JP2790736B2 - Semiconductor laser light source device and bar code reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser light source device using a semiconductor laser. Barcode readers and laser printers are required to be small and inexpensive, so it is necessary to reduce the size of mechanically movable parts such as a laser beam scanning mechanism. Have been. Accordingly, in a laser printer device, a light source device using an infrared semiconductor laser is used in place of a gas laser such as a He-Ne laser, thereby realizing the miniaturization of the entire device. On the other hand, since many products with barcodes that are difficult to read with infrared light are on the market, a visible light source is suitable as the light source of the barcode reader, and the optical scanning device can be downsized by using an infrared semiconductor laser. The method of doing was not applied.

However, in recent years, since a visible light semiconductor laser having an oscillation wavelength of 700 nm or less has been commercialized, a light source device using the semiconductor laser is employed to reduce the size and cost of the entire bar code reader. It is desired.

[0003]

2. Description of the Related Art FIGS. 11 and 12 show the structure of a conventional bar code reader. 11, a laser beam emitted from a He-Ne laser enters a polygon mirror 311 through an opening provided in a concave mirror 301, and according to the rotation of the polygon mirror 311 as shown in FIG. Pattern combining mirrors 303a, 303b, 303c
Are sequentially scanned. These pattern combining mirrors 303a
The laser beam reflected by .about.303c is reflected by the mirror 304 and enters the fixed hologram 305 attached to the reading window (see FIG. 11), and is bent by the diffraction action of the fixed hologram 305, and FIG.
The bar code 103 attached to the object 102 such as a product is illuminated while drawing various scanning patterns as shown in FIG. A part of the light scattered by the barcode is incident on the concave mirror 301 by reversing the optical path of the laser beam, as shown by a dotted line in FIG. 11, and the light is detected by the concave mirror 301 and the mirror 341. The reading processing unit 343 guides the bar code 102 to the bar code 102 based on a change in the output of the photodetector 542.
Is read.

In this structure, a bar code reader is made thinner by obtaining a scanning pattern (indicated by an arrow A in FIG. 13) in a direction perpendicular to the reading window by a diffraction action of a hologram fixed to the reading window. That is,
This is called the hollow-in method. In addition, by providing the fixed hologram 305 with an imaging function, the scattered light from the barcode 103 can be efficiently detected by the photodetector 342.
It is possible to collect light.

Further, a disk provided with a hologram having a plurality of different patterns in the circumferential direction (hereinafter, referred to as a hologram disk) is rotated by a motor, and the laser beam is scanned by irradiating the hologram disk with the laser beam. There is also a method, which is called a hologram disk method.

FIG. 14 shows the configuration of a hologram disk type bar code reader. In FIG. 14, a laser beam enters through an opening provided in a condenser lens 441, is bent by a mirror 401, and enters a hologram disk 402. While continuously changing the angle of the hologram disk 402 with respect to the radial direction, the hologram disk 4
A hologram having a pattern for diffracting a laser beam is provided diagonally below 02.

Therefore, by rotating the hologram disk 402, the laser beam scans several pattern combining mirrors 403 in order, and after being reflected by these pattern combining mirrors 403, is repelled by the mirror 404 and read. Emitted through window 405.
Usually, three to five pattern combining mirrors 403 are provided, but one pattern combining mirror 403 is shown as a representative in the figure.

As a result, various scanning patterns are obtained in the same manner as in the above-described hollow-in system, and the object 1 is scanned by a laser beam that is drawn and scanned.
02 is illuminated. A part of the light scattered by the barcode 102 is shown in FIG.
As shown by a dotted line, the light travels backward in the above-described optical path and is condensed on the photodetector 442 by the condensing lens 441. Based on the output of the photodetector 442, the reading processing unit 443 executes Is read.

Here, since the hologram can have an image-forming function as well as the above-described diffraction function, by using the hologram disk 402 as the scanning means, an image-forming optical system is separately provided to read the image. There is no need to stop down the laser beam emitted from the window, and the optical scanning device can be downsized.

This hologram disk type optical scanning device is also used in a laser printer. FIG. 15 shows the configuration of the laser beam printer.

