JPH0669588A - Semiconductor laser array light source - Google Patents

Abstract

PURPOSE:To make an expensive demagnification projection lens having a large aperture unnecessary, by arranging each couple of a plurality of semiconductor lasers arranged in one-dimensional or two-dimensional array type and convergent optical systems which correspond with the semiconductor lasers and converge casted laser beams, in a spherical surface type or a circular arc type. CONSTITUTION:A plurality of semiconductor lasers 10 arranged in a two-dimensional array type and convergent optical systems 20 which correspond with the semiconductor lasers 10 and converge laser beams casted from the respective semiconductor lasers 10 are installed. Each couple of the semiconductor laser 10 and the convergent optical system 20 is so arranged in a spherical surface type that each laser beam spot 47 gathers on a virtual image surface 40 at specific intervals and forms a laser beam pattern image 45. In order to arrange each of the couples of the semiconductor lasers 10 and the convergent optical systems 20 in a spherical surface type, an arm type fixing part member 33 constituting a part of the spherical surface is used. Penetrating holes 36 are arranged in a two-dimensional type on the fixing part member 33, and each of the couples is inserted into the hole and fixed. All of the penetrating holes 36 stretch toward a center point P0 of the spherical surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser array light source used for an image scanner for plate making, a laser plotter for manufacturing a printed wiring board, a laser printer, a light source for a two-dimensional image processing sensor, and the like.

[0002]

2. Description of the Related Art A laser light source such as a semiconductor laser is
It is used as a light emission source for various devices as described above. For example, in a laser printer, it is used as a device for emitting a laser beam for forming an image such as characters on a photosensitive drum at high speed. Further, in a light source for a two-dimensional image processing sensor, it is used as a laser beam emitting device for obtaining information by reflected light from an object.

As a structure using the above laser light source, for example, a pair of one semiconductor laser and one lens forming a collimator forms one laser beam, and the laser beam is reflected by a polygon scanner and predetermined. It is known to form an image on the surface of. In such a configuration using one semiconductor laser, the processing speed is determined by the scanning speed, so there is a problem in that there is a limit to speeding up.

From this point of view, there is known an apparatus for forming an image with a plurality of laser beams (hereinafter, referred to as "multi-laser beam") in order to increase the processing speed (Japanese Patent Laid-Open No. Hei 2). -110424, 3-15018, etc.). For example, in the apparatus of Japanese Patent Laid-Open No. 3-15018, first, one laser beam emitted from a laser light source (for example, He-Ne laser, Ar laser) is divided into a plurality of beams by a beam splitting means (beam splitter). Thus, a multi-laser beam is formed. Each of the laser beams forming this multi-laser beam can be turned on / off by an electric shutter.

Then, the multi-laser beam is reduced and projected in two steps by an afocal optical system consisting of a telephoto lens and an objective lens to form an array-shaped laser beam pattern image on the photosensitive drum, photosensitive film or the like. The multi-laser beam is reduced to 1/10 in the telephoto lens, and then further reduced to 1/10 in the objective lens (for example, microscope objective lens, LSI stepper lens, etc.).

[0006]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
In the device of No. -15018, first, there is a problem that the device becomes large in size because means for turning on / off each of the laser beams divided by the beam splitter by an electric shutter is required. . Second
In addition, since a two-stage reduction optical system is used, and in particular, an expensive reduction projection lens having a large aperture is required as the first reduction optical system, there is a problem that the apparatus becomes expensive and becomes large in size.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor laser array light source whose cost and size are reduced.

[0008]

To achieve the above object, a semiconductor laser array light source of the present invention includes a plurality of semiconductor lasers arranged in a one-dimensional or two-dimensional array, and the semiconductor lasers corresponding to the semiconductor lasers. Converging optical system for converging the laser beam emitted from each semiconductor laser, each set of the semiconductor laser and the converging optical system, each laser beam spot gather at a predetermined position at a predetermined interval laser beam pattern image Is formed so as to form a spherical surface or an arc shape.

Further, a reduction optical system for reducing the laser beam pattern image and re-imaging it at a predetermined position may be provided.

