JPH0228613A - Semiconductor laser beam source unit - Google Patents

Abstract

PURPOSE:To align the longitudinal section directions of laser beams which are multiplexed in parallel to each other and to making fine adjustments in a polarizing direction and to increase the power of the multiplexed light by adjusting the polarizing direction by using a 1/2-wavelength plate in the case of multiplexing the laser beams by using a polarization beam splitter. CONSTITUTION:A 1st semiconductor laser 1 and a 2nd semiconductor laser 11 are provided so that the longitudinal beam section directions of the 1st laser beam 2 and 2nd laser beam 12 are parallel to each other in the optical paths behind the polarization beam splitter 5. Then a 1st 1/2-wavelength plate 4 is provided between the 1st semiconductor laser 1 and polarization beam splitter 5 and a 2nd 1/2-wavelength plate 14 is provided between the 2nd semiconductor laser 11 and polarization beam splitter 5 respectively. Further, the sum of the angle of rotation of the polarizing direction of the 1st laser beam 2 by the 1st 1/2-wavelength plate and the angle of rotation of the polarizing direction of the 2nd laser beam 2 by the 2nd 1/2-wavelength plate 12 is set to 90 deg.. Consequently, the beam shape of the multiplexed laser beam is made coincident and the utilization efficiency of the laser beams is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a semiconductor laser light source device used in a light beam scanning device, etc., and more particularly, to a semiconductor laser light source device for combining laser beams emitted from a plurality of semiconductor lasers into one laser beam. The present invention relates to a semiconductor laser light source device.

(Prior Art) Conventionally, light beam scanning devices that scan a light beam by deflecting it with an optical deflector have been widely used in, for example, various scanning recording devices, scanning reading devices, and the like. One of the means for generating a light beam in such a light beam scanning device
As one example, semiconductor lasers have been conventionally used. 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 has an output of at most 20 to 30 Tr when continuously oscillated.
Light beam scanning devices that require small LW and therefore high-energy scanning light, such as recording materials with low sensitivity (
It is extremely difficult to use it in a scanning recording device that records on DRAW materials such as metal films, amorphous films, etc.).

Also, some types of phosphors may be exposed to radiation (X-rays, α-rays, β-rays, γ-rays,
When this phosphor is irradiated with excitation light such as visible light, a portion of this radiation energy is accumulated in the phosphor. It is known that stimulable luminescence is exhibited, and by using such a stimulable phosphor, radiation image information of a subject such as a human body can be collected once it has a layer made of a stimulable phosphor (stimulable phosphor). Recording is performed on a stimulable phosphor sheet, the stimulable phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescence light, and the resulting stimulated luminescence light is read photoelectrically to generate an image signal. The present 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. 1983-1991). -1242
No. 9, No. 55-116340, No. 55-163472
No. 56-11395, No. 56-104645, 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 information.

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. In a semiconductor laser light source device that combines multiple laser beams in this way, for example, two laser beams emitted with polarization directions different from each other by 90'' are incident on a polarizing beam splitter from different directions. , a device is known that emits light onto the same optical path and multiplexes it.

However, the cross-sectional shape of the laser beam emitted from the semiconductor laser and made into a parallel beam by the collimator lens is an ellipse whose longitudinal direction is perpendicular to the pn junction surface of the semiconductor laser, and the polarization direction of the laser beam is Since it is in the short axis direction of the ellipse, when two laser beams with polarization directions different by 90'' are input to the polarization beam splitter and combined, the cross section of the combined laser beam is , the ellipses end up intersecting each other in a criss-cross pattern. Light with a cross-section like this is a superposition of mutually incoherent laser beams whose major axes (or minor axes) are perpendicular to each other. Therefore, the diameter of the cross section of the combined laser beam cannot be uniquely determined, which may complicate the design of the scanning optical system, or in some cases, the desired scanning optical system may not exist, which is undesirable in practice. .

