JPH04181384A - Symbol reader - Google Patents

Abstract

PURPOSE:To excellently read symbols corresponding to various read conditions by determining the amplification gain of a variable gain type amplifying means for the output of a photodetecting means irrelevantly to an amplification gain set corresponding to other scanning lines or a scanning line group. CONSTITUTION:A laser beam is scattered by a symbol surface 13 and its scattered light is photodetected by the photodetecting means 15, whose output is supplied to an automatic gain control circuit group 16 which has plural automatic gain control circuits AGC1-AGC3. In this case, the laser beam forms scanning lines alpha, beta, and gamma in mutually different directions on the symbol surface 131. Namely, the output signal of the photodetecting means 15 is amplified with the amplification gain set by the automatic gain control circuit AGC1 in a period where a alpha-directional scan is made without fail and the output signal of the photodetecting means 15 is amplified with the amplification gain set by the automatic gain control circuit AGC2 in a period wherein a beta-directional scan is made without fail. A gamma-directional scan is the same. Thus, the amplification gain of the output signal of the photodetecting means 15 is not affected by scans in other directions.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a symbol reading method that optically reads a symbol such as a bar code by scanning a symbol surface on which a symbol such as a bar code is formed with a beam light such as a laser beam. Regarding equipment.

<Prior Art> As computers have become widely used in recent years, input/output devices connected to computers are required to have more diverse functions. for example,
In optical character readers (OCR) and barcode readers (BCR) that read characters and codes recorded on cards, packaging packages, etc. and instantly identify their contents, the reading head touches the surface of the characters and codes. Rather than reading the characters at a distance, the characters can be read accurately, even if they are far away from the object to be read, or even if they cannot face the object directly.
There is an increasing demand for the ability to read codes.

In order to realize the above functions, recent symbol reading devices:
A laser oscillation device, a scanning mirror such as a polygon mirror or a galvano mirror that scans the laser beam emitted from the laser oscillation device with a fixed angular width, and a light receiving element that receives the light reflected from the symbol surface that forms the symbol to be read. , and a processing circuit for processing the output signal of the light-receiving element to identify the symbol, etc., are integrated into a stationary housing.

Since a symbol reading device with this structure uses a laser beam, it is possible to obtain a small spot even at a distant location, and it is possible to read not only nearby symbols but also symbols far away (reading depth In addition, since the beam is automatically scanned, there is no need to move the tip of the barrel unlike a pen-type symbol reading device, and the object with a symbol formed within the field of view of the laser beam exit window can be held still in the hand, for example. The advantage is that it can be read with a simple operation.

In addition, with the so-called hunt belt type, which incorporates the above parts into a handy pistol-shaped housing and irradiates a laser beam from the tip of the housing, reading can be performed by aiming at the symbol. In addition to the fact that it is handy and can be carried anywhere, it is also possible to easily read objects that cannot be directly contacted, such as small bar codes printed on the surface of a printed circuit board.

In the above-mentioned laser scanning type symbol reading device, the reflected light when a symbol surface is repeatedly scanned with a laser beam is converted into an electrical signal by a light receiving element composed of a foot diode or the like. The output signal of this light-receiving element is amplified by an amplifier circuit and then given to an identifying means, where the symbol is identified through binarization processing or the like. With such a configuration, when attempting to read symbols on symbol surfaces located at various positions within a wide range, for example, distances from the device from a few holes to 1 meter, there is a large difference in the amount of reflected light received by the light receiving element. Become. Therefore, if you adjust the gain of the amplifier circuit to the amount of reflected light from nearby sources, you will not be able to read distant symbols;
If the amplifier circuit is adapted to the reflected light from the nearby symbol surface, the output of the amplifier circuit will easily become saturated with respect to the reflected light from the nearby symbol surface, making it impossible to read the symbol.

For this reason, symbol reading devices with a wide reading range
Generally, an automatic gain control technique is applied that determines the amplification gain for the output of the light receiving element by referring to the amount of reflected light during the previous scan. In other words, by setting a small gain for high-intensity reflected light from a nearby symbol surface, and by setting a high gain for low-intensity reflected light from a distant symbol surface, the signal input to the identification means is The level range is limited to a predetermined range, thereby achieving good symbol identification performance regardless of the distance (reading distance) between the device and the symbol surface.

