JP3810154B2 - Optical symbol reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reading device for optically readable optical symbols such as barcodes, characters and images.
[0002]
[Prior art]
For example, as a barcode reading device, one that reads an optical image of a barcode by forming it on a one-dimensional or two-dimensional image sensor via an optical system is known. There are some that adjust the focal position of the system to widen the focusing range, or use a zoom lens or the like to widen the reading range.
[0003]
For example, in Japanese Patent Laid-Open No. 53-30223, the focus state of an optical system with respect to a barcode is detected based on the output of an image sensor that detects a barcode image formed by the optical system. A device for performing focusing is disclosed. JP-A-62-280978 and JP-A-63-83886 disclose a so-called triangulation method in which near-infrared light is projected onto a bar code and the distance from the bar code is measured by a triangulation system. There is disclosed a technique in which distance information is obtained by active triangulation and an optical system is focused based on the distance information. Further, U.S. Pat. No. 4,877,949 discloses a method in which distance information to a bar code is obtained using an ultrasonic sensor and the optical system is focused based on the information. .
[0004]
[Problems to be solved by the invention]
However, in the reading device disclosed in the above-mentioned Japanese Patent Laid-Open No. 53-30223, the focus information is obtained by detecting the state of the bar code image from the output of the image sensor. There is a problem that it takes a long time to align, and there is a problem that, when a bar code is small and a non-contrast portion such as white paper is detected, the focus state cannot be determined.
[0005]
In addition, in the reading devices disclosed in Japanese Patent Application Laid-Open Nos. Sho 62-280978 and 63-83886, the visual field range by the optical system and the image sensor, that is, the image detection range, and the measurement are measured. The deviation from the distance point is not taken into account, so for example, if the object with the barcode is small, the distance cannot be measured or the erroneous distance measurement occurs and the barcode cannot be read. There's a problem.
[0006]
FIG. 3 shows a configuration of a conventional reading apparatus for explaining such a problem. This reading apparatus includes an optical system 22 having a zoom function for forming an optical image of a barcode (not shown) provided in a main body 21, an image sensor 23 for receiving the optical image, and a near infrared LED 24. , A distance measuring lens 25, a distance measuring unit 26 containing a semiconductor position detector (PSD) (not shown), and the like, and illumination LEDs 27 and 28. The main body 21 is provided with a window 29 on the side facing the barcode. Here, the optical system 22 and the distance measuring unit 26 include an optical axis O ₁₀ of the optical system 22, a distance measuring optical axis O ₂₀ of the distance measuring unit 26 (projection axis of near infrared light from the near infrared LED 24), and Are arranged so as to be parallel with the distance measurement d ₁₀ apart.
[0007]
In FIG. 3, the barcodes are illuminated by the illumination LEDs 27 and 28 through the window 29, and an optical image is formed on the image sensor 23 by the optical system 22 through the window 29. I try to read information. Further, in the distance measuring unit 26, the near infrared light from the near infrared LED 24 is projected toward the bar code through the distance measuring lens 25 and the window 29, and the reflected light on the object with the bar code is projected. Light is received by the PSD to obtain distance information, and based on the distance information, focus adjustment is performed on the barcode of the optical system 22.
[0008]
Here, the visual field range (image detection range) by the optical system 22 and the image sensor 23 varies between V _w10 and V _w20 to V _T10 and V _T20 due to zooming inside the optical system 22, and is F at a distance L _10. It is the width F ₃₀ at ₁₀ and the distance L ₂₀ from the F ₂₀ to the width of F _40. On the other hand, the distance measuring optical axis O ₂₀ of the distance measuring unit 26 is parallel to the optical axis O ₁₀ of the optical system 22 at a distance d ₁₀ . For this reason, when the field of view of the optical system 22 is narrow and the distance is short, the distance measuring optical axis O ₂₀ deviates from the field of view range F ₃₀ , and the portion other than the range of the barcode to be read is measured. In particular, when the object with the barcode is small, distance measurement cannot be performed, or erroneous distance measurement occurs, making reading impossible.
