JP2019101555A - Optical reading device - Google Patents

Abstract

To provide an optical reading device having an autofocus function with good responsiveness.SOLUTION: A device comprises an aimer light irradiation part 101 which irradiates a work with aimer light, an imaging part 103 photographing the work to create a photographed image, a focus adjustment part 104 adjusting a focus distance of the imaging part 103 within a readable area 41, a distance measurement part 105 measuring a distance to the work in a measurable area 42 narrower then the readable area 41 on the basis of a position of the aimer in the photographed image, a decoding part 106 decoding optical information on the basis of a photographed image photographed after adjustment of the focus distance, and a control part 100 that controls the focus adjustment part 104 on the basis of the measured distance if the distance measurement part 105 succeeded in the measurement of the distance and controls the focus adjustment part 104 so that the focus distance moves to predetermined recovery positions R1 to R3 outside the measurable area 42 if the distance measurement part 105 failed in the measurement of the distance.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an optical reader, and more particularly, to an improvement of an optical reader that measures the distance to a workpiece using an aimer light.

  BACKGROUND In recent years, optical reading systems that read symbols such as barcodes and two-dimensional codes as optical information and perform various data processing have become widespread. For example, it is used for settlement processing at a store, inventory management at a distribution base, process control at a factory, and the like.

  The symbol is printed on a work (object to be read) or printed on a label or the like and affixed to the work. Optical reading devices that read symbols include stationary types that move a workpiece to read symbols, and handy types that move an optical reading device to read symbols. A stationary type optical reader often has a fixed focus because it moves and reads a workpiece, whereas a handy type optical reader has an autofocus function because the distance to the workpiece changes. It has been known.

  In order to realize an autofocus function by suppressing an increase in cost, for example, as in the contrast method, a method is known in which imaging is repeated while sequentially changing the focal length to obtain an in-focus point. However, the responsiveness of the autofocus greatly affects the efficiency of the reading operation. For this reason, such a method can not be adopted for the auto focus of the optical reading device that requires high responsiveness. For example, the distance measured by using an ultrasonic wave or the like to measure the distance to the workpiece It is necessary to perform autofocus control to match the focal length.

  There is also known an optical reading apparatus which measures the distance to a work by detecting the size of a symbol in a photographed image before focus adjustment (e.g., Patent Document 1). According to the method of Patent Document 1, the distance from the photographed image to the work can be measured without increasing the cost, but when the symbol size can not be detected due to defocusing, the symbol is read. I can not do it.

Unexamined-Japanese-Patent No. 2010-204792

  There are various methods to measure the distance to the work, but if the distance to the work can be measured using the aimer light, the distance to the work can be measured without increasing the cost. it is conceivable that. The aimer light is a sighting light for showing a user an object to be read. In general, a handy-type optical reader has a function of irradiating a red laser beam or the like as an aimer beam. If the optical axis of the aimer light is inclined with respect to the light receiving axis of the imaging device, it is considered that the distance to the reflection surface of the aimer light can be obtained based on the position of the aimer light in the captured image.

  However, if the distance to the work is long, the amount of reflected light of the aimer light on the work surface decreases, and the distance to the reflection surface can not be measured. In addition, in consideration of safety when the laser beam is viewed directly, there is a limit to increasing the intensity of the aimer beam to extend the measurement distance. On the other hand, since the sighting light is visually confirmed, the aimer light also functions as the sighting light for workpieces farther than the limit of distance measurement. For this reason, in the case of an optical reader capable of reading such a distant symbol, a range in which the distance measurement by the aimer light can not be performed occurs in a part of the distance range in which the symbol can be read. That is, there occurs a state in which the distance range in which the distance can be measured by the aimer light does not cover a part of the distance range in which the symbol can be read.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an optical reader having an autofocus function with good response. Another object of the present invention is to provide an optical reading device that realizes an autofocus function at low cost using an aimer light. Another object of the present invention is to provide an optical reader capable of reading a symbol farther than the measurement limit by the aimer light.

  An optical reading device according to a first aspect of the present invention is an optical reading device for decoding optical information attached to a work, the aimer light irradiation unit irradiating the work with an aimer light, and the captured image by imaging the work The first distance range is narrower than the first distance range on the basis of the imaging portion that generates the focus position, the focus adjustment portion that adjusts the focusing distance of the imaging portion within the first distance range, and the position of the aimer image in the captured image. A distance measurement unit that measures a distance to the work within a second distance range; a decoding unit that decodes the optical information based on the captured image captured after the adjustment of the focusing distance; and the distance measurement Controls the focus adjustment unit based on the measured distance when the unit succeeds in measuring the distance, and the focusing distance is the second when the distance measuring unit fails in the measurement of the distance. Controlling the focus adjustment unit to move in a predetermined recovery position outside distance range and a control unit.

  By adopting such a configuration, when the workpiece is within the second distance range, the distance to the workpiece is measured, and focus adjustment based on the measured distance is performed, so symbol reading can be performed at high speed. It can be carried out. In addition, when the measurement of the distance to the work fails, the work is present outside the second distance range in order to move the in-focus distance to a predetermined recovery position outside the second distance range. Even symbol reading can be performed at high speed.