Recently, in order to improve the operability of the above-mentioned symbol reading devices, symbols have been scanned in multiple directions (omni-scan) as shown in Figure 8, and symbols have been scanned in multiple directions (omni-scan) as shown in Figure 9. In recent years, methods have come to be used that form a plurality of parallel scanning lines s1 to s5 while slightly shifting their positions on the symbol plane (raster scanning).

For example, with a barcode reader that uses omni-scan, it is possible to read the barcode if the entire barcode can be scanned by scanning in either direction, so it is necessary to strictly set the positional relationship between the bar hood and the reading position. This greatly improves the operability during reading.

On the other hand, with raster scanning barcode reading devices, even if the scanning line is slightly inclined to the barcode, as long as any scanning line crosses the entire barcode, the symbol can be identified, making it easier to operate. In addition, even if a part of the barcode is chipped, the barcode can be identified as long as one of the scanning lines crosses the part that is not chipped, which also improves reading performance. be done.

<Problems to be Solved by the Invention> In symbol reading devices that employ omni-scan or raster scan as described above, the scanning position of the symbol plane changes sequentially each time it is scanned. The amount of reflected light may change. In particular, if the light-receiving element and the symbol surface face each other directly during any scanning and specularly reflected light from the symbol surface is received, or if there is an object with high reflectivity such as metal on the scanning line, In scanning, the amount of reflected light becomes extremely large.

Therefore, with the automatic gain control technology described above, which determines the amplification gain of the light receiving element output corresponding to the current scan based on the amount of light received during the previous scan, when the amount of light received increases extremely as described above, In this case, the amplification gain for the light receiving element output corresponding to the current scan becomes extremely small due to the extremely high amount of reflected light from the previous scan.

Therefore, even if the symbol is scanned correctly, the amplification gain for the light receiving element output is extremely small, making it impossible to identify the symbol.

As described above, in a symbol reading device that employs omni-scan or raster scan, application of automatic gain control technology may actually worsen the reading performance. Conversely, it is possible to narrow the range of reading distance (reading range) without applying automatic gain control technology, but in this case, the operability during reading will deteriorate significantly due to the narrow reading range. It turns out.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems and provide a symbol reading device that can read symbols satisfactorily in response to various reading conditions.

<Means and operations for solving the problem> To achieve the above object, the symbol reading device according to claim 1 includes a beam emitting means for emitting a beam light, and a symbol reading device using the beam light from the beam emitting means. a scanning means for sequentially scanning mutually different positions on the formed symbol surface; a light receiving means for receiving reflected light from the symbol surface; a variable gain amplification means for amplifying the output of the light receiving means; and identification means for performing signal processing for identifying the symbol based on the signal from the amplification means, scanning position detection means for detecting which position the scanning means is scanning; Based on the output of the light receiving means obtained for each scanning line or for each scanning line group including a predetermined number of scanning lines, the amplification gain of the variable gain amplification means is set for each scanning line or for each scanning line group. automatic gain control means; and control means for selecting an amplification gain to be set for each scanning line or for each scanning line group in the automatic gain control means based on the output of the scanning position detection means. .

According to the above configuration, the amplification gain of the variable gain type amplification means for amplifying the output signal of the light receiving means is controlled by the automatic gain control means which sets the amplification gain for each scanning line or for each scanning line group. The amplification gain for each scanning line or for each scanning line group is selected by the control means based on the output of the scanning position detection means for detecting the scanning position. That is, as the scanning position changes, the amplification gains corresponding to each scanning line or each scanning line group are sequentially switched and selected.

Therefore, the amplification gain of the variable gain amplification means for the light receiving means output corresponding to each scanning line or each scanning line group is independent of similar amplification gains set corresponding to other scanning lines or scanning line groups. It will be determined. That is,
For example, the amplification gain corresponding to a scanning line or a group of scanning lines is set based on the output of the light receiving means during the previous scan by the scanning means forming the scanning line or group of scanning lines, and It is not affected by the output of the light receiving means corresponding to the scanning line group.

