JPH0528294A - Semiconductor laser light source device and bar code reader - Google Patents

Abstract

PURPOSE:To stably oscillate a semiconductor laser in a single mode. CONSTITUTION:The device is provided with a separating means 111 separating the part of the laser beam injected from the semiconductor laser 101 and injecting it as the laser beam for mode detection, a mode discrimination means 112 discriminating the oscillation mode of the semiconductor laser 101 based on the wave length of light included in the laser beam for mode detection and a control means 113 changing a driving current to supply for the semiconductor laser 101 in accordance with a discrimination result by the mode discrimination means and controlling the laser to the oscillation mode setting the oscillation mode of the semiconductor laser 101 to be an object.

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. For bar code readers and laser printers, there is a demand for small size and low price. Therefore, it is necessary to miniaturize each part including mechanically movable parts such as a laser beam scanning mechanism. Has been done. In response to this, in the laser printer device, a light source device using an infrared semiconductor laser is adopted instead of a gas laser such as a He—Ne laser, whereby the miniaturization of the entire device is realized. On the other hand, since many products with barcodes that are difficult to read with infrared rays are on the market, a visible light source is suitable as the light source for the barcode reader, and the infrared semiconductor laser is used to reduce the size of the optical scanning device. The method to do was not applied.

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

[0003]

14 and 15 show the structure of a conventional bar code reading device. In FIG. 14, the laser beam emitted from the He-Ne laser enters the polygon mirror 504 through the opening provided in the concave mirror 503, and according to the rotation of the polygon mirror 504, as shown in FIG. Pattern synthesis mirrors 505a, 505b, 505c
Are sequentially scanned. These pattern synthesis mirrors 505a
The laser beam reflected by ˜505c is reflected by the mirror 506 and is incident on the fixed hologram 507 attached to the reading window (see FIG. 14), and is bent by the diffraction action of the fixed hologram 507.
As shown in FIG. 3, the barcode 132 attached to the object 131 such as a product is illuminated while drawing various scanning patterns. Also, a part of the light scattered by this bar code travels backward in the optical path of the laser beam described above and enters the concave mirror 503, as shown by the dotted line in FIG. 14, and the concave mirror 503 and the mirror 541 detect light. Based on the change in the output of the photodetector 542, the reading processing unit 543 causes the barcode 132 to be transmitted.
Is configured to read.

In this structure, the scanning pattern (indicated by the arrow A in FIG. 16) in the direction perpendicular to the reading window is obtained by the diffracting action of the hologram fixed to the reading window, thereby reducing the thickness of the bar code reading apparatus. Is intended
It is called the hollowed method. Further, the fixed hologram 507 described above is provided with an image forming function, so that the scattered light from the barcode 132 can be efficiently detected by the photodetector 542.
It is possible to focus on.

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 a laser beam is incident on the hologram disk to scan the laser beam. There is also a system, which is called the hologram disc system.

FIG. 17 shows the configuration of a hologram disc type bar code reader. In FIG. 17, the laser beam enters through the opening provided in the condenser lens 641, is bent by the mirror 601, and enters the hologram disk 602. The hologram disc 602 has a structure in which the hologram disc 602 is continuously changed in angle with the radial direction of the hologram disc 602.
A hologram having a pattern for diffracting the laser beam is provided obliquely below 02.

Therefore, by rotating the hologram disc 602, the laser beam sequentially scans several pattern synthesizing mirrors 603, is reflected by these pattern synthesizing mirrors 603, and then is repelled by the mirror 604 and read. It is ejected through the window 605.
Normally, three to five pattern synthesizing mirrors 603 are provided, but in the figure, one pattern synthesizing mirror 603 is shown as a representative.

As a result, similar to the above-mentioned hollow-line method, various scanning patterns are obtained, and the object 1 is scanned by the laser beam drawing these scanning patterns.
The bar code 132 on 31 is illuminated. In addition, a part of the light scattered by the barcode 132 is shown in FIG.
As shown by the dotted line in FIG. 1, the optical path is reversely traveled, and the light is condensed on the photodetector 642 by the condensing lens 641. Based on the output of the photodetector 642, the reading processing unit 643 causes the bar code described above. Is configured to read.