  An optical reader according to a second aspect of the present invention is, in addition to the above configuration, configured such that the recovery position is a position farther than the second distance range.

  By adopting such a configuration, the reflected light intensity of the aimer light is insufficient because the work is far and symbol reading is possible, but even if the distance to the work can not be measured, high speed is achieved. Symbols can be read.

  In the optical reader according to the third aspect of the present invention, in addition to the above configuration, when the distance measurement unit fails to measure the distance, the in-focus distance sequentially moves to the recovery position of 2 or more. The control unit controls the focus adjustment unit.

  By adopting such a configuration, it is possible to read symbols present in the distance range even if the distance range is within the first distance range and outside the second distance range is wide.

  In the optical reading device according to the fourth aspect of the present invention, in addition to the above configuration, both ends of the distance measuring unit fail to measure the distance and move sequentially to the recovery position where the focusing distance is 3 or more. The control unit controls the focus adjustment unit to move to at least one of the recovery positions other than the both ends prior to the recovery position of.

  Such a configuration makes it possible to increase the probability of being able to read symbols faster and to improve the average reading speed when searching for symbols by sequentially moving three or more recovery positions.

  In the optical reader according to the fifth aspect of the present invention, in addition to the above configuration, decoding based on the captured image captured after the focusing distance is moved to the recovery position outside the second distance range has failed In this case, the control unit controls the focus adjustment unit such that the in-focus distance sequentially moves to two or more predetermined search positions in the second distance range.

  By adopting such a configuration, it is possible to read the symbol even if the measurement of the distance fails although the readable symbol exists within the second distance range.

  An optical reading apparatus according to a sixth aspect of the present invention includes, in addition to the above configuration, a control amount storage unit that stores a control amount in association with the in-focus distance selectable by the imaging unit. The control amount corresponding to the measured distance is read from the control amount storage unit, and the focus adjustment unit is controlled based on the read control amount.

  In the optical reader according to the seventh aspect of the present invention, in addition to the above configuration, the imaging unit has a liquid lens, and the focus adjustment unit adjusts the focal length of the liquid lens.

  By adopting such a configuration, it is possible to perform focus adjustment at high speed, and it is possible to improve the high-level of the symbol reading process.

  According to the present invention, it is possible to provide an optical reader having an autofocus function with good response. In addition, it is possible to provide an optical reading device that realizes an autofocus function at low cost using an aimer light. In addition, it is possible to provide an optical reader that reads a symbol farther than the measurement limit by the aimer light.

FIG. 1 is a view showing an example of an optical reading device 1 according to a first embodiment of the present invention. It is the figure which showed the area | region which the optical reader 1 of FIG. 1 covers. It is the figure which showed an example of the captured image at the time of irradiating an aimer light. It is the figure which showed an example of the captured image at the time of irradiating an aimer light. It is the block diagram which showed an example of the function structure of the optical reader 1 of FIG. FIG. 2 is a view showing an example of the configuration of an imaging lens 131; It is the figure which showed an example of the control amount which the control amount memory | storage part 109 of FIG. 5 hold | maintains. It is the figure which showed the relationship between the center position of an aimer, and a control amount. It is an explanatory view showing an outline of symbol reading operation. It is the flowchart which showed an example of symbol reading processing. FIG. 7 is an explanatory view showing an outline of a symbol reading operation. FIG. 14 is an explanatory view showing an outline of a symbol reading operation according to a second embodiment. FIG. 13 is a flowchart showing an example of symbol reading processing according to Embodiment 2. FIG. FIG. 14 is an explanatory view showing an outline of a symbol reading operation according to a third embodiment.

Embodiment 1
(1) Outline of the Optical Reading Device 1 FIG. 1 is a view showing an example of the optical reading device 1 according to the first embodiment of the present invention. And the side of the optical reader 1 is shown in (b) of the figure.

  The optical reading device 1 is a terminal device for reading optical information attached to a work. The optical information to be read is a bar code, an optical code such as a two-dimensional code, or a symbol composed of characters, etc., and is printed directly on the surface of the workpiece or on a label affixed to the surface of the workpiece It is printed. The read optical information is decoded and then used for data output, data collation, and any other data processing.

  The optical reading device 1 is a portable terminal device (handy terminal) that has a shape that can be held by one hand and can be moved by being carried. A large number of operation keys 10 including a trigger key 10 t and a display screen 11 are provided on the operation surface of the optical reading device 1.

  When the tip of the optical reading device 1 is directed to the work and the trigger key 10 t is pressed, the tip of the optical reading device 1 is irradiated with the aimer light. The user adjusts the orientation of the optical reading device 1 while visually observing the reflected light of the aimer light reflected on the work surface (hereinafter referred to as an aimer), and if the aimer is aligned with the symbol to be read, symbol reading and decoding Is automatically performed, and a buzzer sounds to notify the completion of reading.

