JPH07121645A - Optical information reading device - Google Patents

Abstract

PURPOSE:To expand a readable range of an optical information reading device including the near distances to the far distances. CONSTITUTION:A bar code reader 1 is provided with a reflecting surface 21 where a variable focus mirror 4 serving as a feature part of the reader 1 varies its focal distance in accordance with the voltage applied from a mirror driving circuit 9. The surface 21 is periodically and continuously changed so that the waist position of the laser beam incident on the surface 21 is periodically and continuously changed. That is, the beam waist position, i.e., a readable rang e range is periodically and continuously changed at all times. Thus a readable signal is produced in each prescribed period and the readable range is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reading device, and more particularly, by scanning a laser beam for information such as bar codes used for product management and sales management. , Is adopted in a device that reads information from the reflected light.

[0002]

2. Description of the Related Art In recent years, bar code readers are widely used in various fields such as product management and sales management. For example, a polygon mirror or a galvano mirror scans a light beam, and the scanned light beam is used as a bar code. 2. Description of the Related Art A laser scanning type device is used in which a bar code label is read by reflecting the reflected light on a label and converting the reflected light into an electric signal by a light receiving element. Also, in this type of device, the scanned light beam must have sufficient resolution for the minimum bar width of the bar code label. In other words, the diameter of the light beam reflected on the bar code label must be sufficiently smaller than the minimum width of the bar. It can be read only within a certain range around the waist position). However, recently, there is an increasing need for a bar code reader capable of close contact reading, short distance reading, long distance reading, or the like, that is, a bar code reader having a wide reading range, depending on the application.

Therefore, various proposals have been made as methods for realizing the above needs. For example, Japanese Patent Laid-Open No. 4-1
Japanese Patent No. 95271 proposes an autofocus type laser scanner device in which a distance from a barcode label to a scanner device is measured by a distance meter, and the focal length of an electro-optical lens is made variable according to this distance. There is.
Further, in JP-A-2-7182, based on a bar code signal from a photoelectric conversion unit, a lens is moved by a mechanism using a motor so that the amplitude of the bar code signal becomes maximum, and the focus position is changed. A method of adjusting is proposed.

[0004]

However, in the above-mentioned Japanese Patent Laid-Open No. 4-195271, a range finder and means for controlling the focal length based on information from the range finder are required, and the distance measurement is performed. , Which is difficult to read, such as a bar code printed on a cylindrical can, may not be sufficiently read. Further, in the above-mentioned Japanese Laid-Open Patent Publication No. 2-7182, although a device related to a range finder or the like is not adopted, a driving device such as a motor for mechanically moving the lens is required, which causes a complicated mechanism. I will leave.

Therefore, the present invention has been made in view of the above problems, and is an optical system capable of reading from a short distance to a long distance without incorporating distance information, while suppressing complication of a driving mechanism. An object is to provide an information reading device.

[0006]

Therefore, in the optical information reading apparatus according to the first aspect, a light source (3) for emitting light having directivity and a light emitted from this light source are collected at a predetermined position. Condensing position varying means (4) for irradiating the light and changing the predetermined position for condensing the light periodically and continuously, and scanning means (5) for scanning the light condensed by the condensing position varying means on the object. ) And photoelectric conversion means (7) for receiving the reflected light generated on the object according to the scanning of the scanning means and outputting an electric signal according to the received light intensity, and the photoelectric conversion means (7) The reading means (12, 13) for reading the optical information of the object based on an electric signal is adopted.

Further, in the optical information reader according to the second aspect, the light source (3) for emitting light having directivity.
And a reflection surface (21) whose curvature changes according to the applied voltage and whose focal length changes, and the light collection position of the light reflected by reflecting the light emitted from the light source on the reflection surface. , A driving means (9) for changing the focal length of the reflecting surface by applying a voltage to the reflecting means, and a light reflected by the reflecting surface to scan the object. Scanning means (5), photoelectric conversion means (7) for receiving the reflected light generated on the object in response to the scanning of the scanning means, and outputting an electric signal according to the received light intensity, and Reading means (12, 12) for reading the optical information of the object based on the electric signal from the photoelectric conversion means.
13) is provided, and the focal length of the reflecting surface is periodically and continuously changed by the driving means, and the condensing position of the light reflected by the reflecting surface is periodically and continuously changed. And

Further, in the optical information reader according to a third aspect of the invention, the reflecting means is provided with a drive electrode (23) at a position facing the reflecting surface via a predetermined gap. This drive electrode is characterized by being provided with an intake / exhaust port (25a, 25b) for alleviating a pressure change caused by a change in the volume of the void accompanying a change in the curvature of the reflecting surface.

