JP2012173124A - Optical information reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information reading device that can process ranging faster and more securely.SOLUTION: An optical information reading device 1A is provided with a ranging light emitter 2 that emits ranging light Sa that forms on an object of reading a ranging pattern 101a combining a light-irradiated area 102a and a non-irradiated area 103a, photographs with a solid imaging element 3 the ranging pattern 101a formed on the object of reading to acquire a picture of the ranging pattern 101a, detects any part in which signals drop among picture signals, and performs ranging on the basis of the coordinates of the non-irradiated area 103a in the ranging pattern 101a.

Description

  The present invention relates to an optical information reader having a variable focus function and mainly intended to read code symbols such as bar codes and two-dimensional codes, and images of landscapes and articles.

  For the purpose of merchandise management, inventory management, etc., a barcode which is one-dimensional code information and a two-dimensional code as a code having a higher information density are known. As a device for reading code symbols such as barcodes and two-dimensional codes, code information is photographed with a solid-state image sensor such as a CMOS image sensor or a CCD image sensor, the image is subjected to various processing, and then binarized and decoded. How to do is known.

  The CMOS image sensor used in such a device that reads code information is not functionally different from what is mounted on a digital camera or the like, so it functions as a photographer that normally shoots objects and landscapes. Is required. For example, in the case of inventory management or the like, it is used when an image of a position where the article is stored together with the target article is stored in a database together with code information.

  The mobile phone is equipped with a small camera using the above-described CMOS image sensor. Most of the camera functions of mobile phones include a barcode / two-dimensional code scanner and an OCR (optical character reader), as well as images of landscapes and people, like ordinary digital cameras. is there. That is, a digital camera having a code symbol imaging / decoding function is widely demanded.

  Furthermore, in the field of product management, inventory management, etc. described above, it is necessary to scan the code symbols attached to the articles one after another. At that time, it is desirable to have an autofocus function, and autofocus and imaging processing must be performed at high speed.

  In an optical information reading apparatus having an autofocus function, the distance to a reading object such as a code symbol is measured, and the optical system is controlled so that the focal position matches the measured distance. As a technique for measuring the distance to the reading object, a distance measuring technique using a laser has been proposed (for example, see Patent Document 1).

  In the distance measuring technique based on trigonometry using a laser, a beam is irradiated to form a spot having a high light intensity on a reading object, and a detection spot position on the reading object is measured. The distance of the reading object is determined from the detected spot position.

  On the other hand, in the optical information reading apparatus, if the user can recognize whether or not the code symbol is within the readable range, it is not necessary to repeat the trial, and the reading operation can be speeded up. Thus, a technique including a light source and an optical system for displaying a readable range has been proposed (see, for example, Patent Document 2).

Japanese Patent No. 4473337 JP 2010-140064 A

  In a conventional distance measuring technique using a trigonometry using a laser, a spot-like signal peak having a strong intensity is detected, and a spot position is obtained. However, when the exposure is saturated due to the influence of the amount of ambient light or the like, the signal intensity peak cannot be detected, and a signal necessary for distance measurement may not be obtained. In this case, by correcting the exposure and performing re-imaging, an image with appropriate exposure can be obtained. However, exposure correction and re-imaging processing are necessary, which hinders speeding up of the distance measurement process.

  Moreover, a user's reading operation | movement can be guide | induced by forming a spot with visible light and matching the formation position and reading position of a spot. However, the spot only indicates one point on the object to be read, it cannot indicate whether the entire code symbol is within the readable range, and if the entire code symbol is not within the readable range, retry. Will be repeated.

  If such an optical information reader having an autofocus function is provided with a light source and an optical system for displaying a readable range, the autofocus function can be realized and the readable range can be shown. . However, an independent light source and an optical system are required to indicate the distance measurement and the readable range, which makes it difficult to reduce the size and cost of the apparatus.

  Furthermore, it is possible to indicate the readable range by expanding the irradiation range of the distance measuring laser to a size indicating the readable range, but the distance measurement required for decoding the read code symbol is possible. Accuracy cannot be obtained, and reliable distance measurement cannot be performed.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an optical information reading apparatus capable of speeding up a distance measurement process and reliably performing distance measurement.

  In order to solve the above-described problems, the present invention provides an imaging optical means having a variable focus optical system, an imaging means for imaging a reading object, a distance measuring means for measuring a distance from the reading object, and a measurement. The distance measuring means comprises a control means for calculating the distance to the reading object using the distance means, controlling the imaging optical means based on the calculated distance information, and imaging the reading object by the imaging means, The distance measuring light for forming a distance measuring pattern in which the light irradiation area and the non-irradiation area are combined is formed on the reading object, and the control means images the distance measuring pattern formed on the reading object by the imaging means. An optical information reading device that obtains an image of a distance measurement pattern, detects a portion where the signal falls according to the intensity of light incident on the imaging means, and performs distance measurement based on the coordinates of the non-irradiated area of the distance measurement pattern It is.

  In the present invention, a distance measurement light is irradiated, a distance measurement pattern in which a light irradiation area and a non-irradiation area are combined is formed on a reading object, and the distance measurement pattern formed on the reading object is imaged and measured. A distance pattern image is acquired, a portion where the signal falls in the image signal is detected, and the distance to the reading object is obtained based on the coordinates of the non-irradiation area of the distance measurement pattern.

  According to the present invention, it is possible to increase the processing speed and reliably perform distance measurement regardless of changes in the amount of peripheral light, the size of an object to be read, and the like. If the distance measuring light is visible light, the readable range can be displayed with a single light source and optical system used for distance measuring using the irradiation area of the distance measuring pattern.

It is a functional block diagram which shows an example of the optical information reader of this Embodiment. It is a perspective view which shows the example of mounting of the optical information reader of this Embodiment. It is a perspective view which shows the example of mounting of the optical information reader of this Embodiment. It is a block diagram which shows an example of the ranging light emission part which comprises the optical information reader of this Embodiment. It is a block diagram which shows the other example of the ranging light emission part which comprises the optical information reader of this Embodiment. It is explanatory drawing of the parameter required for calculation of the distance to a reading target object. It is a graph which shows the relationship between the distance to a reading target object, and the signal strength by the ranging pattern which injects into a solid-state image sensor. It is a block diagram which shows an example of the shape of a ranging pattern. It is a perspective view which shows an example of a pattern formation lens. It is optical path explanatory drawing which shows an example of the optical path of the ranging light by a pattern formation lens. It is optical path explanatory drawing which shows the formation principle of the irradiation area | region and non-irradiation area | region by a pattern formation lens. It is a functional block diagram which shows an example of a solid-state image sensor. It is a block diagram which shows the concept of a liquid crystal lens. It is a block diagram which shows the concept of a liquid lens. It is a flowchart which shows the reading operation | movement of the code symbol in the optical information reading apparatus of this Embodiment. It is a flowchart which shows the reading operation | movement of the code symbol in the optical information reading apparatus of this Embodiment. It is a flowchart which shows an example of the ranging operation in the optical information reading apparatus of this Embodiment. It is explanatory drawing which shows the relationship between a ranging pattern and the area to capture. It is explanatory drawing which shows an example of the image signal obtained by imaging a ranging pattern. It is explanatory drawing which shows an example of the effect of the optical information reader of this Embodiment. It is explanatory drawing which shows the subject of the conventional ranging method as a comparative example. It is explanatory drawing which shows the other example of the effect of the optical information reader of this Embodiment. It is explanatory drawing which shows the subject of the conventional ranging method as a comparative example. It is explanatory drawing which shows the subject of the conventional ranging method as a comparative example.

  Embodiments of the optical information reading apparatus of the present invention will be described below with reference to the drawings.

<Example of Configuration of Optical Information Reading Device of the Present Embodiment>
FIG. 1 is a functional block diagram illustrating an example of an optical information reading apparatus according to the present embodiment, and FIGS. 2 and 3 are perspective views illustrating an implementation example of the optical information reading apparatus according to the present embodiment. FIG. 4 is a block diagram showing an example of a distance measuring light emitting unit constituting the optical information reading apparatus of the present embodiment, and FIG. 5 shows distance measuring constituting the optical information reading apparatus of the present embodiment. It is a block diagram which shows the other example of a light-projection part.

  The optical information reading apparatus 1A according to the present embodiment includes a camera unit 10 that images a code symbol 100 that is a reading object, and a decoding that performs control such as imaging, focus adjustment, decoding, and data transfer performed by the camera unit 10. The unit 11 is provided.

  The optical information reading apparatus 1A is called a code scanner and has a configuration capable of imaging the code symbol 100 written on a label attached to an article or the code symbol 100 written directly on the article.

  An optical information reading apparatus 1A shown in FIG. 2 is a code scanner called a manual trigger. For example, components such as a camera unit 10 and a decoding unit 11 are mounted on a housing 201 having a grip unit 200 and used. In this configuration, the person can hold the grip portion 200 and point the camera portion 10 toward the code symbol 100 written on the article 300 so that the code symbol 100 can be imaged.

  An optical information reading apparatus 1A shown in FIG. 3 is a code scanner called an auto trigger. For example, the configuration of the camera unit 10 and the decoding unit 11 is provided on a housing 203 having a mounting unit 202. The code symbol 100 is imaged by directing the code symbol 100 (not shown in FIG. 3) on which the element is mounted and the article 301 to the camera unit 10.

  Next, the overall configuration of the camera unit 10 will be described. The camera unit 10 detects distance of the code symbol 100 that is the object to be read and distance measurement light that forms a distance measuring pattern 101a as shown in FIG. 4 on the object to be read in order to measure the distance to the object to be read. A distance measuring light emitting unit 2 that irradiates Sa or a distance measuring light Sb that forms a distance measuring pattern 101b as shown in FIG.

  In addition, the camera unit 10 includes a solid-state imaging device 3 that captures an image of the distance measurement pattern 101 a or the distance measurement pattern 101 b formed on the reading object and an image of the reading object including the code symbol 100.

  Further, the camera unit 10 has an illumination light emitting unit 4 that emits illumination light, and an autofocus (variable focus) function that forms an image of natural light or illumination light reflected by the code symbol 100 on the solid-state imaging device 3. An imaging optical unit 5 is provided that forms an image corresponding to the pattern of the code symbol 100 based on a difference in reflectance between, for example, a white portion and a black portion of the pattern constituting the symbol 100. The camera unit 10 also includes a driver 6 that drives the distance measuring light emitting unit 2, the illumination light emitting unit 4, and the imaging optical unit 5.

  FIG. 6 is an explanatory diagram of parameters necessary for calculating the distance to the reading object. Next, an outline of distance measurement in the optical information reading apparatus 1A of the present embodiment will be described.

  The distance X to the reading object at any position WD1 to WD3 can be calculated based on the next parameter in FIG. 6 and the following equation (1).

X: distance from the origin plane O passing through the principal point of the imaging optical unit 5 to the reading object a: distance between the optical axes of the ranging light emitting unit 2 and the imaging optical unit 5 at the origin plane O: imaging optical unit 5 Half-angle of view N: Distance from the center of the solid-state image sensor 3 to the short point stretched by the half-field angle n: Position at which the ranging light is reflected in the imaging area of the solid-state image sensor 3 φ: Ranging light emitting unit 2 Between the optical axis of the imaging optical unit 5 and the origin plane O

  When the distance measuring light is irradiated to the reading object and the distance measuring light irradiated to the reading object is imaged by the solid-state imaging device 3, the distance to the reading object is the pixel of the solid-state imaging element 3 that images the distance measuring light. By detecting the coordinates of the pixel of the solid-state imaging device 3 that is indicated by the coordinates and has picked up the distance measuring light, the distance to the reading object can be calculated from the above-described parameters and Equation (1).

  In order to perform distance measurement with high accuracy, a signal that can detect the coordinates of the pixels of the solid-state imaging device 3 that has imaged the distance measurement light by image processing exists at the distance measurement position P to which the distance measurement light is irradiated. It is a condition.