In FIG. 15, light emitted from a semiconductor laser 501 is obliquely incident on the lower surface of a hologram disk 503 after being shaped into a beam by a collimator lens 502. Due to the diffraction effect of the hologram disk 503, the above-described laser beam is bent obliquely upward and, in accordance with the rotation of the hologram disk 503, the tangential direction of its circumference (FIG. 1).
5 (indicated by arrow B). Further, each hologram provided on the hologram disk 503 has an image-forming action together with the above-described diffraction action, and forms an image on the photosensitive drum 504 with the laser beam bent obliquely upward, so that it is sharp on the photosensitive drum 504. It is configured to obtain a perfect image.

As described above, by replacing a scanning mechanism, which has conventionally been composed of a scanning element such as a polygon mirror or a galvano mirror and an optical system for imaging such as a fixed mirror and a lens, with a beam scanning mechanism using a hologram, a bar scanning is realized. Code readers and laser beam printers have been downsized.

[0013]

By the way, as described above, the miniaturization of the beam scanning mechanism has been realized.
The diameter of the oscillation tube of the He-Ne laser used as a light source is relatively large, and the size of the barcode reader is limited by the size of the oscillation tube of the He-Ne laser. ing. Therefore, in order to further reduce the size of the barcode reader, it is necessary to employ a visible light semiconductor laser as a light source.

However, a semiconductor laser having an oscillation wavelength of 700 nm or less (hereinafter simply referred to as a semiconductor laser)
As shown in FIG. 16, the oscillation wavelength changes continuously according to changes in temperature and output, and the oscillation mode changes at a predetermined temperature, so that the oscillation wavelength changes discontinuously. In the vicinity of the transition temperature of the oscillation mode, the semiconductor laser enters a mode competition state, and light beams having wavelengths corresponding to two adjacent oscillation modes are simultaneously emitted.

On the other hand, the beam scanning mechanism using a hologram as described above is based on the premise that the wavelength of a laser beam is constant. This is because the diffraction effect used to deflect the direction of the laser beam is an operation having a very high wavelength dependence.

[0016] For example, when the wavelength of the laser beam incident on the hologram disk 503 of the laser beam printer shown in FIG. 15 is changed from the wavelength lambda _i of the wavelength lambda _{i + 1,} 1
As shown by the dotted line in FIG. 5, the direction of the laser beam emitted from the hologram disk 503 changes, and the photosensitive drum 504 changes.
The above image formation position is shifted. Further, when the mode competition state as described above occurs, the beam diameter of the laser beam is substantially expanded, so that the image on the photosensitive drum 504 is blurred.

The same applies to the bar code readers shown in FIGS. 11 and 14. However, in the bar code reader, a relatively large error is allowed with respect to the position of the scanning pattern drawn by the laser beam. The main problem is that the beam diameter of the laser beam expands due to the mode competition state. In particular, in the hollow-type bar code reader, as shown in FIG. 17, in a mode competition state, the beam diameter expands in the scanning direction and the resolution is reduced, so that the bar code reading accuracy is significantly deteriorated. .

Therefore, simply replacing the light source with a semiconductor laser causes various problems as described above due to the instability of the semiconductor laser. In exchange for the downsizing of the apparatus, reading accuracy and print quality are sacrificed. Will be.

On the other hand, as a technique for fixing a semiconductor laser in a single oscillation mode, a method is known in which a temperature control element such as a Peltier element is arranged adjacent to the semiconductor laser to keep the temperature of the semiconductor laser constant. Have been. But,
Since there is variation among the elements of the semiconductor laser, the transition temperature of the oscillation mode described above varies depending on the semiconductor laser element. Therefore, if the temperature set for the Peltier element is determined uniformly, there is a possibility that the state of the semiconductor laser is fixed to the mode competition state.

In addition to the semiconductor laser drive circuit,
A circuit for driving the Peltier element is required, and the circuit scale of the light source device increases. An object of the present invention is to provide a semiconductor laser light source device that enables a semiconductor laser to stably oscillate in a single mode. It is another object of the present invention to provide a small-sized bar code reader by applying the light source device.

[0021]

FIG. 1 is a block diagram showing the principle of a semiconductor laser light source device according to the present invention. According to the first aspect of the present invention, there is provided a separation means for separating a part of a laser beam emitted from a semiconductor laser as a mode detection laser beam, and a mode competition of the semiconductor laser based on a wavelength of the mode detection laser beam. Detecting means 112 for detecting a state and outputting a detection signal indicating a detection result;
And control means 113 for controlling the oscillation mode of the semiconductor laser 101 by changing the duty ratio of the level change of the drive current supplied to the semiconductor laser 101 in response to the input of the detection signal indicating that the mode competition state has been detected. It is characterized by having.