  As an example, the case where the optical reader 1 is used for picking in the distribution warehouse will be described. When the ordered product is shipped from the distribution warehouse, the required product is picked up from the product rack in the product warehouse. This picking operation is performed while the user holding the order receipt slip in which the barcode is described moves to the product shelf and then collates the barcode of the order receipt slip with the barcode attached to the product or the product shelf. . In this case, while the distance to the order receipt slip is about 10 to 20 cm, the distance to the product shelf is about 2 m at maximum, and the work of alternately reading such barcodes of completely different distances is performed. For this reason, focus adjustment is required to read symbols. In addition, since the time delay until the reading is completed after the aimer is adjusted to the symbol to be read greatly affects the operation efficiency, high responsiveness is required.

  For example, it is required that the symbol be read almost in real time, with a time delay from the alignment of the aimer to the symbol to the beeping being a very short time of less than one second. During this slight time delay, autofocus (automatic focus adjustment) is performed to make the focal length of the imaging unit coincide with the work surface, and symbol imaging and decoding are performed after focus adjustment. In order to realize such high responsiveness, it is necessary to end autofocus in a short time. For this reason, a method is first used to measure the distance to the work surface and adjust the focal length based on the measured distance.

  The measurement of the distance to the work surface is performed using an aimer beam. The outgoing optical axis 13 of the aimer light is arranged to be inclined with respect to the imaging axis 12 which is an incident optical axis to the imaging device, and the distance to the reflective surface of the aimer light is measured using the principle of triangular distance measurement. Ru. For example, as shown in FIG. 1, although both the imaging axis 12 and the outgoing optical axis 13 of the aimer light are parallel to the operation surface of the optical reading device 1, they are arranged to have an angle with each other in the plane There is. If such an aimer is imaged, the position of the aimer in the imaged image changes in a direction parallel to the operation surface according to the distance to the reflection surface. Therefore, the distance to the reflective surface can be measured based on the position of the aimer in the captured image.

  The aimer light is an aiming light indicating the object to be read, and measuring the distance to the work surface using such an aimer light to measure the distance to the work surface without adding new parts. Becomes possible. That is, it is possible to measure the distance to the workpiece surface without increasing the cost.

(2) Distance Measurement by Aimer Light FIGS. 2 and 3 are explanatory diagrams of distance measurement using an aimer light. FIG. 2 is a view showing an area covered by the optical reading device 1 of FIG. 1, and FIG. 3 is a view showing an example of captured images 201 to 204 when the aimer light is irradiated.

  The distances A1 to A4 are an example of the distance from the optical reading device 1 to the work, and are sequentially farther (A1 <A2 <A3 <A4). Further, the captured images 201 to 204 are images obtained by capturing symbols on the surface of the workpiece at distances A1 to A4 from the optical reading device 1, respectively, and are captured during irradiation of the aimer light.

  The captured images 201 to 203 of the distances A1 to A3 include a barcode symbol 20 and a cross-shaped aimer 21. When viewed from the optical reading device 1, the outgoing optical axis 13 of the aimer light is inclined to the right with respect to the imaging axis 12. Therefore, the position of the aimer 21 in the captured images 201 to 203 moves to the right as the distance to the reflective surface increases. Therefore, if the aimer 21 is extracted from the captured images 201 to 203 by image processing, the distance to the workpiece surface can be obtained based on the position in the captured images 201 to 203.

  Only the symbol 20 appears in the captured image 204 at the farthest distance A4, and the aimer 21 does not. If the reflecting surface is far, the reflected intensity of the aimer light decreases, and it becomes impossible to image the aimer. In particular, since imaging of the aimer is performed before focus adjustment, the aimer can not be detected from the captured image unless sufficient reflection intensity is secured. Although the reflection intensity can be increased by increasing the emission intensity of the aimer light, there is a limit from the viewpoint of securing the safety.

  The reading maximum distance L1 shown in the figure is the maximum distance at which the symbol can be read, and is 2 m, for example. The readable area 41 is a distance range from the nearest position of the optical reading device 1 to the reading maximum distance L1, and the optical reading device 1 can read symbols present in the readable area 41. That is, it is possible to visually illuminate the aimer light as the aiming light on the work in the readable area 41, and the symbol on the work surface can be imaged and decoded.

  The measurement maximum distance L2 is the maximum distance at which the distance to the work surface can be measured using an aimer light, and is, for example, 40 cm. The measurable area 42 is a distance range from the immediate vicinity of the optical reading device 1 to the measurement maximum distance L2, and the optical reading device 1 can measure the distance to the workpiece surface present in the measurable area 42.

  The measurement maximum distance L2 is smaller than the read maximum distance L1, and the measurable area 42 is narrower than the readable area 41. For this reason, in the readable area 41, there is a blind area 43 in which the distance can not be measured. That is, the blind area 43 is a distance range within the readable area 41 and outside the measurable area 42.

  Since the distances A1 to A3 are within the measurable area 42, the distance can be measured, but because the distance A4 is within the blind region 43, the symbol can be read but the distance can not be measured. . The reading operation when there is a work in the blind area 43 where the distance can not be measured will be described later.