As a result, during scanning, for example, if specular reflection light from a symbol surface is received by the light receiving means, or when a scanning line or a group of scanning lines crosses a highly reflective object such as a metal, the light receiving means receives a high intensity of light. Even if the amplification gain corresponding to the relevant scanning line or scanning line group becomes extremely small when the light is incident, such an excessively small amplification gain will not be applied to other scanning lines or scanning line groups. is never set.

Therefore, symbols can be favorably identified based on the output of the light receiving means corresponding to the scanning line or scanning line group of the function.

In the symbol reading device according to claim 2, the state of the automatic gain control means is such that the amplification gain corresponding to one or more predetermined scanning lines or scanning line groups is set to a value corresponding to the output of the light receiving means, and the remaining amplification gain is set to a value corresponding to the output of the light receiving means. A state in which the amplification gain corresponding to the scanning line or group of scanning lines is set to a predetermined constant value, and a state in which the amplification gain corresponding to all of the scanning lines or groups of scanning lines is set to a value corresponding to the output of the light receiving means. It is equipped with a switching means for switching between the states.

In this way, by setting the above-mentioned constant value to a sufficiently low value, symbol identification processing can be performed only based on the output of the light receiving means corresponding to one or more predetermined scanning lines or a group of scanning lines. It is possible to prohibit symbol identification processing based on the output of the light receiving means corresponding to the scanning line or group of scanning lines. Therefore, for example, when a large number of symbols are arranged close together, the scanning line or group of scanning lines used to identify the symbol may be limited, and the symbol may be read incorrectly if it is not intended to be read by the operator. It is possible to prevent this.

Further, the above-mentioned constant value may be a value of the amplification gain corresponding to the case where the symbol is located at a predetermined distance near the device.

In this way, for distant symbols, symbol identification can be performed based only on the output of the light receiving means corresponding to the scanning line or group of scanning lines, and only the desired symbol can be accurately read. For nearby symbols, symbol identification can be performed based on the outputs of the light receiving means corresponding to all the scanning lines, thereby improving operability.

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

FIG. 1 is a block diagram showing the basic configuration of a barcode reading device, which is a symbol reading device according to an embodiment of the present invention.

A laser beam 11 from a beam emitting means 11 including a semiconductor laser light source, its driving circuit, and a collimating lens is transmitted from a scanning means 12 including a polygon mirror to an opening formed in a housing (not shown). The light is emitted toward the barcode 14 formed on the symbol surface 13 through the . The laser beam 11 is scattered by the symbol plane 13, and this scattered light 12 is received by a light receiving means 15 including a photodiode. The output of this light receiving means 15 is given to an automatic gain control circuit group 16 which is an automatic gain control means having a plurality of automatic gain control circuits AGCl to AGC3.

The signal amplified with an appropriate amplification gain by the automatic gain control circuit group 16 is given to the identification means J7, where it is binarized at an appropriate threshold level, and the information flj represented by the bar code 14 is
or is reproduced.

The scanning means 12 is, for example, a polygon mirror 20, as shown in FIG.
Around the polygon mirror 20, plane mirrors 21, 22, and 23 are arranged which are inclined at a predetermined angle with respect to the axis 20b of the polygon mirror 20.

The polygon mirror 20 is rotationally driven by a motor 24 at a constant angular velocity.

FIG. 3 is a diagram schematically showing how the bar code I4 is scanned by the scanning means 12 described above. polygon mirror 2
As the angle 0 rotates, the angle of incidence of the laser beam on the deflection reflecting surface 20a changes, so that the laser beam from the polygon mirror 20 first enters the plane mirror 21.
The laser beam from this plane mirror 21 forms a scanning line α on the symbol plane 13. When the polygon mirror 20 further rotates, the laser beam from this polygon mirror 20 becomes 2
The laser beam from this plane mirror 2 forms a scanning line β on the symbol plane 13. Next, the laser beam from the polygon mirror 20 is incident on the third plane mirror 23 to form a scanning line γ on the symbol plane 13. In this way, the laser beam
3, forming scanning lines α, β, and γ in mutually different directions,
This achieves what is called an omni-scan.