Here, since it is possible for the hologram to have an image forming action as well as the above-mentioned diffracting action, by using the hologram disk 402 as the scanning means, a separate image forming optical system is provided and reading is performed. It is not necessary to narrow down the laser beam emitted from the window, and the optical scanning device can be downsized.

The hologram disk type optical scanning device is also used in a laser printer device. FIG. 18 shows the configuration of the laser beam printer device.

In FIG. 18, the light emitted from the semiconductor laser 701 is shaped into a beam by the collimator lens 702 and then obliquely enters the lower surface of the hologram disk 703. Due to the diffracting action of this hologram disc 703, the above-mentioned laser beam is bent obliquely upward, and in accordance with the rotation of the hologram disc 703, the tangential direction of its circumference (see FIG. 1).
8 indicated by arrow B). Further, each hologram provided on the hologram disk 703 has an image forming action in addition to the above-described diffracting action, and a laser beam bent obliquely upward is imaged on the photosensitive drum 704 and sharp on the photosensitive drum 704. It is configured to obtain various images.

As described above, by replacing the scanning mechanism, which has conventionally been composed of a scanning element such as a polygon mirror or a galvanometer mirror, and an imaging optical system such as a fixed mirror and a lens, with a beam scanning mechanism using a hologram, The code reader and the laser beam printer have been downsized.

[0013]

By the way, since the downsizing of the beam scanning mechanism is realized as described above,
The diameter of the oscillation tube of the He-Ne laser used as a light source is relatively large, and the size of the bar code 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 bar code reader, it is necessary to use 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) is
It has the property that the oscillation mode changes according to temperature changes and output changes, and the oscillation wavelength changes. For example, when the temperature of the semiconductor laser changes from the temperature T _i to the temperature T _{i + 1} , the oscillation mode transits from the oscillation mode i to the oscillation mode i + 1, which causes the oscillation wavelength to be the wavelength λ _i as shown in FIG. To the wavelength λ _{i + 1} . Further, in the course of changing from the temperature T _i to the temperature T _{i + 1} , there is a mode competition state in which two oscillation modes are lined up, and in this state, lights having wavelengths corresponding to the two oscillation modes are simultaneously emitted.

On the other hand, the beam scanning mechanism using the hologram described above is premised on that the wavelength of the laser beam is constant. This is because the diffractive action used to deflect the direction of the laser beam has a very high wavelength dependence.

[0016] For example, when the wavelength of the laser beam incident on the hologram disk 703 of the laser beam printer shown in FIG. 18 is changed from the wavelength lambda _i of the wavelength lambda _{i + 1,} 1
8, the direction of the laser beam emitted from the hologram disk 703 changes, and the photosensitive drum 704
The image forming position on the top is displaced. Further, in the mode competition state as described above, the beam diameter of the laser beam is substantially expanded, so that the image on the photosensitive drum 704 is blurred.

The same applies to the bar code reader shown in FIGS. 14 and 17, but 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 mode competition. In particular, in a hollow-line type bar code reading apparatus, as shown in FIG. 20, in a mode competition state, the beam diameter spreads in the scanning direction and the resolution decreases, so the bar code reading accuracy deteriorates significantly. .

Therefore, if the light source is simply replaced with the semiconductor laser, the various problems described above occur due to the instability of the semiconductor laser, and the reading accuracy and the print quality are sacrificed in exchange for the downsizing of the apparatus. Will be.

On the other hand, as a technique for fixing and using a single oscillation mode of a semiconductor laser, there is known a method 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. Has been. But,
Since there are variations among the elements of the semiconductor laser, the temperature at which the above-mentioned oscillation mode transition occurs varies depending on the semiconductor laser element. Therefore, if the temperature set in the Peltier device is uniformly determined, the state of the semiconductor laser may be fixed to the mode competition state. In addition, a circuit for driving the Peltier device is required in addition to the drive circuit for the semiconductor laser, which increases the circuit scale of the light source device.

