JPH01178914A - Source device for multiple semiconductor laser light source device - Google Patents

Abstract

PURPOSE:To enable respective laser beams to make incident on a deflecting surface as linear images by providing an optical system for incidence which has a cylindrical lens between each semiconductor laser and the polarizing surface, and making the direction of refraction by the cylindrical lens coincident with one of two directions where astigmatic difference is caused. CONSTITUTION:A laser beam 2 which is reflected by the deflecting surface 6a is entered in and converged by the cylindrical lens 8 which has focal length suitable to convergence on a convergence position P on a surface to be scanned. At this time, the laser beam travels through an optical path shown by a solid line in a figure unless a rotary polygon mirror slants, but the optical path moves to a position shown by a broken line if the deflecting surface 6a shifts in position to 6a' owing to surface inclination. Further, a laser beam in the optical path shown by the solid line is also emitted from the same point on the deflecting surface 6a, so a scanning lens 5 and the cylindrical converge both the solid-line laser beam and broken-line laser beam on the position P.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a multi-semiconductor laser light source device having a plurality of semiconductor lasers, which is used in an optical scanning device.
In particular, the present invention relates to a multi-semiconductor laser light source device that can accurately combine laser beams emitted from each semiconductor laser at a scanning position.

(Prior Art) As is well known, a laser beam emitted from a laser light source is deflected by an optical deflector, and the laser beam is relatively conveyed (sub-scanned) in a direction perpendicular to the deflection direction onto a scanned surface. Optical scanning devices for scanning are widely used as various image reading devices and image recording devices.

Furthermore, it is known that a semiconductor laser is used as a laser light source in the optical scanning device.

This semiconductor laser is smaller than gas lasers etc.

It has various advantages such as being inexpensive, consuming little power, and being able to perform so-called analog direct modulation, which changes the output by controlling the drive current. Particularly when this semiconductor laser is used in the image recording apparatus, it is extremely convenient because the above-mentioned direct modulation can be performed using a signal emitted according to image information.

However, although semiconductor lasers have the above-mentioned advantages, their current output is only 20 to 30+nV when continuous oscillation is used, and therefore, they are not suitable for optical scanning devices that require high-energy scanning light, such as low-sensitivity recording. It is extremely difficult to use it in image recording devices that record on materials (such as DRAW materials such as metal films and amorphous films).

Also, some types of phosphors are exposed to radiation (X-rays, α-rays.

When irradiated with beta rays, gamma rays, electron beams, 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, the accumulated energy It is known that stimulable phosphors exhibit stimulated luminescence, and by using such stimulable phosphors, radiation image information of subjects such as the human body can be transferred to stimulable phosphors that have a layer made 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 photoelectrically to obtain an image signal. The present applicant has already proposed a radiation image information recording and reproducing system that outputs a radiation image of a subject as a visible image to a recording material such as a photographic light-sensitive material, a CRT, etc. based on an image signal (Japanese Patent Laid-Open No. 12429/1989). , No. 55-116340, No. 55-163472, No. 5
B-11395, 5B-104845, etc.).

In this system, an optical scanning device using a semiconductor laser is considered to be used to scan the stimulable phosphor sheet on which radiation image information is stored and read the image information. In order to produce stimulated luminescence, it is necessary to irradiate the phosphor with sufficiently high-energy excitation light. Therefore, the optical scanning device using the semiconductor laser is used in this radiation image information recording and reproducing system for reading image information. extremely difficult to use.

Therefore, as mentioned above, in order to obtain a sufficiently high-energy scanning beam from a semiconductor laser with low optical output, it is considered to use multiple semiconductor lasers and combine the laser beams emitted from these semiconductor lasers into one beam. It will be done.

When multiple laser beams emitted from multiple semiconductor lasers are combined into one laser beam and used as scanning light as described above, the laser beams emitted from each semiconductor laser are usually collimated into parallel beams using collimator lenses. After that, the optical paths are adjusted so that they take parallel optical paths close to each other, and the beams are reflected and deflected by being incident on the same deflection plane of a reflective optical deflector such as a rotating polygon mirror or a galvanometer mirror. A focusing lens disposed on the optical path focuses the light beams on the same focusing position to perform multiplexing, and scanning is performed at this focusing position (combining position). Therefore, in order to combine laser beams with high precision, it is necessary to precisely control the position of each laser beam so that it is correctly focused at a predetermined focusing position.

