JP3681925B2 - Displacement measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a displacement measuring apparatus such as a positioning or displacement sensor using the coherency (coherence) of a semiconductor laser.
[0002]
[Prior art]
The optical device that this type of conventional method is the target is the paper “We have published a paper“ Ultra-compact hybrid micro-encoder ”. 3, 16a-ZC-1, pp. 879, and Japanese Patent Application No. 9-82821 “Displacement Measuring Device”.
[0003]
FIG. 6 shows a conventional displacement measuring apparatus for detecting a semiconductor laser 5 of a light emitting element provided on an electrode on a base substrate 1 and a solder formation pattern 4, an optical waveguide 3, signals (A and B phase signals) and monitoring. The detection photodiode 6 is a light receiving element such as the above, and an external mirror 7. These are configured so that the core heights of the light receiving light emitting element and the waveguide coincide with each other, and have a scale composed of the reflection mirror 7 on the outside, and measure the displacement, movement amount, rotation angle, etc. of the scale. This type of conventional optical device is very small and built in a small motor or actuator, and has the excellent feature of being able to detect the rotation angle or the amount of movement with high resolution, but the reflected light from the external reflection mirror is directly or directly It has been found that since the light passes through the core of the optical waveguide and enters the light emitting element again, the measurement of the displacement of the external mirror and the like is hindered.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a displacement measuring apparatus configured to prevent return light and not to increase the overall size of the apparatus.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a displacement measuring apparatus in which a coherent light emitting element, a light receiving element, and an optical waveguide are integrally formed on a base substrate, wherein the detection unit of the light receiving element is emitted from the optical waveguide. The beam having the highest light intensity at the center exiting from the exit end face of the optical waveguide is reflected by the reflection mirror provided outside and reaches the detection unit of the light receiving element after being reflected by the reflection mirror. the Yes tilt the displacement measuring device comprising a base substrate, so that the beam which spreads out from the center emitted from the exit end face is prevented from returning to the reflected external reflection mirror the exit end face again Te, the accepted The interference light emitting element or the terrace provided in the vicinity of the front end face of the optical waveguide is cut off .
[0007]
In the displacement measuring apparatus, the coherent light emitting element is a semiconductor laser.
[0008]
According to the present invention, in the displacement measuring apparatus, the light receiving element is a photodiode.
[0009]
That is, a light-shielding terrace having a height close to the emission height is formed in front of the light emission end face from the light-emitting element or the optical waveguide, and the base substrate is tilted so that the emission height of the light-emitting element and the light-receiving portion of the light-receiving element By not matching the heights, there is no return light, thus allowing more accurate measurements. Moreover, the inclination angle of the base substrate for preventing the return light can be greatly reduced by introducing the light shielding terrace.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0011]
[Embodiment 1]
1 to 4 are diagrams for explaining a first embodiment of the present invention. As shown in FIG. 1, an optical waveguide 3, electrodes and a solder formation pattern 4 are formed on a base substrate 1, and a semiconductor laser 5 as a coherent light emitting element and a detection photodiode 6 as a light receiving element are bonded and integrated. Make the configuration. Reference numeral 7 denotes an external mirror.
[0012]
That is, the light reflected from the external mirror 7 of the diffusing (expanding) coherent laser emitted from the optical waveguide 3 is detected, and the relationship between the detected intensity and the amount of movement of the external mirror 7 is used to determine the detected intensity. This is a displacement measuring device for obtaining the amount of movement of the mirror 7. As shown in FIG. 2, a light-shielding terrace 2 is formed on the base substrate 1. The height of the terrace 2 is set to be in the vicinity of the front of the emission end face of the semiconductor laser 5 or the optical waveguide 3. In the first embodiment, the base substrate 1 is formed by forming (100) oriented silicon by anisotropic etching with an aqueous solution of KOH and then forming a 0.5 μm thermal oxide film.
[0013]
As shown in FIG. 3, the heights of the centers of the emission end faces of the semiconductor laser 5 or the optical waveguide 3 are made to coincide with each other. The detection photodiode 6 is bonded so that the light receiving portion 61 is above the emission end face portion of the optical waveguide 3. In the first embodiment, the height h1 of the core 31 of the optical waveguide 3 and the center of the light emitting portion of the semiconductor laser 5 are substantially the same and is 6.5 μm. Further, the height h2 of the light receiving portion 61 of the detection photodiode 6 is about 200 μm.
[0014]