[0010]

With this structure, the laser beams emitted from the respective semiconductor lasers are converged by the converging optical system, so that the diameters of all the laser beam spots become small with uniform characteristics. On the other hand, the laser beam spots gather at predetermined positions at predetermined intervals to form a laser beam pattern. Therefore, a laser beam pattern image smaller than the pattern of the array of the semiconductor laser and the focusing optical system is formed. The laser beam pattern is re-imaged in a small size by the reduction optical system, so that fine exposure becomes possible.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing the outer appearance of the first embodiment of the present invention. FIG. 2 is a sectional view showing the configuration of the main part thereof.

The semiconductor laser array light source of this embodiment has four
The semiconductor laser 10 is provided with a plurality of semiconductor lasers 10 arranged in a two-dimensional array of 4 × 4, and a focusing optical system 20 that focuses the laser beams emitted from the respective semiconductor lasers 10 corresponding to the semiconductor lasers 10. And converging optical system 20
Each of the sets is arranged in a spherical shape so that the laser beam spots gather at a predetermined position (on the virtual image plane 40) at a predetermined interval to form a laser beam pattern image 45.

Further, a reduction optical system for reducing the laser beam pattern image 45 and re-imaging it at a predetermined position may be provided. FIG. 3 is a diagram showing a lens configuration and an optical path of the reduction optical system 50 applicable to this embodiment. As the reduction optical system 50, for example, a microscope objective lens, L
Lens for SI stepper, etc. (JP-A-49-106840)
No.) can be used, but the performance of the reduction optical system 50 used in this embodiment is that the magnification is 1/20, the number of lenses is 7, the numerical aperture (NA) is 0.40, and the depth of focus (λ / 2 (NA) ² )
Is ± 2.1 μm, resolution (λ / 2NA) is 0.8 μm, and usable depth of focus is ± 7 μm.

The semiconductor laser 10 is, as shown in FIG.
It is a general package type semiconductor laser that is hermetically sealed with a can. Inside the semiconductor laser 10, one laser chip (not shown) that emits one laser beam (wavelength: 780.0 nm) is provided.
A laser beam is emitted from the chip bonding surface of the laser chip toward a predetermined position. A monitoring photodiode is provided inside the semiconductor laser 10, and the intensity of laser emission of each semiconductor laser 10 is controlled by monitoring with the photodiode.

The converging optical system shown in FIG. 2 (focal length f = 4 m
m, numerical aperture NA = 0.35) 20 converges the laser beam emitted from the semiconductor laser 10 as shown in FIG. 1 to form a laser beam spot 47 on the virtual image plane 40 with a predetermined size and interval. To form. As a result, a laser beam pattern image 45 as shown in FIG. 1 is formed on the virtual image plane 40.

As described above, in order to arrange each set of the semiconductor laser 10 and the converging optical system 20 in a spherical shape, in this embodiment, a bowl-shaped fixing member 3 forming a part of a spherical surface is used as a fixing member.
3 is used. As shown in FIG. 2, the through holes 36 are provided in the fixing member 33 in a 4 × 4 two-dimensional array, and when each set is inserted and fixed in the fixing member 33, the through holes 36 are arranged in the spherical shape. There is. Note that all the through holes 36 extend toward the center point P ₀ of the spherical surface of the fixing member 33.

Therefore, the laser beam pattern image 45 formed on the virtual image plane 40 has the same arrangement as that of each set of the semiconductor lasers 10 and the like, and any laser beam spot 4
The diameter of 7 also becomes smaller with uniform characteristics. Also,
In the present embodiment, the virtual image plane 40 is a flat surface, but if necessary, the image formation position of each laser beam spot 47 is adjusted by moving the lens frame 25 (arrow m2), which will be described later. It may be done. In FIG. 1, the optical axis AX is shown for one set including the semiconductor laser 10 and the like, but the optical axis AX of all the sets is fixed to the fixing member 3.
The center point of the spherical surface of 3 (that is, the center point of the spherical array of each set of the semiconductor laser 10 and the like) P ₀ is passed.
In this embodiment, the virtual image plane 40 is located in the reduction optical system 20 side from the center point P _0, located between the center point P ₀ is the reduction optical system 20 and the virtual image plane 40, the light It may be in a beam cross state.

