JPH0444751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention provides a semiconductor laser light source device that combines laser beams emitted from a plurality of semiconductor lasers into one, in which the amount of light of the combined beam is controlled to be constant. It is related to the device.

(Technical Background and Prior Art of the Invention) Conventionally, light beam scanning devices that scan a light beam by deflecting it with an optical deflector have been widely put into practical use, for example, in various scanning recording devices, scanning reading devices, and the like. A semiconductor laser has conventionally been used as one of the means for generating a light beam in such a light beam scanning device. This semiconductor laser has many advantages, such as being smaller, cheaper, and consumes less power than gas lasers, and can be directly modulated by changing the drive current.

However, on the other hand, this semiconductor laser
Currently, the output is at most when generating continuous oscillation.
Light beam scanning devices that are small (20 to 30 mw) and therefore require high-energy scanning light, such as recording materials with low sensitivity (metal films, amorphous films, etc.)
It is extremely difficult to use it in scanning recording devices that record on DRAW materials, etc.).

Also, some types of phosphors are exposed to radiation (X-rays, α-rays,
When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc.
It is known that a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. Using such a stimulable phosphor, radiation image information of a copy of a human body or the like is recorded on a stimulable phosphor sheet having a layer of stimulable phosphor, and then this stimulable phosphor sheet is exposed to a laser beam. The stimulated luminescence light is generated by scanning with an excitation light such as, and the resulting stimulated luminescence light is read out photoelectrically to obtain an image signal, and based on this image signal, a radiation image of the subject is recorded on a photographic light-sensitive material, etc. material,
The present applicant has already proposed a radiation image information recording and reproducing system that outputs a visible image on a CRT etc.
No. 55-163472, No. 56-11395, No. 56-104645
number, etc.). In this system, the use of a light beam scanning device using a semiconductor laser has been considered in order to read the image information by scanning the stimulable phosphor sheet on which radiation image information has been stored and recorded. In order to cause the body to stimulate luminescence, it is necessary to irradiate the phosphor with excitation light of sufficiently high energy. It is also extremely difficult to use it for reading image information.

Therefore, as mentioned above, in order to obtain a scanning beam with sufficiently high energy from a semiconductor laser with low optical output,
It is conceivable to use multiple semiconductor lasers and combine the laser beams emitted from these semiconductor lasers into one beam (in this case, even if each laser beam is combined into one beam on the optical path to the scanning point) (or they may be combined into one line on the scanning point). However, as is well known, the light intensity of the laser beam emitted from a semiconductor laser fluctuates due to changes in the semiconductor laser over time, changes in ambient temperature, etc., so in many cases control is required to keep the light intensity of the combined beam constant. It is necessary to do this. Conventionally, the light intensity of the laser beam is detected by a light intensity detector,
It is well known that the light intensity signal is fed back to a laser light intensity control circuit to keep the laser beam light intensity constant. However, when scanning by combining multiple laser beams as described above, each semiconductor laser If the above-mentioned light quantity constant control is performed respectively, the number of light quantity detectors and light quantity control circuits equal to the number of semiconductor lasers will be required, resulting in an increase in the size and cost of the scanning device.

(Objective of the Invention) Therefore, the present invention provides a semiconductor laser light source device that combines laser beams emitted from multiple semiconductor lasers into a single beam, which can maintain a constant light intensity of the combined beam and can be formed compactly and inexpensively. The object of the present invention is to provide a light amount control device that can control the amount of light.

(Structure of the Invention) As described above, the semiconductor laser light source light amount control device of the present invention has a plurality of semiconductor lasers, and each laser beam emitted from these semiconductor lasers is
In a semiconductor laser light source device designed to combine into a main beam, a constant current circuit or a constant output circuit drives each semiconductor laser individually, and the output of a photodetector built into the case of each semiconductor laser. An adder circuit receives the signals and adds these signals. The adder circuit outputs an adder signal and compares it with a reference signal indicating a predetermined amount of light of the combined laser beam, and calculates the deviation between these adder signals and the reference signal. a comparator circuit that outputs a deviation signal indicative of A control circuit for changing the laser drive current of the circuit is provided.

(Embodiments) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 schematically shows a semiconductor laser light source device whose light amount is controlled by the light amount control device of the present invention. As an example, four semiconductor lasers 1
1, 12, 13, and 14 are arranged with their beam emission axes parallel to each other, and these semiconductor lasers 1
Collimator lenses 21, 22, 23, 24 and reflecting mirrors 31, 32, 33, 34 are provided for each of lenses 1, 12, 13, and 14, respectively. The laser beam emitted from each semiconductor laser 11, 12, 13, 14 is directed to the collimator lens 2.
Parallel beam 41 by 1, 22, 23, 24,
42, 43, 44, and these parallel beams 41,
42, 43, 44 are the reflecting mirrors 31, 32,
It is reflected by 33 and 34 and enters a common galvanometer mirror 5.

