JPH06176181A - Optical reader - Google Patents

Abstract

PURPOSE:To provide the optical reader capable of reading optical information with good resolution with deep reading depth over wide range. CONSTITUTION:An integral lens 70 with 1st and 2nd light emitting lenses 4 and 5 and light receiving lens 10 formed is held and fixed to a frame body 9 inside a case 1 of the optical reader. 1st and 2nd light emitting elements 16 and 18 and a light receiving element 80 are fixed to a substrate 44 opposed to these lenses. A light receiving element 80 is arranged on the optical axis of the light receiving lens 10. The 1st light emitting element 16 is arranged close to an optical axis (a) of the 1st light emitting lens 4 and the 2nd light emitting element 18 is arranged close to an optical axis (c) of the 2nd light emitting lens 5. The focusing distances between the 1st light emitting lens 4 and the 2nd light emitting lens are different, the lights from the light emitting elements 16 and 18 are formed at different positions in the optical axis direction.

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 an optical mark such as a bar code displayed on a medium, and more particularly to an optical reader having a deep reading depth.

[0002]

2. Description of the Related Art An optical bar code reader, which is an optical reading device, is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-77890, and the configuration of such a conventional optical reading device will be described with reference to FIGS. explain.

FIG. 5 is a schematic configuration diagram of a general optical reading device,
FIG. 6 is a cross-sectional view showing the configuration of a conventional optical reading device, and FIG. 7 is a cross-sectional view of a main part showing a detection state of a barcode at a position apart from the main body.

As shown in FIG. 5, a pen type bar code scanner, which is generally an optical reading device, is provided with a case 1 having a tip portion 1a, and the base end side of the case 1 is connected to an apparatus body (not shown). The cable 1b for this is arranged. An opening 2 is provided in the tip portion 1a, and when a switch 3 is operated, light is emitted from the opening 2 and is incident on a bar code which is an information recording medium. The barcode, that is, the barcode attached to the product is electrically identified based on the difference in the amount of light reflected from the barcode, that is, the bar or the space, and is used to manage the sales amount or the inventory amount of each product.

In order to hold and fix a lens body 6 in which a light emitting side lens 7 and a light receiving side lens 8 are integrated, as shown in FIG. 6, in a reflection type photo sensor arranged inside a case 1 of an optical reading device. A frame body 9 having an oval cross section and formed in a tubular shape is provided. Lens 6 of this frame 9
A second opening 9a for light transmission, which is opened to detect reflected light with the information recording medium 5, is provided between the opening 2 and the opening 2.

On the side of the second opening 9a of the frame body 9,
A holder 17 for positioning and fixing the lens 6 is press-fitted and fixed, and this holder 17 is formed of a plastic material having the same kind as the light-emitting side and light-receiving side lenses 7 and 8 and having a light-shielding property. One end of the frame body 9 is closed by a conductive substrate 44, and a light emitting element 16 composed of an LED and a light receiving element 80 composed of a photodiode are formed on the surface of the substrate 44 on the frame body 9 side. And are connected and fixed.

Optical axis a of the light receiving side lens 7 and light receiving side lens 8
Are arranged in parallel with each other, the light receiving element 80 is arranged on the line of the optical axis b of the light receiving side lens 8, and the light emitting element 16 is received with respect to the optical axis a of the light emitting side lens 7. 8
It is arranged so as to be offset in the direction opposite to 0.

The light-emitting side lens 7 is composed of an aspherical lens or a spherical lens in which aberration correction is incomplete and produces aberrations. Then, the light emitting side lens 7 arranged so as to cause at least coma aberration is projected from the light emitting side lens 7 and passes through the light receiving side lens 8 to receive the light receiving element 8.
The configuration is such that the ratio of the amount of regular reflection light guided to 0 becomes low.

The maximum value of the numerical aperture (NA) of the light emitting side lens 7 is set to be relatively large with respect to the maximum value of the numerical aperture (NA) of the light receiving side lens 8.

Then, the projection spot converged on the detection surface 100 at the position closest to the opening 2 is configured so that the illuminance distribution in the illuminated range W is averaged. Has been done.

[0011]

In such a conventional optical reading apparatus, the reading depth of the optical information is obtained only by utilizing the coma aberration of the single light-emitting side lens 7, so Has a limit, and if the reading point X is far from the opening 2 as shown in FIG. There is a problem that a reading error occurs. An object of the present invention is to obtain a practical optical reading device which has a deep reading depth and can read optical information with a sufficient resolution over a wide range.

[0012]

In order to achieve the above object, in the optical reading device of the present invention, at least 2
Two light-emitting elements and corresponding to each element are arranged so that the light from the light-emitting element is focused at different positions in the optical axis direction, and the illuminance is kept constant due to aberration between the respective focal points. The light emitting side lens, the light receiving side lens that receives the light that passes through these light emitting side lenses and is reflected from the object near the focal point, and the light receiving element that detects the light that has passed through the light receiving side lens. Characterize.

