JPS6014287B2 - Photoelectric encoder scale - Google Patents

Abstract

PURPOSE:To make an encoder thinner while reducing the number of parts by providing a light interrupting and conductive material and a pn semiconductor layer for converting light into an electrical signal and the like on a light transmitting substrate. CONSTITUTION:A first signal deriving material layer 2 made of a light interrupting and conductive material, for example, a metal film, a pn semiconductor layer 2 for converting light into a electrical signal and a signal deriving layer 4 of a transparent film made of a light transmitting and conductive material, for example, In2O3, SnO2 and Si or a mixture thereof are laminated sequentially on a light transmitting substrate 1 made of glass, for example, and light receiving sections 5 thus made are arranged in a fine strip at a fixed pitch to form a scale S. This enables the integration of the scale and a light receiving element thereby making an encoder thinner while reducing the number of parts.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the scale of a photoelectric esocoder that detects physical quantities from the brightness and darkness of light obtained by relatively moving two optical gratings.

In a conventional photoelectric encoder, a light source emits a beam of light onto one optical grating, and the light beam that passes through this optical grating passes through the other optical grating and then passes through a lens placed on the opposite side. It is arranged to reach the light receiver. Therefore,
The light from the light source must pass through two optical gratings, and along the way it is mixed with complex diffracted light, and is further attenuated by reflection and refraction on the glass surface, which is the base material of the grating, and absorption inside the glass. However, as a result, the signal obtained by the photoreceiver inevitably contains noise and is weak.

Furthermore, in order to arrange the light source, lens, and light receiver, the encoder inevitably had to be large. There is also a reflective photoelectric encoder that allows a light beam to enter obliquely between two optical gratings, but this also causes diffraction, scattering, etc.
In addition to a large loss of light due to reflection and the like, the structure is complicated because the light source and receiver must be mounted at an angle, and miniaturization is not sufficient.

In order to solve the above-mentioned conventional problems, the present applicant has disposed strip-shaped semiconductor layers of opposite conductivity types on a semiconductor substrate at a constant pitch on one optical grating, and this is applied to the other optical grating. A device has been proposed in which a light beam transmitted through a grating is irradiated and output is obtained from the semiconductor substrate and the semiconductor layer.

This proposal omitted the lens on the light receiving side, the light rays from the light source passed through only one optical grating, and the distance between the second optical grating and the light receiver became zero. Miniaturization and efficiency have been improved.

In addition, in response to the above proposal, as a measure to improve the high frequency characteristics of the output from the slit-shaped light receiving element made of the semiconductor substrate and semiconductor layer, the entire surface of the light receiving element is made of a transparent conductive material in order to eliminate or reduce the resistance of the slit. It has been proposed to summarize the output by covering it with

It has also been proposed that an opaque slit be provided on a continuous planar semiconductor layer, thereby improving high frequency characteristics and facilitating manufacturing.

Furthermore, it has been proposed that the semiconductor layer and the semiconductor layer are made of MOS semiconductors, and the opaque film slit is made of a metal part of the MOS semiconductor.

However, the scale of these photoelectric encoders cannot be sufficiently miniaturized, and for example, in the case of scales using MOS semiconductors, the silicon crystal material used is expensive and long products cannot be manufactured, so it is not economical and
It has technically difficult problems.

This is particularly difficult when applied to the main scale. Additionally, reflective encoders are generally smaller than transmissive encoders, but in the case of reflective encoders, the light beam to irradiate the reflective scale must be incident as oblique light, which causes problems such as diffraction, scattering, and reflection. However, there are disadvantages in that the light loss caused by this is large, and the light emitting part and the light receiving part are mounted at an angle, making the structure complicated.

The present invention has been made in view of the above-mentioned conventional problems, and further reduces the size and number of parts, and also improves the scale of photoelectric encoders that do not require the light source to be installed at an angle even in the case of reflective type encoders. The purpose is to provide.

