JPH0816702A - Laser scanner - Google Patents

Abstract

PURPOSE:To vary the scanning angle of laser light corresponding to a distance to a reading object such as a bar code in the case of scanning that reading object with the laser light. CONSTITUTION:When a trigger switch 3 is manipulated and the laser light emitted from a laser light emitting part 4 is reflected back to the bar code, a reflected laser light photodetecting part 7 detects the received light intensity of that reflected light. Based on this received light intensity, a CPU 1 retrieves a correspondence table 10, reads out the manipulating angle corresponding to the received light intensity and sets it in a scanning angle setting amplifier 5. Thus, the shaking angle of a scan mirror provided inside a laser light scanning part 6 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanner for irradiating a laser beam and receiving the reflected light and photoelectrically converting the laser beam to read a bar code or the like.

[0002]

2. Description of the Related Art Conventionally, as laser scanners for irradiating laser light, handheld scanners have been commercialized in addition to stationary scanners. When reading a bar code with this handheld laser scanner, depending on the length (type) of the bar code, the laser scanner should be scanned with a distance of about 50 cm (up to about 1 m). I have to. In other words, when reading a barcode, the laser light is diffused according to the scanning angle that is fixedly fixed in advance, but since the laser light is visible light, the diffusion width of the laser light is not visible to the user. The laser scanner is moved up to a distance beyond which the barcode is scanned.

[0003]

As described above, the distance from the bar code is left to the judgment of the user. Therefore, while the user irradiates the bar code with laser light, the diffusion width of the bar code determines the bar code length. You have to keep the laser scanner away from and close to the bar code many times to cross it,
It has a drawback that it requires extremely troublesome work, puts a heavy burden on the user, and consumes power during that time. An object of the present invention is to make it possible to change the scanning angle of laser light according to the distance to the reading target when scanning the reading target such as a barcode with the laser light.

[0004]

The means of the present invention are as follows. In a laser scanner that irradiates a laser beam and receives the reflected light to perform photoelectric conversion, (1), the detection means detects the received light intensity of the reflected light. (2) The control means controls the scanning angle of the laser light according to the received light intensity detected by the detection means. Further, a correspondence table in which the received light intensity of the reflected light and the scanning angle of the laser light are associated with each other is provided, and the control means sets the scanning angle corresponding to the received light intensity of the reflected light detected by the detection means to the corresponding table. The scanning angle of the laser light may be controlled by searching from.

[0005]

The operation of the means of the present invention is as follows. Now, let us say that, for example, in a handheld laser scanner, a barcode is read. Here, first, the bar code is irradiated with laser light, and the received light intensity of the reflected light is detected. Next, the scanning angle of the laser beam is determined according to the detected light receiving intensity, and the barcode is read by irradiating the laser beam at this scanning angle. Therefore, when scanning an object to be read such as a barcode with the laser light, the scanning angle of the laser light can be changed according to the distance to the object to be read.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. FIG. 1 is a block diagram showing the configuration of a handheld laser scanner. The CPU 1 is a central processing unit that controls the overall operation of the laser scanner according to various programs. When the power switch 2 is operated and then the trigger switch (operation start switch) 3 is operated, C
The PU 1 drives the laser emission unit 4 to irradiate the laser light and sets a scanning angle for oscillating the laser light in the scanning angle setting amplifier 5. The scanning angle setting amplifier 5 performs voltage amplification according to the scanning angle set by the CPU 1, and drives the scan mirror in the laser light scanning unit 6 according to the scanning angle. That is, the deflection angle of the scan mirror in the laser beam scanning unit 6 is adjusted according to the scanning angle set in the scanning angle setting amplifier 5, and the laser beam emitted from the laser emitting unit 4 is of the scanning mirror. It is spread according to the deflection angle,
Scan over the bar code. Here, the laser beam scanning unit 6 detects the position of the scan mirror and outputs the detection result to the CPU.
1 at that time, the CPU 1 determines whether the scan mirror is normally or reversely rotated based on the detected position, and gives the control signal corresponding to the scan mirror to the scan angle setting amplifier 5.

The laser reflected light receiving section 7 receives the reflected light from the bar code and performs photoelectric conversion. The CPU 1 decodes the electric signal photoelectrically converted by the laser reflected light receiving section 7 to obtain the bar code information. read. In this case, C
If the read bar code information is regular bar code information that matches the check digit, the PU 1 stores it in the memory (RAM) 8, but if it recognizes that the bar code information cannot be read, it informs that fact. The error display shown is output from the display unit 9.