In this case, any scanning line α, β, γ or barcode 1
4, the barcode 14 can be read based on the output of the light receiving means 15 at this time. In the following explanation, the scanning of the barcode 14 by the laser beam 11 that forms the above-mentioned scanning lines α, β, and γ, respectively, will be referred to as “α direction scanning,” “β direction scanning j,” and “β direction scanning,” respectively.
It is called γ direction scanning J.

On the optical path from the scanning means 12 to the symbol plane 13, a first
As shown in the figure, scanning in the three directions mentioned above is detected, and the laser beam I! on the symbol plane 13 is detected. Scanning direction detecting means 31, which is a scanning position detecting means for detecting the scanning position of l, is arranged. The detection output of the scanning direction detection means 31 is given to a control means 32 that controls the automatic gain control circuit group 16. This control means 32 selects one of the automatic gain control circuits from the automatic gain control circuits AGCI-AGC3 included in the automatic gain control circuit group 16 based on the scanning direction (scanning position) detected by the scanning direction detection means 31. However, the output signal of the light receiving means 15 is amplified by the amplification gain set by the selected automatic gain control circuit.

The control means 32 has a multi-directional scanning reading state in which barcodes are read based on scanning in all three directions mentioned above, and a scanning state in which barcodes are read based on scanning in one direction arbitrarily selected from the scanning in the three directions mentioned above. A switching means 33 is connected thereto for switching between a unidirectional scanning reading state in which barcodes are read using the unidirectional scanning reading state, and a selecting means 34 is also connected for selecting a scanning direction in which symbol identification processing is performed in the unidirectional scanning reading state. ing.

FIG. 4 is a conceptual diagram showing the basic configuration of the scanning direction detection means 31. For example, an opening 40 for emitting the laser beam fl is formed in the casing 35 in which the beam emitting means 11 and the scanning means 12 are housed. Three light receiving elements 41, 42, 43 are fixed to the inner wall of the body 35,
The scanning direction detection means 31 is configured. Each light receiving element 41, 42, 43 corresponds to the above scanning line α.

It corresponds to β and γ, and when the above-mentioned α direction scanning, β direction scanning, and γ direction scanning is performed, it receives the laser beam il at the end of the scanning. Therefore, for example, when the light receiving element 41 detects the laser beam 11, it is known that the next scan will be a β direction scan. Similarly, from the outputs of the light-receiving elements 41, 42, and 43, the control means 32 can know whether the next scan is α, β, or γ.

In this embodiment, the automatic gain control circuit ACCI-AGC3 in which the automatic gain control circuit group 16 exists corresponds to scanning in the α, β, and γ directions, respectively. That is, the control means 3
2 is based on the output from the scanning direction detection means 31, and during the period when the laser beam 11 forms the scanning line α in FIG.
The automatic gain control circuit ACCI is selected, the automatic gain control circuit AGC2 is selected during the period of forming the scanning line β, and the automatic gain control circuit AGC3 is selected during the period of forming the scanning line γ. That is, automatic gain control circuit ACCI.

AGC2 and AGC3 are selected cyclically as the scanning means 12 scans the laser beam 11.

FIG. 5 is a block diagram showing the basic configuration of the automatic gain control circuit group 16. However, in FIG. 5, the automatic gain control circuits AGC2 and AGC3 are omitted because they have the same configuration as the automatic gain control circuit AGCl.

The signal from the light receiving means 15 is transmitted to the automatic gain control circuit AGC1 via a switching circuit 61 which is switched by the control means 32 in accordance with the detection result of the scanning direction detecting means 31.
~AGC3. For example, the output signal of the light receiving means 15 applied to the automatic gain control circuit ACCI is first amplified by the variable gain amplifier circuit 62. The amplified signal is given to the identification means 17 via a switching circuit 63 which is switched in conjunction with the switching circuit 61. The switching circuits 61 and 63 are connected to the automatic gain control circuit Δ〇CI during the period when scanning in the α direction is performed, and connected to the automatic gain control circuit AG during the period when scanning in the β direction is performed.
C2, and is connected to the automatic gain control circuit AGC3 during any period in which scanning in the γ direction is performed.