Next, in the optical information reader according to a fourth aspect of the present invention, the changing speed of the condensing position of the light reflected by the reflecting surface is sufficiently slower than the scanning speed of the scanning means. Characterize. Further, in the optical information reading device according to claim 5, the light source (3) for emitting light having directivity and the lens surface whose focal length changes due to a change in curvature are emitted from the light source. Lens means (31) for changing the condensing position of the light passing through the lens surface, driving means (36) for changing the curvature of the lens surface and changing the focal length, and A scanning means (5) for scanning the light passing through the lens surface on the object, and a reflected light generated on the object in response to the scanning of the scanning means, and an electric power depending on the received light intensity. A photoelectric conversion means (7) for outputting a signal and a reading means (12, 13) for reading optical information of the object based on an electric signal from the photoelectric conversion means are provided, and the driving means is used to The curvature of the lens surface Periodically and continuously changed, characterized in that for periodically and continuously changing the condensing position of the light passing through the lens surface.

Further, in the optical information reader according to the sixth aspect of the present invention, the lens means (31) are arranged in parallel with each other with a predetermined gap therebetween, and the peripheral portions thereof are sealed and the pressure chambers are provided therebetween. A pair of transparent elastic films (33) at least one of which is made of an elastic body, and the pair of transparent elastic films enclosed in the pressure chamber between the pair of transparent elastic films. Hydraulic fluid (3
5) and pump means (32) for controlling the hydraulic fluid introduced into the pressure chamber so that the pressure acting on the pair of transparent elastic membranes is variably controlled.

Next, in the optical information reader according to the seventh aspect, the changing speed of the condensing position of the light passing through the lens surface is sufficiently slower than the scanning speed of the scanning means. Characterize.

[0012]

In the optical information reader according to the first aspect of the present invention, the light source emits light having directivity, and the condensing position varying means directs the emitted light to a predetermined position. While collecting the light, the predetermined position where the light is collected is periodically and continuously displaced. Then, the scanning unit scans the object with light whose focal position is displaced periodically and continuously, and the photoelectric conversion unit and the reading unit generate reflection on the object in response to the scanning. Read optical information from light. That is, the condensing position changing means cyclically and continuously displaces the condensing position that makes it possible to read optical information within a predetermined range, and if the condensing position is within the moving range of the condensing position, the condensing position is optically changed every predetermined period. It is possible to capture the target information and expand the readable range.

In the optical information reader according to the second aspect of the invention, the reflecting means reflects the light from the light source, and the driving means deforms the reflecting surface of the reflecting means. At this time, the driving means changes the curvature of the reflecting surface periodically and continuously by controlling the voltage applied to the reflecting means. Therefore, the focal length of the reflecting surface changes according to the curvature of the reflecting surface, and the light collecting position of the light reflected by the reflecting surface is periodically and continuously displaced. That is, if it is within the movement range of the condensing position, the optical information can be taken in every predetermined period, and the readable range is expanded. Moreover, the light condensing position can be set relatively easily by changing the voltage applied to the reflecting means. Further, since no mechanical driving means is adopted, complication of the mechanism is suppressed, and high-speed operation is possible as compared with the mechanical driving means. Therefore, the optical information reading device of the present invention has a configuration in which a signal that can be read is sent only every certain predetermined period (in order to move the condensing position periodically and continuously), but high-speed operation is possible. In order to make it possible, the readable range is expanded without causing a trouble that the reading operation takes time.

According to a third aspect of the present invention, the drive electrode is provided with an intake / exhaust port, and by using the intake / exhaust port, a change in pressure of the void caused by a change in volume of the void due to a change in curvature of the reflecting surface is utilized. It is possible to facilitate the inflow and outflow of gas between the air gap and the outside of the air gap, and alleviate the generation of the differential pressure between the air gap and the outside of the air gap. That is, by reducing the pressure change in the void, the responsiveness of the curvature change in the reflecting surface can be improved.

In the fourth and seventh aspects, the changing speed of the light condensing position is sufficiently slower than the scanning speed of the scanning means. That is, the light condensing position when the object is scanned once by the scanning means hardly changes. In other words, the diameter of the light when scanning the object is substantially constant, and the object can be read with sufficient resolution.