As shown in FIG. 2, the semiconductor laser 10 is inserted only into the convex side of the hole 36 formed in the fixing member 33, and the lens frame 25 is inserted into the concave side of the hole 36. ing. The hole 36 has the semiconductor laser 10 and the lens frame 25.
The shapes and sizes of the holes are set so that the optical axes AX1 and AX2 can be adjusted when the and are respectively inserted, and the holes are formed in the required arrangement of the laser beams. A groove may be formed instead of the hole 36,
Further, not only one row but also a plurality of rows may be formed so as to spread in a plane.

As described above, the laser beam spot 4
7 is formed on the virtual image plane 40 shown in FIG. 1, but each laser beam spot does not necessarily have to be on the same plane. For example, the surface of the rotating photosensitive drum or the surface of the photosensitive film fixed on the XY table for scanning may be positioned on the virtual image plane 60. When the laser beam pattern image 45 is re-imaged by the reduction optical system 50 shown in FIG. 3, the laser beam pattern image 45 may be appropriately formed on the virtual image plane 60. Each laser beam spot 4 is placed at a position in consideration of various aberrations of the reduction optical system 50 such as field curvature.
Preferably, 7 is formed.

By the way, not only the emission intensity of each laser beam B emitted from this embodiment is controlled by the photodiode, but also the image forming position, the direction of the laser beam, and the interval (laser beam position) are aligned. Need to be adjusted. The position adjustment of the semiconductor laser 10 and the focusing optical system 20 for aligning these will be described.

As shown in FIG. 2, the Z of the semiconductor laser 10 is
Since the position in the direction is constant, the lens frame (with the converging optical system 20 fixed inside) 25 is used for adjusting the imaging position.
Z of the converging optical system 20 by pushing or pulling the lens frame 25 from the outside of the fixing member 33 (arrow m2) in a state where the focusing optical system 20 is inserted.
This is done by adjusting the position along the direction. In addition, regarding the adjustment of the direction and the interval of the laser beam, the lens frame 25
Has a constant position in the XY directions, so that the semiconductor laser 10
Spherical movement along the convex surface of the fixing member 33 (arrow m1)
Can be done by.

The adjustment of the image forming position, the direction of the laser beam and the interval is carried out by manually moving each semiconductor laser 10 and the lens frame 25 while enlarging and looking at the laser beam spot 47 on the virtual image plane 40. Alternatively, it may be automatically performed by an appropriate detection means. For example, an optical system jig that holds the lens frame 25 from the concave side of the fixing member 33 is used, and the optical system jig is used in the Z direction (optical axis A
By moving along the X2 direction) (arrow m2 in FIG. 2), the position of the converging optical system 20 can be adjusted. In addition, the semiconductor laser 10 from the convex side of the fixing member 33.
The position of the semiconductor laser 10 can be adjusted by using a semiconductor laser jig that holds the semiconductor laser 10 and moving the semiconductor laser jig along the XY directions (arrow m1 in FIG. 2).

When the above position adjustment is automatically performed, the optical system driving means for moving the optical system jig and the driving of the optical system driving means are driven by the light amount value of the laser beam spot 47 on the virtual image plane 40. It is sufficient to use a control unit that controls based on the output result of the detection unit that detects the above. The amount of movement of the semiconductor laser 10 and the lens frame 25 can be determined based on the result of comparison between the output of the detection means and a preset reference value.

The semiconductor laser 10 and the lens frame 25 can be fixed to the fixing member 33 by welding with a YAG laser. For example, a semiconductor laser 10 using a YAG laser
It can be fixed by welding at two points on the surface where it is pressed. In this welding with the YAG laser, it is preferable that the fixing member 33, the lens frame 25, and the semiconductor laser 10 are made of the same material (for example, iron) because the welding can be performed easily and stably.

When the semiconductor laser 10 is turned on in the present embodiment adjusted as described above, the converging optical system 20 is turned on.
Is a 4 × 4 two-dimensional array-shaped laser beam pattern image (laser beam spot diameter: 60 to 80 μm, spot spacing: 200 nm / inch) formed by a semiconductor laser 10 and a focusing optical system 20. 120 μm) 4
5 is formed.

By the way, the resolution of a general laser beam printer is 400 dots / inch. When used in a plate-making color scanner or the like used for making an original plate for offset printing, it is necessary to increase the resolution so as to correspond to a density of about 4000 dots / inch, but only with the converging optical system 20
It can only be reduced to 770 dots / inch. Therefore, in the present embodiment, in order to further reduce the 200 dot / inch pattern in order to create the 4000 dot / inch pattern, it is preferable that the reduction optical system 50 is provided.

That is, the laser beam pattern image 45 is further reduced to 1/20 by the reduction optical system 50 shown in FIG.
Laser beam pattern image with a density of 4000dot / inch (laser beam spot diameter: 3-4μm, spot interval: 6μ
m) can be formed on the surface of the photoreceptor.
Depending on the dot size required as a light source, a converging optical system or a reducing optical system having different magnifications may be used, and the converging optical system 20 alone may be used without using the reducing optical system 50 to obtain 200 dots / inch. Size laser beam pattern image 45
May be formed. Regarding the number of spots, the number of semiconductor lasers 10 or the like may be changed as necessary, but a spot of 4 μm is 6 μm in a 10 × 10 pattern.
It is common in practice to arrange them at m intervals.

When the present embodiment is applied to a laser beam printer, a color scanner for plate making, etc., the laser beam pattern image 45 shown in FIG. Image) can be formed on the surface of the photosensitive drum, for example. However, as shown in FIG.
It is not necessary that all six laser beam spots 47 be formed at the same time. By performing ON / OFF operation of each semiconductor laser 10 according to image information, processing is performed by multi-beam scanning using a plurality of laser beams. It is possible to increase the speed. For example, the scanning speed of the laser beam on the surface of the photosensitive drum can be set to about 16 times the scanning speed by the conventional method of scanning with one laser beam. Further, if the scale of this embodiment is enlarged as necessary, the required speed-up rate can be achieved.

Since the semiconductor laser 10 performs pulse driving, ON / OFF operations are independently repeated. Therefore, it is possible to change the gradation by positively changing the emission intensity of the semiconductor laser 10 that is turned on. Further, since the characteristics of the laser beams aligned by the above-described adjustments are uniform, it is possible to provide the reduction optical system 50 with compatibility as a unit. Further, the semiconductor laser 10, the focusing optical system 20, and the fixing member 3
As No. 3, it is possible to use those having the same performance and the same structure, so that the cost is low, and the position adjustment, replacement repair, etc. are easy. Also, the replacement for each embodiment is easy.

By the way, the above-mentioned Japanese Patent Laid-Open No. 3-150.
The present inventor has proposed the following semiconductor laser array light source in Japanese Patent Application No. 4-169801 as a structure capable of achieving cost reduction and compactness as compared with the device of No. 18. As one specific example thereof, a plurality of semiconductor lasers arranged in an array and a converging optical system for converging a laser beam emitted from each semiconductor laser corresponding to the semiconductor lasers are provided, and the semiconductor lasers In each of the sets of converging optical systems, in which the respective laser beam spots are adjusted to gather at predetermined positions at predetermined intervals to form a laser beam pattern image, the optical axis of the converging optical system is The semiconductor lasers located in parallel to each other and located further outside the semiconductor laser located in the central portion of the array of semiconductor lasers are arranged so that the emission centers of the semiconductor lasers are farther from the optical axis of the converging optical system. Can be mentioned. Therefore,
The beam characteristics formed by such a configuration with parallel eccentricity between the optical axis of the semiconductor laser and the optical axis of the converging optical system were examined as follows.

FIG. 9 shows the arrangement and the optical path of one set of the semiconductor laser 10 and the reduction optical system 20 in the configuration with the above eccentricity. The eccentricity d between the optical axis of the semiconductor laser 10 and the optical axis of the reduction optical system 20 is 6 mm. Distance between the semiconductor laser 10 and the reduction optical system 20 (axial distance between the light emitting point of the semiconductor laser 10 and the front side surface of the reduction optical system 20)
Is 4 mm. The distance between the reduction optical system 20 and the photoconductor surface 60 (the axial upper surface distance between the rear surface of the reduction optical system 20 and the photoconductor surface 60) is 80 mm. According to this configuration,
It has the advantages that the structure is simple and a laser beam spot with a medium density of spot density can be formed.