Therefore, by placing a 1/2 wavelength plate on one optical path of the laser beams that are combined by the polarizing beam splitter and rotating only the polarization direction by 90'' without changing the cross-sectional shape, the two combined laser beams are A semiconductor laser light source device in which the longitudinal directions of the beam cross sections are made to coincide has also been proposed (Japanese Patent Publication No. 80-53857).

(Problem to be solved by the invention) By the way, as mentioned above, the polarizing beam splitter and the 172
In order to maximize the amount of combined light in a device that performs multiplexing using a wavelength plate, the polarization direction of the two laser beams incident on the polarization beam splitter must be set so that the reflectance and transmittance of the beam splitter are maximized, respectively. It is necessary to correctly adjust the wavelength in a predetermined direction, and for this purpose, it is necessary to improve the positional accuracy of the two semiconductor lasers and the 1/2 wavelength plate. However, it is difficult to always fix the semiconductor laser to a laser mount with high precision in the direction of rotation around the laser emission axis, and once the semiconductor laser is fixed, it is usually impossible to adjust the position thereafter. On the other hand, a half-wave plate is generally arranged so that its main axis can be rotated in a plane perpendicular to the optical path of the incident laser beam, and the polarization direction can be finely adjusted even after it is installed in the device. be able to. Therefore, for one laser beam with a 1/2 wavelength plate placed on the optical path,
The polarization direction when incident on the polarizing beam splitter can be adjusted with high precision to maximize the transmittance or reflectance of the polarizing beam splitter. However, regarding the other laser beam, the mounting of the semiconductor laser depends on the precision of the light. Utilization efficiency may become low.

The present invention has been made in view of the above problems, and it is possible to match the beam shape of the combined laser beams in a device that combines laser beams emitted from semiconductor lasers using a polarizing beam splitter. It is an object of the present invention to provide a semiconductor laser light source device that is capable of achieving high efficiency and maximizing the efficiency of laser beam use.

(Means for Solving the Problems) A semiconductor laser light source device of the present invention includes a first semiconductor laser and a second laser beam that respectively emit a first laser beam and a second laser beam that are combined by a polarizing beam splitter. A semiconductor laser is disposed in an optical path after passing through the polarizing beam splitter so that the longitudinal directions of the beam cross sections of the first laser beam and the second laser beam are parallel to each other, and the first semiconductor laser and the polarizing beam splitter A first 1/2 wavelength plate is provided between the second semiconductor laser and the polarizing beam splitter, and a second 1/2 wavelength plate is provided between the second semiconductor laser and the polarizing beam splitter. The present invention is characterized in that the sum of the rotation angle of the polarization direction of the first laser beam and the rotation angle of the polarization direction of the second laser beam by the second half-wave plate is 90''.

Note that when the laser beams are combined here, it means that the optical paths of each laser beam are parallel and close to each other to the extent that they can be practically treated as a single beam, and the optical axes of the laser beams do not necessarily coincide completely. It doesn't have to be.

In addition, if the longitudinal direction of the cross section of the combined laser beam is inclined both from the horizontal direction and the vertical direction and it is difficult to use it as a scanning beam etc. in that state, it is necessary to place the laser beam on the optical path after combining. What is necessary is to provide a beam cross-sectional shape rotation means that rotates the cross-sectional shape of the beam by a predetermined angle and adjusts the longitudinal direction of the beam cross-section to a desired direction.

(Function) In the above light source device, the directions of the two semiconductor lasers are adjusted so that the longitudinal directions of the cross sections of the combined laser beams are close to each other and parallel to each other, and the light of the two laser beams is Since 172-wavelength plates are provided on each road and the polarization direction of each laser beam is rotated in accordance with the polarization beam splitter, both laser beams can be combined with their beam cross sections aligned in a fixed direction. In addition, since a 1/2 wavelength plate is provided on the optical path of both laser beams, even if the mounting position of the semiconductor laser is slightly rotated, the polarization direction can be adjusted by slightly rotating the 1/2 wavelength plate. By adjusting the polarizing beam splitter in a predetermined direction, it is possible to maximize the reflectance and transmittance of the polarizing beam splitter.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of a semiconductor laser light source device according to an embodiment of the present invention.

