JPH07104895B2 - Symbol reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention provides an optical method for displaying symbols such as bar codes and characters formed on the surface of an object such as a bar code reader and an optical character reader (OCR). The present invention relates to a symbol reading device for reading manually.

<Prior Art> In recent years, an optical character reading device or a bar code reading device which reads a character or a bar code recorded on a card, a packaging package or the like and immediately identifies the content thereof has been widely used. These symbol reading devices are now required to have a non-contact function of reading a symbol surface on which symbols such as characters and barcodes are formed. That is, when reading a bar code formed on various objects conveyed on a belt conveyor, it is possible to read the symbol without contacting the symbol surface positioned at various distances from the reading device. is necessary. Further, a so-called hand-held type reading device and the like are also required to have a function of reading a symbol without contact.

A bar code reader that can read the symbol surface in a non-contact manner is, for example, a laser beam from a semiconductor laser light source that passes through a condenser lens, is reflected by a polygon mirror or a galvanometer mirror, and is guided to the symbol surface. The symbol surface is scanned with the laser light by driving a galvanometer mirror or the like. Then, the reflected light from this symbol surface is detected by the light receiving means in the bar code reader constituted by the photoelectric conversion element. That is, if the bar code is scanned in the direction in which the laser beam intersects the bar forming the bar code, the light receiving means detects light of high intensity for the white bar, and the black bar is detected. A small intensity of light is detected for. Therefore, the barcode is read by subjecting the electric signal output from the light receiving means to waveform shaping or the like, level discrimination at an appropriate slice level, and binarization.

In such a bar code reader, the range from the lower limit to the upper limit of the readable distance (hereinafter referred to as "reading distance") between the symbol surface on which the barcode is formed and the bar code reader (hereinafter referred to as "reading range"). That is, it is preferable that it is relatively wide. However, in a device having a condenser lens that condenses light from a semiconductor laser light source, setting a wide reading range becomes a factor that makes design difficult. That is, even if the laser light is used, if the focus is set to infinity and the beam is narrowed down to a perfect parallel light beam, the diameter of the laser light cannot be reduced so much that high resolution cannot be obtained.
On the other hand, if you focus the laser light on a short distance,
When the laser beam is slightly away from the focus position, the diameter of the laser beam abruptly expands, and the resolution abruptly decreases, so that a sufficient reading range cannot be secured.

Generally, the optical system is designed by focusing on the center of the desired reading range or at a position slightly closer to it, but when the barcode reader is brought close to the symbol surface, the scanning width by the laser beam becomes small. Since the reading field of view becomes smaller, it is not possible to read long barcodes. Further, when the reading distance is increased, the diameter of the laser beam on the symbol surface becomes relatively large and the resolution is lowered, so that a thin barcode cannot be read. However, if the operator is required to perform the operation of searching for the optimum reading distance corresponding to the thinness of the bar code (including the operation of moving the lens, for example), the handheld type will significantly reduce the work efficiency, and The position adjustment work of a bar code reader fixedly installed is complicated.

A technique for solving this problem is disclosed in, for example, JP-A-63-83.
No. 886 is disclosed. That is, in this prior art, the symbol surface is irradiated with light from the newly provided infrared light emitting diode, and the reflected light is incident on the PSD (photodetector),
The distance between the bar code reader and the symbol surface is measured by so-called triangulation based on the detected position of the reflected light, and a condenser lens (reflected light from the symbol surface in this prior art is used based on the measured distance information. The optical position of a lens for condensing the light and for forming a barcode image on the two-dimensional image sensor is changed, so to speak, so to speak, automatic focus adjustment is performed. As a result, the reading range is increased.

Still other prior art is, for example, US Pat.
It is disclosed in Japanese Patent No. 18886. That is, in this prior art, in order to accurately read the barcode, the light source,
The optical elements such as the light receiving sensor, the diaphragm member, and the lens are controlled. That is, for example, by changing the curvature of the condensing lens made of an elastic body by a cylindrical piezoelectric element and changing the focal length of this condensing lens to improve resolution (Fig. 4), Technology that tries to respond to changes in reading distance by changing the position of the light source by selecting the light-emitting diode to be driven from the light-emitting diode array that is arranged tilted with respect to the axis (Fig.12, Fig, 13) etc. are shown.