However, if the semiconductor laser 10 located outside the semiconductor laser 10 located in the central portion of the array of the semiconductor lasers 10 has a larger decentering amount d, the central portion of the array of the converging optical system 20 is larger. The light amount of the laser beam incident on the converging optical system 20 is reduced as the converging optical system 20 is located outside the converging optical system 20. Accordingly, the brightness of the beam spot formed on the surface 60 of the photoconductor also becomes darker as the beam spot is farther from the center of the laser beam pattern image.

Further, since the semiconductor laser 10 located outside the semiconductor laser 10 located in the central portion of the array of the semiconductor lasers 10 has the larger decentering amount d, the central portion of the array of the converging optical system 20 is larger. The ellipticity (ratio of the minor axis to the major axis of the ellipse) of the laser beam spot formed on the photoconductor surface 60 becomes larger as the converging optical system 20 located outside the converging optical system 20 located at. I will end up. As a result, it is difficult to construct a large array structure. This is because it is necessary to have a configuration with the above eccentricity at a large inclination angle.

Here, the shapes of the laser beam spots actually formed will be compared and examined. FIG. 5 shows three-dimensionally the result of measuring the intensity distribution on the XY plane at the image forming position of one laser beam spot (FIG. 1) 47 formed by one semiconductor laser in this embodiment. Shown in a graph. The laser beam spot 47 is formed by a laser beam whose principal ray is orthogonal to the virtual image plane 40 on which the surface of the photoconductor or the like is located. Therefore, the tilt angle (an angle formed by the perpendicular to the virtual image plane 40 and the principal ray of the laser beam, and hereinafter represented by “θ”) is 0 °.

Further, I = 20, 50, 80 on the XY plane of the laser beam intensity (hereinafter referred to as "I") in FIG.
The intensity distribution (θ = 0 °) at the% position is shown in FIG. The spot diameter at I = 20% is 47 μm, and the spot diameter at I = 50% is 32 μm. θ = 15, 30 ° (The distance between the semiconductor laser 10 and the like at θ = 0 ° is 21 mm and 42 mm, respectively)
The intensity distribution at is also shown in FIGS. 7 and 8 as in FIG. The configuration with eccentricity (d = 6 m) is also shown in FIG. 10 as in FIG.

Configuration of essential parts of this embodiment shown in FIGS. 5 and 6.
At (θ = 0 °), the diameter of the formed laser beam spot
(The spot diameter at the position where the light intensity is 50%) is 32.
It became a perfect circle of μm. On the other hand, in the configuration shown in FIG. 9, θ = 4.4 °, and the shape of the laser beam spot formed on the surface 60 of the photoconductor was an ellipse having a short axis of 32 μm and a long axis of 38 μm. Further, in the configuration of the main part of this embodiment shown in FIG. 7 (θ = 15 °), the shape of the laser beam spot formed is an ellipse with the short axis of 32 μm and the long axis of 34 μm. In the configuration of the main part of the example (θ = 30
), The shape of the laser beam spot formed was an ellipse with a short axis of 32 μm and a long axis of 37 μm. Therefore,
According to the present embodiment, even in a one-dimensional or two-dimensional array having a large number of beams, the ellipticity of the laser beam spot 47 in the peripheral portion having a large inclination angle θ can be reduced and the spot shape can be made closer to a perfect circle. is there. Therefore, it is possible to form a semiconductor laser array light source having a large number of spots.

FIG. 4 is a schematic perspective view showing the appearance of the second embodiment of the present invention. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals. Instead of using the spherical fixing member 33 in the first embodiment and arranging the semiconductor laser 10 and the converging optical system 20 in a two-dimensional array, in this embodiment, an arc-shaped fixing member 53 is used. The structure is the same as that of the first embodiment except that the semiconductor laser 10 and the converging optical system 20 are arranged in an arc shape and a one-dimensional array shape. The laser beam pattern image 55 formed on the virtual image plane 40 has a linear array, and the optical axes AX of each set are all center points of the arc of the fixed member 53.
(That is, the center point of the arcuate array of each set such as the semiconductor laser 10) P ₀ is passed. As can be seen from the first and second embodiments, according to the present invention, it is possible to form various array-shaped laser beam patterns such as a planar shape and a linear shape.