The output signal of the variable gain amplifier circuit 62 is also provided to an integrating circuit 64. This integrating circuit 64 is connected to the laser beam 1.
Variable gain amplifier circuit 6 during one scan period according to 1
This circuit is for obtaining the average value of the two outputs, and its output is given to the sample and hold circuit 65. The sample and hold circuit 65 samples and holds the output of the integration circuit 64 based on the sampling clock supplied from the control means 32 at the timing when the scanning in the α direction is completed. The holding voltage is applied as a control signal from line 66 to variable gain amplifier circuit 62 to determine its amplification gain.

A specific example of the circuit configuration of the variable gain control circuit 62, the integrating circuit 64, and the sample bold circuit 65 is shown in detail in, for example, Japanese Patent Laid-Open No. 63-93950.

With the above configuration, during the period when the α direction scanning is performed, the output signal of the light receiving means 15 is always amplified by the amplification gain set by the automatic gain control circuit AGC1, and during the period when the β direction scanning is performed, Be sure to use automatic gain control circuit AGC2
The output signal of the light receiving means 15 is amplified by the amplification gain set in .

The same applies to scanning in the γ direction. In this way, the amplification gain of the output signal of the light receiving means 15 corresponding to scanning in each direction is not affected by scanning in other directions. That is, for example, the automatic gain control circuit ACCI
The amplification gain during the current α direction scanning is set based on the output signal level of the light receiving means 15 during the direction scanning, and is not affected by the output of the light receiving means 15 corresponding to the β direction scanning or the γ direction scanning. This also applies to scanning in the β direction and scanning in the γ direction.

Therefore, even if specularly reflected light from the symbol surface 13 or reflected light from the surface of an object with high reflectivity such as a metal is incident on the light receiving means I5 by scanning in the β direction or the γ direction, α Automatic gain control circuit A, G compatible with directional scanning
The amplification gain set by C1 will not become extremely small. Thereby, the barcode I4 can be identified based on scanning in the α direction without being affected by the specularly reflected light described above.

Since it does not use an automatic gain control circuit, it is possible to suppress deterioration of reading performance due to specularly reflected light, etc., so it is possible to read over a wide reading range, and it is also possible to read symbols well under various conditions. becomes.

Next, the function of the switching means 33 shown in FIG. 1 will be explained.

For example, when the direction of the barcode to be read is not constant, as in the case of use at a supermarket cash register, it is possible to improve the operability when reading the barcode by using the multi-directional scanning reading state as described above. . on the other hand,
For example, when multiple barcodes exist side by side, symbol identification processing is performed based on all of the above α, β, and γ direction scanning. This is not desirable as it may be read.

In such a case, the operator may select α direction scanning, β direction scanning, or γ direction scanning using the selection means 34 and set the unidirectional scanning reading state using the switching means 33. In response to this, the control means 32 controls the automatic gain control circuit group! 6
Among the automatic gain control circuits in which ). Specifically, as the switching circuits 61 and 63 in FIG.
These switching circuits 61 .
63 to switch between a state in which it is connected to the automatic gain control circuit corresponding to the scanning direction selected by the selection means 34 and a state in which it is not connected to any automatic gain control circuit.

In this case, for example, if the selection means 34 selects the α direction scanning, the automatic gain control circuit AGC! The automatic gain control circuits AGC2 and AGC3 are prohibited from operating. Then, the control means 32 connects the switching circuits 61 and 63 to the automatic gain control circuit AGC1 only when scanning in the α direction is performed. As a result, the automatic gain control circuit AGCI controls the light receiving means 1 during the previous α direction scanning.
According to the gain set by the control signal held in the sample and hold circuit 65 (see FIG. 5) corresponding to the output of 5, the output of the light receiving means I5 corresponding to the current α direction scanning is outputted by the variable gain amplifier circuit 62. Amplify.