Further, in the optical information reader according to the fifth and sixth aspects, the condensing position of the light passing through the lens surface of the lens means is periodically and continuously displaced by the lens means and the driving means. . Therefore, similarly to the optical information reading device according to the second aspect, if it is within the movement range of the condensing position, it is possible to take in the optical information at every predetermined cycle and expand the readable range. Since the lens means is used, the optical system can be simplified because the light is not turned back as compared with the reflecting means described in claim 2.

[0017]

The present invention will be described below based on the embodiments shown in the drawings. In this embodiment, a case where the present invention is applied to a laser scanning bar code reader will be described. In FIG. 1, a bar code reader 1 is roughly divided into an optical system that scans a bar code label 2 with laser light and receives reflected light generated by the scanning of the laser light, and a drive that drives this optical system. The system and a signal processing system for reading information from the reflected light generated by the barcode label 2 are incorporated in a case (not shown).

First, the above optical system changes the focal length by changing the curvature of the laser diode 3 which emits laser light having directivity and the reflecting surface, and focuses the laser light generated by the laser diode 3. A varifocal mirror 4 for changing the position, an optical scanner 5 for scanning the laser light reflected by the varifocal mirror 4, and reflecting the scanned laser light on the barcode label 2, and scattering on the barcode label 2. A condenser lens 6 for condensing the reflected light
The reflected light condensed by the condenser lens 6 is received,
It is composed of a light receiving element 7 for converting into an electric signal.
An optical system for converting divergent light into convergent light is installed in the laser diode 3, and a beam waist for condensing light at a predetermined position is set.

The drive system comprises a drive circuit 8 for driving the laser diode 3, a mirror drive circuit 9 for driving the variable focus mirror 4, and a scanner drive circuit 11 for driving the optical scanner 5. Furthermore, the signal processing system converts the analog electric signal obtained from the light receiving element 7 into 2
It is composed of a binarization circuit 12 for converting it into a value signal and a decoding circuit 13 for decoding the binary signal obtained by the binarization circuit 12 as information based on the bar code label 2.

Next, the structure of the variable focus mirror 4 will be described with reference to the sectional view shown in FIG. In FIG. 2, the varifocal mirror 4 includes a diaphragm 21 having a mirror surface 21a formed by processing a thin film of Si and subjecting the surface to Al vapor deposition, and a predetermined gap 22 at a position opposite to the diaphragm 21. The drive electrode 23 provided, a spacer 24 for insulating the diaphragm 21 and the drive electrode 23, and setting a predetermined space 22, and the drive electrode 2
3, a plurality of intake / exhaust ports 25a, 25b for connecting the air gap 22 and the outside of the varifocal mirror 4 to the diaphragm 2;
1 and a housing 26. The conductive rubber 27 electrically connects the housing 1 and the housing 26, and the fixing member 28 that insulates and fixes the drive electrode 23 to the housing 26.

The drive state of the variable focus mirror 4 will be described with reference to FIG. Note that FIG. 3A is a cross-sectional view showing a state in which no voltage is applied, and FIG. 3B is a cross-sectional view showing a state in which a voltage is applied. First, when no voltage is applied to the drive electrode 23, the diaphragm 21 has a planar shape as shown in FIG. 3A, and the laser light L1 incident on the mirror surface 21a of the diaphragm 21 converges. Reflects without being damaged.

On the other hand, when a voltage is applied to the drive electrode 23, the diaphragm 21 is electrostatically attracted and is attracted and curved toward the drive electrode 23, as shown in FIG. 3B.
It changes from a flat shape to a concave shape. At this time, the laser light L2 that has entered the mirror surface 21a is converged and reflected according to the curvature of the concave shape. Therefore, the laser light L2
The condensing position (beam waist position) changes according to the curvature of the concave shape. The diaphragm 21
The curvature of the mirror surface 21a changes according to the voltage change applied to the drive electrode 23. Further, when the diaphragm 21 is deformed, the volume of the space 22 between the diaphragm 21 and the drive electrode 23 changes. Therefore, by facilitating the inflow and outflow of air in the gap 22, the pressure difference between the pressure in the gap 22 and the atmospheric pressure is relaxed, and the intake / exhaust ports 25a, 25b are driven in order to improve the time response of the diaphragm. Electrode 23
It is provided in.