  Therefore, in the optical information reading apparatus 1A, as shown in FIG. 4, the distance measurement pattern in which the light irradiation region 102a and the non-irradiation region 103a are combined with the distance measurement light Sa emitted from the distance measurement light emitting unit 2. 101a is formed on the reading object. Alternatively, as shown in FIG. 5, a distance measuring pattern 101b in which the light irradiation area 102b and the non-irradiation area 103b are combined is formed on the reading object by the distance measuring light Sb emitted from the distance measuring light emitting section 2. .

  A distance measuring pattern 101a shown in FIG. 4 is formed as a pattern in which the irradiation region 102a spreads in one horizontal direction, and has a predetermined width at least in the horizontal direction. Further, the distance measurement pattern 101a is a non-irradiation region in a pattern in which the solid-state imaging device 3 can detect the falling and rising of a signal at least at one position between the irradiation regions 102a, in this example, the central portion of the irradiation region 102a. 103a is provided so that at least one signal drop portion exists in the distance measurement pattern 101a.

  Thereby, when the distance measuring pattern 101a is viewed from one horizontal direction, the falling edge signal is detected from the signal output from the solid-state imaging device 3 by imaging the distance measuring pattern 101a. Rising signals that are close to each other with a predetermined width are obtained, and distance measurement processing is enabled by the falling signals and the image signals of the rising signals.

  Similarly, the distance measurement pattern 101a shown in FIG. 5 is also formed with a pattern in which the irradiation region 102b spreads in one horizontal direction and has a predetermined width at least in the horizontal direction. The distance measurement pattern 101b is a non-irradiation area in a pattern in which the signal image can be detected by the solid-state imaging device 3 at least at one position between the irradiation areas 102b, in this example, at the center of the irradiation area 102b. 103b is provided so that at least one signal drop portion exists in the distance measurement pattern 101b.

  Thereby, when the distance measuring pattern 101b is viewed from one direction in the horizontal direction, from the signal output from the solid-state imaging device 3 by imaging the distance measuring pattern 101b, the falling signal and the falling signal are detected. Rising signals that are close to each other with a predetermined width are obtained, and distance measurement processing is enabled by the falling signals and the image signals of the rising signals.

  FIG. 7 is a graph showing the relationship between the distance to the reading object and the signal intensity according to the distance measurement pattern incident on the solid-state image sensor. In FIG. 7, the distance measurement pattern 101a or the distance measurement imaged by the solid-state image sensor 3 for each distance. A signal intensity distribution obtained by scanning the pattern 101b in the horizontal direction of the pixels of the solid-state imaging device 3 is shown.

  In the optical information reading apparatus 1A, the position where the ranging light reflected by the reading object enters in the imaging area of the solid-state imaging device 3 changes according to the distance to the reading object. Therefore, when the distance measuring pattern 101a shown in FIG. 4 or the distance measuring pattern 101b shown in FIG. 5 formed on the reading object is imaged by the solid-state image sensor 3, the distance measuring pattern 101a in the imaging area of the solid-state image sensor 3. Alternatively, the position where the distance measuring pattern 101b is incident changes according to the distance to the reading object.

  In the optical information reading apparatus 1A, when the distance measurement pattern 101a having the non-irradiation region 103a or the distance measurement pattern 101b having the non-irradiation region 103b is imaged by the solid-state image sensor 3, the image of the solid-state image sensor 3 is captured. The position of the non-irradiation region 103a of the distance measurement pattern 101a or the non-irradiation region 103b of the distance measurement pattern 101b in the area changes according to the distance to the reading object.

  As a result, as shown in FIG. 7, the portion where the signal output from the solid-state imaging device 3 falls at a level corresponding to the intensity of light incident on the imaging area of the solid-state imaging device 3 depends on the distance to the reading object. Change.

  Therefore, in the optical information reading apparatus 1A, a portion where the signal output from the solid-state imaging device 3 falls is detected, and the portion where the signal falls is used as a distance measurement signal portion SgD, and the non-irradiation region 103a of the distance measurement pattern 101a, Alternatively, by detecting the coordinates of the pixel of the solid-state imaging device 3 that images the non-irradiated region 103b of the distance measuring pattern 101b, the distance to the reading object is calculated from the above-described parameters and the equation (1).

  Thereby, the distance measurement pattern 101a or the distance measurement pattern 101b formed on the reading object exists as a portion where the signal indicating the non-irradiation region 103a or the non-irradiation region 103b falls, and the non-irradiation region 103a or the non-irradiation region A signal capable of detecting the coordinates of the pixels of the solid-state imaging device 3 that has imaged the region 103b by image processing is present at the distance measurement position P to which the distance measurement light Sa or the distance measurement light Sb is irradiated. Distance can be done.

  Further, by making the distance measuring light Sa or the distance measuring light Sb visible light, the reading range can be visually recognized using the irradiation area 102a of the distance measuring pattern 101a or the irradiation area 102b of the distance measuring pattern 101b. .

  FIG. 8 is a configuration diagram showing an example of the shape of the distance measurement pattern. In FIG. 8, the distance measurement pattern formed by the optical system shown in FIG. 4 will be described as an example, but the same applies to the distance measurement pattern formed by the optical system shown in FIG.

  The non-irradiation region 103a that is the distance measurement position P in the distance measurement pattern 101a is desirably provided at the center of the distance measurement pattern 101a. As shown in FIG. 8A, when the code object 100a is smaller than the distance measuring pattern 101a as shown in FIG. 8A, there is a high possibility that the position of the code symbol 100a is normally aligned with the center of the distance measuring pattern 101a. Therefore, the non-irradiation region 103a that is the distance measurement position P is formed on the code symbol 100a to improve the distance measurement accuracy.

  As shown in FIG. 8B, when a wide code symbol 100b is read, the range of reading can be easily determined by indicating the readable range by the distance measuring pattern 101a, thereby improving the operability. it can. Therefore, it is desirable to form the distance measurement pattern 101a having a width in the horizontal direction at least, rather than irradiating only the distance measurement pattern 101a to the central portion.