  FIG. 4 is a view showing an example of the captured image 205 when the aimer light is emitted. Symbols 20 in the figure are attached near the end of the work 22. For this reason, in the aimer light indicating the symbol 20, a part of the aimer light is not reflected by the work 22, and the aimer 21 is photographed as a partially missing image. That is, when there is unevenness or a change in inclination on the reflective surface, the aimer image is photographed in a partially missing or distorted state. In such a case, it becomes difficult to extract the aimer 21 from the photographed image by image processing, and even within the measurable area 42, the distance to the work can not be measured.

(3) Functional Configuration of Optical Reading Device 1 FIG. 5 is a block diagram showing an example of the functional configuration of the optical reading device 1 of FIG. The optical reading device 1 includes a control unit 100, an aiming light irradiation unit 101, an illumination light irradiation unit 102, an imaging unit 103, a focus adjustment unit 104, a distance measurement unit 105, a decoding unit 106, an operation input unit 107, and a display output unit 108. And a control amount storage unit 109.

  The aimer light irradiation unit 101 emits an aimer light. The aimer light is an aiming light that illuminates the work and indicates the object to be read visually on the work surface, and is made of visible light generated by an LED, a laser diode (LD) or the like. For example, although cross-shaped red laser light can be used as an aimer light, the aimer light applied to the present invention may be any visible light that can be used as aiming light, and its wavelength, shape, intensity, etc. are limited. I will not. It is desirable that the illumination of the aimer light be performed at the time of measuring the distance, and not be performed at the time of symbol imaging.

  The illumination light irradiation part 102 is a light source which irradiates illumination light. The illumination light is light to be illuminated to image a symbol, and for example, white light is used. In a dark environment where ambient light is not sufficient, imaging is performed in a state where the imaging target is illuminated with illumination light. It is desirable that illumination of illumination light be performed at the time of symbol imaging and not at the time of distance measurement. When imaging is performed only in a bright environment, the illumination light irradiation unit 102 can be omitted.

  The imaging unit 103 includes an imaging lens 131 and an imaging element 132, captures an image of an aimer beam and a symbol, and generates a captured image. The imaging unit 103 starts imaging based on the imaging signal from the control unit 100, and outputs the generated captured image to the distance measuring unit 105 or the decoding unit 106. The imaging lens 131 is a lens that condenses incident light and forms an image on the light receiving surface of the imaging element 132. For example, a liquid lens can be used. The imaging device 132 is a photoelectric conversion device that generates a captured image, and for example, a CCD or a CMOS image sensor can be used.

  The focus adjustment unit 104 is a unit that adjusts the focusing distance of the imaging unit 103. When the imaging lens 131 is a liquid lens, the focus adjustment unit 104 applies a voltage corresponding to the distance to the work to the imaging lens 131 to adjust the focal length.

  The distance measuring unit 105 is means for obtaining the distance to the work surface based on the position of the aimer in the captured image. The position of the aimer in the captured image is determined by extracting the aimer image from the captured image by image processing. The measurement of the distance is a process performed for focusing, and is performed based on the image captured before the focusing.

  The decoding unit 106 is a unit that extracts a symbol image from a captured image by image processing and decodes the extracted symbol. The extraction of the symbol image is performed based on the image captured after the focus adjustment. When a plurality of symbols are included in a captured image, symbols designated by the aimer are to be decoded.

  The operation input unit 107 detects an operation input by the user and outputs an operation signal to the control unit. For example, when a pressing operation of the trigger key 10t is detected, a trigger signal is output to the control unit 100.

  The display output unit 108 is a display means for notifying the user of various information, and for example, a liquid crystal display device constituting the display screen 11 is used. While the operation state of the optical reading device 1 is displayed on the display screen 11, the reading result of the symbol is displayed.

  The control amount storage unit 109 is a storage unit that stores the control amount of the imaging lens 131 in association with the distance to the reading target. The control amount corresponding to each distance to the reading object is given in advance, and is stored in the control amount storage unit 109. For example, the applied voltage of the imaging lens 131 is held as a control amount. The focus adjustment unit 104 applies a voltage to the imaging lens 131 based on the control amount held in the control amount storage unit 109.

  When the trigger signal is input from the operation input unit 107, the control unit 100 outputs a lighting signal to the aimer light irradiation unit 101 and the illumination light irradiation unit 102, and the aimer light and the illumination light are emitted toward the work. In addition, the control unit 100 outputs an imaging signal to the imaging unit 103, imaging is started without performing focus adjustment of the imaging lens 131, and a captured image is generated. When the distance measurement unit 105 measures the distance to the work, the control unit 100 reads out the control amount corresponding to the measured distance from the control amount storage unit 109, and outputs the control amount to the focus adjustment unit 104. The focus adjustment unit 104 adjusts the focus of the imaging lens 131 based on the control amount. Further, when the decoding result is output from the decoding unit 106, the control unit 100 outputs the decoding result to the control unit 100, and the decoding result is displayed on the screen as the reading result.

  FIG. 6 is a view showing a configuration example of the imaging lens 131, and (a) and (b) in the figure show states where focal lengths are different. A liquid lens is used for the imaging lens 131. The liquid lens is a lens in which an interface 313 curved between the liquids 311 and 312 having different refractive indexes is formed, and the curvature of the interface 313 can be changed according to the applied voltage, and the focal length can be adjusted instantaneously. it can.