The operation of the bar code reader 1 having the above structure will be described below. It should be noted that the drive electrode 23 has a structure shown in FIG.
It is assumed that a triangular wave similar to the change shown in is applied.
First, in FIG. 1, the laser drive circuit 8 drives the laser diode 3 based on a signal from a control unit (not shown), and the laser diode 3 emits laser light. Then, the laser light emitted from the laser diode 3 is incident on the varifocal mirror 4.

Here, in the varifocal mirror 4, as shown in FIG. 4, the focal length changes from A (state in which no voltage is applied to the drive electrode) to B (curvature changes due to voltage imprinting of the drive electrode). The focal length is the shortest) and changes periodically and continuously. Therefore, the laser beam reflected by the varifocal mirror 4 and scanned by the optical scanner 5 has a beam waist position, which is its converging position, as shown in FIG.
As shown in, the distance C from the barcode reader 1
It changes cyclically and continuously from (corresponding to A) to D (corresponding to B). This is because, when focusing on the beam diameter of the laser light in a certain range, the beam diameter changes periodically, so that the laser light has a bar code readable beam diameter at a certain predetermined time. That is, by utilizing the movement of the beam waist position, the opportunity of barcode recognition can be provided within a wide distance range, and the reading depth of the barcode label 2 can be greatly expanded.

In the present invention, the moving speed of the condensing position of the light beam is about 1/10 of the scanning frequency. Therefore, when the beam light scans the bar code label 2 once, the focus position of the beam light is substantially constant. In other words, it is possible to prevent the problem that the light-condensing position is largely changed during one scanning of the barcode label 2 and the barcode cannot be read. Further, the moving range of the beam waist position can be arbitrarily set by placing an optical system for converting divergent light into convergent light immediately after the laser diode 3.

Next, Table 1 shows measured data obtained by comparing the bar code reader 1 of the present invention and the conventional bar code reader in the readable range. The types of bar code labels that were read were ITF (a code that was expanded and used for physical quantity) and JAN-13 (a common product code for Japan).

[0027]

[Table 1]

As shown in Table 1, the bar code reader 1 of the present embodiment which employs the variable focus mirror 4 is compared with the conventional bar code reader which does not employ the variable focus mirror 4 from the measured data. As is also apparent, the reading depth is increased for both barcode labels. From the above, in the bar code reader 1 of the present invention, the converging position (beam waist position) of the laser light is periodically and continuously changed by periodically and continuously changing the voltage applied to the varifocal mirror 4. By continuously changing, the range of the reading depth is expanded and it is expanded from a short distance to a long distance.

In this embodiment, the laser diode 3 corresponds to a light source, the varifocal mirror 4 corresponds to a focusing position changing means, the optical scanner 5 corresponds to a scanning means, and the light receiving element 7 performs photoelectric conversion. The binarization circuit 12 and the decoding circuit 13 correspond to the reading means. Next, another embodiment will be described with reference to the drawings. In this embodiment, as shown in FIG. 6, a variable focus lens 31 is adopted instead of the variable focus mirror 4 described above.

Here, in the variable focus lens 31, as shown in FIG. 7, a peripheral portion of a pair of transparent elastic films (glass diaphragms) 33 is sealed by a flange 34, and a silicon is formed in a space formed by this sealing. Oil 35
It is a configuration in which is enclosed. The silicon oil 35 in the variable focus lens 31 is configured to be pressurized by the pump 32, and the pressure is freely controlled by the pump 32. Therefore, the transparent elastic film 33 that seals the silicone oil 35 is
The pressure of 5 deforms it into a convex shape as shown in FIG. 7, and the amount of deformation changes according to the pressure of the silicone oil 35. That is, since the lens body is formed by the transparent elastic film 33 that deforms in a convex shape and the silicone oil 35, and the amount of the convex deformation changes by the silicone oil 35, the focal length of the lens body changes by the pressure change of the silicone oil 35. That is, the focal length of the lens body can be freely changed by the pump 32. The refractive index of the silicone oil 35 is the same as that of the pair of transparent elastic films 33.

Therefore, similarly to the above-described embodiment, if the operation of the pump 32 is drive-controlled by the lens drive circuit 36 and the focal length of the varifocal lens 31 is changed periodically and continuously, the following operation is performed. Operate. That is, the laser drive circuit 8 is emitted, passes through the variable focus lens 31,
The laser beam scanned by the optical scanner 5 has a beam waist position, which is a condensing position thereof, from C to D according to the change of the focal length of the varifocal lens 31, as shown in FIG. 5 described above. Changes periodically and continuously between. That is, similar to the above-described embodiment, by utilizing the movement of the beam waist position, the opportunity of barcode recognition can be provided within a wide distance range, and the reading depth of the barcode label can be greatly expanded. Since the variable focus lens 31 is adopted in this embodiment, the optical system can be simplified as compared with the variable focus mirror 4 of the above-described embodiment, because the laser light is not folded back.