A first laser beam 2 emitted from a first semiconductor laser 1 passes through a collimator lens 3 to become a parallel beam, and then passes through a first half-wave plate 4 and enters a polarizing beam splitter 5. do. On the other hand, the second semiconductor laser 11
is arranged such that its laser emission axis is perpendicular to that of the first semiconductor laser 1, and the second laser beam 12 emitted from the second semiconductor laser 11 passes through a collimator lens 13 and becomes a parallel beam. After that, the laser beam passes through the second 172-wavelength plate 14 and enters the polarizing beam splitter 5 from a direction perpendicular to the first laser beam 2.

The polarizing film 5a of the polarizing beam splitter 5 transmits, for example, P-polarized light and reflects S-polarized light. Polarization direction A of the first laser beam 2! The direction corresponding to the P polarization direction is indicated by arrow XI, and the direction corresponding to the S polarization direction is indicated by arrow y1.
The polarization direction A2 of is indicated by the arrow x in the direction corresponding to the P polarization direction.
When the direction corresponding to the S polarization direction in z is represented by an arrow y2, it is tilted 45'' clockwise from the direction of the arrow x2.

Also, the first laser beam 2 after passing through the collimator lens 3
As shown in FIG. 2(a), the cross-sectional shape of the second laser beam 12 is an ellipse with the short axis direction being the polarization direction A, and the cross-sectional shape of the second laser beam 12 after passing through the collimator lens 13 is as follows. As shown in FIG. 2(b), it is an ellipse with the polarization direction A2 as the short axis direction.

The first 1/2 wavelength plate 4 rotates the polarization direction of the incident first laser beam 2 counterclockwise by 45″, and the second 172-wave plate 14 rotates the incident second laser beam 2 by 45″.
The polarization direction of the laser beam 12 is 45 in the counterclockwise direction.
''. Therefore, the first 1/2 wavelength plate 4
The polarization direction of the first laser beam 2 that has passed through is in the direction of arrow Y1 as shown in FIG. 3(a), and the first laser beam 2 becomes S-polarized light. On the other hand, the polarization direction of the second laser beam 12 that has passed through the second 172-wavelength plate 14 is in the direction of arrow x2, as shown in FIG.
The laser beam 12 becomes P-polarized light. Therefore, the first laser beam 2 is reflected by the polarizing beam splitter 5, and the second laser beam 12 is transmitted through the polarizing beam splitter 5, and both laser beams are emitted onto the same optical path and combined. The first and second semiconductor lasers are shown in FIG. 2(a).

As shown in (b), the laser beams 2 and 12 are arranged in advance so that the elongated directions of the ellipses of the cross sections coincide after passing through the polarizing beam splitter 5, and the first laser beam 2 and the second laser beam 12 do not change their cross-sectional shapes even if they both pass through the l/2 wavelength plate 4.14, the light resulting from the combination of the first laser beam 2 and the second laser beam I2 has a P polarization component and an S polarization component. The light has a single elliptical cross-sectional shape with mixed polarization components. Therefore, according to this light source device, it is possible to combine two laser beams to obtain high-output light, and also to focus the obtained light on a desired spot using a scanning lens, cylindrical lens, etc. becomes easier. In addition, in this device, since 172-wavelength plates 4 and 14 are arranged in the optical path of the first laser beam 2 and the optical path of the second laser beam, the semiconductor lasers 1 and 11
If the laser rotates from a predetermined position when it is fixed to a laser mount, etc., and the polarization direction does not correspond to the above-mentioned direction, make a fine adjustment by slightly rotating the 1/2 wavelength plate 4.14. If you do this, the first laser beam 2,
The polarization direction of the second laser beam 12 can always be adjusted to the direction in which the reflectance and transmittance of the polarizing beam splitter 5 are maximized.