The galvanometer mirror 5 swings back and forth in the direction of arrow A in the figure, and the parallel beams 41, 42, 43, 4
Deflect 4. Deflected parallel beam 41,4
2, 43, and 44 are focused into one combined beam spot S by a common focusing lens 6. Therefore, if the surface to be scanned 7 is placed at a position where the spot S is irradiated, the surface to be scanned 7 will be exposed to a high-energy laser beam emitted from each of the semiconductor lasers 11, 12, 13, and 14. The combined beam 45 scans in the direction of arrow B. Note that the surface to be scanned 7 is usually a flat surface, and therefore an fθ lens is used as the focusing lens 6.

FIG. 2 shows a light amount control device according to a first embodiment of the present invention, which controls the light amount of the combined beam 45 to be constant in the semiconductor laser light source device described above. The aforementioned semiconductor lasers 11, 12, 1
3 and 14 are known constant current circuits C1 and C, respectively.
2, C3, and C4, the drive current is set constant and driven. In this way, variations in the amount of light of the laser beams (parallel beams) 41 to 44 emitted by the semiconductor lasers 11 to 14 can be suppressed to some extent, but variations in the amount of light still occur for the reasons described above. If the light intensity of the laser beams 41 to 44 changes, naturally the light intensity of the combined beam 45 will change. Therefore, the constant current circuit C1~
A part of C4, in this example two constant current circuits C3 and C
4 are connected to control circuits D3 and D4 that change the set currents of the constant current circuits C3 and C4.

On the other hand, as is well known, semiconductor lasers 11, 1
2, 13, and 14, the photodetectors 11a and 12, such as photodiodes, are installed in the case.
The output signals of these photodetectors 11a, 12a, 13a, 14a are sent to amplifiers 11b, 12b, 13a, respectively.
b, 14b. Semiconductor laser elements 11d, 12d, 13d,
A portion of the laser beam emitted from 14d is detected by photodetectors 11a, 12a, 13a, 14a, respectively, and amplifiers 11b, 12b, 13b, 1
From 4b, each laser beam 41, 42, 43, 4
Light amount signals S1, S2, S3, S4 indicating the light amount of 4
is output. These light amount signals S1 to S4 are input to an adding circuit 50 and are added together. Therefore, the addition signal output by this addition circuit 50
Sa is the total amount of light of laser beams 41 to 44,
In other words, it indicates the amount of light of the combined beam 45.

The addition signal Sa is input to the comparison circuit 51,
At the same time, a reference signal Sr indicating a predetermined amount of light of the combined beam 45 is input to the comparison circuit 51.
The comparison circuit 51 compares this reference signal Sr with the above-mentioned addition signal Sa, and when the addition signal Sa exceeds the reference signal Sr (that is, when the light quantity of the composite beam 45 exceeds the above-mentioned predetermined light quantity), it outputs a high-level H signal. Output. On the other hand, when the addition signal Sa is less than the reference signal Sr (when the light amount of the combined beam 45 is less than the above-mentioned predetermined light amount), the comparison circuit 51 outputs a low-level L signal.

This L signal or H signal is the control circuit D.
3, input to D4. These control circuits D3,
D4 is a constant current circuit C while receiving an H signal.
3. Lower the set current of C4. As a result, the optical output of the semiconductor lasers 13 and 14 decreases, and the light intensity of the combined beam 45 decreases and approaches the predetermined light intensity. On the other hand, when the L signal is input, the control circuits D3 and D4 increase the set currents of the constant current circuits C3 and C4. As a result, the semiconductor laser 13,1
4 increases, and the light amount of the combined beam 45 approaches the predetermined light amount. By performing the above control, the combined beam 45 is maintained at a predetermined light intensity. In this case, the control circuit D
3. The set current control amount (increase amount, decrease amount) of the constant current circuits C3 and C4 by D4 is a small constant amount, but the comparison circuit 51 corresponds to the deviation between the addition signal Sa and the reference signal Sr. A circuit that outputs a level signal may be used to change the control amount according to the magnitude of this deviation.

Further, the above semiconductor laser light source device focuses the parallel beams 41, 42, 43, and 44 to one point using the focusing lens 6, but the plurality of focused beams are converged at a common point. The present invention is similarly applicable to a semiconductor laser light source device that combines the lights so that they overlap at a spot.

