JPH0365711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a semiconductor laser scanning device that combines laser beams emitted from a plurality of semiconductor lasers into a single beam for scanning, and particularly relates to a semiconductor laser scanning device that combines laser beams emitted from a plurality of semiconductor lasers into a single beam for scanning, This invention relates to a semiconductor laser scanning device having a function of keeping the amount of light constant.

(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.
A light beam scanning device that is small (20 to 30mW) and therefore requires high-energy scanning light, such as a recording material with low sensitivity (metal film, amorphous film, etc.)
It is extremely difficult to use it in scanning recording devices that record on DRAW materials, etc.).

Also, some types of fluorophores are exposed to radiation (X-rays, alpha 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. By using such a stimulable phosphor, radiation image information of a subject such as a human body is recorded on a stimulable phosphor sheet having a layer made of a stimulable phosphor, and then the stimulable phosphor is A light sheet is scanned with excitation light such as a laser beam to generate stimulated luminescence light, the resulting stimulated luminescence light is read out photoelectrically to obtain an image signal, and a radiation image of the subject is created based on this image signal. Recording materials such as photographic materials,
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 phosphor 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 in a recording/reproducing system.

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 (in this case, 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 amount constant control is performed respectively, the number of light amount detectors and light amount 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 scanning device that can maintain a constant amount of light of a laser beam emitted from a plurality of semiconductor lasers and combined into one laser beam, and that is small and inexpensive. The purpose is to

(Structure of the Invention) As described above, the semiconductor laser scanning device of the present invention has a plurality of semiconductor lasers, and performs semiconductor laser scanning in which laser beams emitted from these semiconductor lasers are combined into one beam for scanning. In the apparatus, some of the semiconductor lasers are driven by a light amount control means so that the light amount can be controlled, and the output of a light amount detector that detects the light amount of the combined beam is fed back to the light amount control means to drive some of the semiconductor lasers. This system is characterized by controlling the amount of light of only one beam, thereby keeping the amount of light of the combined beam constant.

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

FIG. 1 schematically shows a semiconductor laser scanning device according to a first embodiment of the present invention. As an example, four semiconductor lasers 11, 12, 13, 14
are arranged with their beam exit axes parallel to each other,
For each of these semiconductor lasers 11, 12, 13, 14, collimator lenses 21, 22,
23, 24, and reflective mirrors 31, 32, 33, 3
4 is provided. Each semiconductor laser 11,1
The laser beams emitted from 2, 13, and 14 are
The collimator lenses 21, 22, 23, 24 form parallel beams 41, 42, 43, 44, and the parallel beams 41, 42, 43, 44 are reflected by the reflecting mirrors 31, 32, 33, 34. , enters a common carbanometer mirror 5.

The galvanometer mirror 5 rotates 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, and each is focused at this spot S. 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 high energy light beams emitted from the respective semiconductor lasers 11, 12, 13, and 14. The scanning beam is scanned 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.

Here, the semiconductor lasers 11, 12, 1 mentioned above
Three semiconductor lasers 11, 12 among 3, 14,
13 is driven by the laser drive circuit 50 with a fixed current (that is, without controlling the amount of light). The other semiconductor laser 14 is driven by a laser drive control circuit 51 with variable output (ie, light amount controllable). Further, a light amount detector 52 made of, for example, a photodiode, for detecting the light amount of the composite beam spot S is disposed at a position on the surface to be scanned 7 that is out of the effective scanning width.
The output of No. 2 is amplified by an amplifier 53 and input as a light amount signal P to the laser drive control circuit 51.

As mentioned above, semiconductor lasers 11, 12, 13, 1
The amount of light emitted from these semiconductor lasers 11, 12, 13, and 14 changes due to changes in the laser beams 41, 12, 13, and 14 over time, changes in ambient temperature, etc., and therefore the parallel beams 41, 42, 43, and 44 are combined. The amount of light at the beam spot S also varies. The light intensity of this spot S is determined by the light intensity detector 5 for each scan.
A light amount signal P detected by 2 and indicating the light amount
is input to the laser drive control circuit 51 as described above. This laser drive control circuit 51 has a light amount signal P
and a reference light amount signal carrying a reference light amount, and if the detected light amount is lower than the reference light amount, the output of the semiconductor laser 14 is increased, and if the detected light amount is higher than the reference light amount, the output of the semiconductor laser 14 is decreased. The semiconductor laser 14 is driven so as to. By driving and controlling the semiconductor laser 14 in this manner, fluctuations in the light amount of the combined beam spot S are canceled out, and the light amount of the spot S is maintained constant. Of course, in this case, the amount of control (amount of increase, amount of decrease) of the output of the semiconductor laser 14 may be changed depending on the amount of difference between the detected light amount and the reference light amount, or it may be set to a small constant amount. You can stay there.