In addition, in the light source device of the present invention, the semiconductor lasers are arranged so that the cross-sectional shapes of the two laser beams substantially match when combined, and two 1/2 wavelength plates are used to input the laser beams into the polarizing beam splitter. Until 1: The polarization directions of the two laser beams need to be different from each other by 90@, and the polarization direction of the laser beam before entering the 1/2 wavelength plate or the rotation of the polarization direction by the 1/2 wavelength plate is sufficient. The angle can be set arbitrarily. For example, in the device shown in FIG. 1, a first semiconductor laser 1 and a second semiconductor laser 11
, and as shown in FIG. 4(a), 1' points in the direction of polarization of the first laser beam 2 in the direction of the arrow y! As shown in FIG. 4(b), the polarization direction A2' of the second laser beam 12 is tilted 30'' clockwise from the direction of the arrow x2. The position of the two-handed conductor laser may be determined so that the direction is the same. In that case, the first 1/2 wavelength plate 4 shall rotate the polarization direction of the first laser beam 2 by 60'' counterclockwise, and the second 1/2 wavelength plate 14 shall rotate the polarization direction of the first laser beam 2 by 60'' counterclockwise. The polarization direction of the laser beam 12 may be rotated by 30 degrees counterclockwise.In addition, the rotation angle of the polarization direction of the first laser beam by the first half-wave plate and the second 1/2 of
The rotation angle of the polarization direction of the second laser beam by the wave plate may be set to 75@, 15@, etc., respectively, and the rotation angles of both rotation angles may be set to 75@, 15@, etc., depending on the direction of the major axis (minor axis) of the cross section of the laser beam. The direction of the main axis of the 1/2 wavelength plate may be adjusted as appropriate so that the sum becomes 90''.

Furthermore, the cross sections of the two laser beams 2 and 12 combined by the polarizing beam splitter do not necessarily have to coincide completely as shown in FIG. If the longitudinal directions are parallel and the combined light can be treated as a single beam, then the
As shown in b), it may be slightly shifted in the short axis direction,
As shown in FIG. 6(c), it may be slightly shifted in the long sleeve direction. Furthermore, a plurality of first semiconductor lasers and a plurality of second semiconductor lasers may be provided, and the laser beams emitted from the first semiconductor laser group are arranged close to each other with equal polarization directions, the same as each other, or parallel to each other. The laser beam emitted from the second semiconductor laser group may also be made to enter the polarizing beam splitter in the same way. good.

By the way, in the light source device of the present invention shown in FIG. 1, it is easier to assemble the device by arranging each optical element so that its optical axis is directed horizontally or vertically.

However, in that case, the cross-sectional shape of the combined laser beam is such that the long sleeve direction is inclined obliquely as shown in FIG. When used as scanning light to scan a surface to be scanned that is conveyed in a direction, it becomes difficult to obtain a beam with a desired spot diameter on the scanning surface. In order to avoid such inconvenience, it is conceivable to rotate the entire light source device around the optical axis of the combined beam to change the cross-sectional shape of the beam to the desired direction. In addition to requiring a large-scale device holding mechanism, it is difficult to make fine adjustments after the device is installed. Therefore, when it is desired to rotate the cross-sectional shape of the combined laser beam, a beam cross-sectional shape that rotates the cross-sectional shape of the combined laser beam by a predetermined angle is placed on the optical path of the laser beam after passing through the polarizing beam splitter 5. A rotating means may be provided. A light source device equipped with such beam cross-sectional shape rotation means is shown in FIG. The light source device shown in FIG. 7 has the same structure as the device shown in FIG. 1 except for the beam cross-sectional shape rotation means, so those parts will not be explained here.