The purpose of this is to use a photoelectric encoder scale that detects physical quantities from the brightness and darkness of light obtained by moving two optical gratings relative to each other. A first signal deriving material layer, a PN semiconductor layer that converts light into an electrical signal, and a second signal deriving material layer made of a light-transmitting and conductive material are laminated in this order, and the light receiving portion is formed into a class band shape. The light-receiving parts are arranged at a constant pitch at a constant pitch, and the light-receiving parts are used as light-blocking slits, and the spaces between the light-receiving parts are used as light-transmitting slits to form an optical grating. This achieves the above objective.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of a scale of a photoelectric encoder according to the present invention, and FIG. 2 is an enlarged sectional view taken along the row 0 line in FIG. 1.

In this embodiment, a first signal deriving material layer 2 made of a light-blocking and conductive material such as a metal film is formed on a light-transmitting base material 1 made of glass, for example, and a PN semiconductor that converts light into an electrical signal. layer 3 and an optically transparent and electrically conductive material such as IQ03;
A scale S is formed by disposing a light receiving part 5 in a thin strip shape at a constant pitch, and a second signal deriving material layer 4 made of a transparent film made of SN02, Si, or a mixture thereof. be.

As shown in FIG. 3, the scale S is arranged so that its reflection section 6 and light receiving section 5 face the reflection type main scale M, and the scale S faces toward the reflection type main scale M. A light beam from a light source 8 is made to enter from the back side through a lens 7.

A non-reflective portion consisting of a light transmitting portion or a light absorbing portion is provided between each reflective portion 6 of the main scale M. That is, the first signal deriving material layer 2 of the light receiving section 5 functions to block the light rays from the light source 8, so that the light receiving section 5 becomes a light blocking slit, and there is a light transmitting slit between each light receiving section 5. The light beam from the light source 8 can be irradiated onto the reflective main scale M through the light-transmitting base material 1.

Furthermore, the light beam reflected by the reflection section 6 of the reflective main scale M passes through the second signal derivation material layer 4 of the light receiving section 5 and reaches the PN semiconductor layer 3, where it is converted into an electrical output of the semiconductor. .

Electrical output in the PN semiconductor layer 3 is taken out from output terminals 9 and 10. That is, the scale S functions as an index sensor in which an index scale and a light receiving element are integrated.

Next, a method for manufacturing the scale S will be explained.

First, a glass substrate, which is a light-transmitting substrate 1, was mounted in a vacuum evaporation equipment, and was heated for 15 minutes in a vacuum environment of 5 × 10 years orr.
Cr is evaporated from the tungsten board by heating to 0 to 20 psi, and Cr is evaporated onto the glass substrate.
A Cr film serving as the first signal deriving material layer 2 is formed with a thickness of 3000 Å. Next, the glass substrate on which the C-shaped layer was formed was placed in a plasma chamber and heated to 300°C.
A gas obtained by diluting Ar gas containing 0.0% by 1 part with a specific gas is introduced into the plasma chamber, and 0.1 to 2br
The first signal deriving material A bran layer is applied on top of layer 2, thereby forming a PN semiconductor layer approximately 1 μm thick. The N-type amorphous silicon film 11 is formed by mixing a certain amount of PH3 into the reaction gas at the initial stage of precipitation, and the P-type amorphous silicon film 12 is formed by mixing the PH3 in the middle.
By switching to B2 day 6, each is precipitated.
Here, the PN semiconductor layer 3 may be formed by other methods such as a thermal decomposition method or a sputter deposition method. Also, when forming a semiconductor layer, first add PH3 to create an N-type layer, then create an i-layer (intrinsic layer) that does not contain impurities, and then add B2-6 to create a P-layer. -i-N structure may be formed and optical power may be obtained by a junction appearing between P-i. In this case, sensitivity improves. Next, the base material 1 on which the PN semiconductor layer 3 was formed was placed in a vacuum deposition tank, and
The ln203 heated to 0oo and placed in an alumina brim was made into ln203 with a thickness of about 1000A by the electron beam plexus method.
A film is deposited, thereby forming a second signal deriving material layer 4 on the PN semiconductor layer 3.

Next, apply a layer of photoresist to a thickness of about two ship's sides using the spin coating method.
Apply this and let it dry.

Furthermore, after shielding the output terminal portion 9 from light with a mask, the photoresist on the output terminal portion 9 is removed by exposure to ultraviolet rays and development. Next, the second signal deriving material layer 4 and the PN semiconductor layer 3 in the output terminal 9 portion are removed by a method such as chemical etching or plasma etching, and the first signal deriving material layer 2 is exposed.