FIG. 2 is a block diagram showing the principle of the bar code reader according to the second and third aspects. According to a second aspect of the present invention, the bar code 103 attached to the object 102 is illuminated by scanning the semiconductor laser light source device 110 according to the first aspect and a laser beam incident from the semiconductor laser light source device 110 according to the wavelength. Beam scanning mechanism 121, reading means 122 for reading bar code 103 based on a change in intensity of scattered light from bar code 103, and semiconductor device in synchronization with laser beam scanning operation by beam scanning mechanism 121. A synchronization control means 123 for controlling the timing of the level change of the drive current by the control means 113 provided in the laser light source device 110 is provided.

According to a third aspect of the present invention, in the bar code reader according to the second aspect, the beam scanning mechanism 121 scans the laser beam while drawing a plurality of scanning patterns in a time division manner. Reference numeral 123 denotes a configuration for performing control for synchronizing switching of a plurality of scanning patterns and timing of level change of the drive current by the control unit 113.

[0024]

According to the first aspect of the present invention, when the detecting means detects a mode competition state of the semiconductor laser based on the wavelength of the mode detecting laser beam separated by the separating means, the control means drives the driving means. By changing the duty ratio of the current level fluctuation, the semiconductor laser 1
By changing the effective value of the power supplied to 01, the semiconductor laser 101 can escape from the mode competition state.

Further, according to the invention of claim 2, in synchronization with the scanning operation of the laser beam by the beam scanning mechanism 121, the synchronization control means 123 controls the timing of the level fluctuation of the drive current by the control means 113 of the semiconductor laser light source device 110. Is controlled, the level of the drive current while the barcode 103 on the object 102 is illuminated can be kept constant, and the optical output of the semiconductor laser 101 can be maintained. This allows the semiconductor laser 10 to be read while the barcode 103 is being read.
Since it is possible to prevent the light output of the bar code 103 from being changed, the reading unit 122 can read the barcode 103 normally by performing the same processing as that in the related art.

The synchronization control means 123 synchronizes the timing at which a plurality of scanning patterns drawn by the beam scanning mechanism 121 are switched with the timing at which the level of the drive current fluctuates, so that the laser beam is scanned in each scanning pattern. In consideration of the light collection efficiency of the scattered light, a section in which the drive current is at a high level and a section in which the drive current is at a low level can be made to correspond to each scanning pattern.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows an embodiment of the semiconductor laser light source device according to the first aspect.

In FIG. 3, the semiconductor laser light source device comprises:
The laser beam from the semiconductor laser (LD) 101 is shaped by a collimator lens (lens) 502 to emit a laser beam.

A part of the laser beam is diffracted and separated by a hologram 211 corresponding to the separating means 111 as shown by a dotted line in FIG. The laser beam forms an image on the light receiving surface of the CCD array 212.

Here, since the diffraction angle of the hologram 211 depends on the wavelength of the incident laser beam, when the semiconductor laser 101 is in the mode competition state, as shown in FIG. 4, the oscillation mode i (wavelength λ _i ) And light in the oscillation mode i + 1 (wavelength λ _{i + 1} ) form images on the CCD array 212 at different positions. Thus, for example, CC
A configuration is provided in which a peak detection unit 213 for comparing the output of each element of the D array 212 to detect the peak position of the incident light intensity is provided, and whether or not two or more peaks are detected is output as a mode competition detection result. I just need.

Thus, the hologram 211 and the CC
The function of the detection unit 112 can be realized by the D array 212 and the peak detection unit 213. In FIG. 3, the control unit 113 includes a pulse generation circuit 221, a selector 222, a driver circuit 223, and a multiplication circuit 224.

The above-described pulse generation circuit 221 generates a rectangular wave having a predetermined duty ratio (for example, 50%).
The input is made to one of the input terminals of the selector 222. Fixed logic "1" is input to the other input terminal of the selector 222, and the selector 222 receives the output of the above-described pulse generation circuit 222 in response to the input of the detection result indicating that the mode competition state has been detected. The configuration is such that fixed logic “1” is alternately selected and transmitted to the multiplication circuit 224.