[0038]

As described above, according to the present invention, a plurality of semiconductor lasers arranged in a one-dimensional or two-dimensional array, and laser beams emitted from the respective semiconductor lasers corresponding to the semiconductor lasers. And a focusing optical system for focusing each of the semiconductor laser and the focusing optical system, wherein each of the semiconductor laser and the focusing optical system is spherical or circular so that each laser beam spot gathers at a predetermined position at a predetermined interval to form a laser beam pattern image. Since they are arranged in an arc shape, a means for turning on / off a laser beam divided by an electric shutter and a large-scale expensive reduction projection lens which are conventionally required are unnecessary. As a result, it is possible to realize a semiconductor laser array light source whose cost and size are reduced. Moreover, it is possible to adjust so that each laser beam spot is gathered at a predetermined position at a predetermined interval and has uniform characteristics to form a laser beam pattern image, and as a result, easy manufacture is possible. A semiconductor laser array light source can be realized with such a structure.

Further, by providing a reduction optical system which reduces the laser beam pattern image and re-images it at a predetermined position, it becomes possible to form a laser beam pattern image having a high resolution, which is high in a plate-making color scanner or the like. It is possible to realize a semiconductor laser array light source that can be applied to applications requiring resolution.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing the configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view of a main portion of the first embodiment of the present invention.

FIG. 3 is a reduction optical system 5 used in the first embodiment of the present invention.
The figure which shows the lens structure of 0, and an optical path.

FIG. 4 is a perspective view schematically showing the configuration of a second embodiment of the present invention.

FIG. 5 is an intensity distribution (θ = 0 °) at an image forming position of a laser beam spot formed by a set of the semiconductor laser 10 and the converging optical system 20 in the first embodiment of the present invention.
A three-dimensional graph.

FIG. 6 shows the intensity distribution (θ = 0) at the image forming position of the laser beam spot formed by the set of the semiconductor laser 10 and the converging optical system 20 in the first embodiment of the present invention.
(°) graph.

FIG. 7 shows the intensity distribution (θ = 15) at the imaging position of the laser beam spot formed by the pair of semiconductor laser 10 and the converging optical system 20 in the first embodiment of the present invention.
(°) graph.

FIG. 8 is an intensity distribution (θ = 30) at an image forming position of a laser beam spot formed by a set of the semiconductor laser 10 and the converging optical system 20 in the first embodiment of the present invention.
(°) graph.

FIG. 9 is a diagram showing a set of the semiconductor laser 10 and the focusing optical system 20 used in the reference example of the first embodiment to the surface 60 of the photosensitive member.
The figure which shows the optical path to.

FIG. 10 shows an intensity distribution (d = 6) at an image forming position of a laser beam spot formed by a set of the semiconductor laser 10 and the converging optical system 20 in the reference example of the first embodiment.
(mm) showing the graph.

[Explanation of symbols]

10 ... semiconductor laser 20 ... focusing optics 25 ... lens frame 33 ... fixing member 40 ... virtual image plane 45 ... laser beam pattern image 47 ... laser beam spot 50 ... reduction optical system 60 ... photoreceptor surface P ₀ ... center point

Claims (2)

[Claims] 1. A plurality of semiconductor lasers arranged in a one-dimensional or two-dimensional array, and a converging optical system for converging a laser beam emitted from each semiconductor laser corresponding to the semiconductor lasers. Each set of the semiconductor laser and the converging optical system is arranged in a spherical shape or an arc shape so that each laser beam spot gathers at a predetermined position at a predetermined interval to form a laser beam pattern image. A semiconductor laser array light source. 2. The semiconductor laser array light source according to claim 1, further comprising a reduction optical system that reduces the laser beam pattern image and re-images it at a predetermined position.