JPH0260163B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a semiconductor laser scanning device that scans a laser beam emitted from a semiconductor laser using a mechanical optical deflector. Moreover, the present invention relates to a semiconductor laser scanning device that is capable of correcting deviations of a scanning beam in a direction perpendicular to a scanning line.

(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 fluorophores are exposed to radiation (X-rays, alpha rays,
When irradiated with beta rays, gamma rays, ultraviolet rays, etc., some of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, it It is known that phosphors exhibit stimulated luminescence, and by using such stimulable phosphors, radiation image information of a subject such as a human body can be stored in a storage layer containing a layer of stimulable phosphors. This stimulable phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescent light, and the resulting stimulated luminescent light is read out photoelectrically to produce an image signal. The applicant has already proposed a radiation image information recording and reproducing system that outputs the radiation image of the subject as a visible image to a recording material such as a photographic light-sensitive material, CRT, etc. based on this image signal (Japanese Patent Application Laid-Open No. No. 55-12429, No. 55-116340, No. 55-
(No. 163472, No. 56-11395, No. 56-104645, etc.) In this system, it has been considered to use a light beam scanning device using a semiconductor laser to scan a stimulable phosphor sheet on which radiation image information is stored and read the image information. In order to stimulate the stimulable luminescence of a stimulable phosphor, it is necessary to irradiate the phosphor with excitation light of sufficiently high energy. It is extremely difficult to use it for reading image information in an information recording and reproducing system.

Therefore, when using semiconductor lasers in optical beam scanning devices, multiple laser beams emitted from multiple beam irradiation systems consisting of semiconductor lasers and optical lenses are combined so as to be focused on a common scanning spot. It has been considered to obtain a scanning beam. In this case, each laser beam may be combined into a single beam before reaching the scanning spot, or may be combined so that they overlap each other at the scanning spot.

On the other hand, conventional optical deflectors that deflect light beams include rotating polygon mirrors, hologram scanners, etc.
Rotating optical deflectors having a plurality of optical deflecting sections are widely used. In a light beam scanning device that uses this type of rotary optical deflector, scanning is performed by the surface tilt of the deflection part of the rotary deflector (for example, a mirror surface in the case of a rotating polygon mirror, or a diffraction grating in the case of a hologram scanner). The beam may deviate from the reference scan position in a direction perpendicular to the scan direction, resulting in distortion of the scan line. Conventional methods for correcting such distortions in the scanning line include methods that use optical means, and the provision of a correction optical deflector that deflects the scanning beam in a direction perpendicular to the scanning direction. A method of driving the correction optical deflector based on the following is known.

However, if the above-mentioned optical means and a correction optical deflector are provided, the scanning device becomes larger, and the correction optical deflector is expensive, so when the optical deflector is used, the cost of the scanning device also increases significantly. Resulting in.

(Objective of the Invention) Therefore, the present invention provides an optical means and a correction optical deflector in a semiconductor laser scanning device that combines a plurality of laser beams and deflects and scans a scanning beam using a rotating optical deflector as described above. It is an object of the present invention to provide a semiconductor laser scanning device capable of correcting the distortion of the scanning line due to the surface tilt of the rotary optical deflector without using the rotary optical deflector.

(Structure of the Invention) The semiconductor laser scanning device of the present invention is a semiconductor laser scanning device using a rotary optical deflector that combines and scans a plurality of laser beams as described above, and includes a semiconductor laser and an optical lens. A plurality of beam irradiation systems are configured so that each laser beam is shifted by a minute pitch from each other in a direction perpendicular to the scanning direction at the scanning spot, and each laser drive circuit that drives the semiconductor laser is formed so that the beam light intensity can be independently adjusted. A beam position detector is provided to detect the deviation of the center of the scanning spot from the reference scanning position (deviation in a direction perpendicular to the scanning direction), and the beam position detector receives the output of the beam position detector and detects the deviation from the reference scanning position. A light amount weighting control circuit that controls each of the laser drive circuits accordingly weights the light amount of each laser beam to maintain the effective center of the scanning spot at the reference scanning position. be.

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

FIG. 1 shows a semiconductor laser scanning device according to one embodiment of the present invention. As an example, four semiconductor lasers 11, 12, 13, and 14 are arranged with their beam emission axes aligned almost parallel to each other (this point will be explained in detail later), 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. Each of the semiconductor lasers 11, 12, 13, and 14 is driven by a laser drive circuit 51, 52, 53, and 54 so that the amount of light can be adjusted independently, and the light beam emitted from these semiconductor lasers 11, 12, 13, and 14 is is the collimator lens 21, 22, 2
Parallel beams 41, 42, 43,
44, and these parallel beams 41, 42, 43,
44 is reflected by the reflecting mirrors 31, 32, 33, and 34, and enters the common rotating polygon mirror 5.

The rotating polygon mirror 5 is rotated in the direction of arrow A in the figure and deflects parallel beams 41, 42, 43, and 44. Deflected parallel beams 41, 42, 43, 4
4 are focused into one scanning spot S by a common focusing lens 6 and are each focused in 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 the respective semiconductor lasers 11,
Parallel beam 4 emitted from 12, 13, 14
1, 42, 43, and 44 are combined and scanned in the direction of arrow B by a scanning beam that has high energy. 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, 13, 14 and the reflecting mirrors 31, 32, 33, 34 produce parallel beams 41, 42, 4 at the spot S.
3 and 44 are arranged so that they do not completely overlap at one point, but are shifted by a minute pitch from each other in a direction perpendicular to the scanning direction (see FIG. 2).

As mentioned above, each mirror surface of the rotating polygon mirror 5 may have a surface tilt, and when this surface tilt exists, the scanning spot S is scanned from the reference scanning device (indicated by L in FIG. 2). It deviates in a direction perpendicular to direction B (vertical direction in FIG. 2). In order to detect this deviation, a semiconductor position detection element 60 is disposed at a position on the surface to be scanned 7 away from the effective scanning width toward the scanning start side, and the output of this semiconductor position detection element 60 is used to detect the semiconductor position. The signal is input to a signal processing circuit 61 which together with the element 60 constitutes a beam position detector. FIG. 3 shows the configuration of the signal processing circuit 61 in detail. The upper terminal output I ₁ and the lower terminal output I ₂ of the semiconductor position detection element 60 are input to the addition circuit 62 and subtraction circuit 63 of the signal processing circuit 61.
Addition signal (I ₁ + I ₂ ) and subtraction signal (I ₁ −
I ₂ ) is required. These added signals (I ₁ + I ₂ )
and the subtraction signal (I ₁ −I ₂ ) are then input to the division circuit 64. The division circuit 64 generates a subtraction signal (I ₁ −
The normalized signal (I ₁ -I ₂ )/(I ₁ +I ₂ ) obtained by dividing I 2 ₎ by the sum signal (I ₁ +I ₂ ) indicates the direction and amount of deviation of the spot S. This deviation signal (I ₁ −I ₂ )/(I ₁ +I ₂ ) is input to the light amount weight control circuit 65.

The light amount weight control circuit 65 receives a deviation signal (I ₁ −I ₂ )/
The laser drive circuits 51, 52, 53, and 54 are controlled according to the direction and amount of the deviation carried by (I ₁ +I ₂ ). That is, to explain with reference to FIG. 2, the spot S is deviated downward from the reference scanning position L, and the amount of deviation is, for example, for each beam 41, 42, 43,
44, the semiconductor laser 11 is set to the highest output, and the parallel beam 41 is weighted to have a larger amount of light than the other parallel beams 42, 43, and 44, and each laser is driven. circuit 5
1, 52, 53, and 54. Similarly, the spot S is deviated downward from the reference scanning position L, and the amount thereof is, for example,
4, each laser drive circuit 51, 52, 5 is adjusted so that the parallel beam 42 has a larger light intensity than the other beams 41, 43, 44.
3,54 is controlled. On the other hand, when the spot S is deviated upward from the reference scanning position L, the parallel beam 43 or the parallel beam 44 is weighted to have a large amount of light.