<Problems to be Solved by the Invention> However, in the prior art disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-83886, in order to measure the distance between the bar code reader and the symbol surface, the bar code is read. Since an infrared light emitting diode is used in addition to the light source for this purpose, and a structure for driving the light emission is also required, there is a risk of cost increase. In addition, power consumption increases, which is disadvantageous particularly in a battery-operated bar code reader. Further, in the prior art disclosed in US Pat. No. 4,818,886, in the technology using the cylindrical piezoelectric element, the cost is high and it is difficult to drive because the piezoelectric element of this unique shape is used. I have a problem. Further, in the technology using the light emitting diode array tilted with respect to the optical axis of the condenser lens, when the light emitting diode deviated from the optical axis is selected, the image forming position of the light in the light receiving sensor is on the optical axis. There is a problem in that the light emitting element is displaced from the image forming position when it is selected, and therefore accurate reading cannot be achieved.

Therefore, the present invention solves the above-mentioned technical problems, and provides a symbol reading device which is capable of automatically and accurately reading a symbol in a wide reading distance range and which is advantageous in reducing the cost. To aim.

<Means for Solving the Problems> The symbol reading device of the present invention for achieving the above object is
A first condenser lens that narrows the light from the light source, a scanning mirror that scans the symbol surface on which a symbol is formed by the light from the first condenser lens, and an electric signal that receives the reflected light from the symbol surface. In a symbol reading device having a first photoelectric conversion element for converting the light into a symbol and optically scanning the symbol surface to read the symbol, the distance between the light source and the first condenser lens is First adjusting means for changing, a light selective transmitting member having reflected light from the symbol surface and having at least two pupils, and a second condenser lens for condensing light from the light selective transmitting member. A second photoelectric conversion element that receives light from the second condenser lens and detects each image forming position of light corresponding to the at least two pupils; By changing the distance between the photoelectric conversion element 2 and Second adjusting means for forming images corresponding to two pupils at the same position in the second photoelectric conversion element, wherein the first adjusting means is configured such that the light corresponding to the two pupils is equal to the first adjusting means. The light source receives the control signal from the second adjusting means corresponding to the distance between the second condenser lens and the second photoelectric conversion element in a state where the second photoelectric conversion element forms an image at the same position. The distance between the first condenser lens and the first condenser lens is adjusted.

<Operation> According to the above configuration, the symbol surface is optically scanned by the light source light focused by the first condenser lens, and the reflected light from the symbol surface is detected by the first photoelectric conversion element. The symbol is read. The reflected light from the symbol surface is also guided to the second condenser lens through at least two pupils of the light selective transmission member, and the two lights corresponding to the at least two pupils are coupled to the second photoelectric conversion element. Image. The second photoelectric conversion element detects each image forming position of the two lights.

The distance between the second condenser lens and the second photoelectric conversion element is adjusted by the second adjusting means so that the two lights are imaged at the same position in the second photoelectric conversion element. It The distance between the second condensing lens and the second photoelectric conversion element after the adjustment corresponds to the distance between the second condensing lens and the symbol surface, and eventually, the distance between the device and the symbol surface. It corresponds to the distance (reading distance).

Utilizing this fact, the distance between the light source and the first condenser lens is adjusted to the first position adjusting means corresponding to the distance between the second condenser lens and the second photoelectric conversion element. If the light source light is changed by, the light source light can be satisfactorily focused on the symbol surface, and various reading distances can be dealt with.

<Examples> Detailed description will be given below with reference to the accompanying drawings showing examples.

FIG. 1 is a plan view showing the basic configuration of a bar code reader which is an embodiment of the symbol reading device of the present invention. The laser light L from the semiconductor laser light source 1 is generated by the first condenser lens 2
The light is focused by and is incident on the deflection reflection surface 3a of the polygon mirror 3 which is a scanning mirror. The first condenser lens 2 is displaced in the direction of arrow 5 along the optical axis by the first adjusting means using a drive mechanism such as a step motor or a rack and pinion, whereby the semiconductor laser light source 1 and the first condenser lens 2 are moved. The distance to the condenser lens 2 is adjusted. The polygon mirror 3 is a regular hexagonal prism whose side surfaces are deflective reflection surfaces, and is driven to rotate in a direction of an arrow 6 at a constant angular velocity by a driving means (not shown). The laser light L after being reflected by the deflecting / reflecting surface 3a is guided to a symbol surface 8 having a barcode 7 as a symbol.
When the polygon mirror 3 rotates, the incident angle of the laser light L on the deflective reflection surface 3a changes with time, whereby the reflected laser light L scans the symbol surface 8 in the direction of arrow 9 at a constant speed. . Since the laser light L is incident on different deflecting and reflecting surfaces one after another by the rotation of the polygon mirror 3, the symbol surface 8 is repeatedly scanned in synchronization with the rotation of the polygon mirror 3. The reflected light from the symbol surface 6 forms an image on the first photoelectric conversion element 11 via the imaging lens 10.

The output signal of the first photoelectric conversion element 11 is applied to a signal processing circuit (not shown) to be converted into a digital signal, and this digital signal is processed by an operation means including a microcomputer or the like to be represented by the bar code 7. Information is recognized.