  Next, details of the distance measuring light emitting unit that forms the distance measuring pattern described above will be described with reference to the drawings. The distance measuring light emitting unit 2 is an example of distance measuring means, and forms a distance measuring light Sa that forms a distance measuring pattern 101a or a distance measuring pattern 101b from a light source 20 that emits light and light emitted from the light source 20. A pattern forming lens 21 that converts the distance measuring light Sb to be measured.

  In the example illustrated in FIG. 4, the light source 20 includes a light emitting diode (LED) that emits light having a wavelength in the visible region. Further, the example shown in FIG. 5 is configured by a semiconductor laser (LD) that emits light having a wavelength in the visible region.

  In the distance measuring pattern 101a or the distance measuring pattern 101b formed by the distance measuring light Sa or the distance measuring light Sb emitted from the distance measuring light emitting unit 2, the irradiation area 102a or the irradiation area 102b, which is the majority of the image signal, is solid. In order to be able to be detected by the image pickup device 3, the light source 20 is preferably an LED light source or a laser light source having a high intensity with a pulse as described above.

  FIG. 9 is a perspective view showing an example of a pattern forming lens, FIG. 10 is an optical path explanatory view showing an example of an optical path of distance measuring light by the pattern forming lens, and FIG. 11 is an irradiation region and a non-irradiation region by the pattern forming lens. It is an optical path explanatory drawing which shows a formation principle, and next, an example of the optical system which forms the ranging pattern 101a or the ranging pattern 101b is demonstrated with reference to each figure.

  In the distance measuring light emitting unit 2, the non-irradiated area 103a of the distance measuring pattern 101a shown in FIG. 4 or the non-irradiated area 103b of the distance measuring pattern 101b shown in FIG. An optical system having a predetermined angle α is configured.

  In the distance measuring light emitting unit 2, the distance measuring pattern 101a or the distance measuring pattern 101b is made of visible light, and the irradiation area 102a of the distance measuring pattern 101a or the irradiation area 102b of the distance measuring pattern 101b is the imaging optical unit. The optical system is configured so as to be a readable range that is determined by the angle of view of 5 and the size of the imaging area of the solid-state imaging device 3 and changes according to the distance to the reading object.

  In the distance measuring light emitting unit 2, the light emitted from the light source 20 spreads at a predetermined radiation angle in a horizontal direction as one direction and a vertical direction as another direction. Therefore, the ranging light emitting unit 2 uses the horizontal spread of the light emitted from the light source 20 to form the irradiation region 102a of the ranging pattern 101a or the irradiation region 102b of the ranging pattern 101b. In this example, the horizontal emission angle of the light emitted from the light source 20 and the readable range are matched.

  In the distance measuring light emitting unit 2, the non-irradiated area 103b of the distance measuring pattern 101a or the non-irradiated area 103b of the distance measuring pattern 101b is formed in a part of the light emitted from the light source 20 in the horizontal direction.

  For this reason, the pattern forming lens 21 transmits the light emitted from the light source 20 and spreading in the horizontal direction while maintaining the radiation angle matched to the readable range, and the light spreading in the vertical direction is refracted into, for example, parallel light. For example, the incident surface 21a is a flat surface, the output surface 21b is a flat surface along the horizontal direction, and a cylindrical lens formed with a curved surface curved in a convex shape along the vertical direction.

  Further, the pattern forming lens 21 changes the optical path of a part of the light emitted from the light source 20 by utilizing refraction or reflection of light, and the non-irradiation region 103a of the distance measurement pattern 101a or the distance measurement pattern 101b is not changed. In order to form the irradiation region 103b, a prism-shaped slit 21c is formed in a part of the emission surface 21b along the vertical direction. The slit 21c is formed by providing a groove having a V-shaped cross section at the central portion along the horizontal direction of the emission surface 21b of the pattern forming lens 21.

In FIG. 11, the refractive index of the pattern forming lens 21 is n ₁ , and the refractive index in air is n ₂ . The light emitted from the light source 20 and incident on the pattern-forming lens 21 and incident on the output surface 21b other than the portion where the slit 21c is formed is perpendicular to the boundary surface between the output surface 21b and air. Can be considered.

  As a result, the light that is emitted from the light source 20 and spreads in the horizontal direction and is incident on the emission surface 21b other than the portion where the slit 21c is formed is, as shown in the optical path L1 in FIG. 11, the boundary between the emission surface 21b and air. The light does not substantially refract in the horizontal direction on the surface, and passes through the pattern forming lens 21 while maintaining the radiation angle at the light source 20.

  On the other hand, the light incident on the slit 21c is refracted at a refraction angle γ corresponding to the refractive index of the pattern forming lens 21 and air, where β is the incident angle to the boundary surface between the exit surface 21b and air. Further, the light is reflected at the boundary surface between the emission surface 21b and the air.

  As a result, the light that is emitted from the light source 20 and spreads in the horizontal direction and is incident on the slit 21c is refracted or reflected at the boundary surface between the emission surface 21b and air, as indicated by the optical paths L2 and L3 in FIG. , The optical path is converted.

  Therefore, as shown in FIG. 10, the pattern forming lens 21 can generate an angle at which light does not radiate, with the formation site of the slit 21c as the center. Therefore, in the ranging light emitting unit 2, the light that is emitted from the light source 20 and spreads in the horizontal direction is emitted through the pattern forming lens 21 so as to avoid the central portion in the horizontal direction, as shown in FIG. Ranging light Sa forming a distance measuring pattern 101a in which a non-irradiated area 103a is formed at the center of the irradiated area 102a is emitted. Alternatively, as shown in FIG. 5, distance measuring light Sb that forms a distance measuring pattern 101b in which a non-irradiation area 103b is formed at the center of the irradiation area 102b is emitted.

  The pattern forming lens 21 has an angle at which light is not transmitted using total reflection of light, such as by forming a reflective film at the center in the horizontal direction of the emission surface 21b, or by forming a reflective film at the slit 21c. Can also be generated.