  For example, a sealed space is formed by two transparent substrates 301 and 302 facing each other and a cylindrical holder 303, and two types of immiscible liquids 311 and 312 having different refractive indexes are sealed in the sealed space. ing. The cylindrical holder 303 is provided with two electrodes 304 and 305 in the optical axis direction, one of the liquids 311 uses non-conductive oil, and the other liquid 312 uses a conductive aqueous solution. . Therefore, when a voltage is applied between the electrodes 304 and 305, and the conductive liquid 312 is drawn to one of the electrodes 304, the non-conductive liquid 311 changes into a droplet-like shape, and both liquids 311, A curved interface 313 is formed between 312. Since the curvature of the interface 313 changes according to the voltage, the focal length can be changed at high speed.

(4) Control Amount of Focus Adjustment FIG. 7 is a diagram showing an example of the control amount held by the control amount storage unit 109 of FIG. 5, where the horizontal axis is the distance to the reading object, and the vertical axis is the control amount. The voltage value is shown as. As the distance to the object to be read increases, the control amount decreases and the focal length increases. In general, the rate of change of the focal length with respect to the distance to the subject of the optical lens decreases as the subject gets farther. Therefore, as shown in the drawing, the control amount with respect to the distance to the reading object is a curve in which the rate of change decreases as the distance to the reading object increases.

  The width of the readable area 41 is about 2 m, and only a part (600 mm or less) is shown in the figure. In a region exceeding 600 mm, the focal length hardly changes even if the distance to the object to be read changes. Further, the closest distance to the optical reading device 1, for example, 20 mm or less, is the limit of focus adjustment of the imaging lens 131, so the control amount is constant, but the distance to the symbol is sufficiently short. Symbols can be read even if

  FIG. 8 is a diagram showing the relationship between the center position of the aimer and the control amount, and the abscissa represents the center position of the aimer and the ordinate represents the control amount. The distance to the work can be determined based on the position in the left and right direction in the aimer center pickup image, and the control amount can be determined by reading out the control amount storage unit 109 based on the determined distance.

(5) Symbol Reading Process FIGS. 9 and 10 are diagrams showing an example of a symbol reading process according to the first embodiment of the present invention. FIG. 9 is an explanatory view showing an outline of the symbol reading operation.

  If the work is within the measurable area 42, it is possible to measure the distance to the work using an aimer light. If the measurement of the distance to the work is successful, the work is imaged after the focus adjustment is performed so that the measured distance is in focus, and the symbol is decoded. On the other hand, if the distance to the work is out of the measurable area 42, the distance to the work can not be measured. If the measurement of the distance to the work fails, the focus is adjusted so that the recovery positions R1 to R3 are in focus, and the work is imaged and symbol decoding is performed.

  The two or more recovery positions R1 to R3 are in-focus distances at which arbitrary symbols in the recovery areas 431 to 433 can be read, and are predetermined. The two or more recovery areas 431 to 433 are areas obtained by dividing the blind area 43, and are predetermined. For this reason, when the work is present in the blind area 43, the in-focus distance is sequentially moved to the recovery positions R1 to R3, and decoding is successfully performed by performing imaging and decoding for each of the recovery positions R1 to R3. it can.

  That is, when the measurement of the distance to the work is successful, the symbol is read at high speed by focusing on the measured distance. On the other hand, when the measurement of the distance to the work fails, a search process for focusing on two or more recovery areas 431 to 433 and finding a decodable symbol is performed. As a result, the entire readable area 41 can be covered.

  When the focusing distances are sequentially moved to three or more recovery positions R1 to R3, they can be moved in any order. However, when the focus adjustment is performed by the relative movement of the imaging lens 131, the responsiveness of the focus adjustment is poor, and it is necessary to move the focusing distance in one direction in order to avoid a further decrease in responsiveness. That is, the in-focus distance needs to move in the order of R1, R2 and R3 or in the order of R3, R2 and R1 along the arrangement order of the recovery positions R1 to R3.

  On the other hand, focusing by the liquid lens is extremely responsive, and the decrease in responsiveness due to the movement order of the focusing distances can be ignored. For this reason, when a liquid lens is employed for the imaging lens 131, it is desirable to move to recovery positions R2 other than both ends prior to the recovery positions R1 and R3 at both ends. That is, it is desirable that the focusing distance is moved in the order of R2, R1 and R3 or in the order of R2, R3 and R1.

  Generally, even if the image is not completely in focus and the captured image is somewhat defocused, the symbol is successfully decoded with a certain probability. In addition, as the work gets farther, the rate of change of the focal distance with respect to the in-focus distance decreases, and even if the focal point is out of focus, large defocusing hardly occurs. Therefore, when the in-focus distance is moved to the recovery position R2, not only the corresponding recovery area 432 but also the symbols in the adjacent recovery areas 431 and 433 can be read with a certain probability. Therefore, by preferentially moving the in-focus distance to the recovery positions R2 other than the both ends, decoding can be succeeded faster with a certain probability.