[0013]

By providing at least two light emitting elements and corresponding light emitting side lenses having different focal lengths so as to pass light from the light emitting elements at different positions in the optical axis direction, respectively. The reading depth as a whole becomes deep, and the illuminance can be kept substantially constant between the focal positions due to the coma aberration of each light emitting side lens.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a bar code scanner will be described below with reference to FIGS. The same components and (configuration) used in the conventional optical reading device are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, a bar code scanner according to the present invention includes a case 1 and a tip portion 1 of the case 1.
a, the first light emitting side lens 4 for converging light so as to focus the light near the opening 2, and the first light emitting side lens 4.
A second light emitting side lens 5 connected to the light emitting side lens 4 of
The light emitting element 16 for generating the light incident on the first light emitting side lens 4, the light emitting element 18 for generating the light incident on the second light emitting side lens 5, the first light emitting side lens 4, and the above The second light-emitting side lens 5 and the light-receiving side lens 10 are arranged between the second light-emitting side lens 5 and the second light-emitting side lens 5, and the light-emitting elements 16 and 18 are arranged on the opposite side of the opening 2 with the lenses therebetween.
It is provided on the 4th. In this embodiment, the light emitting lenses 4 and 5 are at the same position but have different focal lengths, so that the lights from the light emitting elements 16 and 18 are focused at different positions near the opening 2. It is like this. The light-receiving side lens 10 arranged between the first light-emitting side lens 4 and the second light-emitting side lens 5 is, as shown in FIG. 2, the first light-emitting side lens 4 and the second light-emitting side lens 10. The side lens 5 and the light receiving side lens 10 are integrally molded lens body 7
0 is integrally formed. The light receiving side lens 10
The light receiving element 80 for converting the light converged by
The light emitting elements 16 and 18 are arranged in the same row on the substrate 44. The integrally molded lens body 70 is a case 1
It is fixed by the inner frame 9 and the value of the numerical aperture (NA) is defined by the second opening 9a. The first light emitting element 16 is arranged so as to be offset from the optical axis a of the first light emitting side lens 4 on the substrate 44 in the outer peripheral direction of the case 1, and the second light emitting element 18 is arranged on the second light emitting side lens. It is arranged on the substrate 44 in the outer peripheral direction of the case 1 from the optical axis c of 5. Since the light emitting elements 16 and 18 are arranged so as to be deviated from the optical axes a and c, at least the coma is generated in the spot connected at the reading point X ′. The focus position of the first light emitting side lens 4 and the focus position of the second light emitting side lens 5 are different from each other in the optical axis direction, and at the same time, the first spot 30 and the first spot 30 are formed on the barcode from the opening 2. It connects two spots 40. The respective focal positions of the light-receiving side lenses 4 and 5 are arranged and formed substantially on the optical axis of the light-receiving side lens 10. Spots 30 and 4 above
0 is a reading depth W ′ that can be detected by the light receiving element 80 so that the light reflected from the barcode can be converted into an electric signal,
That is, it is within the resolvable area, and the reading depth due to the coma aberration of each lens is secured in this way, and the focus position is shifted, so that a substantially constant illuminance is secured.

Next, the operation of the bar code scanner having the above structure will be described. First, the first light emitting element 1
The light generated from 6 is incident on the first light emitting side lens 4. The light is converged by the first light-emitting side lens 4, and a first spot 30 is connected near the outside of the opening 2 of the case 1.
On the other hand, the light emitted from the second light emitting element 18 enters the second light emitting side lens 5. The light is converged by the second light emitting side lens 5 and is farther from the opening 2 than the position of the first spot 30 outside the opening 2 of the case 1 and by the light emitted from the first light emitting side lens 4. Second spot 40 at the position
Tie When this barcode scanner scans over the barcode, the amount of reflected light differs due to the difference in the light reflectance of the space of the detection surface 100 and the barcode consisting of black bars. If the barcode is near opening 2,
The first spot 30 formed by the first light emitting side lens 4 is connected to the barcode. Then, the reflected light whose amount of light has changed due to the change of the bar and the space of the barcode enters the light receiving side lens 10 through the opening 2 of the case 1, is converged by the light receiving side lens 10, and enters the light receiving element 80. On the other hand, the second spot 40 formed by the second light-emitting side lens 5 is focused on a position farther from the opening 2 than the first spot 30, for example, a position several mm away from the opening 2. On the bar code near the opening 2, the first spot 30 that is condensed and has a high light intensity and the second light emitting side lens 5 that is not condensed and has a low light intensity because it is still far from the focus position. Part of the emitted light overlaps.
Similarly, when the barcode is distant from the vicinity of the opening 2, the second spot 40 by the second light emitting side lens 5 is formed.
Is tied on the barcode. Then, the reflected light enters the light emitting side lens 10 through the opening 2 of the case 1, is converged by the light receiving side lens 10, and enters the light receiving element 80. At this time, on the bar code located away from the vicinity of the opening 2, the second spot 40 having a large light intensity is condensed and the second spot 40 is already past the focus position, so that the light is not condensed and the light intensity is small. A part of the light emitted from the first light emitting side lens 4 overlaps each other. Therefore, the light emitted by the first light-emitting side lens and the light emitted by the second light-emitting side lens complement each other for the lack of light intensity so that the light intensity becomes constant within the reading depth W ′.

In the embodiment constructed as described above, there are two focal points for producing spots, and it becomes possible to keep the illuminance within the reading depth W'almost constant, and the reading depth is sufficiently larger than that of the conventional example. It can be lengthened.

Next, a second embodiment of the present invention will be described with reference to FIG. The parts having the same functions as those described in the conventional example and the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. First, the structure will be described. Two press-fitting fixing portions 25 are provided on the inner wall of the cylindrical frame body 9 fixed by a lens.
Of the lenses 4, 5, and 10 integrally formed, one ends of the first light emitting side lens 4 and the second light emitting side lens 5 are fixed to the press-fitting fixing portions 25, 26, respectively. In this embodiment, the first light emitting side lens 4 and the second light emitting side lens 5
3 have the same focal length, but their relative positions are displaced in the optical axis direction so that the positions of the focused reading spots are different as shown in FIG. Although the light emitting side lenses 4 and 5 can be integrally formed by the integrally molded lens body 90, the respective lenses 4 and 5 can be individually formed and combined. Also in the second embodiment, the same action and effect as those of the first embodiment described with reference to FIGS. 1 and 2 are produced.

Further, a third embodiment of the present invention will be described with reference to FIG. Similarly, parts having the same functions as those described in the conventional example, the first embodiment, and the second embodiment are designated by the same reference numerals, and the description thereof will be omitted. In the frame body 9, an optical path emitted from the first light emitting element 16, passing through the first light emitting side lens 4, reflected by the information recording medium, and passing through the light receiving lens 10 to the light receiving element 80, A light-shielding frame for blocking the optical path emitted from the second light-emitting element 18, passing through the second light-emitting side lens 5, reflected by the information recording medium and guiding the light passing through the light-receiving lens 10 to the light-receiving element 80 from each other. 35 are provided. The elongated light shielding frame 35 extends from the vicinity of the light receiving element 80 to the vicinity of the junction of the lenses 4, 5, 10 in parallel with the optical axis direction of the light receiving side lens 10. Therefore, the light from the first light emitting element 16 enters only the first light emitting side lens 4 and does not enter the second light emitting side lens 5. On the other hand, the light from the second light emitting element 18 enters only the second light emitting side lens 5. Then, with respect to the light reflected by the information recording medium, the light from the first light emitting element 16 passes through only the first lens 4 and further passes through the light receiving side lens 10, and enters the light receiving element 80. On the other hand, the second light emitting element 1
The light from 8 passes through only the second light-emitting side lens 5, further passes through the light-receiving side lens 10, and is incident on the light receiving element 80. Therefore, the light shielding frame 35 can remove the offset light incident on the light receiving element 80 and simplify the signal processing circuit. Here, the offset light refers to light emitted from the light emitting element, reflected by the lens surface of the light emitting element of the light emitting side lens, and incident on the light receiving element. By using such a light-shielding frame 35, it is possible to prevent the offset light from entering the light receiving element, and therefore it is not necessary to provide an offset circuit for removing a signal component due to the offset light on the circuit side which is normally performed. Furthermore,
Also in the third embodiment, the same actions and effects as those of the first and second embodiments are produced.

[0020]

As described above, according to the present invention, the two light emitting elements are provided, and the light emitting side lenses having different focal lengths are provided so as to pass the light from the light emitting elements at different positions corresponding to the respective light emitting elements. By providing it, the reading depth can be deepened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of an optical reading device of the present invention.

FIG. 2 is a perspective view of a lens forming a part of the optical reading device shown in FIG.

FIG. 3 is a cross-sectional view of essential parts showing a second embodiment of the present invention.

FIG. 4A is a cross-sectional view of a main part showing a third embodiment of the present invention. (B) is a principal part sectional view when it sees from BB 'of (a).

FIG. 5 is a schematic assembly diagram of a general optical reader.

FIG. 6 is a sectional view of a main part of a conventional optical reading device.

FIG. 7 is a cross-sectional view of essential parts showing a detection state at a distant position of a reading spot in the conventional optical reading device shown in FIG.

[Explanation of symbols]

 4 First light emitting side lens 5 Second light emitting side lens 10 Light receiving side lens 16, 18 Light emitting element 80 Light receiving element

Claims (2)

[Claims] 1. At least two light-emitting elements, and the light from the light-emitting elements are focused at different positions in the optical axis direction corresponding to the respective light-emitting elements, and the illuminance is changed by aberration between the respective focus positions. The light-emitting side lenses are arranged and formed so as to keep them almost constant, the light-receiving side lens that receives the light that passes through these light-emitting side lenses and is reflected from the object near the focal point, and the light that passes through the light-receiving side lens An optical reader consisting of a light receiving element for detection. 2. The optical reading device according to claim 1, wherein each focal position of the light emitting side lens is substantially on the optical axis of the light receiving side lens.