  Next, other components of the camera unit 10 will be described. The solid-state imaging device 3 is an example of an imaging unit, and in this example, is configured by a CMOS (complementary metal oxide semiconductor) image sensor. The solid-state imaging device 3 detects light incident through the imaging optical unit 5 by the imaging device, and outputs a detection signal from each imaging device to the decoding unit 11 as digital image data. Take an image.

  As described above, a pulsed and strong LED light source or laser light source is used as the light source 20 of the distance measuring light emitting unit 2 that forms the distance measuring pattern 101a shown in FIG. 4 or the distance measuring pattern 101b shown in FIG. In the configuration, it is desirable that the solid-state imaging device 3 is a global shutter that can release the shutter at the same time for all pixels. In order to increase the processing speed related to the distance measurement pattern, the solid-state imaging device 3 that can process the image of the distance measurement pattern by sub-sampling (ROI function: Region of Interest) is desirable.

  FIG. 12 is a functional block diagram illustrating an example of a solid-state image sensor. Next, a CMOS image sensor that is an example of the solid-state image sensor 3 will be described in detail with reference to FIG. The imaging area 30 provided in the solid-state imaging device 3 has each pixel of the pixel unit 31 transfer a photodiode, an FD (floating diffusion) region, and a transfer for transferring charges from the photodiode to the FD region. The pixel includes a transistor and a reset transistor for resetting the FD region to a predetermined potential, and a plurality of pixels are formed in a matrix.

  In the imaging area 30, a vertical shift register 32 for controlling a vertical signal is arranged on a side of a pixel matrix in which pixels are formed in a matrix, and a horizontal shift register 33 for controlling a horizontal signal is provided below the pixel matrix. Is arranged.

  The vertical shift register 32 and the horizontal shift register 33 are analog circuits that generate voltages necessary for pixel driving. Signals from the vertical shift register 32 and the horizontal shift register 33 are output to the outside via the analog processor 34, the A / D converter 35, and the digital processor 36 in order.

  The analog processor 34 includes functions such as voltage amplification and gain adjustment, and performs predetermined analog signal processing. The A / D converter 35 converts the analog image signal of the analog processor 34 into a digital image signal. The digital processor 36 includes functions such as noise cancellation and data compression, performs digital processing on the digital image signal from the A / D converter 125, and outputs the processed digital image signal to the outside.

  The control register 37 inputs / outputs external signals, causes the timing controller 38 to synchronize the clock timings of the analog processor 34 and the digital processor 36, and outputs image data from the pixels of the pixel unit 31 in a predetermined order. .

  Furthermore, in the solid-state imaging device 3, a global shutter that controls the start and stop of charge accumulation in accordance with the amount of received light in each pixel substantially simultaneously in all pixels is employed. For this purpose, a plurality of comparators for individually comparing a value corresponding to the accumulated charge in each pixel with a common reference value, a terminal for outputting a logical sum signal of these output signals, and the like are provided. When at least one of the outputs of the plurality of comparators of the pixel unit 31 indicates that the accumulated charge is larger than the reference value, the global shutter is controlled to stop accumulating the charge in each pixel.

  Returning to FIG. 1, the illumination light emitting unit 4 is an example of an illuminating unit, and illuminates the reading object with illumination light Sc under the control of the decoding unit 11. Irradiation of the illumination light Sc is performed by irradiation of pulsed light synchronized with the imaging frame of the solid-state imaging device 3, and by adjusting the irradiation time, solid-state imaging is performed by reflected light from the reading object within an imaging period of one frame. The amount of charge accumulated in each photodiode of the element 3 can be adjusted. That is, if the illumination time is lengthened, the image obtained by imaging by the solid-state imaging device 3 becomes a bright image, and if it is shortened, the image becomes a dark image.

  The imaging optical unit 5 is an example of imaging optical means, and includes an imaging lens 50 and a variable focus lens 51. In this example, the imaging lens 50 is a fixed focus lens that includes one or a plurality of glass or plastic optical lenses.

  The variable focus lens 51 may include, for example, a mechanism that mechanically moves one or a plurality of optical lenses along the optical axis to realize an autofocus function. On the other hand, the variable focus lens 51 is configured by a liquid crystal lens or a liquid lens capable of adjusting a focal length by an applied voltage, as an autofocus function without using a mechanism for mechanically moving the lens. May be.

  FIG. 13 is a configuration diagram showing the concept of the liquid crystal lens. The liquid crystal lens 51 a has a configuration in which a liquid crystal layer 53 having a homogeneous (non-twisted) molecular arrangement is sealed between glass plates 54, and transparent electrodes 55 a and 55 b made of metal oxide are formed on each glass plate 54. The The liquid crystal lens 51a applies a voltage to the transparent electrodes 55a and 55b and adjusts the applied voltage, whereby the alignment state of the liquid crystal molecules 53a changes. The liquid crystal lens 51a changes the refractive index by changing the alignment state of the liquid crystal molecules 53a, and the focal length changes by changing the refractive index. As a result, the liquid crystal lens 51a can adjust the voltage to be applied to move the focal position and perform focusing.

  FIG. 14 is a configuration diagram showing the concept of the liquid lens. In the liquid lens 51b, a highly conductive aqueous solution 56 and an insulating oil 57 are sealed in a container 58 having two transparent windows that transmit light. The liquid lens 51b includes an electrode 59a that is in contact with the aqueous solution 56, and an electrode 59b that is in contact with both the aqueous solution 56 and the oil 57 via an insulating portion.

  The liquid lens 51 b can change the shape of the boundary surface 56 a between the aqueous solution 56 and the oil 57 when electricity is applied from the electrodes 59 a and 59 b and a voltage is applied to the aqueous solution 56. Such a phenomenon is called an electrowetting phenomenon. By changing the curvature of the boundary surface 56 a between the aqueous solution 56 and the oil 57, the focal position can be moved and focusing can be performed.