Control amounts for focusing on the respective recovery positions R1 to R3 are held in the control amount storage unit 109. Further, the movement order of each recovery position R1 to R3 is also held in the control amount storage unit 109. Table 1 is an example of information regarding the recovery positions R1 to R3 held in the control amount storage unit 109. The distances to the recovery positions R1 to R3 are 500 mm, 600 mm, and 750 mm, respectively, and the control amounts for focusing on these distances are 38.8 V, 38.3 V, and 38.0 V, respectively. Also, the moving order is in the order of R2, R1 and R3. These pieces of information are predetermined and held in the control amount storage unit 109. In addition, if the control amount is held, the distance can be omitted. Further, since the control amount storage unit 109 holds the control amount in association with the distance, the control amount can be omitted if the distance is held.

  Steps S <b> 101 to S <b> 110 in FIG. 10 are a flowchart showing an example of the symbol reading process by the optical reading device 1. The symbol reading process is started by the user operating the trigger key 10t. The flow of the symbol reading process is controlled by the control unit 100.

  First, the focal length of the imaging lens 131 is set to an initial value (step S101). The initial value of the focal position is, for example, preselected by the user either as a fixed value or a focal distance last successfully read for the symbol. When the last successful focal length for symbol reading is used as the initial value of the focal length, the first imaging succeeds in decoding if there is no significant change in the distance to the symbol compared to the last successful reading. , High responsiveness can be obtained. In addition, when a fixed value is used as an initial value, the fixed value may be designated by the user. For example, if a focal distance that is frequently used is known, by designating the focal distance in advance as an initial value, it is possible to increase the probability of successful decoding in the first imaging. Further, the user may be configured to select either the near-side fixed value or the far-side fixed value.

  Next, imaging and decoding are performed (step S102). That is, the imaging unit 103 generates a captured image without performing the distance measurement to the work and the focus adjustment, and the decoding unit 106 extracts and decodes a symbol from the captured image. As a result, when the decoding is successful, the decoding result is output as the reading result, and the symbol reading process is ended (step S106).

  On the other hand, when the decoding fails in step S103, the distance to the work is measured (step S103). The distance to the workpiece is measured by imaging the workpiece irradiated with the aimer light to generate a captured image and detecting the position of the aimer in the captured image.

  When the distance measurement is successful in step S102, focus adjustment is performed such that the in-focus distance of the imaging unit 103 matches the measured distance (step S104). Specifically, the control unit 100 reads out the control amount corresponding to the measured distance from the control amount storage unit 109, and the focus adjustment unit 104 applies a voltage according to the control amount to the imaging lens 131, and the imaging lens The focal length of 131 is adjusted.

  Next, imaging and decoding are performed (step S105). That is, the imaging unit 103 generates a captured image after adjustment of the focusing distance, and the decoding unit 106 extracts and decodes a symbol from the captured image. As a result, when the decoding is successful, the decoding result is output as the reading result, and the symbol reading process is ended (step S106). On the other hand, if the decoding fails, the process returns to step S103, and the distance measurement is performed again. Decoding failure may occur, for example, when the optical reader 1 moves during imaging, when the symbol is dirty, when the surface condition of the workpiece is not good, and the like.

  On the other hand, if the measurement of the distance fails in step S103, the measurement of the distance is repeated until the predetermined number of times is reached (step S107). If the aimer can not be extracted from the captured image, the distance measurement fails. For example, when the distance to the work is outside the measurable area 42 (for example, FIG. 3D) or when the image is taken in a state where a part of the aimer is missing (for example, FIG. 4) Fail. In such a case, the distance measurement is performed again.

  If it fails in step S107 to measure the distance continuously and reaches a predetermined number of times, the in-focus distance is sequentially moved to two or more predetermined recovery positions R1 to R3 and imaging is performed for each of the recovery positions R1 to R3 And decoding is performed (steps S108 to S110). That is, search processing for finding decodable symbols in the blind area 43 is performed. As a result, if decoding is successful at any of the recovery positions R1 to R3, the process proceeds to step S106, and the reading result is output. On the other hand, if decoding fails at all recovery positions R1 to R3, the process returns to step S103, and the distance measurement is performed again.

  When an arbitrary symbol in the blind area 43 can be read by the same focusing distance, there is no need to divide the blind area 43 into two or more recovery areas 431 to 433.

  FIG. 11 is a diagram showing another example of the symbol reading process according to the first embodiment of the present invention, and is an explanatory diagram showing an outline of an operation at the time of symbol reading. The recovery position R is a focusing distance at which any symbol in the blind area 43 can be read, and the blind area 43 directly becomes the recovery area 430 without being divided. For this reason, in step S107 in FIG. 10, when the distance measurement fails by a predetermined number of times, the in-focus distance is moved to the recovery position R, and imaging and decoding are performed to decode symbols in the blind area 43. it can. In this case, step S110 is unnecessary.

