JPH01147304A - Evaluating device for light emission point position - Google Patents

Abstract

PURPOSE:To obtain the device which detects the position of the light emission point of a semiconductor laser in three dimensions with high accuracy by detecting an optical axis deviation and defocusing by using two four-division photodetectors and driving a stage and an actuator with their signals. CONSTITUTION:Light from a semiconductor laser element 3 on a sample table 4 is entered an optical box 19 on the XY stage 17. A collimator lens 12 and the actuator 13 which drives it are provided in the optical box 19, and the two four-division photodetectors 14 and 26 are provided across the optical system composed of total reflection mirrors 20 and 21, a half-mirror 22, and lenses 23-25. Then the outputs of those two four-division photodetectors 14 and 26 are inputted to a signal processing circuit 15 to detect the optical axis deviation and defocusing of the semiconductor laser element 3, and the XY stage 17 and actuator 13 are driven and controlled according to the detected values in such a direction that the deviation and defocusing are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an evaluation device for detecting the position of a light emitting point of a semiconductor laser element.

[Conventional technology]

In applied optical systems that use semiconductor laser elements as light sources,
The position of the light emitting point must be aligned with the optical axis.

For example, in a pickup optical system for a compact disk or the like, in order to miniaturize and mass-produce the semiconductor laser element, the package must be simply inserted into a predetermined position, and the optical axis must be aligned without adjustment. Therefore, a technique for assembling the light emitting point of the semiconductor laser element at the center of the package with an accuracy of approximately ±50 μm and an apparatus for evaluating it are required.

FIG. 5 is a configuration diagram showing a conventional device, and FIG. 6 is an explanatory diagram showing a semiconductor laser element 3. As shown in FIG. Next, a method for evaluating the position of a light emitting point using this device will be described. This light emitting point position evaluation method is primitive, and measurements are performed using a microscope 1 and an XY stage 2 with a micrometer. A semiconductor laser element 3 is fixed to a sample stage 4 on an X-Y stage 2 with a micrometer perpendicular to the microscope 1. The package outer diameter dimension L1 of the semiconductor laser element 3 is measured with a micrometer, and the center position 4 of the package is determined.

The light emitting point position 5 within the package is determined visually from the external dimensions of the semiconductor laser chip 6 and measured with a micrometer.

From the above measurement results, the positional deviation amounts ΔX and ΔY of the light emitting point position 5 from the center position of the bag 7 cage are determined. Note that the center axis of the microscope 1 and the top surface of the sample stage 4 form an angle θ of 90 degrees.

[Problem that the invention seeks to solve]

Since the conventional device is configured as described above, the position of the light emitting point of the semiconductor laser chip is inaccurate and has poor reproducibility.
Measurement took time. Also, in this method, X-Y
There was a problem that the positional deviation in the direction perpendicular to the stage 2 could not be measured.

The present invention has been made in view of these points, and its purpose is to provide a device that can easily measure the position of the light emitting point of a semiconductor laser element three-dimensionally with high accuracy and in a short time. be.

[Means for solving problems]

In order to achieve such an object, the present invention provides a sample stage for fixing a semiconductor laser device, a drive power source for causing the semiconductor laser device to emit light, an optical box for taking in the laser light from the semiconductor laser device, and a system for combining the optical box and the sample. The optical box includes an actuator, a collimator lens, first and second 4-split photodetectors, and at least one optical box. The above-mentioned total reflection mirror, half mirror, cylindrical lens, and plano-convex lens are provided, and the signal processing circuit processes the signals of the first and second 4-split photodetectors,
The stage drive section and the actuator control section are configured to output based on the output of the signal processing circuit.