For β direction scanning and γ direction scanning, the light receiving means 15
Since the amplification gain for the output of
will be identified.

In this way, for example, when multiple barcodes are present in close proximity, there is a risk that a nearby barcode will be read by mistake in a multi-directional scan reading state, which will actually reduce the efficiency of data input work. In such cases, data can be inputted more easily by switching to the unidirectional scanning/reading state. In this manner, the operator can select between the unidirectional scanning reading state and the multidirectional scanning reading state according to the usage conditions, thereby greatly improving the workability of data input by barcode reading.

In this embodiment, the scanning direction in which barcode identification processing is performed in the unidirectional scanning reading state is selected by the selection means 3.
The reason why it is possible to select from 4 is to improve versatility in response to various usage conditions. In other words, in the case of a barcode reader fixedly placed above a belt conveyor, for example, the direction in which the barcode is formed on the object conveyed on the conveyor is independent of the installation direction of the barcode reader. Is it possible to respond to this?

In addition, in the case of a handheld barcode reading device, if the scanning direction can be appropriately selected depending on the scanner's dominant hand or personal preference, the reading operation can be performed more efficiently.

In this embodiment, when the unidirectional scanning reading state is specified by the switching means 33, the amplification gain corresponding to the scanning direction not selected by the selecting means 34 is not set to 0, and the symbol plane is placed near the apparatus. It is also possible to set a fixed value corresponding to the case where 13 is located. Specifically, for example, when α direction scanning is selected by the selection means 34, control is performed to determine the gain for variable gain amplification circuits in automatic gain control circuits AGC2 and AGC3 corresponding to β and γ direction scanning. A constant voltage may be input as a signal.

In this way, if the distance between the barcode and the device is short, the barcode identification process will be performed in a multi-directional scan reading state, and if the distance between the barcode and the device is long, the barcode identification process will be performed in a unidirectional scanning state. Barcode identification processing can be performed in the scan reading state.

This prevents the operator from accidentally reading a barcode that the operator did not intend to read when the barcode is far away, and also prevents reading of nearby barcodes by adjusting the positional relationship between the barcode and the device. This can be done with good workability without strict settings.

FIG. 6 is a simplified perspective view of another example of scanning direction detection means that can be used in place of the scanning direction detection means 31 shown in FIG. 4. A permanent magnet piece 5 is attached to the drive shaft 24a of the motor 24 that rotationally drives the polygon mirror 20.
1 is fixed, and a plurality of coils 52 are arranged near the rotation orbit of this permanent magnet piece 51. The output of this coil 52 is given to an angle detection circuit 53, which creates information representing the rotation angle of the motor 24 and supplies it to the control means 32.

With this configuration, since the rotational position of the polygon mirror 20 is detected, it is possible to know which plane mirror 21 to 23 the laser beam 11 from the beam emitting means 11 is incident on, and therefore α, β , scanning in the γ direction can be detected.

FIG. 7 is a block diagram showing the electrical configuration of a part of the second embodiment of the present invention. FIG. 7 shows an automatic gain control means to be used in place of the automatic gain control circuit group 16 shown in FIG.

That is, in this embodiment, one variable gain amplifier circuit 70 is shared for scanning in the α, β, and γ directions, and sample and hold circuits 71, 72, and 73 are provided for each scan. Then, the signal amplified by the variable gain amplifier circuit 70 is subjected to integration processing over a period corresponding to one scan of the laser beam 11 in an integrator circuit 74, and is passed through a switching circuit 75 to either The sample and hold circuits 71 to 73 sample and hold the data. A sampling signal is given to the sample and hold circuits 71 to 73 from the control means 32 based on the output of the scanning direction detection means 31.

A switching circuit 76 selects one of the outputs of the sample and hold circuits 71 to 73 and supplies the selected output to the variable gain amplifier circuit 70 via a line 77 as a control signal for setting the amplification gain thereof.