(Problems to be Solved by the Invention) However, in a semiconductor laser, the emission position of the light component diverged within the same plane as the pn junction surface of the laser element, and the emission position of the light component that is emitted within the same plane as the pn junction surface of the laser element, and within the plane perpendicular to the pn junction surface including the laser emission axis. Since the emission positions of the diverging light components differ, a so-called astigmatism difference occurs, so there is a problem that the light cannot be completely focused on one point depending on the spherical lens such as the collimator lens or the focusing lens. Problems caused by this astigmatism difference will be explained with reference to FIG.

FIG. 3 shows, as an example, one semiconductor laser extracted from a multi-semiconductor laser light source device for multiplexing, and the optical path of the laser beam emitted from this semiconductor laser is developed and shown. In FIG. 3, optical elements that do not perform a lens function, such as a reflecting mirror and a deflector, are omitted, and only the deflection surface of the deflector is shown with a dashed line.

Laser beam 102 emitted from semiconductor laser 101
is made into a substantially parallel beam by a collimator lens 103, and then passes through a focusing lens 105 to be focused. FIG. 3(a) shows the optical path of the laser beam 102 at the pn junction surface 1 of the laser element 101a in the semiconductor laser 101.
It is a plan view seen from the direction perpendicular to otb, and is
) is a side view of the optical path viewed from a direction parallel to the pn junction surface totb.

The light emitting point of the semiconductor laser lot that emits the laser beam 102 is different between the direction shown in FIG. 3(a) and the direction shown in FIG. 3(b). Therefore, if the collimator lens 103 is arranged so as to make the laser beam 102 a parallel beam in the plane shown in FIG. 3(a), for example, this collimator lens 103 will be arranged as shown in FIG. 3(b). The laser beam 102 cannot be made into a completely parallel beam within the plane shown, and the laser beam that has passed through the collimator lens 103 becomes a beam that is focused slightly inward, for example, as shown in the figure, and there is also a slight inward beam on the deflection plane. incident as a focused beam. Therefore, if the position where the parallel beam is focused by the focusing lens 105 is a predetermined focusing position, the focusing position P of the laser beam in the direction shown in FIG. 3(a) is the predetermined focusing position. In the direction shown in FIG. 3(b), the laser beam focused slightly inwardly enters the focusing lens 105, so the focusing position P' of the laser beam deviates from the predetermined focusing position by Δ2.

In this way, if the focusing positions of the laser beams are different in two directions perpendicular to each other and the laser beams are not accurately focused at one predetermined point, it will not be possible to correctly combine the laser beams at the predetermined focusing position.

Furthermore, since the degree of the astigmatic difference differs from semiconductor laser to semiconductor laser, the combination of laser beams becomes even more inaccurate.

The present invention has been made in view of the above-mentioned problems, and is capable of accurately combining laser beams in an optical scanning device while avoiding the influence of the astigmatism difference, and provides a scanning light generating means. It is an object of the present invention to provide a multi-semiconductor laser light source device that can be suitably used as a multi-semiconductor laser light source device.

(Means for Solving the Problem) In an optical scanning device equipped with a reflection type optical deflector as described above, axial wobbling is likely to occur in the deflector, and therefore it is difficult to scan a deflected surface to be scanned. There is a problem in that the scanning lines created tend to be distorted in the sub-scanning direction. In addition, especially when a rotating polygon mirror is used as a deflector, it is technically difficult to make each deflection surface on which the laser beam of the rotating polygon enters completely parallel to the rotation axis.
There is a problem in that the pitch of the scanning line becomes uneven due to the surface tilt of the rotating polygon mirror.

Therefore, in order to correct this surface tilt etc., an optical element such as a cylindrical lens is installed between the laser light source and the deflector.
A method is known in which a laser beam is made incident on the deflection surface of a deflector as a line image perpendicular to the drive axis of the deflector. If the laser beam is linearly incident on the deflection surface in this way, the laser beam that is reflected and deflected by the deflector will be emitted from a predetermined point within the plane where the surface tilt etc. occur, regardless of the presence or absence of the surface tilt etc. Since the light becomes light, it can be focused at a predetermined position by a common optical system provided in the optical path after reflection and deflection. Even when a multi-semiconductor laser light source device is used as the scanning light generating means as described above, it is desirable to provide the optical element for surface tilt correction on the optical path of each laser beam. In that case, multiple laser beams are incident on the same deflection plane, so the line images on the deflection plane by each laser beam must be formed on a common straight line perpendicular to the drive axis of the optical deflector. be.

As a result of repeated studies in view of this point, the present applicant has found that if the above-mentioned optical element for surface tilt correction is incorporated into a multi-semiconductor laser light source device used in an optical scanning device, this optical element can be used to achieve the above-mentioned results. We have found that it is possible to eliminate the effects of astigmatism at the same time. The multi-semiconductor laser light source device of the present invention, which was derived based on such knowledge, is a light source device that makes a plurality of semiconductor laser beams enter the same deflection plane of the above-mentioned reflective optical deflector.On the optical path of each laser beam, Each of the laser beams has a first lens that refracts the entire incident laser beam, and a cylindrical optical element provided behind the first lens, and each of the laser beams is refracted by the reflective optical deflector on the deflection surface. An input optical system is provided for inputting the laser beam as a line image on a predetermined straight line perpendicular to the drive axis, and a light component of the laser beam emitted from each of the semiconductor lasers is emitted in the same plane as the pn junction surface. , characterized in that it is arranged so that only one of the light components diverged in a plane that includes the laser emission axis and is perpendicular to the pn junction surface is refracted by the cylindrical optical element of the incident optical system. It is something to do.

(Function) According to the multi-semiconductor laser light source device, each laser beam is made incident on the same deflection plane by the incident optical system as a line image perpendicular to the drive axis of the optical deflector. The effects of shaft wobbling, surface tilting, etc. that occur can be avoided. At the same time, in this device, the cylindrical optical element in the incident optical system refracts only the light component in one of the two directions with an astigmatism difference. By finely adjusting the position of each semiconductor laser in advance according to the state of astigmatism difference, the optical path of one light component can be adjusted without affecting the other light component.
Each of the two light components can be made incident on the deflection surface in a predetermined state. Therefore, all the laser beams that are incident on the deflection surface and reflected and deflected are correctly focused as a point image at a predetermined position, and high-precision scanning is realized by the combined high-energy laser beam.

(Embodiment) FIG. 1 is a schematic perspective view of an optical scanning device equipped with a multi-semiconductor laser light source device according to an embodiment of the present invention.

The multi-semiconductor laser light source device of this embodiment includes, for example, three semiconductor lasers 1, 1', 1', and these semiconductor lasers are arranged with their laser emission axes parallel to each other. This light source device uses the semiconductor laser 1.
1', 1', and a first laser beam disposed on the optical path of the laser beam emitted from these semiconductor lasers.
spherical lenses 3.3', 3', cylindrical lenses 4.4', 4', and reflecting mirrors 7.
7'.

The input optical system 10.10' and to' are composed of the input optical system 10.10' and to'.
10' are laser beams 2. and 10', respectively, as will be described later.
2'.

2' on a straight line perpendicular to the rotation axis 6b of the rotating polygon mirror 6 on the same deflecting surface (deflection surface 8a in FIG. 1) of the rotating polygon mirror 6, which is a reflective optical deflector of the optical scanning device. It focuses the light as a line image. The rotating polygon mirror 6 rotates at high speed in the direction of arrow B to reflect and deflect the laser beams 2.2' and 2', and the laser beams 2.2' and 2' reflected and deflected by the rotating polygon mirror 6 on the straight line are reflected and deflected. 2' and 2' are focused at a predetermined focusing position P by a scanning lens 5 and a long cylindrical lens 8 arranged on the optical path, and are focused by this focusing position. Therefore, if the surface to be scanned is arranged along the locus of this focusing position, the surface to be scanned will be exposed to the high-energy scanning beam obtained by combining the laser beams emitted by the semiconductor lasers 1.1' and 1'. scanned. Note that the surface to be scanned is usually a flat surface, and therefore an fθ lens is used as the scanning lens 5.

In this device, each of the incident optical systems 10, 10'.