The driver circuit 223 outputs a predetermined reference current to be supplied to the semiconductor laser 101 similarly to the conventional driver circuit. By 224,
After being multiplied by the output of the selector 222, it is supplied to the semiconductor laser 101.

As described above, every time the detecting means 112 detects the mode competition state, the selector 222 switches and outputs the fixed logic "1" and the above-mentioned rectangular wave.
As shown in FIG. 5, the duty ratio of the level change of the drive current can be changed. However, FIG. 5 shows the change of the drive current after the state in which the selector 222 selects the fixed logic “1” corresponding to the rectangular wave with the duty ratio of 100% as the initial state.

Thus, the duty ratio of the drive current can be changed in accordance with the detection of the mode competition state. Since the effective value of the drive current changes in accordance with the change in the duty ratio, the energy supplied to the semiconductor laser 101 can be changed to change the temperature of the junction of the semiconductor laser 101.

Here, as shown in FIG. 16, since the temperature range in which the semiconductor laser 101 is in the mode competition state is extremely narrow, the temperature of the junction of the semiconductor laser 101 is set to 0.2 degrees to 0.2 degrees. By changing only three times, the mode competition state can be escaped. Therefore, by changing the effective value of the drive current as described above, it is possible to provide a temperature change required for the semiconductor laser 101 to escape from the mode competition state, and to escape from the mode competition state. Transition to single mode is possible.

As described above, by changing the duty ratio of the drive current according to the detection of the mode competition state,
The oscillation mode of the semiconductor laser 101 can be controlled, and a semiconductor laser light source device that stably emits light of a single mode can be realized.

Further, as described above, since the temperature change required to escape from the mode competition state is extremely small, the above-described pulse generation circuit 22 is considered in consideration of this.
The amplitude and the duty ratio of the rectangular wave generated in step 1 may be determined so as not to fall below the threshold of the light amount required for the light source (indicated by the dotted line in FIG. 5).

The duty ratio of the drive current is not limited, and the point is that the control means 113 may change the duty ratio of the drive current in response to the detection of the mode competition state.

For example, as shown in FIG. 6, two pulse generating circuits 231a and 231b for generating rectangular waves having different duty ratios are provided to form a control means 113, and these rectangular waves are input to an input terminal of a selector 222. , Respectively.

Further, the difference between the oscillation wavelength of the semiconductor laser 101 obtained from the imaging position of the mode detection laser beam and the target wavelength is obtained, and the pulse generation circuit 221 described above is obtained.
However, a configuration may be adopted in which a rectangular wave having a duty ratio corresponding to this difference is generated.

For example, when the difference between the oscillation wavelength and the target value is large, the pulse generation circuit 221 generates a rectangular wave with a small duty ratio, and when the difference is small, generates a rectangular wave with a relatively large duty ratio. What is necessary is just to be a structure.

FIG. 7 shows an embodiment of a laser beam printer device to which the semiconductor laser light source device of claim 1 is applied. In FIG. 7, a semiconductor laser (LD) 101
Is emitted from the hologram disk 5 after being shaped into a beam by the collimator lens 502.
03 from obliquely below, the hologram disk 5
03, the light is diffracted obliquely upward, and the photosensitive drum 50
4 is configured to scan.

In this case, a hologram 211 is arranged between the collimator lens 502 and the hologram disk 503, and the CCD array 21 is located at a position crossing the mode detection laser beam separated by the hologram 211.
2 may be arranged. Further, the output of the CCD array 212 is sent to the peak detecting unit 213, and a detection result indicating that a mode competition state is detected when a plurality of peaks are detected is sent to the control unit 113, as in the above-described embodiment. In response to this, the control means 113 may change the duty ratio of the drive current to perform control for causing the oscillation mode of the semiconductor laser 101 to escape from the mode competition state.

As a result, the wavelength of the laser beam incident on the hologram disk 503 can be stabilized to a wavelength corresponding to a single oscillation mode. Does not spread, and the laser beam that scans the photosensitive drum 504 can be kept in a narrowed state.

Here, if the fluctuation range of the level of the drive current is determined so that the light output of the semiconductor laser 101 does not fall below a predetermined threshold value for preventing the print density from decreasing, the semiconductor can be processed as described above. Controlling the oscillation mode of the laser 101 does not cause deterioration in print quality such as uneven print density.