The encoder body including the base substrate 1 is installed at an angle α with respect to the external mirror 7 of the scale. The optimum tilt angle α is given by α = (1/2) ^* Arctan {(h2−h1) / d1}. At this optimum angle α, the beam 8 having the highest light intensity emitted from the emission end face of the optical waveguide 3 reaches the light receiving portion 61 of the detection photodiode 6 after reflection by the external mirror 7. Here, d1 is the distance from the external mirror 7 to the detection photodiode 6. In the displacement measuring apparatus used in the first embodiment, since d1 = 1330 μm, α is inclined by 4 degrees. When the height h3 of the light-shielding terrace 2 having the effect of preventing return light is 4.5 μm, that is, 2 μm below the boundary between the core 31 and the lower cladding 32 of the optical waveguide 3, the length of the terrace 2 (light guide If the distance d2 from the emission end face of the waveguide 3 to the front face of the terrace 2 is 100 μm, light can be shielded even when the optimum inclination angle α is 4 degrees, and return light can be prevented. In the case of the inclination angle α, of the beams emitted from the exit end face of the optical waveguide 3 and spreading out of the center, the beam having the spread angle γ of the vicinity of the angle α is reflected by the external mirror 7 and again on the exit end face of the optical waveguide 3. May come back. Therefore, by shielding the beam 9 spreading at an angle equal to or larger than the angle α with the terrace 2, it is possible to block the light reflected by the external mirror 7 and returning to the end face of the optical waveguide 3 again.
[0015]
The longer the terrace 2 is, the greater the improvement can be achieved by raising the terrace 2 to the borderline between the core 31 and the lower clad 32 of the optical waveguide 3. If the height h3 of the terrace 2 is 6.5 μm, that is, the height of the terrace 2 is increased to the boundary between the core 31 and the lower clad 32 and the length d2 of the terrace 2 is increased to 200 μm, the base necessary for preventing the return light The inclination angle α of the substrate 1 can be reduced to about 1.5. If a terrace for light shielding is not introduced, as shown in FIG. 4, the tilt angle α necessary to completely prevent the return light is about 10 degrees equal to the beam vertical spread angle (full value half angle) γ. And it becomes a tremendous big angle.
[0016]
[Embodiment 2]
FIG. 5 shows a second embodiment of the present invention, which is a displacement measuring device that measures the same displacement without an optical waveguide. In FIG. 5, the same parts as those in FIG. When light emitted from the semiconductor laser 5, which is a light emitting element, is used directly instead of light emitted from the optical waveguide, the vertical spread angle (full value half angle) γ is 30 to 50, which is the optical waveguide of the first embodiment. Spread 3 to 5 times the case. However, it has been found that the light shielding effect is determined only by the height and length of the terrace 2 formed on the front surface of the emission end, and is independent of the spread angle of the emitted light from the semiconductor laser 5.
[0017]
As described above, in the first and second embodiments, the method for preventing the return light is described for the displacement measuring device using the spread of the beam. Basically, the displacement measuring device having the light emitting element and the light receiving element on the base substrate. Needless to say, this is effective. Further, although the light-shielding terrace is manufactured by using anisotropic etching of silicon, it is obvious that the same effect can be expected by a method of depositing another metal film.
[0018]
【The invention's effect】
As described above, according to the present invention, since light can be shielded at an optimum base tilt angle, a signal having high strength and low noise can be realized with a simple structure and a large size (so that the size of the light shielding terrace can be reduced) Although the length of the terrace was large, it was realized because the length of the terrace was as small as 200 μm.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of the present invention.
FIG. 2 is a perspective view showing a light-shielding terrace according to Embodiment 1 of the present invention.
FIG. 3 is an explanatory diagram showing an operation of the first embodiment of the present invention.
FIG. 4 is a perspective view for explaining Embodiment 1 of the present invention.
FIG. 5 is a perspective view showing a second embodiment of the present invention.
FIG. 6 is a perspective view showing a conventional displacement measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base substrate 2 Terrace for light shielding 3 Optical waveguide 31 Core 32 Lower clad 4 Electrode and solder formation pattern 5 Semiconductor laser (light emitting element)
6 Photodiode for detection (light receiving element)
61 Light-receiving part 7 of detection photodiode (light-receiving element) External mirror 8 Beam 9 radiating from the waveguide exit end face The beam 9 having the highest light intensity at the center.

Claims (3)

In a displacement measuring device in which a coherent light emitting element, a light receiving element and an optical waveguide are integrated on a base substrate,
The detection part of the light receiving element is at a position higher than the emission end face of the optical waveguide,
The base substrate with respect to the reflection mirror includes the base substrate so that a beam having the highest light intensity at the center emitted from the emission end face of the optical waveguide is reflected by the reflection mirror provided outside and reaches the detection unit of the light receiving element. The displacement measuring device is tilted,
Near the front of the coherent light emitting element or the output end face of the optical waveguide so that the beam exiting from the center exiting from the exit end face is reflected by the external reflection mirror and does not return to the exit end face again. Displacement measuring device characterized in that it is blocked by a terrace . 2. The displacement measuring apparatus according to claim 1 , wherein the coherent light emitting element is a semiconductor laser. 3. The displacement measuring apparatus according to claim 1 , wherein the light receiving element is a photodiode.

Images