Similarly, parts other than the light transmitting slit I3 between the light receiving parts 5 are covered with photoresist, and the light transmitting slit 13
The first and second signal deriving material layers 2 and 4 and the PN semiconductor layer 3 corresponding to the above are removed by plasma etching or the like, and the light-transmitting base material 1 is polished out.

Here, it is convenient for the width of the light transmitting slit 13 to be at least twice the height of the light receiving section 5 from the surface of the light transmitting base material 1 in order to detect brightness and darkness.

Next, the first signal deriving material layer 2 and the second signal deriving material layer 4
Conductive wires for extracting an output current from the PN semiconductor layer are attached to the output terminals 9 and 10 using a conductive adhesive, and finally, a thin layer of silicone varnish is applied to the entire surface to protect the PN semiconductor layer and is dried to complete the process.

Next, another embodiment of the present invention will be described with reference to FIG.

Here, the same or similar parts as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted. In this embodiment, in the scale S, a light source 14 is provided on the opposite side of the light receiving section 5 through the light transmitting base material 1, and light from this light source 14 passes through the light transmitting base material 1 on the opposite side. A reflecting mirror 15 is provided to reflect the light to the side.

The reflecting mirror 15 is formed by providing a light reflecting film such as a vapor-deposited metal film on the outside of a substantially hemispherical transparent resin 16 that is integrally provided on the light source 14 side of the light-transmitting substrate 1. be.

The transparent resin 16 is made of a light-transmitting material having the same refractive index as the light-transmitting base material 1, and is filled around the light source 14, so that the light from the light source 14 is not affected while it reaches the light-transmitting base material 1. The refractive index in the optical path is improved.

In this embodiment, the light source 14 is attached to the index scale S itself and is integrally molded with the transparent resin 16, so that an encoder can be constructed by simply arranging two scales. Furthermore, since the light source and the index scale S are integrated, there is an advantage in that failures due to vibrations or problems caused by vibrations are eliminated. Since the present invention is configured as described above, it is possible to integrate the scale and the light receiving element, and therefore the encoder can be made thinner and the number of parts can be reduced. Furthermore, since light can be projected from the back of the light receiving element, the index scale and the main scale can be parallel and close to each other in a reflective scale, which has the effect of reducing light loss due to light diffraction, scattering, etc. Furthermore, by integrating the index scale and the light-receiving element, the scale can be made smaller than when the light-receiving element is provided on the main scale, making manufacturing easier and lower cost.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the scale of a photoelectric encoder according to the present invention, FIG. 2 is an enlarged sectional view taken along the Rolo line in FIG. 1, and FIG. FIG. 4 is a schematic side view showing a second embodiment of the present invention. S... Scale, M... Main scale, 1... Light transmitting base material, 2... First signal deriving material layer, 3...
...PN semiconductor layer, 4...second signal deriving material layer,
5... Light receiving part, 11... N-type amorphous silicon film, 12... P-type amorphous silicon film, 1
3...Light transmission slit section. Kane'boxune 2 figures, 3 figures, 4 figures

Claims (1)

[Scope of Claims] 1. In the scale of a photoelectric encoder that detects a physical quantity from the brightness and darkness of light obtained by relatively moving two optical gratings, a light-blocking and conductive material is provided on a light-transmitting base material. A light-receiving device in which a first signal-deriving material layer made of a material, a PN semiconductor layer that converts light into an electrical signal, and a second signal-deriving material layer made of a light-transmitting and conductive material are laminated in this order. The light-receiving portions are arranged as thin strips at a constant pitch, and the light-receiving portions are light-blocking slits, and the light-receiving portions are light-transmitting slits, and an optical grating is formed. A photoelectric encoder scale characterized by the following: 2. The scale for a photoelectric encoder according to claim 1, wherein the height of the light-receiving portion from the surface of the light-transmitting base material is set to one-half or less of the width of the light-transmitting slit. 3. The scale for a photoelectric encoder according to claim 1 or 2, wherein the PN semiconductor layer is made of an amorphous semiconductor. 4. The scale for a photoelectric encoder according to claim 1, wherein the semiconductor layer has a P-i-N structure.