In the bar code reading apparatus, various scanning patterns are generated by the beam scanning mechanism, and the laser beam is drawn by drawing the scanning patterns.
The bar code 103 is read based on the scattered light when the bar code 103 on 02 is scanned. Therefore,
While the laser beam is drawing one scanning pattern,
It is desirable that the optical output of the semiconductor laser 101 is constant.

Hereinafter, a method of synchronizing the fluctuation of the driving current value with the scanning of the laser beam will be described. FIG.
2 is a block diagram showing an embodiment of the bar code reader according to the present invention.

In FIG. 8, the bar code reader is the semiconductor laser light source device shown in FIG. 3 as a light source device in place of the conventional He-Ne laser device in the hollow window type bar code reader shown in FIG. It is provided with. In this case, light emitted from the semiconductor laser (LD) 101 is shaped into a beam by a collimator lens (lens), and is incident on the polygon mirror 311 via the opening of the concave mirror 301.

The polygon mirror 311 and the motor 312
, Motor control circuit 313 and pattern combining mirror 303a
303c, the mirror 304, and the fixed hologram 305 form a beam scanning mechanism 121, and the motor 312 operates according to the drive current from the motor control circuit 313 to rotate the polygon mirror 311. . The motor control circuit 313 includes the motor 31 described above.
2 is provided with a position sensor that outputs a rotational position signal indicating that the reference position of the second has passed the predetermined position. Based on the rotational position signal, a drive signal supplied to the motor 312 is controlled to control the motor 312. It is configured to rotate at a constant speed. The beam scanning mechanism 121 adjusts the scanning range of the laser beam by each mirror surface of the polygon mirror 311 by three in correspondence with the pattern combining mirrors 303a to 303c.
And generate different scanning patterns,
The bar code 103 on the object 102 is illuminated.

In FIG. 8, the clock generation circuit 3
21 and the delay circuit 322 correspond to the synchronization control means 123. In response to the input of the above-described rotation position signal, the clock signal generation circuit 321
11 generates a clock signal whose period is an integral multiple of the time τ during which the laser beam is scanned by each mirror surface, and the delay circuit 322 outputs the clock signal delayed by a predetermined delay time δ. It has become.

Here, the above-mentioned time τ is a time obtained by dividing the rotation period T of the polygon mirror 311 by the number n of mirror surfaces constituting the polygon mirror 311. It can be easily configured using a frequency divider. Further, since the relative position between the reference position of the motor 312 and each mirror surface of the polygon mirror 311 does not change, the polygon mirror 31 is input from the input of the rotation position signal.
The time until the scanning of the laser beam by one predetermined surface is started may be set as the delay time δ in the delay circuit 322 described above.

In this manner, a clock signal synchronized with the laser beam scanning operation by the polygon mirror 311 can be obtained. Further, the control means 113 includes a trigger flip-flop 331 instead of the pulse generation circuit 221 shown in FIG. 3, and if the above-described clock signal is input to the trigger flip-flop 331, the scanning of the laser beam is performed. Since a rectangular wave synchronized with the operation is obtained, it is possible to synchronize the timing of the change in the level of the drive current with the switching of the mirror surface of the polygon mirror 311 facing the laser beam. In this case, while the laser beam is being scanned by one mirror surface of the polygon mirror 311, the output value of the semiconductor laser 101 can be maintained at a constant value while keeping the current value of the drive current constant.

In this case, a mode race condition is detected,
Even when the duty ratio of the change in the current value of the drive current is changed, the current value of the drive current supplied to the semiconductor laser 101 is constant at least during the period when the laser beam is being scanned by one mirror surface of the polygon mirror 311. Is kept. Therefore, concave mirror 303 and mirror 34
1, the intensity of the scattered light guided to the photodetector 342 does not change during the reading of the barcode 103.

Further, by changing the duty ratio of the drive current as described above,
Since the oscillation mode No. 01 is controlled and stabilized in the single mode state, the beam diameter of the laser beam scanned by the above-described beam scanning mechanism can always be kept small. Therefore, the reading processing unit 343 is
By performing the same processing as before on the output of 2,
The barcode 103 can be read with high accuracy.

Further, if the range of the drive current value is determined so that the drive current value does not fall below the threshold value of the current corresponding to the minimum light amount required for reading the bar code 103, the drive current Even when the level is lowered, the barcode 103 can be read normally.