  Here, in the configuration in which the liquid crystal lens 51a or the liquid lens 51b is used as the variable focus lens 51, temperature compensation is required in order to correct the shift of the focal position due to temperature fluctuation. For this reason, the optical information reading apparatus 1A is, as shown in FIG. 1, as temperature detecting means for detecting the temperature in the vicinity of the variable focus lens 51 and the variable focus lens 51 constituted by the liquid crystal lens 51a or the liquid lens 51b. A temperature sensor 7 is provided in the camera unit 10.

  The optical information reader 1A uses the temperature sensor 7 to determine the focal position of the liquid crystal lens 51a or the liquid lens 51b derived from the distance information to the code symbol 100 obtained by emitting the distance measuring light from the distance measuring light emitting unit 2. Corrects the detected temperature information to achieve accurate autofocus.

  Next, the decoding unit 11 will be described. The decoding unit 11 is an example of a control unit. The decoding unit 11 is used as a work area when the CPU 12, the ROM 13 that stores programs and tables executed by the CPU 12, and the CPU 12 executes various processes. RAM 14 is provided.

  For example, an ASIC (Application Specific Integrated Circuit: ASIC) can be used as the CPU 12. Further, a flash ROM (FROM) can be used as the ROM 13, and an SDRAM (Synchronous Dynamic Random Access Memory) can be used as the RAM 14.

  The CPU 12 controls the overall operation of the optical information reading apparatus 1A by executing a program stored in the ROM 13 using the RAM 14 as a work area, and also reads an object to be read based on digital image data imaged by the solid-state imaging device 3. Detection, detection of the distance to the object to be read, focus control based on the obtained distance, decoding of the code symbol 100, output of the decoding result to the outside or accumulation, etc. are performed.

<Example of Operation of Optical Information Reading Device of Present Embodiment>
FIG. 15 and FIG. 16 are flowcharts showing the code symbol reading operation in the optical information reading apparatus of the present embodiment. Next, referring to the drawings, the optical information reading apparatus 1A of the present embodiment will be described. The operation will be described.

  Here, FIG. 15 shows a reading operation by a code scanner called a manual trigger shown in FIG. 2, and FIG. 16 shows a reading operation by a code scanner called an auto trigger shown in FIG.

  First, the reading operation by the manual trigger code scanner will be described. When the manual trigger is turned on by operating an operation button (not shown) or the like in step SA1 in FIG. 15, the CPU 12 controls the ranging light emitting unit 2 to control the ranging light Sa or the ranging light Sb in step SA2. Irradiation is started, and the solid-state imaging device 3 is controlled to start imaging the distance measuring pattern 101a shown in FIG. 4 or the distance measuring pattern 101b shown in FIG.

  In step SA3 in FIG. 15, the CPU 12 calculates the exposure from the image obtained by imaging the distance measurement pattern 101a or the distance measurement pattern 101b with the solid-state imaging device 3. Further, as described above, the non-irradiation region 103a or the non-irradiation region 103b, which is a distance measurement position, is detected at the falling edge of the signal and the rising edge of the signal. Then, the distance to the reading object is calculated from the coordinates of the non-irradiation region 103a or the non-irradiation region 103b.

  In step SA4 of FIG. 15, the CPU 12 controls the irradiation time of the illumination light Sc by the illumination light emitting unit 4 to adjust the exposure, and controls the imaging optical unit 5 to focus on the code symbol 100 that is a reading object. Match. In the configuration in which the variable focus lens 51 constituting the imaging optical unit 5 is the liquid crystal lens 51a or the liquid lens 51b, a distance-voltage table (not shown) based on the distance to the reading object and the temperature detected by the temperature sensor 7. Set the applied voltage with reference to and focus.

  In step SA5 of FIG. 15, the CPU 12 controls the solid-state imaging device 3 to start imaging of the code symbol 100 that is a reading target to be decoded, and includes the code symbol 100 from the solid-state imaging device 3 in step SA6. The image of the reading object is transferred to the decoding unit 11.

  In step SA7 in FIG. 15, the CPU 12 determines whether the image transferred from the solid-state imaging device 3 is a decodable image. If it is determined that the image transferred from the solid-state image pickup device 3 is not a decodable image, the process returns to step SA2, and distance measurement light irradiation, distance measurement, and imaging of the reading object are performed.

  If it is determined that the image transferred from the solid-state imaging device 3 is a decodable image, the CPU 12 starts the decoding process in step SA8 in FIG. 15, and determines that the decoding process is possible in step SA9. Then, the code symbol 100 is decoded and the reading process is terminated. If it is determined in step SA9 that the decoding process is not possible, the process returns to step SA2 to perform irradiation of distance measuring light, distance measurement, and imaging of the reading object.

  Next, the reading operation by the auto trigger code scanner will be described. When the auto-trigger is turned on in step SB1 in FIG. 16 due to an article being held over or the like, in step SB2, the CPU 12 controls the distance measuring light emitting unit 2 to start irradiation of the distance measuring light Sa or the distance measuring light Sb. At the same time, the solid-state imaging device 3 is controlled to start imaging the distance measuring pattern 101a shown in FIG. 4 or the distance measuring pattern 101b shown in FIG.

  In step SB3 of FIG. 16, the CPU 12 determines from the output of the solid-state imaging device 3 whether there is an image signal from the reading object, and when determining that there is no image signal from the reading object, the CPU 12 returns to step SB2. Distance light irradiation and imaging are performed.

  If it is determined that there is an image signal from the reading object, in step SB4 in FIG. 16, the CPU 12 calculates the exposure from the image obtained by imaging the distance measurement pattern 101a or the distance measurement pattern 101b with the solid-state image sensor 3. . Further, the non-irradiation region 103a or the non-irradiation region 103b is detected, and the distance to the reading object is calculated from the coordinates of the non-irradiation region 103a or the non-irradiation region 103b.

  In step SB5 of FIG. 16, the CPU 12 controls the irradiation time of the illumination light Sc by the illumination light emitting unit 4 to adjust the exposure, and controls the imaging optical unit 5 to focus on the code symbol 100 that is a reading object. Match.