The reflected light from the symbol surface 8 also has two pinholes 121 and 12
From the light selective transmission member 12 having 2, the light selective transmission member 1
Via the second condenser lens 13 which collects the light passing through 2.
The light is received by the one-dimensional photoelectric conversion element 15, which is the second photoelectric conversion element. Light selective transmission member 12 and second condenser lens 13
Is fixed to the holding member 14 in common with the holding member 14.
14 is displaced in the direction of arrow 25 along the optical axis of the second condenser lens 13 by the second adjusting means 16 using a drive mechanism such as a step motor or a rack and pinion,
As a result, the second condenser lens 13 and the one-dimensional photoelectric conversion element 15
The distance between and is adjusted.

The output signal of the one-dimensional photoelectric conversion element 15 is given to the control circuit 17, and the control circuit 17 corresponds to the output signal of the one-dimensional photoelectric conversion element 15 from the lines 18 and 19, respectively, to the first and second adjusting means 4, Give control signal to 16.

FIG. 2 is a diagram for explaining the operation, and shows a state in the vicinity of the one-dimensional photoelectric conversion element 15. The laser light L reflected by the polygon mirror 3 forms a spot on the symbol surface 8, and the reflected light from this spot is incident on the light selective transmission member 12 while being diffused. At this time, as shown in FIG. 2A, the lights L1 and L2 respectively passing through the pinholes 121 and 122 of the light selective transmission member 12 are different from each other in the two elements 20 constituting the one-dimensional photoelectric conversion element 15. When the image is formed on the element, this is detected by the control means 17, and this control means 17
Provides a control signal from line 19 to the second adjusting means 16.
As a result, the second adjusting means 16 drives the holding member 14 (not shown in FIG. 2) in the directions of the arrows 25a and 25b, and the light selective transmission member 12 and the second condenser lens. 13
To displace. From the state shown in FIG.
13 and the like are separated from the one-dimensional photoelectric conversion element 15 by an arrow 25a
When it is displaced in the direction, light will eventually come out as shown in Fig. 2 (b).
The L1 and L2 are commonly focused on one element 20 of the photoelectric conversion elements 25, so to speak, in a focused state. Light selective transmission member 12 and second
The condenser lens 13 of the arrow 25 is the defocus direction, so to speak.
When displaced in the b direction, the distance between the elements 20 and 20 on which the lights L1 and L2 are imaged increases, which causes the control means 1
The control means 17 detects the control signal for reversing the displacement direction of the second condenser lens 13 and the like detected by the second adjusting means.
Give to 16. In this way, the in-focus state shown in FIG. 2 (b) can be reliably achieved.

In the state shown in FIG. 2B, the second condenser lens 13
And the one-dimensional photoelectric conversion element 15 are detected, and from this distance information, the distance between the housing (not shown) in which the configuration shown in FIG. The distance between the reader body and the symbol surface 8, that is, the reading device) is calculated by the control means 17. The image formation state shown in FIG. 2 (b) is realized because the positional relationship among the symbol surface 8, the light selective transmission member 12, the second condenser lens 13, and the one-dimensional photoelectric conversion element 15 is well known. This is a case where there is a fixed relationship determined by the imaging formula, and therefore the distance between the second condenser lens 13 and the one-dimensional photoelectric conversion element 15 at that time, the second condenser lens 13 and the symbol surface 8 There is a one-to-one correspondence with the distance between and. Therefore,
At this time, the second condenser lens 13 and the one-dimensional photoelectric conversion element 15
The above reading distance can be calculated from the distance between and.

When a control signal corresponding to this reading distance is given from the line 18 to the first adjusting means 4, the first adjusting means 4 causes the laser beam L to form a spot of the smallest diameter on the symbol surface 8. The first condenser lens 2 is displaced. This ensures that the barcode 7 is read with high resolution.

When the distance between the second condenser lens 13 and the like and the one-dimensional photoelectric conversion element 15 is larger than the state shown in FIG. 2 (b), the state shown in FIG. 2 (c) is obtained. , In this case also
It is detected by two different elements 20 such as lights L1 and L2. Therefore, by the same control operation as in the above case, the lights L1 and L2 are set to 1
It is possible to reach the state shown in FIG. 2 (b) in which two elements 20 are commonly imaged.