  The optical reading device 1 according to the present embodiment includes an aimer light irradiation unit 101 that irradiates a workpiece with an aimer light, an imaging unit 103 that images a workpiece to generate a captured image, and an imaging unit 103 in a readable area 41. A focus adjustment unit 104 that adjusts a focusing distance, and a distance measurement unit 105 that measures the distance to a workpiece within a measurable area 42 narrower than the readable area 41 based on the position of the aimer image in the captured image; The decoding unit 106 decodes optical information based on the captured image captured after the adjustment of the focusing distance, and the focus adjustment unit 104 based on the measured distance when the distance measurement unit 105 succeeds in measuring the distance. If the distance measuring unit 105 fails to measure the distance, the in-focus distance is moved to a predetermined recovery position R1 to R3 outside the measurable area 42. And a control unit 100 for controlling the focus adjustment unit 104 so as to.

  Therefore, when the workpiece is in the measurable area 41, the distance to the workpiece is measured, and the focus adjustment based on the measured distance is performed, so that the symbol can be read at high speed. Also, if the measurement of the distance to the work fails, in order to move the in-focus distance to the recovery positions R1 to R3 outside the measurable area 42, even if the work is outside the measurable area 41, symbol reading is performed. It can be carried out. In particular, when the measurement of the distance to the work fails, the focus distance is sequentially moved across the entire readable area 41, and symbol reading is performed at a high speed as compared with the method of finding readable symbols. Can.

Second Embodiment
In the first embodiment, the distance to the work is measured, and if the measurement of the distance fails, the symbol in the blind area 43 is searched, and if the search of the symbol also fails, the distance is measured again. An example of symbol reading processing has been described. On the other hand, in the present embodiment, symbol reading processing for searching for symbols in measurable area 42 when symbol search in blind area 43 fails will be described.

  12 and 13 show an example of symbol reading processing according to the second embodiment of the present invention. FIG. 12 is an explanatory view showing an outline of the symbol reading operation. As compared with FIG. 9, the measurable area 42 is divided into two or more search areas 51, and a search position 50 corresponding to each search area 51 is determined.

  If the measurement of the distance to the work fails and the symbol search in the blind area 43 also fails, the work is adjusted after focusing so that two or more search positions 50 in the measurable area 42 are in focus. The image is captured and symbol decoding is performed.

  The two or more search positions 50 are in-focus distances at which arbitrary symbols in the corresponding search area 51 can be read, and are predetermined. The two or more search areas 51 are areas obtained by dividing the measurable area 42, and are predetermined. Therefore, when the work is present in the measurable area 42, the focusing distance can be sequentially moved to the search position 50, and imaging and decoding can be performed for each search position 50, whereby decoding can be successful.

  That is, when a symbol search in the blind area 43 fails, two or more search positions 50 are sequentially focused to perform search processing for finding a decodable symbol. As a result, all of the readable area 41 is covered by the symbol search process.

  Even if a symbol is present in the measurable area 42 and readable, the measurement of the distance to the workpiece may fail. For example, if imaging is performed with a part of the aimer missing (for example, FIG. 4), the measurement of the distance fails. Even in such a case, the symbol can be read by performing a symbol search process on the measurable region 42.

  Steps S201 to S213 in FIG. 13 are flowcharts showing an example of the symbol reading process according to the second embodiment. Steps S201 to S210 are the same as steps S101 to S110 (Embodiment 1) of FIG. 12, and thus redundant description will be omitted.

  In the search process (steps S208 to S210) in the blind area 43, if the decoding fails at all the recovery positions R1 to R3, the search process in the measurable area 42 is performed (steps S211 to S213). That is, the focusing distance is sequentially moved to two or more predetermined search positions 50 (step S211), and imaging and decoding are performed for each search position 50 (step S212). As a result, if decoding is successful at any of the search positions 50, the process proceeds to step S206, and the read result is output. On the other hand, if decoding fails at all the search positions 50, the process returns to step S203, and distance measurement is performed again.

  In the optical reading device 1 according to the present embodiment, when the distance measurement unit 105 fails to measure the distance, the control unit 100 controls the focus adjustment unit to move sequentially to the recovery position where the in-focus distance is 2 or more. Control 104; By adopting such a configuration, it is possible to read symbols present in the distance range even if the distance range outside the second distance range is wide within the readable region 41.

  The optical reading device 1 according to the present embodiment can measure the in-focus distance of the focusable area 42 if the decoding based on the captured image captured after the in-focus distance moves to the recovery position R1 to R3 of the blind area 43 fails. The control unit 100 controls the focus adjustment unit 104 so as to sequentially move to two or more predetermined search positions 50 of them. By adopting such a configuration, although there are readable symbols in the measurable area 42, the symbols can be read even if the distance measurement fails.

Third Embodiment
In the second embodiment, an example of symbol reading processing for searching for symbols in the measurable area 42 when the measurement of the distance in the measurable area 42 fails and the search in the blind area 43 also fails is described. On the other hand, in this embodiment, a simple search is performed in the blind area 43, and symbol reading processing for searching for symbols in the entire readable area 41 when this simple search fails is described. .

  FIG. 14 is a diagram showing an example of symbol reading processing according to the third embodiment of the present invention, and is an explanatory diagram showing an outline of symbol reading operation. The flowchart of the symbol reading process according to the present embodiment is the same as that of FIG. 12 (Embodiment 2).

