JPH0484713A - Graduation disk of optical encoder - Google Patents

Abstract

PURPOSE:To increase adhesion to a substrate and to make it possible to protect a reflecting surface by forming a phase-lattice forming projections on the substrate at a constant pitch, and forming a metal reflecting film on the region where the projections are formed by vapor deposition. CONSTITUTION:A chromium film 2A having the thickness of 0.1 - 0.2 mum is formed on a glass substrate 1 by vapor deposition. Then, positive resist 6 is formed on the chromium film 2A. An original plate 9 on which light transmitting parts 7 and non- transmitting parts 8 are continuously formed at a constant pitch is brought into close contact with the resist. Ultraviolet rays are emitted on the original plate 9 from the upper side. The resist parts corresponding to the light transmitting parts 7 are exposed. Then the original plate 9 is removed, and development is performed. The parts corresponding to the non-lihgt-transmitting parts 8 are removed. The resist 6 is made to remain at a constant pitch. The, the side of the resist 6 is treated with etching liquid. The exposed chromium film 2A is removed. The resist 6 is removed, and aluminum is formed by vapor deposition 3. Then, transparent glass is bonded on the aluminum vopor deposition film 3 by using an ultraviolet hardening type bonding agent 4, and the reflecting surface is covered. Thus, the adhesion to the substrate 1 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a scale plate of an optical encoder used to measure the amount of movement of an object to be measured.

(Prior Art) Conventionally, a binary amplitude grating and a binary phase grating are used as a scale plate of an encoder.

A binary phase grating has a constant amplitude and a binary phase distribution, and its amplitude transmittance distribution is given by:

In the above formula, 5in-=1, that is, θ-π must be satisfied.

There are two types of binary phase gratings: a reflective type and a transmissive type, with the reflective type having higher resolution than the transmissive type.

In a reflective phase grating, the optical path length difference between the four parts and the convex part is 2.
Xd (where d is the grating height), and if the angle of light corresponding to this optical path length difference is θ, in order to obtain the maximum diffraction efficiency for the first-order diffracted light, the maximum diffraction efficiency is θ - π as mentioned above. Efficiency λ,', d-1 (4) As is clear from equation (4), the grating height d at which the maximum diffraction efficiency is obtained is 1/4 of the wavelength λ of the light.

Therefore, in the semiconductor laser (λ-0.86μ), the grating height of the reflective phase grating, that is, the thickness of the metal film for forming the grating, is selected to be 0.215μ.

(Problems to be Solved by the Invention) The thinner the metal film for grating formation formed on the substrate, the better the adhesion and the less likely it will peel off. However, in order to improve the diffraction efficiency,
As mentioned above, when the thickness is 0.2μ or more, there is a problem that it is easy to peel off. In addition, the reflective film generally uses an aluminum film, which has the problem of being easily damaged.

The present invention aims to solve these conventional problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method in which phase grating forming protrusions are formed at a constant pitch on a substrate by a photoresist method, and the phase grating forming protrusions are formed. A metal reflective film is deposited on the region, and transparent glass is bonded onto the metal reflective film via a transparent adhesive layer having a refractive index higher than that of air.

(Function) The height of the phase grating forming protrusion is determined by the adhesive whose refractive index Δn>1, since the concave portion is filled with adhesive. Furthermore, since the reflective surface is covered with surface glass, the reflective surface is protected.

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

FIG. 1 shows a scale disk according to an embodiment of the present invention used in a rotary encoder.

In the figure, reference numeral 1 denotes a glass substrate, on which chrome protrusions 2 are formed in parallel and at the same pitch, and on the top surface of the protrusions 2 and between the protrusions 2 on the glass substrate 1 as a reflecting mirror. , an aluminum vapor-deposited film 3 is deposited on the aluminum vapor-deposited film 3, and a transparent glass 5 is coated on the aluminum vapor-deposited film 3 via a transparent, for example, ultraviolet curing adhesive layer 4 having a refractive index of Δn-1.5. -0,8674 with this reflection grating
, d-0,14μ. Therefore, the thickness of chromium (height of the phase grating) is set to 0.14μ.

This scale disc is manufactured as follows.

That is, as shown in FIG. 2(A), two chromium films having a thickness of 0.1 to 0.2 .mu.m are first deposited on a glass substrate 1. As shown in FIG. Next, as shown in FIG. 2(B), a positive resist 6 is formed on the chromium film 2A, and light transmitting parts 7 and light non-transmitting parts 8 are continuously formed thereon at a constant pitch. The original plate 9 is brought into close contact. Then, ultraviolet rays are irradiated from above the original plate 9 to expose the resist portions corresponding to the light transmitting portions 7. Then, the original plate 9 is removed and treated with a developer to remove the portion corresponding to the UV non-exposed area (light non-transmissive area 8) as shown in FIG. 2(C), leaving the resist 6 at a constant pitch. . Next, as shown in FIG. 2(D), the resist 6 side is treated with an etching solution to remove the two exposed chromium films, and as shown in FIG. 2(E), the resist 6 side is treated with an etching solution.
is removed and aluminum is deposited (3). As shown in FIG. 2(F), a transparent glass 5 is bonded onto the aluminum vapor-deposited film 3 using an ultraviolet curing adhesive 4 (transparent) to cover the reflective surface.

FIG. 3 shows the optical path configuration of an optical rotary encoder using the scale disk of the present invention.

In the figure, 10 is a scale disk, which corresponds to the laser 1
It can move freely across the front of 1.

The laser light emitted by the laser 11 passes through the beam splitter 12
The image is divided into two parts and each image is projected onto the scale disk IO via a mirror 131132. +1st-order diffracted light 14 and - formed by reflection on scale disk 10
The 1st-order diffracted light 14° passes through the mirrors 15 and 152, the mirror 16, and the beam splitter 17, respectively, to the light receiving element 1.
At 8, light is received, 3...aluminum vapor deposited film 5...transparent glass 4...adhesive layer, and by counting the output pulses of the light receiving element 18, the amount of rotation of the scale disk 10 is measured. Ru.

(Effects of the Invention) Since the present invention is configured as described above, the height of the protrusions of the reflection type diffraction grating constituting the scale disk can be lower than that of the conventional one, and therefore the adhesion to the substrate can be improved. increases. Furthermore, since the reflective surface is covered with surface glass, it has the effect of protecting the reflective surface.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the main part of an embodiment of the present invention applied to a rotary encoder, FIGS. 2(A) to (P) are sectional views showing the manufacturing process, and FIG. FIG. 2 is a diagram illustrating the optical path configuration of a rotary encoder using a scale disk. 1... Glass substrate 2... Chrome Protrusion Co., Ltd. Figure 1

Claims (1)

[Claims] Projections for forming a phase grating are formed at a constant pitch on the substrate by a photoresist method, a metal reflective film is deposited on the area where the projections for forming a phase grating are formed, and the refractive index is lower than that of air on this metal reflective film. An optical encoder scale disc characterized by transparent glass bonded through a highly transparent adhesive layer.