[Effect]

In the light emitting point position evaluation device according to the present invention, the first four
A split photodetector detects a signal corresponding to the optical axis shift of the light emitting point, and a second 4-split photodetector detects a signal corresponding to the focal shift of the light emitting point and a signal corresponding to a minute optical axis shift. . By moving the stage and actuator so that the signals corresponding to the optical axis deviation and focal deviation are minimized, the optical axis and focus of the light emitting point can be aligned.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a light emitting point position evaluation device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall structure of this embodiment. In FIG. 1, 3 is a semiconductor laser device, 4 is a sample stage for fixing the semiconductor laser device 3, and 11
is a driving power source for the semiconductor laser element, and in this embodiment, A P C (
AutomaticPower Control) power supply is used. 12 is a collimator lens for collimating the laser beam, 13 is an actuator that moves the collimator lens 12 in the optical axis direction, 14 is a 4-split photodetector that detects the laser beam, and 15 is the output of the 4-split photodetector. a signal processing circuit for calculating the signal and correcting the optical axis and focus shift of the light emitting point; 16 is an actuator control unit; 17
moves the optical box 19 in a plane perpendicular to the optical axis direction
This is stage Y. Note that the optical system of the optical box 19 is the optical system when viewed from the side of the optical box. Reference numeral 18 denotes an X-Y stage drive unit that drives the x-y stage 17 by the signal processing circuit 15.

FIG. 2 is a configuration diagram showing the configuration of the optical system when the optical box 19 of FIG. 1 is viewed from above. In FIG. 2, laser light that has been made into parallel light by a collimator lens 12 is totally reflected by a total reflection mirror 20, and is separated into transmitted light and reflected light by a beam splitter 22. The reflected light passes through the second total reflection mirror 2
1, and the plano-convex lens 25 causes a large area of the first 4
The light is focused onto a split photodetector 26. On the other hand, the transmitted light of the beam splinter 22 is transmitted to a second 4-split photodetector 14 with a small area.
A cylindrical lens 23 and a plano-convex lens 24 tilted at 45 degrees relative to each other converge the light onto a small-area four-part photodetector 14. Each of the optical components configured as shown in FIG. Designed to focus light at the center.

FIG. 3 shows a diagram of the principle of signal processing by the 4-split photodetector 26.
FIGS. 4 fa) to fc) illustrate the principle of signal processing by the four-split photodetector 14. In FIG. 3, reference numeral 27 indicates a focal spot on the four-split photodetector 26 when the optical axis is shifted. In FIG. 4, reference numeral 28 is a light spot diagram on the four-split photodetector 14 when the focus is out of focus after the optical axis adjustment.

Next, the operation of the above embodiment will be explained. When the actuator 13 is stationary at the origin position, the light emitting point is displaced from the focal position of the collimator lens 12 by ΔZ in the optical axis direction, and by ΔX and ΔY in the X and Y axis directions in a plane perpendicular to the optical axis direction. Suppose there is. Here, ΔX, ΔY, and ΔZ are the amount of positional deviation (finally measured (Iff)) of the light emitting point with respect to the package center position 4 of the semiconductor laser element 3 (see FIG. 6).
shall be.

That is, at the origin position in the measurement start state of this apparatus, the center position 4 of the package is aligned with the focal position of the collimator lens 12. The semiconductor laser element 3 is driven at a constant optical output of about 3 mW, and the laser light incident on the collimator lens 12 is reflected by a total reflection mirror 20 and a half mirror 22.
A large-area 4-split photodetector 2 is formed using a plano-convex lens 25.
The light is focused on 6. As shown in FIG. 3, the light intensity distribution is determined by the photodetectors divided into four parts corresponding to 27a, 27b, 27c, and 27d. '13.14 is divided into four signals, and the sum signal of adjacent detectors (11+1
2) and (13+14) (II+12) - (13+1
4) and the difference (I
By determining 1+14)-(12+i) in the signal processing circuit 15, the amount corresponding to the optical axis deviation (ΔX, ΔY) is detected. Therefore, (11+12) −(13+14)
The optical axis deviation (ΔX, ΔY) is corrected by driving the X-Y stage 17 with the pulse motor 18 as the x-Y stage drive unit so that the two values of (11+l4)-(12+13) Do this.