  If the measurement of the distance in the measurable area 42 fails, a first search for finding decodable symbols in the blind area 43 is performed. If this first search fails, a second search is performed to find decodable symbols in the readable area 41. That is, for the blind area 43, both the first search and the second search are performed.

  The second search is a search of the readable area 41, and after focus adjustment is performed so that the search position 50 is in focus, the work is imaged and symbol decoding is performed. The two or more search positions 50 are focusing distances at which arbitrary symbols in the search area 51 can be read, and are predetermined. The two or more search areas 51 are areas obtained by dividing the readable area 41, and are predetermined. Therefore, when the work is present in the readable area 41, decoding can be successful by sequentially moving the in-focus distance to the search position 50 and performing imaging and decoding for each search position 50.

  On the other hand, the first search is a search in the blind area 43, and after focus adjustment is performed so that the recovery positions R1 and R2 are in focus, the work is imaged and symbol decoding is performed. The one or more search positions R1 and R2 are focus distances which are smaller in number than the search positions 50 in the blind area 43 and arranged at wider intervals, and are predetermined.

  For this reason, it is not possible to focus on an arbitrary symbol in the blind area 43 only by moving the focusing distance to the recovery positions R1 and R2. As a result, while the first search can be executed faster than the second search, it may not be possible to find decodable symbols present in the blind area 43, which is more uncertain than the second search. Have sex.

  However, as described above, even if the focused image is not completely in focus and some defocusing occurs in the captured image, it is possible to successfully decode the symbol with a certain probability. In addition, as the work gets farther, the rate of change of the focal distance with respect to the in-focus distance decreases, and even if the focal point is out of focus, large defocusing hardly occurs. Therefore, for symbols that are relatively easy to read such as barcodes, speeding up the symbol reading process while suppressing uncertainty by appropriately determining the number and position of the recovery positions R1 and R2. Can.

  In the present embodiment, an example in which the first search and the second search are performed has been described. However, the second search may be omitted and only the first search may be performed. That is, when the measurement of the distance in the measurable area 42 fails, only the simple search may be performed on the blind area 43. In addition, when the first search fails, it is also possible to configure so as to search only for the measurable region 42 as in the second embodiment.

DESCRIPTION OF SYMBOLS 1 optical reading device 10 operation key 10 t trigger key 11 display screen 12 imaging axis 13 light axis of emitting aimer light 20 symbol 21 aimer 22 workable area 42 readable area 42 measurable area 43 blind area 50 search position 51 search area 100 control unit 101 Emer light irradiation unit 102 illumination light irradiation unit 103 imaging unit 104 focus adjustment unit 105 distance measurement unit 106 decode unit 107 operation input unit 108 display output unit 109 control amount storage unit 131 imaging lens 132 imaging elements 201 to 205 captured images 301 and 302 Transparent substrate 303 Cylindrical holder 304, 305 Electrode 311, 312 Liquid 313 Interface 430 to 433 Recovery area A1 to A4 Work distance L1 Reading maximum distance L2 Measurement maximum distance R, R1 to R3 Recovery position

Claims (7)

In an optical reader for decoding optical information attached to a work,
An aimer light irradiation unit for irradiating the work with an aimer light;
An imaging unit that images the work and generates a captured image;
A focus adjustment unit configured to adjust a focusing distance of the imaging unit within a first distance range;
A distance measuring unit that measures the distance to the work within a second distance range narrower than the first distance range based on the position of the aimer image in the captured image;
A decoding unit that decodes the optical information based on the captured image captured after the adjustment of the focusing distance;
When the distance measuring unit succeeds in measuring the distance, the focus adjusting unit is controlled based on the measured distance, and when the distance measuring unit fails in measuring the distance, the focusing distance is the An optical reader comprising: a control unit that controls the focus adjustment unit to move to a predetermined recovery position outside a distance range of 2.   The optical reading device according to claim 1, wherein the recovery position is a position farther than the second distance range.   The control unit controls the focus adjustment unit to sequentially move to the recovery position where the in-focus distance is two or more when the distance measurement unit fails to measure the distance. The optical reader according to claim 1 or 2.   In the control unit, when the distance measuring unit fails to measure the distance and sequentially moves to the recovery position where the in-focus distance is 3 or more, the recovery positions other than both ends are earlier than the recovery positions at both ends. The optical reading device according to claim 3, wherein the focusing unit is controlled to move to at least one.   The control unit is configured such that, when the in-focus distance fails to be decoded based on the captured image captured after moving to the recovery position outside the second distance range, the in-focus distance is the second distance range The optical reading device according to claim 1 or 2, wherein the focus adjustment unit is controlled to sequentially move to two or more predetermined search positions. The control amount storage unit stores a control amount in association with the in-focus distance selectable by the imaging unit.
The control unit reads the control amount corresponding to the measured distance from the control amount storage unit, and controls the focus adjustment unit based on the read control amount. The optical reader in any one of -3. The imaging unit has a liquid lens,
The optical reading apparatus according to any one of claims 1 to 4, wherein the focus adjustment unit adjusts a focal length of the liquid lens.

Images