In this manner, a bar code reader capable of reading a bar code with high accuracy can be realized while miniaturizing the apparatus by employing a semiconductor laser as a light source.

If the control means 113 is constituted by using a counter circuit which performs a counting operation in synchronization with a clock signal instead of the above-described trigger type flip-flop 331,
Drive currents of various duty ratios are applied to the semiconductor laser 101.
Can be supplied to

The present invention is not limited to the hollow-in type beam scanning mechanism using the polygon mirror described above, and the present invention may be applied to a barcode reading apparatus including a beam scanning mechanism using a galvanometer mirror or a hologram disk. .

For example, in the case of a bar code reader having a beam scanning mechanism 121 using a hologram disk, the synchronization control means 123 generates a clock signal synchronized with the hologram switching, and the control means 113
This clock signal may be input to control the timing of the level change of the drive current.

By the way, among the plurality of scanning patterns generated by the beam scanning mechanism of the bar code reader, there are a scanning pattern having high reading efficiency and a scanning pattern which is relatively difficult to read. For example, in the hollow-in-type bar code reading device, the reading process using the scanning pattern corresponding to the pattern combining mirrors 303a and 303c is focused on the photodetector 342 as compared with the scanning pattern corresponding to the pattern combining mirror 303b. In many cases, the amount of scattered light is insufficient.

Next, a description will be given of a method of controlling the oscillation mode in consideration of the difference in the reading conditions depending on each scanning pattern. FIG. 9 is a block diagram showing an embodiment of the bar code reader according to the third aspect.

Referring to FIG. 9, the bar code reading apparatus includes a clock generation circuit 321 and a delay circuit 32 shown in FIG.
In place of 2, a synchronous control unit 123 formed by photodetectors 621 a and 621 b and an OR gate 622 is provided.

The above-described photodetectors 621a and 621b are
The three pattern combining mirrors 303a to 303c are arranged in gaps between each other, detect a laser beam incident from the corresponding gaps, and transmit a pulse-like output signal to the OR gate 622. The output of the OR gate 622 (see FIG. 10A) is input to the trigger flip-flop 331 of the control means 113 as a clock signal. Thereby, as shown in FIG. 10B, a rectangular wave whose level switches at the timing when the laser beam passes through the above-described gap is obtained by the trigger flip-flop 331.

Therefore, according to the detection of the mode race condition,
When the above-described rectangular wave is superimposed on the reference current from the driver circuit 223, driving during a period in which the laser beam is scanning the pattern combining mirror 303a and the pattern combining mirror 303c (indicated by a symbol C in FIG. 10B). The current level becomes a high level (reference current), and at this time, the amount of scattered light that reaches the photodetector 342 becomes equal to that in the related art.

In this manner, it is possible to allocate a section of a high drive current level to a scan pattern having a low read efficiency, so that the read conditions of the bar code 103 can be made equal to those in the related art.

In this case, the pattern combining mirror 303b
Is assigned to the scan pattern corresponding to the scan pattern, the scattered light when the barcode 103 is illuminated by this scan pattern is collected more efficiently than in the case of the two scan patterns described above. Since the light can be emitted, the reading operation of the barcode 103 is not hindered unless the driving current falls below a predetermined threshold.

As described above, by changing the driving current of the semiconductor laser 101 in synchronization with the switching of the scanning pattern, a section in which the level of the driving current is high in each scanning pattern is considered in consideration of the reading conditions depending on the scanning pattern. And a low section can be assigned, and the oscillation mode of the semiconductor laser 101 can be controlled and stabilized in a single mode state while maintaining the overall reading efficiency. Thus, in a small barcode reader employing a semiconductor laser as a light source, it is possible to improve the reading accuracy while minimizing a decrease in reading efficiency.

[0069]

As described above, according to the present invention, the oscillation mode of the semiconductor laser is controlled by changing the duty ratio of the level change of the drive current in accordance with the detection of the mode competition state, thereby controlling the single mode. Can be stabilized to
A stable semiconductor laser light source device can be realized.

Further, by synchronizing the timing of the level change of the drive current with the scanning of the laser beam by the beam scanning mechanism of the bar code reader, the above-described oscillation is maintained while the light amount is kept constant during the reading of the bar code. Since the mode can be controlled, the barcode can be read normally by performing the same processing as in the related art.