FIG. 3 shows a light amount control device according to a second embodiment of the present invention. Note that in FIG. 3, elements that are equivalent to those in FIG. In the light amount control device shown in FIG. 3, the constant current circuit C used in the device shown in FIG.
Constant output circuits E1 to E4 are provided in place of circuits E1 to C4. These constant output circuits E1, E2, E
3 and E4 are the amplifiers 11b and 12, respectively.
Light amount signals S1, S2, S from b, 13b, 14b
3 and S4, so that the light amount signals S1 to S4 each have a predetermined value (that is, the laser beam 4
(so that the light intensity of 1 to 44 becomes a predetermined value)
Controls laser drive current. However, even with this arrangement, variations in the light amount of the combined beam 45 may occur due to the reasons described above. Therefore, as an example, the two constant output circuits E3 and E4 include the control circuit D3,
D4 is connected, and the laser drive currents of constant output circuits E3 and E4 are controlled in the same manner as in the device of FIG. By performing such control, the combined beam 45 can be maintained at a predetermined light intensity in this case as well.

Next, FIG. 4 schematically shows a third embodiment of the present invention. In the semiconductor laser light source device of FIG. 4, six semiconductor lasers 6
The laser beams emitted from the collimator lenses 71, 72,
Parallel beam 8 through 73, 74, 75, 76
1, 82, 83, 84, 85, 86, and these parallel beams 81, 82, 83, 84, 85, 8
6 are combined into one high-energy beam 87 by a hologram element 90. For example, this combined beam 87 is deflected by a rotating polygon mirror 91 and scans a surface to be scanned (not shown). In addition to the hologram element 90, for example, two laser beams are required to combine multiple laser beams into one as described above.
Known beam combining means such as an axial crystal element may be used.

The above six semiconductor lasers 61, 62, 63, 6
4, 65, and 66 are driven at a constant current by constant current circuits C1 to C6, as in the device shown in FIG. As an example, a constant current circuit C6 that drives one semiconductor laser 66 is configured to be able to change a set current amount in response to a control signal from a control circuit D6. In this device as well, the light amount signals S1 to S6 output from the photodetectors (not shown) of the respective semiconductor lasers 61 to 66 and amplified by the amplifiers 11b to 16b are input to the adding circuit 50. Addition signal output from
By comparing Sa and the reference signal Sr and controlling the set current of the constant current circuit C6 in the same way as in the apparatus shown in FIG. 2, the combined beam 87 can be maintained at a predetermined light intensity.

Note that the number of laser beams to be combined in the present invention is not limited to four or six in the embodiments described above. Furthermore, the number of semiconductor lasers driven by light intensity control is not limited to one or two, and when the number of laser beams to be combined increases and the light intensity fluctuation range of the combined beam becomes large,
The number of semiconductor lasers to be driven for light intensity control may be increased appropriately to ensure a light intensity control range that is greater than the light intensity fluctuation range of the combined beam.

(Effects of the Invention) As explained in detail above, according to the semiconductor laser light source light intensity control device of the present invention, it is possible to accurately maintain the light intensity of the combined beam constant, and the constant light intensity can be partially achieved. This is achieved by controlling the amount of light from a semiconductor laser, which simplifies the circuitry and makes the device extremely compact and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an example of a semiconductor laser light source device to which the device of the present invention is applied, and FIGS. 2 and 3 are block diagrams showing first and second embodiment devices of the present invention, respectively. FIG. 4 is a schematic diagram showing a third embodiment of the device of the present invention. 11, 12, 13, 14, 61, 62, 63,
64, 65, 66... semiconductor laser, 11a, 12
a, 13a, 14a...photodetector, 41, 42, 4
3, 44, 81, 82, 83, 84, 85, 86
... Parallel beam (laser beam), 45, 87 ... Combined beam, 50 ... Addition circuit, 51 ... Comparison circuit, 9
0... Hologram element, C1 to C6... Constant current circuit,
D3, D4, D6...control circuit, E1-E4...constant output circuit, S1-S6...light amount signal, Sa...addition signal,
Sr...Reference signal.

Claims (1)

[Scope of Claims] 1. A semiconductor laser light source device configured to combine laser beams emitted from a plurality of semiconductor lasers into one, comprising: a plurality of constant current circuits or constant output circuits that respectively drive the semiconductor lasers; , an adder circuit that receives output signals from a photodetector built in the case of each of the semiconductor lasers and adds these signals; a comparison circuit that compares the added signal with a reference signal and outputs a deviation signal indicating a deviation between the added signal and the reference signal; A semiconductor laser light source light amount control device comprising: a control circuit that receives a deviation signal and changes a laser drive current of the part of the circuit so that the deviation is eliminated.