In the light source device shown in FIG. 7, a Dove prism 1o is provided as the beam cross-sectional shape rotation means on the optical path of the first laser beam 2 and the second laser beam 12 that are combined by the polarizing beam splitter 5. ing. As mentioned above, this Dove prism IO rotates the cross section of the combined laser beam by 45 degrees clockwise with its long sleeve tilted at 45 degrees from the horizontal direction. The combined beam that has passed has a beam cross-sectional shape whose longitudinal direction extends in the horizontal direction. Therefore, such a combined beam can be suitably used as a scanning beam that scans a horizontal or vertical plane, and there is no need to tilt the entire light source device. In addition,
The above-mentioned Dove prism does not necessarily have to rotate the beam cross section of the incident combined beam so that its longitudinal direction is horizontal; it can be rotated so that its longitudinal direction is vertical, etc. The beam cross section may be rotated in any direction depending on the purpose of the laser beam. Furthermore, the beam cross-sectional shape rotating means is one that can rotate the cross-sectional shape of the beam around the emission axis of the laser beam, and the rotation angle can be arbitrarily determined by selecting a rotating means with appropriate characteristics. Any member other than the above-mentioned Dove prism may be used.

(Effects of the Invention) As explained above, according to the semiconductor laser light source device of the present invention, when a polarization beam splitter is used to create a white wave of a laser beam, the polarization direction is adjusted using a 1/2 wavelength plate. By doing so, the longitudinal directions of the cross sections of the combined laser beams can be aligned in parallel. In addition, in the device of the present invention, the optical path of the first laser beam and the second
Since a 1/2 wavelength plate is disposed on each of the optical paths of the laser beams, it is possible to finely adjust the polarization direction after the device is assembled, and the power of the combined light can be maximized.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a semiconductor laser light source device according to an embodiment of the present invention, FIG. 2(a), (b), FIG. 3(a), (b)
. Figure 4 (a), (b), Figure 5 (a), (b)
6(a), (b), and (C) are schematic diagrams showing the cross-sectional state of the combined laser beam, and FIG. 7 is a schematic diagram showing the polarization direction and beam cross section of the laser beam. FIG. 3 is a schematic perspective view of a semiconductor laser light source device according to another embodiment. 1...First semiconductor laser 2...First laser beam 3.13...Collimator lens 4...First 1/2 wavelength plate 5...Polarizing beam splitter lO...Dub Prism 11...Second semiconductor laser 12...Second laser beam 14...1/2 wave plate (G) (b) (a) (b)

Claims (1)

[Claims] 1) A first laser beam emitted from a first semiconductor laser and a second laser beam emitted from a second semiconductor laser are polarized so that their respective polarization directions differ by 90 degrees from each other. In the semiconductor laser light source device, the first semiconductor laser and the second semiconductor laser are made to enter a polarizing beam splitter from different directions, and after passing through the polarizing beam splitter, are emitted onto substantially the same optical path and combined. is arranged such that the longitudinal directions of the beam cross sections of the first laser beam and the second laser beam are parallel to each other in the optical path after passing through the polarizing beam splitter, and the first laser beam and the polarizing beam A first half-wave plate is provided between the splitters, a second half-wave plate is provided between the second semiconductor laser and the polarizing beam splitter, and the first half-wave plate is provided between the second semiconductor laser and the polarizing beam splitter. the rotation angle of the polarization direction of the first laser beam, and the rotation angle of the polarization direction of the first laser beam, and
A semiconductor laser light source device characterized in that the sum of rotation angles of the polarization direction of the second laser beam by the /2 wavelength plate is 90°. 2) Beam cross-sectional shape rotation means for rotating the cross-sectional shapes of both laser beams by a predetermined angle is provided on the optical paths of the first laser beam and the second laser beam after passing through the polarizing beam splitter. Claim 1
The semiconductor laser light source device described above.