[0009]
In addition, in the reading device disclosed in US Pat. No. 4,877,949, the distance is measured using an ultrasonic sensor, and therefore, particularly when the detection target is relatively small. In this case, the distance cannot be measured accurately, and the same problem as described above occurs.
[0010]
The present invention has been made paying attention to the conventional problems described above, and has a wide reading distance range, and is also suitable for reading high-density symbols and symbols on small objects. It is an object of the present invention to provide an optical symbol reading device such as a barcode.
[0011]
More specifically, the focus of the optical system to the symbol on the object can be reliably ensured even when using an optical system having a zoom function that reduces the erroneous distance measurement and the like, and thus narrows the viewing angle. It is intended to provide a suitably configured optical symbol reader.
[0012]
[Means for Solving the Problems]
The invention according to claim 1, which achieves the above object, is an optical symbol reader, and receives an optical system that forms an optical image of the optical symbol and the optical image formed by the optical system. An image sensor; and distance measuring means for measuring a distance between the optical symbol and the reader main body, and the optical system and the image sensor are within a predetermined distance range in the optical axis direction of the optical system. The optical symbol is configured to be readable, and the distance measuring unit is configured so that the distance measuring optical axis crosses the optical axis of the optical system approximately in the middle of the predetermined distance range. It is.
[0013]
According to a second aspect of the present invention, in the optical symbol reading device according to the first aspect, the optical system has a zoom function with a variable image magnification.
[0014]
According to a third aspect of the present invention, there is provided the optical symbol reading device according to the second aspect, wherein the distance measuring optical axis of the distance measuring means within the predetermined distance range is the narrowest field of view of the optical system having the zoom function. It is characterized in that it is configured not to deviate from the field of view at the angle of view.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of the present invention. FIG. 1 is a transverse sectional view and FIG. 2 is a longitudinal sectional view. This reading device is of a handy type and has a head portion 1 and a grip portion 2. The head unit 1 includes a two-dimensional image sensor having an optical system 3 having a zoom function for forming an optical image of, for example, a barcode (not shown) and a rectangular detection surface for receiving the optical image. 4, a focus adjustment mechanism (not shown) for focusing the optical system 3, a distance measuring unit 5 for measuring the distance between the head unit 1 and the barcode to be read, the optical system 3 and the distance measuring unit. Four illumination LEDs 6 to 9 for illuminating a barcode arranged in the vicinity of 5 are provided, and a window 10 is provided outside the side facing the barcode.
[0016]
In the optical system 3, the reading field range by the image sensor 4 can be varied between V _{W1 to} V _W4 and V _{T1 to} V _T4 by the zoom function of the optical system 3, and F ₁₁ and F ₁₂ to F at the distance L _{1. 31,} the width of the F ₃₂ is obtained from the distance L ₂ in F _21, F ₂₂ as the width of the F _41, F ₄₂ is obtained, among these distance L ₁ L _2, an image of the bar code An image is formed on the image sensor 4. Note that the image sensor 4 is a rectangle whose F ₁₁ direction is larger than the F ₁₂ direction.
[0017]
The distance measuring unit 5 is arranged in the vicinity of the optical system 3 in the longitudinal direction of the detection surface of the image sensor 4. The distance measuring unit 5 is provided with a near infrared LED 11, a light projecting lens 12, a light receiving lens 13 and a PSD 14, and its distance measuring optical axis O ₂ (projection axis of near infrared light from the near infrared LED 11) is The optical system 3 is configured to cross the optical axis O ₁ . In this embodiment, the distance measuring optical axis O ₂ is in the cross section shown in FIG. 1 with respect to the optical axis O ₁ of the optical system 3, that is, in the longitudinal direction of the optical axis of the optical system 3 and the detection surface of the image sensor 4. As viewed from the directions orthogonal to each other, it traverses approximately halfway between the distances L ₁ and L _2, and is orthogonal to the longitudinal section shown in FIG. 2, ie, the optical axis of the optical system 3 and the short side direction of the detection surface of the image sensor 4. When viewed from the direction of the optical system 3, the optical system 3 is configured to be substantially parallel to the optical axis O ₁ with a distance d ₃ . Depending on the layout, d ₃ can be set to 0. In this way, the distance measuring optical axis O ₂ and the projection light beam for distance measurement are within the range of the fields of view F ₃₁ , F ₃₂ , F ₄₁ , and F ₄₂ even at the zoom position of V _{T1 to} V _{T4 with} the minimum viewing angle. A _{1 to} A ₄ should be accommodated.