The switching circuits 75 and 76 are switched in conjunction with the control signal from the control means 32, and the sample and hold circuits 71
, and is connected to the sample-and-hold circuit 72 during the period when the β-direction scanning is performed, and to the sample-and-hold circuit 73 during the period when the γ-direction scan is performed.

By applying such a configuration, it is clear that the first
Similar effects and effects as in the embodiment are achieved.

Furthermore, compared to the configuration shown in FIG. 5 described above, the number of variable gain amplifier circuits and integration circuits can be reduced to simplify the configuration, which is advantageous for cost reduction.

Next, a third embodiment of the present invention will be described.

In each of the embodiments described above, scanning is performed in three directions, and automatic gain control means are provided for each scanning direction. However, for example, when scanning is performed in eight directions as shown in FIG. 8, and the eight scanning lines 31 to S8 or the laser beam 11 are formed, the positions scanned by adjacent scanning lines are not very close to each other. It does not change. I wanted to,
There is no practical problem even if the amplification gain for the output signal of the light receiving means is set equally for two or three adjacent scanning lines.

Therefore, in this embodiment, for example, the scanning lines 5l-S3, S4
~S6;S7. The scanning lines are classified into three groups as in S8, and one automatic gain control circuit of the configuration shown in FIG. 5 is applied to each scanning line group (the configuration shown in FIG. 7 is applied). (When using a sample/hold circuit, a sample and hold circuit is provided for each scanning line group.)

With such a configuration, the number of automatic gain control circuits (or the number of sample and hold circuits) can be made smaller than the number of scanning lines, so when the number of scanning lines is large, the above first and second Almost the same effect as the example can be achieved at low cost.

Note that the present invention is not limited to the above embodiments. For example, in each of the above embodiments, a barcode reading device employing so-called omni-scanning, in which a plurality of scanning lines in mutually different directions are formed by the laser beam 11, has been described, or a barcode reading device as shown in FIG. Raster
The present invention can also be easily applied to barcode reading devices that perform scanning. In this case, an automatic gain control circuit may be provided for each scanning line 81 to S5, and the scanning lines 81 to S5 may be divided into groups and one automatic gain control circuit may be provided for each group. You may also do so. The configuration shown in FIG. 7 can also be easily applied in the same manner.

Furthermore, in the embodiments shown in FIGS. 1 to 6 or 7 above, three scanning lines are formed, but these embodiments can be applied to any number of scanning lines greater than or equal to two. This method can be easily applied to the case where several scanning lines are formed. In this case, when the scanning lines used for symbol identification processing are limited by the setting of the switching means 33, the number of scanning lines may be two or more.

Further, the present invention can be widely implemented not only in bar code reading devices but also in other optical symbol reading devices such as optical character reading devices. In addition, various design changes can be made to the concave circle without changing the gist of the invention.

<Effects of the Invention> As described above, according to the symbol reading device of the present invention, the amplification gain of the variable gain type amplification means for amplifying the output signal of the light receiving means is set for each scanning line or for each scanning line group, and The amplification gain of the variable gain amplification means for the output of the light receiving means corresponding to a line or each scanning line group is determined independently of similar amplification gains set corresponding to other scanning lines or scanning line groups.

As a result, during scanning, for example, if specularly reflected light from a symbol surface is received by the light receiving means, or when a scanning line or a group of scanning lines crosses a highly reflective object such as metal, the light receiving means receives a high intensity of light. Even if the amplification gain corresponding to the relevant scanning line or scanning line group becomes extremely small when the light of It will not be done. Therefore, it is possible to effectively identify the symbol based on the output of the light receiving means corresponding to the other scanning line or scanning line group.

In this way, by applying the automatic gain control means, it is possible to ensure a wide reading range, and at the same time, it is possible to read symbols satisfactorily in response to various reading conditions.