As described above, according to this embodiment, the two lights L1 and L2 that have passed through the light selective transmission member 12 are imaged at the same position in the one-dimensional photoelectric conversion element 15, and the second light collection in this state is performed. Lens 13
The reading distance is calculated from the distance between the one-dimensional photoelectric conversion element 15 and the one-dimensional photoelectric conversion element 15. The first condenser lens 2 is displaced along the optical axis in accordance with the reading distance, so that the laser light L is focused on the symbol surface 8. As a result, the barcode 7 can be reliably read in a wide reading range with high accuracy. Further, since no special light source such as an infrared light emitting diode is used for measuring the reading distance, the cost does not increase and the power consumption does not increase. Etc. are extremely advantageous.

Further, by displacing the first condenser lens 2 and adjusting the distance between the semiconductor laser light source 1 and the first condenser lens 2, various optical paths from the semiconductor laser light source 1 to the symbol surface 8 are obtained. Since it is adapted to a long length, it is possible to perform a so-called automatic focus adjustment operation with a simple and inexpensive structure. Moreover, since the laser light L from the semiconductor laser light source 1 is always generated from the position on the optical axis of the condenser lens 2, and the laser light has good directivity,
The detection of the reflected light in the photoelectric conversion element 11 is also performed satisfactorily.

The present invention is not limited to the above embodiment. That is, for example, in the above-described embodiment, the first adjusting lens 4 is used to displace the first condenser lens 2, but instead of the first condenser lens 2 or the first condenser lens 2 is used.
The semiconductor laser light source 1 may be displaced together with the condensing lens 2 of FIG. In the above embodiment, the light selective transmission member 12
The second condensing lens 13 and the second condensing lens 13 are commonly held by the holding member 14, and the holding member 14 is displaced to displace the second condensing lens 13 together with the light selective transmission member 12. Only the condenser lens 13 may be displaced, or the condenser lens 13 may be fixed and the one-dimensional photoelectric conversion element 15 may be displaced.

Further, instead of the semiconductor laser light source 1, a gas laser device such as a He—Ne laser device or another light source device may be used.

Further, in the above embodiment, two pinholes 121 and 122 are used.
Although the light selective transmission member 12 having the above-described structure is used, three or more pinholes may be formed to have three or more pupils, and two or more slits may be formed instead of the pinholes. You may Forming the slit is advantageous in that the slit image can be reliably detected by the one-dimensional photoelectric conversion element. Various other design changes can be made without departing from the scope of the present invention. Furthermore, the present invention is not limited to a bar code reader, and can be easily applied to a symbol reading device for reading an arbitrary symbol formed by utilizing contrast on a symbol surface, such as an optical character reading device. It can be applied.

<Effects of the Invention> As described above, according to the symbol reading device of the present invention, the light from the light source can be satisfactorily focused on the symbol surface regardless of the size of the optical path length from the light source to the symbol surface. It becomes possible to reliably and highly accurately read a symbol within a wide reading range. Moreover, since a reliable reading operation is possible with a simple and inexpensive structure, it is also advantageous for cost reduction.

[Brief description of drawings]

FIG. 1 is a plan view showing a simplified basic configuration of a bar code reader which is an embodiment of the symbol reading apparatus of the present invention, and FIG. 2 is an enlarged view of the vicinity of the one-dimensional photoelectric conversion element 15. It is a top view shown. 1 ... Semiconductor laser light source, 2 ... First condenser lens, 3
...... Polygon mirror (scanning mirror), 4 ... First adjusting means, 7 ... Bar code (symbol), 8 ... Symbol surface, 11 ...
… First photoelectric conversion element, 12 …… Optical transmission member, 13 ……
Second condensing lens, 15 ... One-dimensional photoelectric conversion element (second photoelectric conversion element), 16 ... Second adjusting means, 17 ... Control means

Claims (1)

[Claims] 1. A first condenser lens for narrowing light from a light source, a scanning mirror for scanning a symbol surface on which a symbol is formed by the light from the first condenser lens, and a reflected light from the symbol surface. In a symbol reading device having a first photoelectric conversion element that receives light and converts it into an electric signal, and optically reads the symbol surface to read the symbol, the light source and a first condenser lens. A first adjusting means for changing the distance between the two, a light selective transmission member having reflected light from the symbol surface and having at least two pupils, and a first light condensing member for condensing light from the light selective transmission member. A second condensing lens; a second photoelectric conversion element that receives light from the second condensing lens and detects each image forming position of the light corresponding to the at least two pupils; By changing the distance between the condenser lens and the second photoelectric conversion element, A second adjusting means for forming an image of light corresponding to at least two pupils at the same position in the second photoelectric conversion element, wherein the first adjusting means is configured so that the light corresponding to the two pupils is In response to the control signal from the second adjusting means corresponding to the distance between the second condenser lens and the second photoelectric conversion element in the state where the image is formed at the same position of the second photoelectric conversion element, The reading device, wherein a distance between the light source and the first condenser lens is adjusted.