The received light intensity / scanning angle correspondence table 10 stores the distance from the bar code as the received light intensity of the reflected light so that the scanning angle of the laser beam becomes an optimum angle according to the distance from the bar code. It has a table structure that stores the optimum scanning angle in association with this received light intensity.
The table contents are fixedly stored in advance. FIG. 2 shows the structure of the correspondence table 10. In this embodiment, the received light intensity level Level has eight levels.
(1), Level (2), ... Level (8) The optimum scanning angle is stored in association with “numerical data”. Here, the received light intensity level Level
(1) shows the received light intensity level when the distance from the bar code is too large, and in this case, the bar code is out of the range in which the bar code cannot be recognized, so the scanning angle corresponding to this level is not set. However, the scanning angles Degree (A), (B), (C), ... (G) corresponding to the other received light intensity levels Level (2), (3), ... (8).
Is set. When the reflected light from the bar code is received by the laser reflected light receiving section 7, the CPU 1 searches the correspondence table 10 based on the received light intensity of the reflected light,
The scanning angle corresponding to the received light intensity is read from the correspondence table 10 and set in the scanning angle setting amplifier 5.

FIG. 3 is a diagram showing the construction of the laser beam scanning unit 6, which is composed of a scan mirror 11 for reflecting and diffusing the laser beam, and a coil wound around a field core. Bipolar electromagnet 12, position detecting element 13 for detecting the position of scan mirror 11, scan mirror 11
And a maximum deflection angle stopper 14 for controlling the deflection so that the deflection does not exceed a predetermined maximum angle. The scan mirror 11 is rotatably provided between the two poles of the electromagnet 12, and the deflection angle of the scan mirror 11 is controlled according to the drive voltage supplied from the scan angle setting amplifier 5 to the electromagnet 12. The position detection signal of the scan mirror 11 detected by the position detection element 13 is C
It is given to PU1. The CPU 1 determines the current position of the scan mirror 11 according to this detection signal, and gives a control signal indicating whether the scan mirror 11 is rotated normally or reversely to the scan angle setting amplifier 5. Scan angle setting amplifier 5
Controls the direction of the current flowing through the coil of the electromagnet 12 according to the control signal.

FIG. 4 shows how the laser beam scanning section 6 controls the laser deflection angle (the deflection angle of the scan mirror 11) according to the drive voltage PW from the scan angle setting amplifier 5. When the drive voltage PW is low, its amplitude is small, and when it is high, its amplitude is large. That is, the deflection angle of the scan mirror 11 changes according to the drive voltage PW, and FIG. 4A shows a deflection curve when the drive voltage PW is low. If this case is taken as the natural frequency, the drive voltage PW becomes high. By doing so, a deflection curve as shown in FIG. 4B is obtained, and the deflection angle of the scan mirror 11 is increased.

Next, the operation of this embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing an operation which is started every time the trigger switch 3 is operated after the power switch 2 is operated. First, when the trigger switch 3 is operated, the CPU 1 drives the laser emission unit 4 and at the same time, outputs the minimum scanning angle “scanning angle De corresponding to the received light intensity level Level (2)” from the correspondence table 10.
By reading "gree (A)" and setting it in the scanning angle setting amplifier 5, laser light is emitted at the minimum scanning angle (step S1). As a result, it is determined based on the output of the laser reflected light receiving unit 7 whether the reflected light from the bar code has returned or whether the received light intensity is below a certain level even if it returns (step S2). Now, as shown in FIG. 6 (A), when the distance from the bar code is too long, the reflected light does not return, or even if it returns, the received light intensity level Level
Since it is less than or equal to l (1), the CPU 1 detects this and causes the display unit 9 to output an error display to that effect (step S9).

On the other hand, the received light intensity of the reflected light is at the level Level.
If l (2) or more, the CPU 1 discriminates the received light intensity of the reflected light as a distance from the bar code based on the output of the laser reflected light receiving unit 7 and digitizes it (step S3), and based on this received light intensity. The correspondence table 10 is searched and the corresponding scan angle is read from the correspondence table 10 and set in the scan angle setting amplifier 5 (step S4). As a result, in the laser beam scanning unit 6, the deflection angle of the scan mirror 11 is controlled by the drive voltage according to the scanning angle set in the scanning angle setting amplifier 5, so that the laser beam is scanned at a scanning angle according to the distance from the bar code. (Step S5). That is, FIG.
As shown in (B), when the distance from the bar code is relatively long, the deflection angle of the scan mirror 11 becomes small,
As shown in FIG. 6C, in the case of a relatively short distance, the deflection angle of the scan mirror 11 becomes large, so that the laser light is emitted at a scanning angle according to the distance from the barcode.

As a result of scanning the bar code at a scanning angle corresponding to the distance from the bar code in this manner, it is checked whether the bar code information can be normally read (step S6). As a result, when the reading can be performed normally, the value (bar code information) is stored in the memory 8 (step S7) and the reading completion is notified (step S8). On the other hand, when the unreadable state is recognized in step S6, an error display indicating that is displayed (step S9).

As described above, in the present embodiment, when the trigger switch 3 is operated, first, the laser beam is emitted at the minimum scanning angle, the received light intensity of the reflected light is detected, and the received light intensity is detected. The scanning angle is automatically determined by referring to the correspondence table 10 and then the bar code is scanned at the determined scanning angle. Therefore, the bar code is scanned at the optimum scanning angle according to the distance from the bar code. The code can be scanned. Therefore, the user can read the bar code at the optimum scanning angle that is automatically determined without being strictly aware of the distance from the bar code. Also, when the laser beam is irradiated to automatically determine the optimum scanning angle according to the distance to the barcode, it is determined whether the distance to the barcode is within the readable range according to the reflected light. However, if the distance is outside the reading range, the user is informed of that fact. Therefore, the user can immediately bring the laser scanner close to the readable range, and quick response is possible.

Although the above embodiment assumes a case where the length of the bar code is constant, for example, a relatively small bar code attached to a product or a relatively large size attached to a cardboard box or the like. When the types of barcodes are different, such as barcodes, the scanning angles differ greatly even if the distance from the barcode is the same. As described above, the following methods may be used together as a means for determining the optimum scanning angle according to the distance between different types of barcodes. The scanning angle automatically determined by the above embodiment, that is, the optimum scanning angle automatically determined by referring to the correspondence table 10 according to the distance from the bar code (received light intensity of the reflected light) is the depth of pushing of the trigger switch 3. To correct based on That is, the trigger switch 3 has a volume structure, a decoder for converting the volume value into a numerical value is provided, and a scanning angle correction unit for correcting the scanning angle automatically determined in the above embodiment based on the output of the decoder is provided. The scanning angle corrected by the unit is set in the scanning angle setting amplifier 5. As a result, the user adjusts the pushing depth of the trigger switch 3 according to the type of barcode, and the optimum scanning angle is automatically determined according to the distance between the type and the barcode. Therefore, the user only has to push the trigger switch 3 deeply when the bar code is long and shallowly push it when the bar code is short, and it is not necessary to be aware of the distance from the bar code, as in the above-described embodiment. .

Further, in the above embodiment, in order to determine the optimum scanning angle according to the distance from the bar code, when the trigger switch 3 is operated, first, the scanner mirror is swung at the minimum scanning angle, and the laser is scanned. Although the light is emitted, the laser light may be emitted with the scanner mirror fixed. Further, although the above embodiment shows the case of applying to a bar code scanner for reading a bar code, it is not limited to a bar code and may be another code, for example, a cell-shaped black and white code or the like, Further, the image data such as a figure may be read.

[0017]

According to the present invention, when scanning an object to be read such as a bar code with a laser beam, the scanning angle of the laser beam can be changed according to the distance to the object to be read. When reading the code, the user does not need to be aware of the distance from the bar code, which makes it possible to greatly improve operability and shorten the operating time of the laser light source to extend its life. Not only can it be achieved, but it is also advantageous in terms of power consumption.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a handheld laser scanner according to an embodiment.

FIG. 2 is a diagram showing a configuration of a correspondence table 10.

FIG. 3 is a diagram showing a configuration of a laser beam scanning unit 6.

FIG. 4 shows a scan mirror 11 in the laser beam scanning unit 6.
6 is a diagram showing a state in which the deflection angle of the image changes according to the drive voltage PW from the scanning angle setting amplifier 5. FIG.

FIG. 5 is a flowchart showing an operation when the trigger switch 3 is operated.

FIG. 6: Scan mirror 1 according to the distance from the barcode
The figure which showed concretely the state where the deflection angle of 1 changes.

[Explanation of symbols]

 1 CPU 2 Power Switch 3 Trigger Switch 4 Laser Emitting Section 5 Scanning Angle Setting Amplifier 6 Laser Light Scanning Section 7 Laser Reflected Light Receiving Section 8 Memory 9 Display Section 10 Corresponding Table 11 Scan Mirror 12 Electromagnet 13 Position Detecting Element

Claims (2)

[Claims] 1. A laser scanner for irradiating a laser beam and receiving the reflected light and photoelectrically converting the reflected light, and detecting means for detecting the received light intensity of the reflected light, and the received light intensity detected by the detecting means. A laser scanner comprising: a control unit that controls a scanning angle of laser light. 2. A correspondence table is further provided in which the received light intensity of the reflected light and the scanning angle of the laser light are associated with each other, and the control means sets the scanning angle corresponding to the received light intensity of the reflected light detected by the detection means. The laser scanner according to claim 1, wherein the scanning angle of the laser beam is controlled by searching the correspondence table.