It is an object of the present invention to provide a semiconductor laser light source device capable of stably oscillating a semiconductor laser in a single mode. It is another object of the present invention to provide a small barcode reader by applying this light source device.

[0021]

FIG. 1 is a diagram showing a structure of a semiconductor laser light source device according to a first aspect of the present invention. The invention according to claim 1 is based on a separating means 111 for separating a part of a laser beam emitted from the semiconductor laser 101 and emitting it as a mode detecting laser beam, and a wavelength of light included in the mode detecting laser beam. , The semiconductor laser 1 according to the mode determination means 112 for determining the oscillation mode of the semiconductor laser 101 and the determination result by the mode determination means 112.
Drive current supplied to the semiconductor laser 10
The control means 113 for controlling the first oscillation mode to the target oscillation mode is provided.

FIG. 2 is a diagram showing the structure of the semiconductor laser light source device according to the second to fourth aspects. According to a second aspect of the present invention, based on the separation means 111 that separates a part of the laser beam emitted from the semiconductor laser 101 and emits it as a mode detection laser beam, and the wavelength of the light included in the mode detection laser beam. A detecting means 121 for detecting the mode competition state of the semiconductor laser 101, and a detecting means 121.
The control means 122 is provided for controlling the oscillation mode of the semiconductor laser 101 by changing the drive current supplied to the semiconductor laser 101 in accordance with the detection result of the semiconductor laser 101.

According to a third aspect of the present invention, in the semiconductor laser light source device according to the second aspect, the control means 122 normally supplies a predetermined reference current to the semiconductor laser 101, and after a mode conflict state is detected. A feature is that a predetermined drive current different from the reference current is supplied to the semiconductor laser 101 only for a predetermined time.

According to a fourth aspect of the present invention, in the semiconductor laser light source device according to the second aspect, the control means 122 causes a reference current and a predetermined drive current different from the reference current each time a mode conflict state is detected. And is switched to supply to the semiconductor laser 101.

FIG. 3 is a view showing the arrangement of the bar code reading apparatus according to claim 5. The invention of claim 5 scans the semiconductor laser light source device 110 according to claim 2 and a laser beam incident from the semiconductor laser light source device 110 in accordance with its wavelength, and displays a bar code 132 attached to an object 131. A beam scanning mechanism 133 for illuminating and a reading means 134 for performing a barcode reading process based on the intensity change of the scattered light from the barcode 132 are provided.

[0026]

According to the invention of claim 1, the mode discriminating means 112 discriminates the oscillation mode of the semiconductor laser 101 based on the wavelength of the mode detecting laser beam separated by the separating means 111, and the control is carried out according to the discrimination result. By changing the drive current supplied to the semiconductor laser 101 by the means 113,
The optical output of the semiconductor laser 101 can be controlled to stabilize the oscillation mode of the semiconductor laser 101 to a target oscillation mode.

According to the second aspect of the invention, the detecting means 121 detects the mode competition state based on the wavelength of the mode detecting laser beam separated by the separating means 111, and the controlling means 122.
However, by changing the drive current according to the detection result, it is possible to change the optical output of the semiconductor laser 101 and escape from the mode competition state.

Further, the control means 122 supplies a predetermined drive current to the semiconductor laser 101 for a predetermined time after the mode competition state is detected, thereby giving a predetermined energy change to the semiconductor laser 101 to perform the mode competition. It is possible to escape from the state and oscillate in a single mode.

Further, the control means 122 switches the reference current and the predetermined drive current every time when the mode conflict state is detected, thereby giving a predetermined energy change to the semiconductor laser 101 to escape from the mode conflict state. , Can be oscillated in a single mode.

According to the fifth aspect of the present invention, since the semiconductor laser light source device 110 emits the laser beam from the semiconductor laser 101 oscillating in a single mode, regardless of the wavelength dependence of the beam scanning mechanism 133. , A bar code 132 on an object 131 with a finely focused laser beam
Can be illuminated. Therefore, the reading means 134
Is capable of reading the bar code 132 with the same accuracy as the conventional one based on the intensity change of the scattered light from the bar code 132, and the size of the bar code reader can be reduced without sacrificing the reading accuracy. You can

[0031]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 4 shows the configuration of an embodiment of the semiconductor laser light source device according to claim 1.

In FIG. 4, the semiconductor laser light source device is
The laser beam from the semiconductor laser (LD) 101 is shaped by a collimator lens 702 to emit a laser beam.

A part of the laser beam described above is diffracted by the hologram 211 corresponding to the separating means 111, as shown by the dotted line in FIG.
An image is formed on 12 light receiving surfaces. Hereinafter, the laser beam diffracted by the hologram 211 is referred to as a mode detection laser beam.

Since the diffraction angle of the hologram 211 depends on the wavelength of the incident laser beam, the semiconductor laser 101 oscillates in the oscillation mode i (wavelength λ _i ) and the oscillation mode i + 1 (wavelength λ _i). When oscillating at ₊₁ ), as shown in FIG. 5, the imaging position of the mode detecting laser beam is different on the CCD array 212. Therefore, the wavelength can be obtained from the imaging position of the mode detecting laser beam, and the oscillation mode corresponding to this wavelength can be determined.

For example, the laser beam for mode detection when the semiconductor laser 101 is oscillating in each oscillation mode is C
As imaged on the corresponding elements of the CD array 212,
The hologram 211 and the CCD array 212 described above are arranged, and the peak detector 213 causes the CCD array 212 to operate.
The element whose output has a peak value may be detected as the imaging position from among the elements. In this case, the oscillation mode corresponding to the element number obtained by the peak detector 213 may be output as the determination result.

In this way, the hologram 211 and the CC
The D array 212 and the peak detector 213 can realize the function of the mode detector 112. In addition,
A beam splitter may be used as the separating unit 111, and the mode detecting unit 112 may be configured to disperse the mode detecting laser beam using a spectroscope or the like.

Further, in FIG. 4, the comparison circuit 221 and the driver circuit 222 correspond to the control means 113, and the comparison circuit 221 compares the above-mentioned discrimination result with a predetermined threshold value, and the comparison result. Accordingly, the driver circuit 222 is configured to change the drive current supplied to the semiconductor laser 101.

For example, the number of the element of the CCD array 212 corresponding to the wavelength in the predetermined oscillation mode is set as the threshold value in the comparison circuit 221, and the input measurement result by the comparison circuit 221 is set to the above-mentioned threshold value. If it does not match with the above, the driver circuit 222 may determine that the oscillation mode shift has occurred and change the drive current.

In this way, the drive current supplied to the semiconductor laser 101 can be changed according to the discrimination result by the mode discrimination means 112, whereby the optical output of the semiconductor laser 101 is changed and the semiconductor laser is changed. 101
Oscillation mode can be controlled.

In particular, the driver circuit 222 fixes the semiconductor laser 101 in a predetermined oscillation mode by increasing or decreasing the drive current according to the direction of the deviation of the oscillation mode detected by the above-mentioned comparison circuit 221. It can oscillate stably in the state.

In this way, a semiconductor laser light source device that can obtain a stable oscillation wavelength using a visible light semiconductor laser having a wavelength of 700 nm or less can be realized. Further, the driver circuit 222 is an indispensable element for driving the semiconductor laser 101, and by using the driver circuit 222 to control the oscillation mode of the semiconductor laser 101, a Peltier element is used. It is possible to suppress an increase in the amount of hardware as compared with, and to achieve cost reduction and downsizing.

This semiconductor laser light source device is suitable for a device such as the laser beam printer device shown in FIG. 18, which does not allow the deviation of the scanning position of the laser beam and the expansion of the beam diameter due to the change of the oscillation mode of the semiconductor laser. .

FIG. 6 is a block diagram showing an embodiment of a laser beam printer to which the semiconductor laser light source device shown in FIG. 4 is applied. In FIG. 6, the laser beam printer device is
A conventional laser beam printer (see FIG. 18) has a hologram 221, which corresponds to the separating means 111, the hologram 211, the CCD array 212, and the peak detector 21.
3 and the mode discriminating means 112 and the comparison circuit 221.
A control means 113 including a driver circuit 222 and a driver circuit 222 is added, and the driver circuit 222 includes the semiconductor laser 101.
The drive current is supplied to the.

In this case, the hologram 211 is arranged between the collimator lens 702 and the hologram disc 703, and the hologram 211 is arranged in the same manner as in the above-mentioned embodiment.
The CCD array 212 may be arranged at a position that intersects the mode-detecting laser beam diffracted by.

As a result, as described above, the output of the semiconductor laser 101 can be controlled by the mode discriminating means 112 and the control means 113 to stabilize the oscillation mode of the semiconductor laser 101 to a predetermined oscillation mode. Therefore, it is possible to prevent the deviation of the scanning position of the laser beam on the photosensitive drum 704 and the blurring of the image. Therefore, unlike the conventional case, it is not necessary to compensate for the wavelength variation due to the variation of the oscillation mode by the optical system, the design of the optical system can be facilitated, and the cost of the laser beam printer can be reduced.

On the other hand, when the semiconductor laser light source device is applied to the bar code reading device, unlike the above-described laser beam printer device, it is sufficient to avoid only the mode competition state and the oscillation mode is fixed to a predetermined oscillation mode. No control is needed.

A method of avoiding the mode competition state in the semiconductor laser light source device will be described below. FIG. 7 shows a configuration diagram of an embodiment of the semiconductor laser light source device of claim 2.

In FIG. 7, the semiconductor laser light source device is
Similar to the semiconductor laser light source device shown in FIG. 4, the hologram 21 is converted from the laser light emitted from the semiconductor laser 101.
1 to separate the mode detection laser beam,
An image is formed on the D array 212.

Further, in FIG. 7, this hologram 21
1, CCD array 212, comparison circuit 321, and determination circuit 3
The reference numeral 22 forms a detection means 121, and the comparison circuit 3
21 sequentially compares the output of each element of the CCD array 212 with a predetermined threshold value, and the determination circuit 322 determines by the comparison circuit 321 whether the outputs of the plurality of elements have exceeded the above-mentioned threshold values. It is composed.

Here, if a value that is sufficiently larger than the noise level of the CCD array 212 is set in the comparison circuit 321 as the above-mentioned threshold value, the element of the CCD array 212 that obtains an output exceeding this threshold value is set to the mode. Only the element corresponding to the image formation position of the detection laser beam. Therefore,
The fact that there are a plurality of corresponding elements means that the mode detection laser beam contains light having wavelengths corresponding to a plurality of oscillation modes, that is, that the semiconductor laser 101 is in a mode competition state. There is.

Therefore, the above-mentioned judgment circuit 322 indicates whether the outputs of the plurality of elements have exceeded the threshold value by, for example, logic "1" and logic "0", respectively, and the judgment result indicates that the mode conflict state is detected. It may be sent to the driver circuit 323 corresponding to the control means 122 as the detection result of the above.

In accordance with the detection result, the driver circuit 32
By changing the driving current supplied to the semiconductor laser 101 by the laser diode 3, the optical output of the semiconductor laser 101 changes, and the mode competition state can be escaped.

In this way, it is possible to control the oscillation mode to escape from the mode competition state in accordance with the detection of the mode competition state, so that the semiconductor laser 101 can be kept in a single mode and unstable characteristics can be obtained. A stable semiconductor laser light source device can be realized by using the visible light semiconductor laser.

Next, the method of controlling the drive current by the above-mentioned control means 122 will be concretely described. FIG. 8 shows a block diagram of an embodiment of the control means 122 of claim 3.

In FIG. 8, the control means 122 has a switching signal generating circuit 420 for generating a switching signal according to the detection result obtained by the detecting means 121, and a predetermined predetermined current different from the reference current I ₀ according to the switching signal. A driver circuit 424 for switching and outputting the drive current I ₁ is provided.

As described above, by the detecting means 121,
When it is indicated by the logic "1" and the logic "0" whether or not the mode race condition is detected, as shown in FIG. 8, the switching signal generation circuit is composed of the AND gate 421, the D-type flip-flop 422 and the timer 423. 420 may be formed. In this case, the switching signal generation circuit 420 is configured to read the detection result of the detection means 121 described above according to the input of the clock signal and output the output of the D-type flip-flop 422 as the switching signal. Also,
The timer 423 is configured to start operation in synchronization with the rising edge of the output of the AND gate 421, and to clear the D flip-flop 422 described above after a predetermined time τ. Further, the driver circuit 424 outputs the reference current I ₀ when the logic “0” is input as the switching signal,
A predetermined drive current I ₁ may be output and supplied to the semiconductor laser 101 when the logic “1” is input.

As a result, the reference current I ₀ is normally supplied to the semiconductor laser 101, and the predetermined drive current I ₁ can be supplied for the predetermined time τ in accordance with the detection of the mode competition state. Then, the optical output of the semiconductor laser 101 changes as shown in FIG. However, in FIG.
The optical output P ₀ is an optical output corresponding to the reference current I ₀ , and is an optical output corresponding to the optical output P ₁ and the drive current I ₁ .

Here, the time τ set in the timer 423 described above is such that the energy represented by (P ₁ −P ₀ ) × τ is equivalent to the energy required for the semiconductor laser 101 to escape from the mode competition state. You can decide to do so. In this case, according to the drive current from the driver circuit 424, while the semiconductor laser 101 emits the optical output P ₁ , the semiconductor laser 101 escapes from the mode competition state and becomes the single mode, and thereafter, It emits a light output P ₀ of a wavelength corresponding to a single mode. As the above-mentioned clock signal, a clock signal having a period sufficiently longer than this time τ may be input to the switching signal generation circuit 420.

In this case, since the drive currents I ₀ and I ₁ can be switched and output in the driver circuit 424, it is not necessary to have a configuration for continuously changing the drive current,
The configuration of the driver circuit can be simplified. Also,
Since the switching signal generation circuit 421 can be realized by a simple logic circuit as described above, a stable semiconductor laser light source device can be realized without increasing the circuit scale.

Further, since the energy required to escape from the mode competition state is minute, the above-mentioned optical output P
The difference between ₀ and P ₁ may be small, and the optical output of the semiconductor laser 101 can be kept substantially constant.

FIG. 10 shows a block diagram of an embodiment of the control means 122 of claim 4. In FIG. 10, the control means 122
Is the switching signal generation circuit 4 of the control means 122 shown in FIG.
Instead of 20, the switching signal generating circuit 430 is provided.

The switching signal generation circuit 430 is composed of an AND gate 431 and a T-type flip-flop 432, and detects the detecting means 12 according to the input of the clock signal.
The detection result of No. 1 is read. In this case, the output of the T-type flip-flop 432 is inverted in synchronization with the rising edge of the clock signal every time when the logic "1" indicating the mode conflict state is input as the output of the detection means 121. Type flip-flop 432
The output of 1 may be input to the driver circuit 424 as a switching signal.

In response to this switching signal, the driver circuit 42
4, the reference current I ₀ and the predetermined drive current I ₁ are alternately output. Therefore, the optical output of the semiconductor laser 101 changes every time the mode competition state is detected, as shown in FIG.

Also in this case, the driver circuit 4 having a simple structure
24, the semiconductor laser 1
It is possible to provide a stable semiconductor laser light source device without increasing the circuit scale by giving the value 01 to the mode conflict state. Further, the light amount of the output laser beam can be kept substantially constant.

Next, a bar code reading device to which the semiconductor laser light source device according to the second aspect is applied will be described. 12
FIG. 7 shows a block diagram of an embodiment of the bar code reading apparatus of claim 5.

In FIG. 12, the bar code reader is
In the conventional bar code reading apparatus shown in FIG. 14, a hologram 211 corresponding to the separating means 111, a detecting means 121 including the hologram 211, a CCD array 212, a comparing circuit 321, and a judging circuit 322, and a switching signal generating circuit 420. And a driver circuit 424
And are added. Further, a semiconductor laser 101 and a collimator lens 702 are provided in place of the He-Ne laser, and the driver circuit 424 described above is configured to supply a drive current to the semiconductor laser 101.

In this case, the hologram 211 described above may be arranged between the collimator lens 702 and the concave mirror 503, and the CCD array 212 may be arranged at a position intersecting the laser beam diffracted by the hologram 211. As a result, the mode conflict state can be detected by the comparison circuit 321 and the determination circuit 322 based on the output of the CCD array 212.

Further, according to the detection result, the switching signal generating circuit 421 and the driver circuit 422 switch the output of the semiconductor laser 101 so that the semiconductor laser 1
The oscillation mode of the semiconductor laser 101 can be maintained in a single mode by controlling the oscillation mode of 01.

As a result, it becomes possible to keep the beam diameter of the laser beam scanned by the beam scanning mechanism including the element having the diffractive action, like the fixed hologram 507, small. Therefore, by applying the semiconductor laser light source device according to the above-mentioned claim 2 to the barcode reading device, the barcode reading device can be downsized without sacrificing the reading accuracy.

In this case, in the same manner as in the conventional case, the concave mirror 5
03 and the mirror 541 guide the scattered light from the bar code 132 to the photodetector 542, so that the reading processing unit 543.
Can read the bar code 132 with the same accuracy as that of the conventional bar code reading device from the change in the output of the photodetector 542.

The semiconductor laser light source device described above may be applied to a hologram disc type bar code reader. FIG. 13 shows a block diagram of another embodiment of the bar code reading apparatus according to claim 5.

In FIG. 13, the bar code reader is
In the conventional bar code reader shown in FIG. 17, a hologram 211 corresponding to the separating means 111, a detecting means 121 including the hologram 211, a CCD array 212, a comparing circuit 321, and a judging circuit 322, and a switching signal generating circuit. Control means 12 consisting of 420 and driver circuit 424
2 is added. A semiconductor laser 101 and a collimator lens (lens) 702 are provided in place of the He-Ne laser, and the driver circuit 424 described above is configured to supply a drive current to the semiconductor laser 101.

In this case, the hologram 211 described above may be arranged between the collimator lens 702 and the condenser lens 641 and the CCD array 212 may be arranged at a position intersecting the laser beam diffracted by the hologram 211. From the output of this CCD array 212 to the comparison circuit 3
21 and the determination circuit 322 can detect the mode conflict state, and the control means 12 can detect the detected result according to the detection result.
2 makes it possible to control the oscillation mode of the semiconductor laser 101.

As a result, the hologram disc 602,
Since the laser beam scanned by the beam scanning mechanism including the pattern synthesizing mirror 603 and the mirror 604 can be kept in a finely narrowed state, the condenser lens 641,
The reading unit 134 including the photodetector 642 and the reading processing unit 643 allows the barcode 132 to have the same accuracy as the conventional one.
Can be read.

[0075]

As described above, the present invention oscillates the semiconductor laser by changing the drive current supplied to the semiconductor laser in accordance with the result of discrimination of the oscillation mode of the semiconductor laser or the result of detection of the mode competition state. Since it is possible to control the oscillation mode to stabilize the semiconductor laser to a target single mode by controlling the mode and the oscillation mode to escape the mode competition state, it is possible to stabilize by using an unstable visible light semiconductor laser. It is possible to realize a different semiconductor laser light source device. Further, by applying this semiconductor laser light source device to a barcode reading device, it is possible to reduce the size of the barcode reading device without sacrificing reading accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a semiconductor laser light source device according to claim 1.

FIG. 2 is a diagram showing a configuration of a semiconductor laser light source device according to any one of claims 2 to 4.

FIG. 3 is a diagram showing a configuration of a bar code reading apparatus according to claim 5;

FIG. 4 is a diagram showing a configuration of an embodiment of a semiconductor laser light source device according to claim 1;

FIG. 5 is an explanatory diagram of a wavelength measuring method.

FIG. 6 is a configuration diagram of an embodiment of a laser beam printer device to which the semiconductor laser light source device of claim 1 is applied.

FIG. 7 is a configuration diagram of an embodiment of a semiconductor laser light source device according to claim 2;

FIG. 8 is a block diagram of an embodiment of the control means of the invention of claim 3;

FIG. 9 is a diagram showing changes in optical output.

FIG. 10 is a block diagram of an embodiment of the control means of the invention of claim 4;

FIG. 11 is a diagram showing changes in optical output.

FIG. 12 is a configuration diagram of an embodiment of a bar code reading apparatus according to claim 5;

FIG. 13 is a configuration diagram of another embodiment of the bar code reading device of claim 5;

FIG. 14 is a configuration diagram of a conventional barcode reading device.

FIG. 15 is a diagram showing an arrangement of pattern synthesizing mirrors of a barcode reading device.

FIG. 16 is an explanatory diagram of a hollow-line scanning pattern.

FIG. 17 is a configuration diagram of a hologram disc type bar code reader.

FIG. 18 is a configuration diagram of a laser beam printer.

FIG. 19 is an explanatory diagram of mode transition of a semiconductor laser.

FIG. 20 is a diagram showing the spread of the beam diameter in the mode competition state.

[Explanation of symbols]

101 Semiconductor laser (LD) 110 Semiconductor laser light source device 111 Separation means 112 Mode discrimination means 113, 122 control means 121 detection means 131 objects 132 barcode 133 beam scanning mechanism 134 reading means 211 hologram 212 CCD array 213 Peak detector 221, 321 comparison circuit 222, 323, 424 driver circuit 322 Judgment circuit 420,430 Switching signal generation circuit 421, 431 AND gate 422 D-type flip-flop 423 timer 432 T-type flip-flop 503 concave mirror 504 polygon mirror 505,603 Pattern synthesis mirror 506, 541, 601, 604 Mirror 507 Fixed hologram 542,642 photo detector 543, 643 read processing unit 602,703 Hologram disk 605 reading window 641 condenser lens 702 Collimator lens 704 photosensitive drum

Claims (5)

[Claims] 1. A separating means (111) for separating a part of a laser beam emitted from a semiconductor laser (101) to emit a laser beam for mode detection, and a wavelength of light included in the laser beam for mode detection. On the basis of the above, the mode discrimination means (112) for discriminating the oscillation mode of the semiconductor laser (101), and the drive current supplied to the semiconductor laser (101) according to the discrimination result by the mode discrimination means (112). A semiconductor laser light source device, further comprising: a control unit (113) for changing the oscillation mode of the semiconductor laser 101 to a target oscillation mode. 2. A separation means (111) for separating a part of a laser beam emitted from a semiconductor laser (101) and emitting it as a mode detection laser beam, and a wavelength of light included in the mode detection laser beam. Based on the detection means (121) for detecting the mode competition state of the semiconductor laser (101), and the drive current supplied to the semiconductor laser (101) is changed according to the detection result by the detection means (121). Then, a semiconductor laser light source device comprising a control means (122) for controlling the oscillation mode of the semiconductor laser (101). 3. The semiconductor laser light source device according to claim 2, wherein the control means (122) normally supplies a predetermined reference current to the semiconductor laser (101), and a predetermined value is detected after the mode competition state is detected. A semiconductor laser light source device, characterized in that a predetermined drive current different from the reference current is supplied to the semiconductor laser (101) only during the time. 4. The semiconductor laser light source device according to claim 2, wherein the control means (122) switches between the reference current and a predetermined drive current different from the reference current each time a mode conflict state is detected. The semiconductor laser light source device is configured to supply the semiconductor laser (101). 5. A semiconductor laser light source device (110) according to claim 2, and a laser beam incident from the semiconductor laser light source device (110) is scanned according to its wavelength to obtain an object (131).
A beam scanning mechanism (133) for illuminating the bar code (132) attached to the bar code (132), and a reading means (1) for performing the bar code reading process based on the intensity change of the scattered light from the bar code (132).
34) and a bar code reader.