By driving the semiconductor lasers 11, 12, 13, and 14 in such a manner that the weighting is performed as described above, the effective center of the spot S moves so as to cancel out the deviation, and in the end, it always remains at the reference scanning position. L
The deviation of the spot S is corrected.
Such correction is performed every time a scan is started, and the distortion of the scanning line due to the inclination of each mirror surface of the rotating polygon mirror 5 is appropriately corrected.

In addition to the combination of the semiconductor position detection element 60 and the signal processing circuit 61, the beam position detector for detecting the deviation of the spot S may be, for example, an image pickup device such as a CCD, an image pickup tube such as a vidicon, a photodiode array, etc. Other known materials may also be used. In addition to the rotating polygon mirror 5, a hologram scanner may be used as the rotating optical deflector.

As described above, the beam irradiation system includes semiconductor lasers 11, 1
2, 13, 14 and collimator lenses 21, 22,
23, 24 and the focusing lens 6 has been described, but the collimator lens 21,
Even if lenses that focus the laser beams are used instead of the laser beams 22, 23, and 24, and the focusing lens 6 is removed, and the directions of the semiconductor lasers 11, 12, 13, and 14 are appropriately set, the four laser beams will not be focused. It is possible to combine beams so that their convergence points are concentrated in one spot, and the present invention is also applicable to the case where beams are combined in this way. Furthermore, it is also possible to combine multiple laser beams into a single beam in front of the scanning spot using, for example, a hologram element or a biaxial crystal element, and the present invention can combine the beams in this way. It is also applicable in cases where

(Effects of the Invention) As explained in detail above, the semiconductor laser scanning device of the present invention is capable of synthesizing a plurality of laser beams to obtain a high-energy scanning beam. It can be suitably used for reading image information in a radiation image information recording and reproducing system. Furthermore, since the semiconductor laser scanning device of the present invention can correct the distortion of the scanning line due to the surface tilt of the optical deflector, it is possible to perform precise scanning. Since no optical deflector or the like is used, the device can be formed compactly and inexpensively.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the semiconductor laser scanning device of the present invention, FIG. 2 is an explanatory diagram showing details of the scanning spot in the above embodiment, and FIG. 3 is an electrical diagram of the beam position detector in the above embodiment. FIG. 3 is a block diagram showing the circuit. 5...Rotating polygon mirror, 6...Focusing lens, 7...
Scanned surface, 11, 12, 13, 14... Semiconductor laser, 21, 22, 23, 24... Collimator lens, 41, 42, 43, 44... Parallel beam (laser beam), 51, 52, 53, 54... Laser drive circuit, 60... Semiconductor position detection element, 6
1...Signal processing circuit, 65...Light amount weight control circuit, S...Scanning spot, L...Reference scanning position.

Claims (1)

[Claims] 1. In a semiconductor laser scanning device using a rotary optical deflector that focuses each laser beam emitted from a plurality of beam irradiation systems consisting of a semiconductor laser and an optical lens onto a common scanning spot and scans, the beam irradiation The system is configured such that each laser beam is shifted from each other by a minute pitch in a direction perpendicular to the scanning direction at the spot, and detects a deviation of the center of the spot from a reference scanning position due to a surface tilt of the optical deflector. a laser drive circuit that drives each of the semiconductor lasers so that the beam intensity can be adjusted independently; and a laser drive circuit that receives the output of the beam position detector and weights the light intensity of each laser beam according to the deviation. and a light amount weight control circuit for controlling each of the laser drive circuits so as to maintain the effective center of the spot on the reference scanning position.