JPH02219013A - Laser bar code scanner - Google Patents

Abstract

PURPOSE:To prevent the light utilization efficiency from decreasing by providing a 1st light converging member which converges light emitted from a laser source part, and further providing a 2nd light converging member which stops down the light being converged by the 1st light converging member, to a specific beam diameter for reading. CONSTITUTION:The 1st light converging lens 7 is provided on the optical path of the light emitted by the semiconductor laser 1 and has a large lens diameter enough to converge the light emitted by the semiconductor laser 1 almost without any leak. Further, the 2nd light converging lens 8 is provided on the optical path of the light which is stopped down once by the 1st light converging lens 7 and passed through a light convergence point R to the specific beam diameter for reading. Then almost all of the light emitted by the semiconductor laser 1 is converged and stopped down once, then converged by the 2nd converging lens 8 to scan a bar code surface 6 having the specific beam diameter for reading, thereby reading stored information. Consequently, the light is prevented from being eclipsed to improve the light utilization efficiency more.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser barcode scanner that reads information on a barcode surface by scanning a hologram disk or the like with light emitted from a laser light source.

2. Description of the Related Art A conventional laser barcode scanner will be described with reference to FIG. First, the overall configuration will be briefly described. Light emitted from a semiconductor laser 1 as a laser light source is collimated by a collimator lens 2, and an aperture 3 removes unnecessary extraneous light from the collimated light to form an effective beam diameter for reading. After removing the beam, the parallel light is focused by a condenser lens 4 and passed through a hologram scanner 5 as a light scanning member. The light that has passed through the hologram scanner 5 is in a scanning state and scans over the barcode surface 6 as a reading surface, thereby reading the information recorded on the barcode surface 6. In addition to the hologram scanner 5, a polygon mirror, a galvano mirror, etc. (not shown) can be used as the optical scanning member.

In the devices described above, the effective beam diameter used for reading information is generally very small, around 200 μm, and in order to increase the reading depth, the small beam diameter is kept the same for a certain distance. need to be kept. For this reason, conventionally, the aperture 3 is used to narrow down the emitted light to about 2 to 5 mm in advance, thereby obtaining an effective beam diameter.

In addition, in order to prevent the reduction in the amount of light emitted from the semiconductor laser 1 and increase the light utilization efficiency, the distance from the semiconductor laser 1 to the collimator lens 2 located at the next position or the distance to the hologram disk 5 should be made as short as possible. I keep it short.

Furthermore, in order to obtain a reading depth, the distance between the barcode surface 6, which is the condensing point, and the condensing lens 4, which is the closest lens, is usually about 200 to 400 II 1 m. The vertical magnification is often about 10oO to 3000x. Note that this vertical magnification is defined as the vertical magnification, where a is the distance from the emission point P to the condensing lens 4, and b is the distance from the condensing lens 4 to the condensing point Q, as shown in Fig. 3. The magnification C is expressed as c#(b/a)'' (1).

Problems to be Solved by the Invention In the conventional device as described above, the semiconductor laser 1
Since the divergence angle of the emitted light is as large as 20° to 40', it is necessary to narrow down the beam diameter of the emitted light using the aperture 3 in advance in order to obtain an effective beam diameter for reading as described above. However, if such a method using the aperture 3 is adopted, the light utilization efficiency will be poor.

In addition, since the divergence angle of the emitted light is large, the distance between the semiconductor laser l and the collimator lens 2 (or condensing lens 4) that comes in the next position should be kept as short as possible, thereby preventing a reduction in light utilization efficiency. However, on the other hand, in order to obtain a reading depth, the distance between the barcode surface 6 and the condensing lens 4 is usually set to 2.00 mm.
Since the width is approximately 400 mm, the vertical magnification is approximately several hundred times to several thousand times. For this reason, even if there is an error of about 1 μm when installing the collimator lens 2, which is an optical component that comes next to the semiconductor laser 1, the error (1 μm) will be reflected by the number of errors (1 μm) on the barcode surface 6, which is the focal point. The beam position will shift by a factor of 100 to several thousand times. In order to eliminate this deviation in the beam position, it is sufficient to make the distance fia long in equation (1), but in conventional devices, for the reasons mentioned above, the distance a,
That is, the distance between the semiconductor laser l and the collimator lens 2 cannot be increased. For this reason, assembly of the optical system requires very high precision in adjustment, and the adjustment requires a great deal of effort and time.

Means for Solving the Problems Therefore, in order to solve such problems, the present invention scans the light emitted from a laser light source with a light scanning member, and irradiates the reading surface with the scanning light. A laser barcode scanner that reads information recorded on the reading surface is provided with a first condensing member that condenses the light emitted from the laser light source, and the light condensed by the first condensing member is directed to a predetermined area. A second condensing member was provided to focus the beam to a reading beam diameter of .

As a result, the light emitted from the laser light source is focused with almost no leakage by the first focusing member and once focused, and then transformed into a beam diameter for predetermined reading by the second focusing member. This eliminates the need to use an aperture as in the past.
Furthermore, there is no need to shorten the distance between the laser light source and the collimator lens, and the vertical magnification can be made much smaller than in the past.

Example An embodiment of the present invention will be described based on FIG.

Note that a description of the same parts as in the prior art (see FIG. 2) will be omitted, and the same parts will be denoted by the same reference numerals.

The first condensing lens 7 as a first condensing member is provided so as to be located on the optical path of the light emitted from the semiconductor laser 1, and the divergence angle of the semiconductor laser 1 (usually 20° to 40°) is provided.
The lens has a large diameter that allows it to condense the light emitted from the lens with almost no leakage. Also,
The second condensing lens 8 as a second condensing member is located on the optical path of the light that has been narrowed down by the first condensing lens 7 and passed through the condensing point R. The lens diameter is large enough to narrow down the beam to a predetermined beam diameter (approximately 200 μm).

In such a configuration, most of the light emitted from the semiconductor laser l is focused by the first condensing lens 7 and narrowed down once, and then condensed by the second condensing lens 8 to form a hologram. By scanning with the disk 5, the barcode surface 6 is scanned with a predetermined beam diameter for reading, thereby reading the stored information.

In this case, by providing the first condensing lens 7, there is no need to provide the aperture 3 as in the conventional case, so there is no vignetting of the light, and the light utilization efficiency of the emitted light can be further increased. Furthermore, by using the first condensing lens 7, the distance a between the semiconductor laser 1 and the first condensing lens 7 can be made longer than in the past.
1) The value of the vertical magnification obtained from the formula can be made much smaller than the conventional value (several hundred to several thousand times).

Therefore, in the past, the assembly of the distance a (distance between the semiconductor laser l and the collimator lens 2) had to be performed with very high precision within several μm, but in the present invention, the accuracy of the assembly for the distance a (distance between the semiconductor laser l and the collimator lens 2) must be maintained at a very high level of accuracy within several μm. Because of this, it is not necessary to assemble the distance Ha as precisely as conventionally, and as a result, the assembly can be adjusted with some margin. Furthermore, by keeping a sufficient distance a between the semiconductor laser 1 and the first condensing lens 7 and moving the second condensing lens 8 by several millimeters, the condensing position on the barcode surface 6 can be maintained without changing. , the assembly of the optical system can be adjusted with high precision.

In addition, the first light condensing member and the second light condensing member according to the present invention are as follows:
It only needs to have the function of focusing light, for example,
A hololens or a hologram scanner may also be used.

Effects of the Invention In the present invention, since most of the light emitted from the laser light source is focused by the first light focusing member, it is possible to eliminate the vignetting of light that occurs when an aperture is used as in the past. This makes it possible to further increase light utilization efficiency. In addition, since the first light condensing member can be placed away from the laser light source, it is possible to make the vertical magnification much smaller than in the past, which makes it possible to assemble the optical system with extremely high precision, unlike in the past. Moreover, by moving the second condensing member 111 in the optical axis direction, the assembly of the optical system can be adjusted accurately without shifting the condensing position on the barcode surface. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is an optical path diagram showing an embodiment of the present invention, FIG. 2 is an optical path diagram showing a conventional example, and FIG. 3 is an explanatory diagram showing the relationship between vertical magnifications. DESCRIPTION OF SYMBOLS 1... Laser light source, 5... Light scanning member, 6... Reading surface, 7... First condensing member, 8... Second condensing member Applicant Rico Co., Ltd.

Claims (1)

[Claims] In a laser barcode scanner that scans the light emitted from a laser light source with an optical scanning member and irradiates the scanning light onto the reading surface to read information recorded on the reading surface, the light emitted from the laser light source is used. A laser barcode characterized by being provided with a first condensing member that condenses the light, and a second condensing member that narrows the light condensed by the first condensing member to a predetermined beam diameter for reading. scanner.