Note that the semiconductor laser 1 due to the reasons mentioned above
The cycle of light intensity fluctuations of 1, 12, 13, and 14 is
Since it is extremely long compared to the period of scanning by the composite beam spot S, the light amount of the composite beam spot S does not vary during one scan.
Therefore, the light intensity of the spot S can be kept constant by simply controlling the output of the semiconductor laser 14 according to the light intensity of the spot S for each scan as described above. Further, the above-described embodiment device has parallel beams 41,
42, 43, and 44 are focused on one point by the focusing lens 6, but it is also possible to use a semiconductor laser scanning device that combines a plurality of focused beams so that their respective focused points overlap at a common spot. , the invention is equally applicable.

FIG. 2 schematically shows a second embodiment of the invention. In this embodiment, six semiconductor lasers 61, 62, 63, 64, 65, 6 are used.
The laser beam emitted from 6 passes through collimator lenses 71, 72, 73, 74, 75, 76 into parallel beams 81, 82, 83, 84, 85, 86.
These parallel beams 81, 82, 83, 8
4, 85, 86 are 1 by the hologram element 90
It is combined into a high-energy beam 87 of the book. For example, this combined beam 87 is deflected by a rotating polygon mirror 91 and scans a surface to be scanned (not shown).

The above six semiconductor lasers 61, 62, 63, 6
Five semiconductor lasers 61 to 4, 65, and 66
65 is driven with a fixed current by the same laser drive circuit 50 as in the first embodiment,
Another semiconductor laser 66 is a laser drive control circuit 5 similar to that in the first embodiment.
1 with variable output. A half mirror 92 is disposed in the optical path of the composite beam 87, and the light intensity of a part of the composite beam 87 (beam 87a) split by the half mirror 92 is as follows:
It is detected by the light amount detector 52. Since the light intensity of the beam 87a and the scanned combined beam 87b correspond, the light intensity of the scanned combined beam 87b can be detected by detecting the light intensity of the beam 87a. The light amount signal P amplified by the amplifier 53 is input to the laser drive control circuit 51, and the laser drive control circuit 51 receives the light amount signal P.
Accordingly, it operates in the same manner as in the first embodiment, and the amount of light of the scanned composite beam 87b is kept constant.

As in the second embodiment, in order to combine the laser beams emitted from a plurality of semiconductor lasers into one beam before the scanning point, in addition to the hologram element 90, a biaxial crystal is required. A known beam combining means such as an element may be used. In addition to the galvanometer mirror 5 and rotating polygon mirror 91 described above, a hologram scanner or the like may be used as an optical deflector for scanning the laser beam.

The number of laser beams to be combined in the present invention is not limited to four or six in the embodiments described above. In addition, the number of semiconductor lasers driven by light intensity control is not limited to one; if 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 driven by light intensity control may be increased. Increase the number to 2 or more as appropriate,
It is sufficient to ensure a light amount control range that is greater than the light amount fluctuation width of the combined beam.

(Effects of the Invention) As explained above in detail, according to the semiconductor laser scanning device of the present invention, it is possible to keep the light intensity of the scanned composite beam constant, and the constant light intensity is achieved by Since this is achieved by controlling the light amount of the semiconductor laser, the light amount control circuit is simplified, and the present device can be made extremely small and inexpensive.

[Brief explanation of drawings]

FIG. 1 shows a first diagram of a semiconductor laser scanning device according to the present invention.
FIG. 2 is a schematic perspective view showing a second embodiment of the semiconductor laser scanning device of the present invention. 5... Galvanometer mirror, 11, 12, 1
3, 14, 61, 62, 63, 64, 65, 66
...Semiconductor laser, 41, 42, 43, 44, 8
1, 82, 83, 84, 85, 86...Parallel beam (laser beam), 50...Laser drive circuit, 51...
Laser drive control circuit, 52...light amount detector, 53...
Amplifier, 87, 87a, 87b... Combined beam, 9
0... Hologram element, 91... Rotating polygon mirror, S... Combined beam spot.

Claims (1)

[Claims] 1. In a semiconductor laser scanning device that combines laser beams emitted from a plurality of semiconductor lasers into one beam for scanning, some of the semiconductor lasers among the plurality of semiconductor lasers are driven by a light amount control means so that the amount of light can be controlled. and the light amount control means receives an output from a light amount detector that detects the amount of light of the combined beam, and controls the amount of light of the some of the semiconductor lasers so as to keep the amount of light of the combined beam constant. A semiconductor laser scanning device characterized by: