the code symbol is read based on the focus adjustment by the first focus means. The code reader according to claim 1, wherein Storage means for storing image data acquired by the imaging means;
The code according to any one of claims 1 to 4, wherein the control means stores the acquired image data in the storage means, and reads a code symbol included in the image data. Reader. The control means causes the storage means to store only image data of a predetermined part of the imaging range by the imaging means,
The code reading apparatus according to claim 5, wherein the first focus unit and the second focus unit perform focus adjustment based on the image data in the partial range. When the focus position of the movement destination has already been obtained by the focus setting or the focus adjustment by the second focus means, the first focus means determines the focus position of the variable focus lens at the nearest movement destination. The focus setting is performed by causing the imaging unit to acquire image data in a state in which the laser light beam is emitted from the light emitting unit after being adjusted to a focal position. The code reader according to item. The second focus means, when the focus position of the movement destination has already been obtained by the focus adjustment by the first focus means or the focus adjustment by the second focus means, the second focus means starts from the focus position of the movement destination. 8. The focus adjustment is performed by causing the imaging unit to acquire image data of an imaging target for each focal position that is changed back and forth within two execution times. 8. Code reader. The variable focus lens is a liquid lens,
The said 2nd focus means changes the said focus position by applying a voltage to the said variable focus lens with a predetermined voltage interval by the said focus drive means. The any one of Claims 1-8 characterized by the above-mentioned. The code reader according to claim 1. Illuminating means for illuminating the imaging direction,
The code reading unit according to any one of claims 1 to 9, wherein the control unit turns on the illumination unit during focus adjustment by the second focusing unit and when reading the code symbol. apparatus. A variable focus lens, focus drive means for adjusting the focal position of the variable focus lens, imaging means for acquiring image data in the imaging direction by the variable focus lens, and light emission for emitting a laser light beam in the imaging direction And a computer used for the code reader,
A program that controls operations of the focus driving unit, the imaging unit, and the light emitting unit, and functions as a control unit that reads a code symbol included in acquired image data.
The control means includes
Focus is performed by repeatedly performing focus setting within the first execution time based on the coordinates in the image data of the bright spot formed in the plane including the code symbol by the emitted laser beam. First focusing means for adjusting;
Focus adjustment is performed by changing the focus position within a second execution time and moving the focus position based on the magnitude of contrast calculated for each of the image data acquired for each changed focus position. Second focusing means to perform,
Counting means for counting the number of executions of focus adjustment by the first focus means and focus adjustment by the second focus means;
The first execution time is set to be shortened from a predetermined first initial setting time so that the first execution time becomes shorter as the number of executions of focus adjustment by the first focus means increases, and the second A focus adjustment time setting means for setting the second execution time to be shortened from a predetermined second initial setting time so that the second execution time is shortened as the number of times of focus adjustment by the focus means increases;
A program comprising: