JPH0398181A - symbol reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial application field> The present invention scans a laser beam emitted from a laser oscillation device, directs the laser beam toward a distant object, and receives the reflected light. , concerning symbol reading devices that read symbols such as characters and codes displayed on the surface of objects, especially so-called handheld type symbol reading devices that can be read by simply holding the casing in your hand and pointing the tip of the cylinder toward a distant target surface. Regarding.

In recent years, optical character readers (OCRs) and barcode readers (BC
R) is widely used. These symbol reading devices are
There is a need for devices to be smaller and lighter so that they can be carried and used in any location, and they can be read not only by touching characters or code surfaces, but also from a certain distance from the object to be read, or even from a certain distance from the object to be read. There is also a need for the ability to accurately read symbols even if the user cannot face them head-on.

In order to realize the above functions, recent symbol reading devices:
Called the handheld type, it has a handy pistol-shaped housing that includes a small laser oscillator, a lens that narrows down the diameter of the laser beam emitted from the laser oscillator, and a rotating polygon mirror that scans the laser beam with a fixed angular width. There is a structure in which a light-receiving element that receives the reflected light when the emitted beam is reflected from the object to be read, and a processing circuit that processes the light-receiving signal of the light-receiving element to identify the symbol are integrated. .

A symbol reading device with this structure automatically scans the beam, so unlike pen-type symbol reading devices, there is no need to move the tip of the barrel in contact with the symbol; all you have to do is aim at the object to be read. In addition to the fact that it is handy and can be carried anywhere, it is also possible to perform reading operations very easily even on objects that cannot be directly touched, such as codes printed on the surface of a printed circuit board. .

<Problems to be Solved by the Invention> However, in the above-mentioned symbol reading device, since the distance to the reading object is undefined, the beam spot diameter on the reading plane of symmetry is not fixed.

In other words, the spot diameter of the beam narrowed down by the lens has the property that it becomes minimum at a position (optimal position) at a constant distance M DO from the symbol reading device, and increases both when moving away from or approaching the optimum position. If the distance to the object to be read is incorrectly set, the spot diameter will become larger than the width of the symbol, the symbol reading ability will sharply decrease, and eventually a situation will occur where the processing circuit will no longer be able to identify the symbol.

Now, let us say that the spot diameter of the beam is ω, then ω is a function of the wavelength, the arrangement of the laser oscillation device and the lens, the focal length of the lens, the distance D from the symbol reading device to the reading surface, etc.
As shown in the figure, the minimum value (beam waist) ω0 is taken at the optimum position Do, and the distance jllD is D. As the spot gets closer or farther away, the spot diameter ω increases. becomes larger than Note that the diagonal lines in FIG. 3 are equiphase fronts of the beams.

On the other hand, since the spot diameter ω needs to be smaller than the bar width h of the barcode to be read, the range of distance D at which the symbol can be read is limited to the range D1 to D2 that satisfies ω×h. or more number h,
Taking Do, D,, D2 as an example, the minimum width h of the bar is JA
0 if it is an N code. 2 mms Do is determined by design, but for example, D. -300mmsD,,
D is 200 mm and 400 mm, respectively.

As described above, there is a limit to the reading distance that can be covered by one symbol reading device. Therefore, in order to deal with objects to be read at various distances, D. It is necessary to prepare several types of symbol reading devices with different values and use them while replacing them, which causes problems in that the operation is troublesome and the price is high.

The present invention has been made in view of the above problems, and
The purpose is to provide a symbol reading device that can reliably read symbols even when the distance from the object to be read differs.

Means for Solving the Problems> The symbol reading device of the present invention for achieving the above object has the following features:
A plurality of lenses with different focal lengths are prepared as lenses for narrowing down the laser beam, and the distance D is such that the spot diameter of the laser beam becomes the minimum. In order to change the focal length, a lens changing means for replacing the lens with one having a different focal length is provided inside the housing.

Moreover, the present invention may be provided with a moving means for moving the relative position of the laser oscillation device or the lens within the housing, instead of the lens changing means.

Effect> According to the above configuration, the lens changing means is manually or automatically operated to change the lens and change the distance D according to the distance to the reading target. By varying the symbol reading device, objects at various distances can be read by only one symbol reading device.

Also, instead of replacing the lenses, the distance l can be reduced even if the relative positions of the laser oscillation device or the lenses are moved. liDo
can be changed, so the same effect as the former can be achieved.

Example Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments.

Figure 1 shows how to read symbols such as characters and barcodes.
This figure shows a handheld type symbol reading device with laser beam output. This symbol reading device is housed in a pistol-shaped housing 1, includes a semiconductor laser oscillation device 2, a condenser lens 3 that narrows down the diameter of the output beam of the semiconductor laser oscillation device 2, and a rotating device that scans the output beam over a fixed angular width. a polygon mirror 4 of the formula; a motor 11 for rotating the polygon mirror 4;
A cylindrical lens 5 that images the light emitted from the aperture 13 and reflected by hitting the reading target 6 placed a distance D apart, and a light receiving element 7 such as a photodiode placed on the image plane of the cylindrical lens 5. , and semiconductor laser oscillation device 2
The output of the light receiving element 7 is feedback driven and controlled according to a certain control procedure, and the output signal of the light receiving element 7 is waveform-shaped and binarized at an appropriate slice level to obtain a signal corresponding to the object to be read, for example, a bar code. It houses a processing circuit 9 that identifies the contents of a barcode based on the following information.

A cord 10 extending from the housing 1 is a signal cord and a power supply cord for providing an output signal of the processing circuit 9 to the outside, and a lever 8 serves as a reading switch of the symbol reading device.

As shown in the figure, the condensing lens 3 is one of several pieces attached to a rotary plate 3a with teeth on its circumferential surface, and the teeth protruding from the top of the housing 1 can be manually touched. By moving the rotating plate 3a, the lens can be replaced. Each lens has a different focal length.

In the symbol reading device described above, when the rotary plate 3a is rotated to select one lens and the lever 8 is operated, the motor 1
1 rotates the polygon mirror 4, and
A laser beam is irradiated from the semiconductor laser oscillation device 2. The irradiated laser beam hits one of the reflecting surfaces of the rotating polygon mirror 4 and is reflected, and is repeatedly scanned over a fixed angle in accordance with the rotational movement of the reflecting surface. This scanned beam passes through the aperture 13 and is irradiated onto the reading object 6, and the light reflected from the reading object 6 is received by the light receiving element 7.

FIG. 2 is an optical path diagram depicting the optical path of a laser beam. The beam emitted from the semiconductor laser oscillation device 2 is focused by a condensing lens 3, reflected by a polygon mirror 4, and read through a cylindrical lens 5. It is narrowed down to 6 as a spot on top. Distance D at which this spot diameter ω takes the minimum value. varies depending on the focal length of the lens 3. Each lens attached to the rotary plate 3a is represented as 31, 32, 33, and each lens? DOI, Do2,
Represented by [)oi. The range of distance D where the symbol can be read is DI1 to D21, D, 2 to D22, and D13 to D2, respectively.
, then the focal length of each lens 31, 32, 33 is appropriately selected to obtain the range D. ~D21, range DI2~D2■,
The ranges D1 and D23 can be selected so that they partially overlap each other. An example of a number is D. 1-30
0mms Do2=500, mmq Dog-700m
m, and D H 1 to D 2 1- 1 8 0
~420 mm% DI2 ~Dzz-38
0~620mmSD+i~Dzi-580~820mm
It is.

Therefore, before using the symbol reading device, the operator only needs to predict the distance D to the reading target 6 and select one of the lenses 31 to 33 corresponding to that distance by rotating the rotary plate 3a. Codes can be read reliably.

FIG. 4 shows another embodiment of the present invention, in which a motor 3b is connected to the rotating shaft of a rotating plate 3a for automatic rotation. By controlling the drive of the motor 3b, the lenses 31 to 31 most suitable for the distance to the object to be read 6 are selected.
One of 33 can be selected. To drive the motor 3b, a control lever (not shown) may be attached to the housing 1 and operated by operating the control lever, and a drive command for the motor 3b is written in a program set according to the reading conditions. You may do so by doing so.

FIG. 5 shows still another embodiment, in which instead of replacing the lens 3, the laser oscillation device 2 is
c shows a structure that moves back and forth along the elongated hole 14. FIG. 6 shows a structure in which the lens 3 is moved back and forth along the elongated hole 14 by a lever 3c.

Moreover, FIG. 7 shows a structure in which the laser oscillation device 2 is attached to a rack 3d, and the rack 3d is moved by a pinion 3e connected to a motor 3b. In either structure, by moving the laser oscillation device 2 or the lens 3, the distance D is such that the spot diameter ω takes the minimum value. can be changed.

Therefore, even if the distance D to the reading target 6 is different, each can be read accurately.

Note that the present invention is not limited to the above-mentioned embodiments. For example, before replacing the lens 3 or the rotary plate 3a or moving the laser oscillation device 2 or the lens 3, the distance to the reading target 6, litD is measured with an automatic distance meter, and motor 3
The selection of the lens and the determination of the moving distance may be performed automatically in conjunction with the driving of the lens b.

Furthermore, in the above embodiment, before using the symbol reading device, the operator predicts the distance llitD to the reading target 6, and selects one lens or moves its position according to the distance D. For example,
The distance MD to the reading target 6 is not predicted, and the rotary plate 3a is constantly rotated to calculate the distance MD. may be changed periodically so that an object to be read at an unspecified distance can be correctly read by one of the lenses.

Furthermore, the present invention is an OC that reads characters rather than barcodes.
Needless to say, it can also be applied to R.

Various other design changes can be made without changing the gist of the present invention.

Effects of the Invention> As described above, according to the symbol reading device of the present invention, it is possible to replace the lens with one having a different sunspot distance, or to move the relative position of the laser oscillation device or the lens within the housing. The distance i! at which the laser beam spot diameter is the minimum is determined by Since iiDo can be changed, the range in which barcodes can be read becomes wider than before. Therefore, even if the distance to the object to be read differs greatly, the symbol can be read reliably.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the internal state of the symbol reading device, Fig. 2 is an optical path diagram of the laser beam, Fig. 3 is a diagram depicting how the beam spot diameter ω changes along the optical path, and Fig. 4 The figure shows a motor connected to a rotary plate equipped with multiple lenses, Figure 5 shows a structure for manually moving a laser oscillation device, Figure 6 shows a structure for manually moving a lens, FIG. 7 is a diagram showing a structure in which the laser oscillation device is moved by a rack and pinion mechanism. 1... Housing, 2... Semiconductor laser oscillation device, 3...
・Lens, 3a... Rotating plate, 3b... Motor, 3c... Lever 3d... Rack, 3e... Pinion, 6... Barcode surface, 13
...Aperture, ω...Laser beam spot diameter

Claims (1)

[Claims] 1. Laser emitting device built into a handheld case The laser beam output from the vibration device is At the same time as narrowing down the lens, That laser from the opening formed in the end Do not scan the beam toward a distant target surface. The light is emitted from the target surface and the reflected light from the target surface is received. is attached on the target surface by In a symbol reading device that reads symbols, The above lenses have different focal lengths. Prepare multiple items, The laser beam spots from the above opening. The distance D_0 to the position where the diameter is the minimum is In order to change the focal length of the above lens, Lens replacement hand to replace with a different one It is characterized by having a stage inside the housing. symbol reading device. 2. Laser oscillation instead of lens replacement means The relative position of the device or lens above the housing equipped with means of transportation to move within the The symbol reading according to claim 1, characterized in that removal device.