The cylindrical lenses 4, 4' and 4' at 10' are the semiconductor lasers 1, 1' and 1', respectively, and the rotating polygon mirror 6.
Laser beams 2°2' and 2' with different optical path lengths are selected to have different focal lengths on the rotating polygon mirror so that they can be focused in the direction of the rotation axis of the rotating polygon mirror. . In this light source device, an optical system 1o for incidence includes these cylindrical lenses on each laser beam.

By providing 10' and 10', the rotating polygon mirror 6
Even if surface tilting or axial wobbling occurs, it is possible to prevent pitch unevenness of the scanning line, and it is also possible to eliminate the influence of astigmatism difference of the semiconductor laser.

Hereinafter, as an example, only the laser beam 2 emitted from the semiconductor laser 1 and the optical elements on the optical path of this laser beam 2 are taken out and shown in FIG. 2, and the operation of the above-mentioned incident optical system 10 will be explained. In addition, in FIG. 2, the reflecting mirror 7 that does not perform a lens function is omitted, and the rotating polygon mirror 6 is shown.
shows only the position of the deflection plane, and the optical path of the laser beam is shown spread out on a plane.

FIG. 2(a) is a plan view of the laser beam 2 and optical elements on its optical path, and FIG. 2(b) is a side view thereof.

The semiconductor laser 1 has a pn junction surface 1b of its laser element 1a.
is arranged perpendicular to the rotation axis of the rotating polygon m6, and FIG. 2(a) shows the light component emitted in the same plane as the pn junction surface, and FIG. 2(b) shows the light component emitted from the laser beam. Light components emitted in a plane including the exit axis and perpendicular to the pn junction surface 1b are shown.

The laser beam emitted from the light emitting point A of the semiconductor laser 1 in the plane shown in FIG. Becomes a beam. The laser beam 3, which has become a parallel beam, passes through the cylindrical lens 4, but this cylindrical lens 4 does not have refractive power in the direction parallel to the pn junction surface, and the laser beam 2 passes through the cylindrical lens 4 as shown in FIG. In a), the parallel beam enters the deflection surface of the rotating polygon mirror 6 and is reflected and deflected. The reflected and deflected laser beam enters the scanning lens 5 disposed on the optical path, and is focused at a predetermined focusing position P that is far away from the scanning lens 5 by its own focal length f. A cylindrical lens 8 extending in the main scanning direction of the laser beam is provided between the scanning lens 5 and the focusing position, and this cylindrical lens 8 directs the incident light in the direction of the rotation axis of the rotating polygon mirror. It is a lens that focuses only the
In a), the laser beam 2 is allowed to pass through as is.

On the other hand, as shown in FIG. 2(b), the light emission position A2 in a plane that includes the laser emission axis of the semiconductor laser 1 and is perpendicular to the pn junction surface 1b is farther from the spherical lens 3 than the light emission position Al. In FIG. 2(b), the laser beam 2 passes through the spherical lens 3 and becomes a beam that is focused slightly more inwardly than the parallel beam. This laser beam then enters the cylindrical lens 4, which has refractive power in the direction perpendicular to the pn junction surface 1b and focuses the laser beam on the deflection surface 6a. Therefore, the laser beam is incident on the deflection surface 6a as a line image perpendicular to the rotation axis of the rotating polygon mirror 6. In FIG. 2(b), the laser beam 2 reflected by the deflection surface 6a spreads outward again, enters the scanning lens 5 disposed on the optical path, passes through the scanning lens, and is refracted slightly inward. . This laser beam is incident on and focused on the cylindrical lens 8, which has a focal length suitable for focusing the laser beam at the focusing position P on the surface to be scanned. At this time, if the rotating polygon mirror 6 has no surface tilt, the laser beam 2 will pass through the optical path shown by the solid line in the figure, but if the rotating polygon mirror has a surface tilt, etc. If it shifts to position 6a',
The optical path will move to the position shown by the broken line. However, since both the laser beam in the optical path shown by the solid line and the laser beam in the optical path shown by the broken line are emitted from the same point on the deflection surface 6a, the scanning lens 5 and the cylindrical lens 8 are Both the beam and the laser beam indicated by the dashed line can be focused at the position P,
Therefore, even if the optical path of the laser beam 2 deviates in the vertical direction in FIG. 2(b) due to surface tilt or the like, the deviation can be corrected on the surface to be scanned.