In addition, the state of the automatic gain control means is changed such that only the amplification gain corresponding to one or more predetermined scanning lines or scanning line groups among the amplification gains set for each scanning line or scanning line group is the output of the light receiving means. If a switching means is provided that can set the amplification gain corresponding to the remaining scanning line or scanning line group to a constant value, for example, the constant value can be set to a sufficiently low value. By specifying a value, symbol identification processing is performed based only on the output of the light receiving means corresponding to any one scanning line or group of scanning lines, and the output of the light receiving means corresponding to the other scanning line or group of scanning lines is used. It is possible to prohibit symbol identification processing based on therefore,
For example, when a large number of symbols are arranged close together,
By limiting the scan line or group of scan lines on which symbols are identified, it is possible to prevent symbols that the operator does not intend to read from being erroneously read.

In addition, if the above constant value is the amplification gain value corresponding to the case where the symbol is located at a predetermined distance near the device, then for a symbol located far away, it corresponds to the scanning line or group of scanning lines. It is possible to accurately read only the desired symbol by performing symbol identification based only on the output of the light receiving means that corresponds to the scanning line, and for nearby symbols, symbol identification is performed based on the output of the light receiving means corresponding to all scanning lines. can be performed to improve operability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a barcode reading device which is an embodiment of the symbol reading device of the present invention, FIG. 2 is a perspective view showing a simplified configuration of the scanning means 12, and FIG. 3 4 is a conceptual diagram showing the structure of the scanning direction detection means 31, FIG. 5 is a block diagram showing the basic structure of the automatic gain control circuit group 16, FIG. 6 is a simplified perspective view of another configuration example of the scanning direction detection means, and FIG. 7 is a block diagram showing the basic configuration of automatic gain control means that can be applied in place of the automatic gain control circuit group 16. , FIG. 8 is a diagram showing an omni-scan mode, and FIG. 9 is a diagram showing a raster scan mode. 11... Beam emission means, 12... Scanning means, 13
...Symbol surface, 14...Barcode (symbol), 15.
... Light receiving means, 16 ... Automatic gain control circuit group (automatic gain control means), 17 ... Identification means, 31 ... Scanning direction detection means (scanning position detection means), 32 ... Control means, 33...Switching means, 34...-Selection means, AGC
I-AGC3... automatic gain control circuit, 62... variable gain amplification circuit, 65... sample hold circuit, 7o
...Variable gain amplifier circuit, 71-73-sample bold circuit Patent applicant Sumitomo Electric Industries Co., Ltd. Representative Patent attorney Hiroshi Kamei (and 2 others)
) 1...Beam emission + stage 12...Travel f+stage 13...Symbol plane 32...Control means 33...Switching means 34...Selection means AGCI, AGC2, AGC3...Automatic control Shock control circuit Fig. 1 Fig. 2 2 S13... Symbol surface 14... Bar code 31... Scanning direction detection means α, β, γ... Scanning line Fig. 3 2'2 Fig. 4

Claims (1)

[Scope of Claims] 1. A beam emitting means for emitting a beam light, a scanning means for sequentially scanning mutually different positions of a symbol surface on which a symbol is formed with the beam light from the beam emitting means, and a light receiving means for receiving the reflected light of the light receiving means, a variable gain amplifying means for amplifying the output of the light receiving means, and an identification means for performing signal processing for identifying the symbol based on the signal from the variable gain amplifying means. a symbol reading device comprising: a scanning position detection means for detecting which position the scanning means is scanning; and the light receiving means for detecting a position for each scanning line or for each scanning line group including a predetermined number of scanning lines. automatic gain control means for setting the amplification gain of the variable gain type amplification means for each scanning line or for each scanning line group based on the output of the scanning position detection means; A symbol reading device comprising: control means for selecting the amplification gain set for each scanning line or for each scanning line group in the means. 2. The state of the automatic gain control means is such that the amplification gain corresponding to one or more predetermined scanning lines or scanning line groups is set to a value corresponding to the output of the light receiving means, and the amplification gain corresponding to the predetermined one or more scanning lines or scanning line groups corresponds to the remaining scanning lines or scanning line groups. switching means for switching between a state in which the amplification gain of the scan line or all of the scan line groups is set to a predetermined constant value and a state in which the amplification gains corresponding to all of the scanning lines or groups of scanning lines are set to values corresponding to the output of the light receiving means; 2. The symbol reading device according to claim 1, further comprising a symbol reading device.