JPH11282949A - Optical reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a device and to improve operability while preventing normal reflected light from being made incident on an image sensor. SOLUTION: The center of the image sensor 19 is installed at a position parallelly shifted from the center optical axis 29 of an optical system 18 to the side of a light source 21 for a fixed distance D. Also, the light source 21 is installed inside an area where the normal reflected light from a read object is not made incident on the image sensor 19. Also, the light source 21 is provided on the position near the hand side of an operator from the center optical axis 29. Also, the image sensor 19 is installed at the position where the center is parallelly shifted from the center optical axis 29 to a light source side for a required distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reader for reading characters, symbols such as bar codes or two-dimensional symbols.

[0002]

2. Description of the Related Art As an optical reader for reading characters, symbols, etc., an illumination light from a light source is radiated to an object to be read, and its diffuse reflection light is imaged on an image sensor by an optical system such as a lens. It is known that an output signal obtained by scanning is processed and output to an external host computer or the like.

When an object to be read of characters or symbols is read by using such an optical reader, when the object to be read is attached to a laminate-coated sheet, illumination light from a light source is specularly reflected on the surface of the sheet. The specularly reflected light may enter the image sensor. Since the specularly reflected light has an order of magnitude greater intensity than the diffused light, when the specularly reflected light is incident on the image sensor through the optical system, the signal in that part is saturated or the other signals become minute,
In any case, normal reading cannot be performed.

FIG. 5 shows such a state, wherein 1 is a light source, 2 is a reading object, 3 is an optical system, and 4 is an image sensor. Of the illumination light emitted from the light source 1,
Illumination light incident on the image sensor 4 with a reflection angle equal to the incident angle on the surface of the reading target 2 is regular reflection light 5, and other illumination light incident on the image sensor 4 is diffuse reflection light 6.

[0005]

The area where the light source 1 can be arranged so that the above-mentioned regular reflection light 5 does not enter the image sensor 1 is the regular reflection light entering the end of the image sensor 4 as shown in FIG. 5 is the area A outside the incident optical path 6.
Since the area A shifts outward as the angle of view of the optical system 3 increases, this causes an increase in the size of the apparatus.

Further, if the light source is disposed in front of the field of view of the apparatus in the area A as described above, the front end of the apparatus becomes large, which hinders the user from aiming at the apparatus for reading. Further, if the device is arranged behind the field of view of the device, the portion protrudes backward, which hinders grasping of the device. Therefore, it is desirable that the light source be closer to the optical axis from such a viewpoint.

On the other hand, in order to reduce the size of the device, it is necessary to reduce the optical path length (distance between objects) of the optical system, and there is a problem that it becomes difficult to place the object to be read in the field of view.

In order to eliminate the influence of the specular reflection light and reduce the size of the apparatus, a pair of prisms having a diffusion surface are interposed between the light source and the object to be read, and the light is diffused to reduce the influence of the specular reflection light. Although there is a proposal to reduce the number (refer to Japanese Patent Application No. 7-271890), in this case, there is a problem that the use of a pair of prisms increases the cost. In addition, there has been proposed a device in which illumination light is guided by an optical system such as a mirror or a light guide element. However, this also has a problem in that the structure and assembly are complicated and the number of parts is increased, thereby increasing the cost.

Accordingly, the present invention can perform reading without the influence of specular reflection light, and can realize a reduction in the size of the apparatus.
Moreover, it is an object to provide an optical reader that does not increase the cost.

[0010]

In order to solve the above-mentioned problems, the present invention accommodates an illuminating means, an image sensor and an image forming means in a hand-held housing, and illuminates an object to be read by the illuminating means. The reflected light is imaged on the image sensor, the output signal of the image sensor is processed and output to an external device. It is configured to be installed at a position shifted parallel to the center optical axis by a required distance.

It is also possible to adopt a configuration in which the illuminating means is installed in an area where specularly reflected light from the object to be read does not enter the image sensor.

In addition, a configuration in which the illumination means is provided at a position closer to the operator's hand with respect to the center optical axis, or the image sensor is arranged such that the center of the image sensor is located from the center optical axis to the illumination means side. It is also possible to adopt a configuration that is installed at a position shifted in parallel by a required distance.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a housing 10 of the optical reader according to the embodiment comprises a grip portion 11 and a head portion 12. The head portion 12 is formed by bending at a right angle to the tip of the grip portion 11, and has a front wall 13, a rear wall 14, and both side walls 1.
5 and a reading window 16 is provided at the lower end. An output cable 17 is connected to the rear end of the grip 11.

An optical bench 20 is provided inside the head section 12 so as to be separated from the inside of the grip section 11. The optical bench 20 faces the reading window 16 and has an optical system comprising a lens as an image forming means. 18 is attached, and the optical system 1
An image sensor 19 is provided behind the image sensor 8.

The optical bench 2 to which the above-mentioned optical system 18 is attached
The light source 21 is mounted between the rear end of the rear panel 0 and the rear wall 14, and the light source 21 is mounted along the rear wall 14 whose optical axis is inclined toward the reading window 16.

A pair of circuit boards 22 are provided inside the grip 11, and the output section is connected to the output cable 17.

In FIG. 1, reference numeral 30 denotes a sheet to which a reading target 23 is attached.

FIG. 2 is a block diagram of a control system, in which the CPU
The light source 21 is driven from 24 via a light source driving circuit 25,
The object 2 to be read on the paper 30 by the illumination light of the light source 21
3 is illuminated, and the reflected light is imaged on the image sensor 20 via the optical system 18. The image sensor 20 is a CPU 2
The scanning is performed via the image sensor scanning circuit 26 under the control of the controller 4. The signal obtained by the scanning is amplified by an amplifier 27
And is input to the binarization circuit 28. The binarized signal is input to the CPU 24, and a reading process is performed. The read signal is output to an external host computer via an output cable 17.

FIG. 3 shows an optical system 18 and an image sensor 19.
2 shows the arrangement relationship of the light source 21 and the light source 21. The image sensor 19 uses the center optical axis 29 of the optical system 18 as a reference.
The center is arranged at a position shifted rearward (toward the grip portion 11 of the housing 10) in parallel by a distance D (= 0.5 mm). The limit of the area A in which the light source 21 can be arranged is as follows.
As described above with reference to FIG.
Is determined by the incident optical path 32 of the specularly reflected light 31 incident on the front end of. Reflection angle of the specular reflection light 31 in this case a (= incident angle) indicated by theta _1.

The specific numerical value of the image sensor 19 is 4.8.times.3.6 mm, which is generally called a 1/3 inch size. The field of view of the reading area is 14.4 × 10.8 mm, and the image sensor 1
The distance from 9 to the reading target 23 is 40 mm.

FIG. 4 shows a comparative example, in which the arrangement of the optical system 18, the image sensor 19 and the light source 21 in the prior art is shown. The light source 21 is arranged in the area A, and is designed so that specularly reflected light does not enter the image sensor 19.
The image sensor 19 is arranged at a position where the center coincides with the central optical axis 29 of the optical system 18. Reflection angle of the specular reflection light 31 in this case a (= incident angle) indicated by theta _2.

When FIG. 3 is compared with FIG. 4, since the center of the image sensor 19 is shifted backward from the center optical axis 29 by the distance D in FIG. 3, the reflection angle θ ₁ of the specularly reflected light 31 is Is smaller than the reflection angle θ ₂ , and the light source 21 approaches the central optical axis 29 by that amount.

The distance Y from the object 23 to be read to the light source 21
(= 20 mm) line and regular reflection light 3 indicating the limit of the area A.
Assuming that the intersection of the first incident light path 32 with S is S,
The distance X in the direction perpendicular to the central optical axis 29 from the front end of the third field of view to the intersection S is a factor that determines the size of the device. This distance X is X = 14.4 mm in the case of FIG. 4, while X = 13.4 mm in the case of FIG.
mm, and the size of the device can be reduced accordingly. This is, as described above, the light source 2 in the case of FIG.
This is because 1 was able to approach the central optical axis 29. Other specific numerical values are entered in FIG. 3 and FIG.

In the case of FIG. 3, since the reading area is shifted forward with respect to the image sensor 19 as compared with the case of FIG. 4, the inclination of the front wall 13 of the housing 10 can be increased. Therefore, the user reads the device to be read 2
When the distance is closer to 3, the reading target 23 can be easily put in the field of view.

If it is desired to prevent specularly reflected light from entering even when the apparatus is slightly tilted, the position of the light source 21 in the area A can be selected by adding the tilt angle. I just need.

[0027]

As described above, according to the present invention, the installation position of the image sensor is set at a position where the center thereof is displaced parallel to the center optical axis of the optical system by a certain distance, so that the size of the apparatus can be reduced. By setting the light source at a position where specular light from the object to be read is not incident on the image sensor, accurate reading can be performed.

Further, since the distance between the light source and the image sensor is reduced, providing the light source on the gripping portion prevents the head portion from expanding toward the gripping portion, facilitates gripping, and reduces the reading area. Since the housing is shifted forward, the inclination of the front wall of the housing can be increased, and there is an effect of improving operability such as making it easier to read the object to be read.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a block diagram of a control system according to the first embodiment;

FIG. 3 is a layout diagram of the image sensor and the like according to the embodiment;

FIG. 4 is a layout diagram of an image sensor and the like of a comparative example.

FIG. 5 is an explanatory view of a conventional example.

FIG. 6 is an explanatory view of a conventional example.

DESCRIPTION OF SYMBOLS 10 Housing 11 Gripping part 12 Head part 13 Front wall 14 Rear wall 15 Side wall 16 Reading window 17 Output cable 18 Optical system 19 Image sensor 20 Optical bench 21 Light source 22 Circuit board 23 Object to be read 24 CPU 25 Light source drive Circuit 26 Image sensor scanning circuit 27 Amplifying circuit 28 Binarization circuit 29 Central optical axis 30 Paper 31 Regular reflection light 32 Incident optical path

Claims (4)

[Claims] An illumination means in a hand-held housing;
An image sensor and an image forming unit are housed, and the object to be read is illuminated by the illuminating unit and the reflected light is imaged on the image sensor. The output signal of the image sensor is processed and output to an external device. The optical reading device according to claim 1, wherein the image sensor is installed at a position where the center of the image sensor is displaced parallel to a center optical axis of the imaging means by a required distance. 2. The optical reading apparatus according to claim 1, wherein the illuminating means is provided in an area where specularly reflected light from a reading target does not enter the image sensor. 3. The optical reader according to claim 1, wherein the illuminating means is provided at a position closer to an operator's hand with respect to the central optical axis. 4. The image sensor according to claim 1, wherein the image sensor is installed at a position where the center of the image sensor is displaced in parallel from the central optical axis toward the illumination means by a required distance. Optical reader.