Furthermore, in the device of this embodiment, the cylindrical lens 4 has refractive power only in one of the two directions in which astigmatism occurs, so a cylindrical lens suitable for the emission position of one of the light components is selected. By selecting, regardless of the emission position of the other light component,
One light component can be focused on the deflection surface. Therefore, the laser beam will always be incident on the deflection surface as a line image, and if the laser beam is incident as a line image, then by arranging a predetermined lens system on the optical path, the laser beam will be focused at a single point. It can be imaged. In addition, the state of the astigmatism difference described above differs for each semiconductor laser, and the optical path length from the semiconductor laser to the rotating polygon mirror differs for each laser beam, so a cylindrical lens with an appropriate focal length should be selected according to each semiconductor laser. laser beams 2.2' emitted from the three semiconductor lasers 1, 1', 1'.
, 2' can all be incident on the same straight line on the deflection surface as a line image, and can be focused at one point at the final combining position.

In the device of the present invention, the light component emitted in the same plane as the pn junction surface is focused on the deflection surface, and the light component emitted in the plane perpendicular to the pn junction surface is made to enter as a parallel beam. The direction of the semiconductor laser may be rotated by 90 degrees from the above-described embodiment so that the direction of the semiconductor laser is rotated by 90 degrees. In that case, it goes without saying that the cylindrical lens of the input optical system can be replaced with one having characteristics suitable for converging the emitted light component in the same plane as the pn junction surface. In addition, each laser beam only needs to be incident as a linear image on the same straight line on the deflection plane, and the laser beams do not necessarily have to be parallel beams in the plane perpendicular to the rotation axis of the rotating polygon mirror, and the incident The optical axes of the respective laser beams may not be parallel to each other.

Further, instead of the cylindrical lens in the input optical system, a concave cylindrical lens mirror having the same refractive power may be provided. Furthermore, a plurality of cylindrical optical elements may be provided in the incident optical system, and the above-mentioned correction may be performed using the plurality of cylindrical optical elements. Further, the reflective optical deflector may be a galvanometer mirror.

(Effects of the Invention) As explained above, according to the multi-semiconductor laser light source device of the present invention, an incident optical system having a cylindrical lens is provided between each semiconductor laser and the deflection surface, and the refraction direction by the cylindrical lens is By matching one of the two directions in which the point distance difference occurs, each laser beam can be made incident on the deflection surface as a line image regardless of the astigmatism difference. Therefore, in a scanning device using this light source device, it is possible to suppress the pitch unevenness of the scanning line by avoiding the influence of the surface tilt of the optical deflector, and at the same time, it is possible to perform highly accurate scanning by using the multiplexed light that is correctly focused at a predetermined position. can be done.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical scanning device equipped with a multi-semiconductor laser light source device according to an embodiment of the present invention, FIG. 2(a),
(b) is a plan view and side view showing the optical path of the laser beam in the above device; FIGS. 3(a) and 3(b) are a plan view and side view showing the optical path of the laser beam and the arrangement of optical elements in the conventional light source device. It is a diagram. 1.1', 1'... Semiconductor laser ■b... pn junction surface 2.2', 2'... Laser beam 3, 3', 3'... Spherical lens 4.4',
4'... Cylindrical lens 6... Rotating polygon mirror 6a... Deflection surface 7.7', 7'... Reflecting mirror

Claims (1)

[Scope of Claims] A multi-semiconductor laser light source device comprising a plurality of semiconductor lasers and in which each laser beam emitted from these semiconductor lasers is incident on the same deflection plane of a reflective optical deflector, comprising: A first lens for refracting the entire incident laser beam and a cylindrical optical element provided behind the first lens are provided on the road, and each of the laser beams is directed to the reflective optical deflector on the deflection surface. An input optical system is provided for inputting the laser beam as a line image on a predetermined straight line perpendicular to the drive axis of the semiconductor laser, and the optical component of the laser beam emitted from each of the semiconductor lasers is emitted within the same plane as the pn junction surface. and the arrangement is such that only one of the light components diverged in a plane including the laser emission axis and perpendicular to the pn junction surface is refracted by the cylindrical optical element of the incident optical system. Features of multi-semiconductor laser light source device.