  In step SB6 of FIG. 16, the CPU 12 controls the solid-state imaging device 3 to start imaging of the code symbol 100 that is a reading object to be decoded, and includes the code symbol 100 from the solid-state imaging device 3 in step SB7. The image of the reading object is transferred to the decoding unit 11.

  In step SB8 in FIG. 16, the CPU 12 determines whether the image transferred from the solid-state imaging device 3 is a decodable image. If it is determined that the image transferred from the solid-state imaging device 3 is not a decodable image, the process returns to step SB5, and exposure adjustment, focus adjustment, and imaging of the reading object are performed.

  If it is determined that the image transferred from the solid-state imaging device 3 is a decodable image, the CPU 12 starts decoding processing in step SB9 in FIG. 16, and determines that decoding processing is possible in step SB10. Then, the code symbol 100 is decoded and the reading process is terminated. If it is determined in step SB10 that the decoding process is not possible, the process returns to step SB5, and exposure adjustment, focus adjustment, and imaging of the reading object are performed.

  FIG. 17 is a flowchart showing an example of a distance measuring operation in the optical information reading apparatus of this embodiment, FIG. 18 is an explanatory diagram showing the relationship between the distance measuring pattern and the area to be captured, and FIG. 19 is an image of the distance measuring pattern. FIG. 15 is an explanatory diagram illustrating an example of an image signal obtained in this manner. Next, with reference to each drawing, the distance measurement described in steps SA2 and SA3 of the flowchart shown in FIG. 15 and steps SB2 and SB4 of the flowchart shown in FIG. Details of light irradiation, imaging of a distance measurement pattern, and distance calculation will be described.

  In step SC1 of FIG. 17, the CPU 12 controls the distance measuring light emitting unit 2 to start irradiation of the distance measuring light Sa or the distance measuring light Sb. In step SC2, the CPU 12 controls the solid-state imaging device 3 to read Imaging of the distance measurement pattern 101a or the distance measurement pattern 101b formed on the object is started. When the imaging of the distance measurement pattern 101a or the distance measurement pattern 101b is completed, the irradiation of the distance measurement light Sa or the distance measurement light Sb is ended in step SC3, and in step SC4, the image of the distance measurement pattern 101a or the distance measurement pattern 101b is displayed. take in.

  When the image of the distance measurement pattern 101a or the distance measurement pattern 101b is captured, the CPU 12 scans a predetermined sampling area E1 of the distance measurement image as shown in FIG. 18 in step SC5 of FIG.

  The distance measurement pattern 101a or the distance measurement pattern 101b is a signal having a width in the horizontal direction, and as shown in FIG. 18, the sampling area E1 is set in accordance with the shape of the distance measurement pattern 101a or the distance measurement pattern 101b. Then, for example, until the non-irradiation region 103a or the non-irradiation region 103b can be detected from the vicinity of the center of the image acquired by the solid-state image pickup device 3, that is, the signal drop portion that is the distance measurement signal unit SgD shown in FIG. Scan sequentially until possible.

  Thus, as shown in FIG. 18, if the sampling area E1 of the distance measurement image for capturing the distance measurement pattern image is set, it is not necessary to scan the image for all pixels, and the time required for distance measurement can be shortened. .

  When the distance measurement image sampling area E1 is scanned, in step SC6 in FIG. 17, the CPU 12 determines whether or not the captured image includes a signal of the distance measurement pattern 101a or the distance measurement pattern 101b. If it is determined that there is no signal of the distance measurement pattern 101a or the distance measurement pattern 101b, the process is terminated.

  If it is determined that there is a signal of the distance measurement pattern 101a or the distance measurement pattern 101b in the captured image, in step SC7 of FIG. 17, the CPU 12 coordinates the pixel of the signal drop portion which is the distance measurement signal portion SgD shown in FIG. Calculate

  When the coordinates of the pixel of the signal drop portion are calculated, in step SC8 in FIG. 17, the CPU 12 refers to the distance measurement table set in advance based on the above-described parameters and equation (1), and the code that is the object to be read. The distance to the symbol 100 is obtained, and in step SC9, the imaging optical unit 5 is controlled to adjust the focus.

<Example of effects of optical information reading apparatus of this embodiment>
In the optical information reading apparatus 1A of the present embodiment, the distance measuring pattern 101a is irradiated with the distance measuring light Sa (Sb) and the non-irradiation area 103a (103b) is provided between the light irradiation areas 102a (102b). (101b) is formed on the object to be read, and from the image signal obtained by imaging the distance measurement pattern 101a (101b), a signal drop portion is detected to obtain a signal necessary for distance measurement, and the distance to the object to be read is determined. Therefore, regardless of the change in the amount of peripheral light, the size of the object to be read, and the like, the processing speed can be increased and the distance can be reliably measured.

  The range-finding light Sa (Sb) is visible light, and the irradiation area 102a (102b) is a readable range corresponding to the angle of view of the imaging optical unit 5, the size of the pixel portion of the imaging area of the solid-state imaging device 3, and the like. Therefore, the readable range can be displayed with a single light source and optical system used for distance measurement.

  Accordingly, it is not necessary to provide another light source for displaying the readable range and an optical system for matching the light emitted from the light source to the readable range, and the apparatus can be reduced in size and cost. In addition, by displaying the readable range, it is not necessary to repeat the trial of the reading operation due to the code symbol 100 not being in the readable range, and the reading operation can be speeded up.

  Furthermore, since the distance measuring pattern 101a (101b) can be formed using an optical lens such as a cylindrical lens, the cost can be reduced as compared with an optical system using a diffraction grating or a hologram.

  FIG. 20 is an explanatory diagram showing an example of the effect of the optical information reading apparatus according to the present embodiment. FIG. 21 is an explanatory diagram showing a problem of a conventional distance measuring method as a comparative example. Details of the effect of distance measurement using the portion will be described.

  In the operation of acquiring the image of the distance measurement pattern 101a or the distance measurement pattern 101b in step SA2 of the flowchart of FIG. 15 or step SB2 of the flowchart of FIG. When the amount of light is large, the exposure may be saturated by the first imaging.