[0018]
In addition, the grip unit 2 is provided with a signal processing circuit 16 that processes the outputs of the image sensor 4 and the PSD 14 and controls the operation of each unit, and a trigger for starting a reading operation outside. A switch (not shown) is provided.
[0019]
Hereinafter, an operation example of this embodiment will be described.
When the operator holds the grip part 2 of the apparatus in his hand and points the window 10 to the barcode to be read and presses the trigger switch, the distance measuring unit 5 and the object (not shown) having the barcode and the head part 1 Ranging is performed. In this distance measuring operation, the near-infrared LED 11 is turned on, and the near-infrared light is projected by the light projecting lens 12 into parallel projected light beams A _{1 to} A ₄ having the distance measuring optical axis O ₂ as a central ray. Projected onto the object. The reflected light from the object is received by the PSD 14 through the light receiving lens 13, and the distance between the head unit 1 and the object is measured by the signal processing circuit 16 based on the output.
[0020]
When the distance between the head unit 1 and the object is measured by the distance measuring operation, focus adjustment (not shown) is performed so that a barcode image is formed on the image sensor 4 based on the distance information. The optical system 3 is automatically focused by the mechanism. When the focusing is completed, the illumination LEDs 6 to 9 are turned on in synchronization therewith, whereby the barcode is illuminated, and the optical image is formed on the image sensor 4 by the optical system 3. The photoelectric output (image signal) of the image sensor 4 is supplied to the signal processing circuit 16 and decoded, and the decoded barcode information is transferred to the host computer via a cable (not shown).
[0021]
According to this embodiment, the distance measuring unit 5 is disposed in the vicinity of the optical system 3 in the longitudinal direction of the detection surface of the image sensor 4, and the distance measuring optical axis O ₂ is within the cross section shown in FIG. at a distance L _1, approximately midway reading distance ranging between L _2, so as to traverse the optical axis O ₁ of the optical system 3, within the longitudinal section shown in FIG. 2, substantially parallel Ryohikarijiku O _1, O ₂ Therefore, the distance measurement range does not deviate from the visual field range in the entire reading distance range even in a narrow angle of view by zooming. Therefore, the barcode information can always be accurately read within the reading distance range between the distances L ₁ and L ₂ . Further, since the lighting LEDs 6 to 9 are arranged in the vicinity of the periphery of the optical system 3 and the distance measuring unit 5, there is an advantage that the entire apparatus can be made compact.
[0022]
In addition, this invention is not limited only to embodiment mentioned above, Many deformation | transformation or a change is possible. For example, in the above-described embodiment, the image signal output from the image sensor 4 is decoded by the signal processing circuit 16 in the apparatus, and the decoded barcode information is transferred to the host computer. The binarized signal of the optical image of the barcode obtained by binarizing the image signal from the image sensor 4 without transferring the image signal may be transferred as it is, or the image signal of the image sensor 4 may be transferred as it is. it can. Alternatively, it can be configured as a so-called handy terminal that accumulates barcode information in the apparatus or performs arithmetic processing.
[0023]
Further, the imaging optical system 3 can be configured with a single focal point that does not have a zoom function, or can be a fixed focal point by omitting the focus adjustment function. In the case of a fixed focus, whether or not the object is within the readable distance range by the depth of focus can be determined from the distance information by the distance measuring means and displayed on the LED or the like.
[0024]
Further, the distance measuring method by the distance measuring means may be a passive triangular distance measurement in addition to the near infrared active type. Further, the image sensor 4 is not limited to a two-dimensional one, and a one-dimensional one can also be used. Furthermore, in the embodiment described above, the illumination LED is provided in the apparatus to illuminate the barcode, but the barcode can be read with external light such as natural light without using the illumination light source, Alternatively, a light source for illumination can be installed outside the apparatus.
