JPS60256010A - Optical displacement detecting device - Google Patents

Abstract

PURPOSE:To facilitate assembly and stabilize detecting signals, by bringing parallel slits between light source and movable slits, allowing only parallel fluxes and nearly parallel fluxes among the fluexes from the source to pass and allowing the light fluxes from the source to assume apparently parallel fluexes. CONSTITUTION:Parallel slits 2 consisting of parallel laminations of extremely thin plates are inserted between light source 1 and movable linear scale 3. On a fixed scale 4, an opening is provided with a pitch deviated by an angle of 180 deg.C of output phase detected by a light receiving surface 6 corresponding to the surfaces 6 and 7 of a light receiving element 5 in accompaniment with the movable scale 3. As the flux from the source 1 enters into the scale 3 after passing through the parallel slits 2, the flux is restricted by the slit widths of the slits 2 and the parallel fluexs and only nearly parallel fluxes out of the light from the source can be taken out.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an optical displacement detection device, and particularly to an optical displacement detection device suitable for detecting the position of a linearly moving carriage or a rotating actuator. .

[Background of the invention]

In conventional optical position detection devices using parallel slits (linear encoders, rotary encoders, etc.), the light from the light source is diffused or focused by a lens, so the light flux is not parallel to the light flux. It wasn't. Therefore, there is a problem of a decrease in detection accuracy due to the influence of leakage light, and in order to prevent this, it is necessary to strictly control the alignment accuracy when mounting the detection section.

This will be explained using one drawing. FIG. 1 is a plan view of a conventional displacement detection device (for example, JP-A-57-18
1434), light source 1. Condensing lens 8° movable linear scale 3. Fixed scale4. It consists of a light receiving element 5 and the like. The scales 3 and 4 have equally spaced apertures made by a method such as etching.The light emitted from the light source 1, such as a light emitting diode, is passed through a condenser lens 8. Opening of movable linear scale 3.

The light receiving surface 6 of the light receiving element 5 passes through the opening of the fixed scale 4.
reach. If the movable linear scale 3 is moving at this time, light is repeatedly transmitted or blocked depending on the relative position with respect to the fixed scale 4, and ideally a triangular wave signal output is detected by the light receiving element 5. Since one pitch of this waveform corresponds to the width of the opening, by counting it, the distance traveled can be determined. However, a gap of 50 to 100 μm is provided between the movable linear scale 3 and the fixed scale 4 to prevent wear.

Further, the fixed scale 4 and the light receiving surface 6 of the light receiving element 5 using a photodiode or the like cannot be brought into close contact due to their structure, so there is a gap. For this reason, if there is obliquely incident light, the light leaks in, and even if the movable linear scale 3 is moved, the output will not be a triangular wave but a form close to a sine waveform, and the degree of modulation will be poor. However, the light emitting diode used as a light source cannot be considered a point light source, but rather a surface light source.
The light beam passing through the movable linear scale 3 was not completely parallel, and was susceptible to leakage from gaps.

Conventionally, the solution to the above problem has been to separate the light source so that a visually parallel beam of light is incident on the light receiving element, but this results in a decrease in light intensity, an increase in the occupied area, and is not completely complete. I couldn't get rid of the frustration.

[Purpose of the invention]

An object of the present invention is to provide an optical displacement detection device that is easy to assemble and provides a stable detection signal by improving the apparent properties of the light source.

[Summary of the invention]

In order to achieve this object, the present invention provides a parallel slit between the light source and the movable slit, allows only the parallel light flux and the light flux close to it to pass among the light from the light source, and makes the light flux from the apparent main light source into parallel light. It is characterized by this.

[Embodiments of the invention]

The present invention will be explained below using examples. FIG. 2 is a plan view showing an embodiment of the displacement detection device according to the present invention. A parallel slit 2 formed by arranging extremely thin plates in parallel is inserted between the light source 1 and the movable linear scale 3. The fixed scale 4 has openings whose pitch is shifted so that the phase of the output detected on the light receiving surfaces is shifted by 180° in correspondence with the light receiving surfaces 6 and 7 of the light receiving element 5 as the movable linear scale 3 moves. is provided.

This opening can be created by etching or other methods. Since the light flux emitted from the light source 1 passes through the parallel slit 2 and enters the movable linear scale 3, the light flux is restricted by the slit width of the parallel slit 2, and it is possible to extract only the parallel light flux of the light source and a portion close to it. According to this embodiment, between scales and fixed scales4. Light receiving surface 6.
Even though there is a gap at 7, there is a good modulation degree and the signals detected at the light receiving surface 6.7 do not interfere with each other.

A phase shift of 180 m can be achieved accurately. Therefore, it is possible to make the assembly precision of the parts of each detection part more relaxed than in the past, which has the effect of shortening the assembly adjustment time and improving the stability of the detection signal.

FIG. 3 shows another embodiment of the present invention using another parallel slit 2. The parallel slit 2 of this embodiment has equally spaced openings formed in a thin flat plate using a method such as etching. It is formed by making many layers and stacking them on top of each other. This provides the same effect as the previous embodiment.

FIG. 4 shows another embodiment of the present invention, in which the moving object is a rotating body, and this is used to detect the rotation angle of the rotating body.
According to this embodiment, there is an effect that a rotation angle signal with a good degree of modulation can be detected with good stability.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to change the appearance of the light source into one with good coherence simply by adding a simple parallel slit, and therefore the position detection accuracy can be improved even if the mutual mounting alignment accuracy of the detection components is made loose. This has the effect of making it possible to reduce the accuracy of one assembly without degrading it.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a conventional example, Fig. 2 is a plan view of an embodiment of the present invention, Fig. 3 is a plan view showing another embodiment, and Fig. 4 is a perspective view showing still another embodiment. It is a diagram.

Claims (1)

[Claims] 1. An optical displacement detection device comprising a movable light source scale, a fixed scale, and a light receiving element, characterized in that a parallel slit is provided that allows only a parallel beam of light and a light beam close to it to pass among the light from the light source. Detection device.