  Therefore, in step SA3 in FIG. 15 or step SB4 in FIG. 16, the exposure is calculated from the image acquired by imaging the distance measurement pattern 101a or the distance measurement pattern 101b with the solid-state imaging device 3, and the exposure is saturated. When the signal is not capable of ranging, exposure is corrected to obtain a signal capable of ranging.

  As shown in FIG. 21A, in the conventional distance measuring method for detecting a spot-like strong signal Sp4 set for distance measurement, when exposure is saturated, as shown in FIG. It is impossible to detect the intensity peak and to obtain a signal necessary for distance measurement. When detecting a signal intensity peak, the allowable exposure value is narrow and exposure correction is required, which hinders speeding up of the distance measurement process.

  On the other hand, as shown in FIG. 20 (a), in the optical information reading apparatus 1A of the present invention in which distance measurement is performed using a portion where the signal falls, even if the exposure is saturated, FIG. 20 (b) As shown in FIG. 5, the distance measurement signal section SgD can be detected from the signal falling edge and the signal rising edge, and the coordinates of the signal drop portion can be uniquely obtained.

  As a result, the distance measuring method according to the present embodiment for detecting the drop of the signal has a wider allowable exposure value of the signal that can be measured, compared to the conventional method for detecting the peak of the signal intensity level, and The number of exposure corrections can be reduced to speed up the distance measurement process.

  FIG. 22 is an explanatory view showing another example of the effect of the optical information reading apparatus of the present embodiment, and FIGS. 23 and 24 are explanatory views showing problems of a conventional distance measuring method as a comparative example. Next, the effect of performing distance measurement using a light source having a radiation angle, forming a non-irradiation region between irradiation regions indicating a readable range, and using a portion where a signal falls will be described.

  As a conventional distance measuring method using a barcode scanner having a variable focus function, there is a technique in which a spot formed on an object to be read with light emitted from a laser light source is imaged with a solid-state image sensor, and distance measurement is performed using the coordinates of the spot. Are known. On the other hand, as shown in FIG. 23A, even with a light source having a radiation angle, a spot portion Sp having a high intensity can be used as a distance measuring point.

  That is, when ranging light Sd emitted from a light source having a radiation angle is used to form a pattern having a spot portion Sp having a high intensity as a center, and this pattern is imaged by a solid-state imaging device, FIG. Thus, the signal Sp1 corresponding to the spot can be confirmed at the central portion. Thus, distance measurement can be performed by obtaining the coordinates of this signal.

  However, as shown in FIG. 23B, when the reading object 105 on which the code symbol 100 is formed is smaller than the radiation angle of the light source, the portion irradiated with the distance measuring light Sd. There is a portion that is not irradiated and a portion where the distance measuring light Sd is not reflected is generated.

  For this reason, as shown in FIG. 24B, if a portion lacking a signal is present in an image obtained by picking up a pattern formed by distance measuring light Sd having a radiation angle with a solid-state imaging device, it is set for distance measurement. In addition to the strong signal Sp1, the signal Sp3 having the same shape as the strong signal Sp2 set for distance measurement may be generated due to the close rise and fall of the signal.

  Therefore, if there is another signal having the same shape as the strong signal set for distance measurement, the signal intensity peak cannot be detected to uniquely determine the coordinates, and distance measurement cannot be performed.

  On the other hand, in the optical information reading apparatus 1A of the present invention, as shown in FIG. 22A, the reading object 105 on which the code symbol 100 is formed is compared with the distance measuring pattern 101a or the distance measuring pattern 101b. Even if a portion where the distance measurement pattern 101a or the distance measurement pattern 101b is not reflected is generated, there are a plurality of signal drop portions which are the distance measurement signal portion SgD as shown in FIG. 22B. Never do.

  Therefore, in the optical information reading apparatus 1A according to the present embodiment, by detecting the falling edge of the signal and the rising edge of the signal, it is possible to uniquely determine the coordinates of the drop portion of the signal, the size of the reading object, etc. Regardless of the conditions, distance measurement can be performed reliably.

  The present invention can be used for a barcode reader, a two-dimensional code reader, and the like, and can realize autofocus with high ranging accuracy.

  DESCRIPTION OF SYMBOLS 1A ... Optical information reader, 2 ... Ranging light emission part, 3 ... Solid-state image sensor, 4 ... Illumination light emission part, 5 ... Imaging optical part, 10 ... Camera 11, decoding unit 100, code symbol 101 a, 101 b distance measurement pattern 102 a 102 b irradiation region 103 a 103 b non-irradiation region

Claims (5)

Imaging optical means having a variable focus optical system;
An imaging means for imaging a reading object;
Distance measuring means for measuring the distance to the reading object;
Control means for calculating the distance to the reading object using the distance measuring means, controlling the imaging optical means based on the calculated distance information, and imaging the reading object by the imaging means;
The distance measuring means emits distance measuring light that forms a distance measuring pattern in which a light irradiation area and a non-irradiation area are combined on a reading object,
The control means obtains an image of the distance measurement pattern by imaging the distance measurement pattern formed on the object to be read by the imaging means, and a portion in which the signal falls according to the intensity of light incident on the image pickup means The optical information reading apparatus is characterized in that the distance is measured based on the coordinates of the non-irradiation area of the distance measurement pattern. 2. The optical information reading apparatus according to claim 1, wherein the distance measurement pattern has one non-irradiation region formed in a central portion of the irradiation region. The optical information reading apparatus according to claim 1, wherein the distance measuring pattern is formed by irradiating a reading object with distance measuring light in a visible region. The optical information reading device according to claim 3, wherein the distance measurement pattern indicates a readable range in the irradiation area that spreads in one direction. The distance measuring means includes a light source that emits light at a predetermined radiation angle in at least one direction;
A pattern forming lens that forms the distance measuring pattern in which the non-irradiation area is provided between the distance measuring areas by refraction or reflection of a part of the light emitted from the light source or changing the optical path by refraction and reflection. The optical information reader according to any one of claims 1 to 4, further comprising:

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