[0025]
Further, the present invention is not limited to the barcode reading apparatus described above, but can be effectively applied to an optical symbol reading apparatus such as an OCR reader that reads normal characters and an image scanner that reads images.
[0026]
Additional Notes 1. The optical symbol reader according to claim 1, 2 or 3,
The image sensor has a rectangular detection surface;
The distance measuring means is configured such that the distance measuring optical axis crosses the optical axis of the optical system when viewed from the direction orthogonal to the optical axis of the optical system and the longitudinal direction of the detection surface of the image sensor. An optical symbol reader.
2. The optical symbol reader according to claim 1, 2, 3 or claim 1,
The optical symbol reader is characterized in that the distance measuring means is configured to perform distance measurement by an active triangular distance measuring method.
3. The optical symbol reader according to claim 1, 2, 3 or claim 1,
2. The optical symbol reader according to claim 1, wherein the distance measuring means is configured to measure a distance by a passive triangular distance measuring method.
4). In the optical symbol reader according to any one of claims 1 to 3 and appendices 1 to 3,
The optical system has a zoom function with a variable image magnification, and an optical symbol reader.
5). In the optical symbol reader according to appendix 4,
The distance measuring means is configured such that the distance measuring optical axis is inclined so as not to deviate within the predetermined distance range from the field of view at the narrowest field angle of view of the optical system having the zoom function. An optical symbol reader.
6). In the optical symbol reader according to any one of claims 1 to 3 and appendices 1 to 5,
An optical symbol reading apparatus comprising means for automatically adjusting the focus of the optical system based on the output of the distance measuring means.
7). In the optical symbol reader according to any one of claims 1 to 3 and appendices 1 to 5,
An optical symbol reading apparatus comprising: means for notifying whether or not the optical symbol is within the predetermined distance range based on an output of the distance measuring means.
8). In the optical symbol reader according to appendix 1,
The distance measuring means has a distance measuring optical axis that substantially coincides with the optical axis of the optical system when viewed from directions orthogonal to the optical axis of the optical system and the short side direction of the detection surface of the image sensor. An optical symbol reader characterized by comprising.
9. In the optical symbol reader according to any one of claims 1 to 3 and appendices 1 to 8,
An optical symbol comprising: at least one illuminating means for illuminating the optical symbol, wherein the distance measuring means is disposed between at least one of the illuminating means and an optical axis of the optical system. Reading device.
[0027]
【The invention's effect】
According to the present invention, since the distance measuring optical axis of the distance measuring means is substantially in the middle of the predetermined distance range and crosses the optical axis of the optical system, even when an optical system with a narrow viewing angle is used for zooming or the like. The ranging detection area does not deviate from the visual field range. Therefore, there is no false distance measurement even for small objects with high-density barcode labels, etc., and it is possible to perform reliable focus adjustment, and a simple reading device that can reliably read over a wide reading distance range. Can be realized at low cost and in a small size.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a reading device according to an embodiment of the present invention.
FIG. 2 is also a longitudinal sectional view.
FIG. 3 is a diagram for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Head part 2 Grip part 3 Optical system 4 Image sensor 5 Ranging unit 6, 7, 8, 9 LED for illumination
10 Window 11 Near-infrared LED
12 Light Emitting Lens 13 Light Receiving Lens 14 PSD
16 Signal processing circuit

Claims (3)

An optical symbol reader,
An optical system for forming an optical image of the optical symbol;
An image sensor for receiving the optical image formed by the optical system;
Ranging means for measuring the distance between the optical symbol and the reader body;
The optical system and the image sensor are configured to be able to read the optical symbol in a predetermined distance range in the optical axis direction of the optical system,
2. The optical symbol reader according to claim 1, wherein the distance measuring means is configured so that the distance measuring optical axis crosses the optical axis of the optical system substantially in the middle of the predetermined distance range . 2. The optical symbol reading apparatus according to claim 1 , wherein the optical system has a zoom function with a variable image magnification . Distance measuring optical axis of the distance measuring means within said predetermined distance range, according to claim 2, characterized in that configured so as not to deviate from the field of view at the most narrow viewing angle of the optical system having the zoom function Optical symbol reader.

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