Further, by synchronizing the timing of the level change of the driving current with the switching of the scanning pattern,
It is possible to assign a high-level section and a low-level section in consideration of the difference in the reading conditions of each scanning pattern, without lowering the overall reading efficiency.
Oscillation mode control can be performed.

[Brief description of the drawings]

FIG. 1 is a principle block diagram of a semiconductor laser light source device according to claim 1;

FIG. 2 is a block diagram showing the principle of a bar code reader according to claims 2 and 3;

FIG. 3 is a configuration diagram of an embodiment of the semiconductor laser light source device of the present invention.

FIG. 4 is an explanatory diagram of a mode conflict state detection process.

FIG. 5 is a diagram showing a level variation of a drive current.

FIG. 6 is a configuration diagram of another embodiment of the semiconductor laser light source device of the present invention.

FIG. 7 is a configuration diagram of an embodiment of a laser beam printer device to which the semiconductor laser light source device of the present invention is applied.

FIG. 8 is a block diagram of an embodiment of a bar code reader according to claim 2;

FIG. 9 is a block diagram of an embodiment of a bar code reader according to claim 3;

FIG. 10 is a timing chart showing the operation of the synchronization control means.

FIG. 11 is a configuration diagram of a conventional barcode reading device.

FIG. 12 is a diagram showing an arrangement of a pattern combining mirror of the barcode reader.

FIG. 13 is an explanatory diagram of a hollow-in scanning pattern.

FIG. 14 is a configuration diagram of a hologram disk type bar code reader.

FIG. 15 is a configuration diagram of a laser beam printer device.

FIG. 16 is an explanatory diagram of the oscillation mode transition of the semiconductor laser.

FIG. 17 is a diagram showing the spread of a beam diameter in a mode competition state.

[Explanation of symbols]

 Reference Signs List 101 semiconductor laser 102 object 103 barcode 110 semiconductor laser light source device 111 separation means 112 detection means 113 control means 121 beam scanning mechanism 122 reading means 123 synchronization control means 211 hologram 212 CCD array 213 peak detection parts 221 and 231 pulse generation circuit 222 selector 223 Driver circuit 224 Multiplier 301 Concave mirror 303,403 Pattern synthesis mirror 304,341,401,404 Mirror 305 Fixed hologram 311 Polygon mirror 312 Motor 313 Motor control circuit 321 Clock generation circuit 322 Delay circuit 331 Trigger type flip-flop 342,442, 621 Photodetector 343, 443 Read processing unit 402, 503 Hologram disk 405 Read window 441 Condenser lens 50 2 Collimator lens (lens) 504 Photosensitive drum 622 OR gate

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Okawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Within Fujitsu Limited (58) Field surveyed (Int.Cl. ⁶ , DB name) G06K 7/10 H01S 3 / 18

Claims (3)

(57) [Claims] A separation means (111) for separating a part of a laser beam emitted from a semiconductor laser (101) as a mode detection laser beam, and a semiconductor laser (101) based on a wavelength of the mode detection laser beam. 101) detecting means for detecting the mode competition state and outputting a detection signal indicating the detection result; and detecting the mode of the semiconductor laser (1) in response to the input of the detection signal indicating that the mode competition state has been detected.
A semiconductor laser light source device comprising: a control unit (113) for changing a duty ratio of a level change of a driving current supplied to the semiconductor laser (01) and controlling an oscillation mode of the semiconductor laser (101). 2. A semiconductor laser light source device according to claim 1, wherein a laser beam incident from said semiconductor laser light source device is scanned according to the wavelength thereof.
A beam scanning mechanism (121) for illuminating a bar code (103) attached to an object (102);
Reading means (122) for reading the bar code (103) based on a change in the intensity of the scattered light from the light receiving element (03).
And the semiconductor laser light source device (1) in synchronization with the scanning operation of the laser beam by the beam scanning mechanism (121).
Synchronous control means (1) for controlling the timing of the level change of the drive current by the control means (113) provided in (10).
23) A bar code reader comprising: 3. The bar code reader according to claim 2, wherein the beam scanning mechanism scans the laser beam while drawing a plurality of scanning patterns in a time-division manner. However, the bar code reading device is characterized in that the bar code reading device is configured to perform control for synchronizing the switching of the plurality of scanning patterns and the timing of the level change of the driving current by the control means (113).