Further, in both of the above-mentioned embodiments,
The reflected light of the bar code label 2 is condensed on the light receiving element 7 using the condenser lens 6, but the present invention is not limited to this. For example, if an element that directly receives the reflected light and can photoelectrically change is used, the condenser lens 6 May be omitted.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the variable focus mirror shown in FIG.

FIG. 3 is a diagram showing a driving state of a variable focus mirror.

FIG. 4 is a diagram showing a change in focal length of a varifocal mirror.

FIG. 5 is a diagram showing a change state of a focus position of laser light.

FIG. 6 is a configuration diagram showing another embodiment of the present invention.

7 is a cross-sectional view of the variable focus lens shown in FIG.

[Explanation of symbols]

 3 Laser diode 4 Variable focus mirror 5 Optical scanner 7 Light receiving element 12 Binarization circuit 13 Decoding circuit

Claims (7)

[Claims] 1. A light source that emits light having directivity, and a light collection position variable that collects light emitted from the light source at a predetermined position and periodically and continuously changes the predetermined position where the light is collected. Means, scanning means for scanning the light condensed by the condensing position varying means on the object, and reflected light generated on the object in response to the scanning of the scanning means, and the received light Optical information comprising: a photoelectric conversion unit that outputs an electric signal according to the intensity; and a reading unit that reads the optical information of the object based on the electric signal from the photoelectric conversion unit. Reader. 2. A light source that emits light having directivity and a reflecting surface whose curvature changes and focal length changes according to an applied voltage, and the light emitted from the light source is reflected by the reflecting surface. A reflecting means for changing the condensing position of the reflected light, a driving means for applying a voltage to the reflecting means to change the focal length of the reflecting surface, and a light reflected by the reflecting surface. Scanning means for scanning the object, photoelectric conversion means for receiving the reflected light generated on the object in response to the scanning by the scanning means, and outputting an electric signal according to the intensity of the received light, A reading means for reading the optical information of the object based on an electric signal from the converting means, wherein the driving means periodically and continuously changes the focal length of the reflecting surface, The focal point of the reflected light An optical information reader characterized in that it is changed periodically and continuously. 3. A driving electrode is provided in the reflecting means at a position facing the reflecting surface via a predetermined gap, and the driving electrode is provided with a gap of the gap due to a change in curvature of the reflecting surface. 3. An intake / exhaust port for reducing a pressure change caused by a volume change is provided.
The optical information reading device described. 4. The optical information reading device according to claim 2, wherein the changing speed of the condensing position of the light reflected by the reflecting surface is sufficiently slower than the scanning speed of the scanning means. 5. A light source that emits light having directivity and a lens surface whose focal length changes due to a change in curvature, and the light emitted from the light source passes through the lens surface. Means for changing the focal position of the lens, driving means for changing the curvature of the lens surface to change the focal length, scanning means for scanning the light passing through the lens surface on the object, Photoelectric conversion means for receiving the reflected light generated on the object according to the scanning of the means, and outputting an electric signal according to the received light intensity, and based on the electric signal from the photoelectric conversion means, A reading unit for reading optical information of an object, the curvature of the lens surface is changed cyclically and continuously by the driving unit, and the condensing position of light passing through the lens surface is changed periodically and continuously. Target An optical information reading device characterized by changing to 6. The pair of lens means are arranged in parallel with each other with a predetermined gap therebetween, and a peripheral portion of the lens means is sealed so that a pressure chamber is formed between them. A transparent elastic film, a working fluid having a refractive index equivalent to that of the pair of transparent elastic films enclosed in the pressure chamber between the pair of transparent elastic films, and acting on the pair of transparent elastic films 6. The optical information reader according to claim 5, further comprising pump means for controlling the hydraulic fluid introduced into the pressure chamber so that the pressure applied to the pressure chamber is variably controlled. 7. The optical information reading device according to claim 5, wherein the changing speed of the condensing position of the light passing through the lens surface is sufficiently slower than the scanning speed of the scanning means.