The laser beam whose optical axis has been adjusted passes through the half mirror 22,
The light passes through a cylindrical lens 23 and a plano-convex lens 24 and is focused on a small-area four-part photodetector 14. The light intensity distribution is divided into four signals 11, 12, 13, and 14 by a photodetector divided into four corresponding to 28a, 28b, 28c, and 28d. As shown in FIG. 4 (al~(C1), the deviation (ΔZ) in the optical axis direction appears as a diagram of the optical spot 7 on the 4-split photodetector 14), so the sum signal of the opposing detectors (11+13) The difference (1) between and (+2+14)
The amount of defocus (ΔZ) is detected by calculating 1+13)−(12++4) by the signal processing circuit 15. Fourth
Figure (a) shows that the amount of defocus ΔZ is negative, and (b) shows that ΔZ
When is approximately zero, fc) indicates the case where ΔZ is positive. Therefore, the focal shift can be corrected by moving the actuator 13 in the optical axis direction using a signal from the actuator control section 16 so that the value of (I1+13)-(12+14) is minimized.

Furthermore, the optical axis alignment is again finely adjusted using the small-area 4-split photodetector I4 to improve measurement accuracy.

Through the above operations, the amount of movement of the X-Y stage 17 and the displacement of the actuator 13 can be controlled by the X-Y stage drive unit 18.
By outputting this from the actuator control unit 16, it is possible to three-dimensionally evaluate the amount of positional deviation of the light emitting point of the semiconductor laser element.

In the above embodiment, the actuator 13 is used to adjust the focal shift in the optical axis direction, but the XY stage 17 may be replaced by an XYZ stage.

Further, in the above embodiment, the optical box 19 is moved to the X-Y stage 17.
Although the sample stage 4 on which the semiconductor laser element 3 is fixed may be moved.

Furthermore, by coupling the semiconductor laser element 3 and the collimator lens 12 with an optical fiber, the position and orientation of the semiconductor laser element 3 are not subject to any restrictions with respect to the optical box 19. Although the above embodiment describes the case of detecting the position of a light emitting point, this embodiment can also be used as an alignment device for capturing laser light from a semiconductor laser element into an optical fiber when an optical fiber is used. You can also do that.

〔Effect of the invention〕

As explained above, the present invention includes an optical box, a signal processing circuit, a stage, and an actuator, so that the position of a light emitting point of a semiconductor laser element can be measured three-dimensionally with respect to a reference point. Accurately and quickly measure the amount of positional deviation.
There are effects that can be evaluated in three dimensions.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of a light emitting point position evaluation device according to the present invention, Fig. 2 is a block diagram showing an optical box constituting the device of Fig. 1, and Figs. 3 and 4 are signal FIG. 5 is an explanatory diagram for explaining the principle of processing, FIG. 5 is a configuration diagram showing a conventional device, and FIG. 6 is an explanatory diagram for explaining a light emitting point position evaluation method in the conventional device. 3... Semiconductor laser element, 4... Sample stage, 11...
・APC power supply, 12...Collimator lens, 13...
・Actuator, 14.26...4-split photodetector,
15...Signal processing circuit, 16...Actuator control unit, 17...X-Y stage, 18...X-Y stage drive unit, 19...Optical box, 20.21...All Reflection mirror, 22...Beam splitter, 23...
Cylindrical lens, 24.25... plano-convex lens.

Claims (1)

[Claims] A sample stage for fixing a semiconductor laser element, a driving power source for causing the semiconductor laser element to emit light, an optical box for taking in the laser light from the semiconductor laser element, a stage for changing the relative position of the optical box and the sample stage, and a signal. The optical box includes a processing circuit, a stage drive unit, and an actuator control unit, and the optical box includes an actuator, a collimator lens, first and second 4-split photodetectors, and at least one total reflection mirror, half mirror, or cylindrical mirror. and a plano-convex lens, and the signal processing circuit includes the first and second lenses.
A light emitting point position evaluation device characterized in that the stage driving section and the actuator control section output signals based on the output of the signal processing circuit.