JPS6378021A - Optical rotary encoder - Google Patents

Abstract

PURPOSE:To obtain a rotary encoder which can be manufactured easily and has a high performance, by providing a micro-lens array which has a function of a slit, and also, has a condensing action, on a rotary plate. CONSTITUTION:A micro-lens array 12 having lenses 11 is placed along the periphery. Also, this rotary encoder is provided with a rotary plate 13 which is fixed to a shaft 10, a light source 14 such as a laser diode, etc. for allowing a light beam to be made incident on the lens 11, a collimator lens 15, a fixed light shielding plate 16, and a photodetector 17 for detecting a light beam which is transmitted through the lens 11. In such a state, when the rotary plate 13 rotates together with the shaft 10, the light beam is condensed in the lens 11 part and goes into the photodetector 17, therefore, the output is large. However, the light beam is shielded by other part than the lens 11, and also, even if the light beam is made incident on the adjacent lens, a focus is formed in a position shifted from the photodetector 17 by a lens action, therefore, a malfunction is not caused.

Description

[Detailed Description of the Invention] [Summary] This is an optical rotary encoder, and by arranging a microlens array in place of a slit on the rotary plate, the degree of light condensation is increased, making it possible to perform simple and highly accurate measurements. .

[Industrial application field]

The present invention relates to an optical rotary encoder for measuring the rotation angle of a shaft.

In recent years, rotary encoders that measure rotation angles and rotational speeds have been widely used in factory automation equipment and robots, but highly accurate encoders are required for advanced control.

[Conventional technology]

As shown in FIG. 4, a conventional optical rotary encoder includes a rotating plate 2 fixed to a shaft (not shown) and having a number of radially formed slits 1 at equal intervals, and a rotating plate 2 through which light is transmitted to the slits 1 of the rotating plate. A light source 3 and a collimator lens 4 for projecting the light, a photodetector 5 for detecting the light passing through the slit 1,
It is constructed with fixed slits 6 and 7 that cut off excess light, and the rotation angle or rotation speed of the shaft is measured by detecting the diffracted light of the light that has passed through the slit 1.

[Problem that the invention seeks to solve]

In the conventional optical rotary encoder described above, in order to improve measurement accuracy, it is necessary to reduce the width of the slits l and increase the number of slits. However, fine slits are difficult to process, and the narrower the slit width, the more light wraps around due to diffraction, which reduces the difference between brightness and darkness, making detection difficult.

The present invention was created in view of these points, and an object of the present invention is to provide an optical rotary encoder that is easy to manufacture and has high performance.

[Means for solving problems]

Therefore, in the present invention, as illustrated in FIG.
A microlens array 12 consisting of a large number of lenses 11 is arranged along the circumference, a rotary plate 13 fixed to a shaft 10, a light source 14 that inputs light to the lens 11, and a light transmitted from the lens 11. It is characterized in that it is configured to include at least a photodetector 17 for detecting.

[For production]

By arranging the microlens array 12 on the rotary plate 13, the light transmitted through the lens 11 is condensed and enters the photodetector 17, but otherwise the light is not condensed, resulting in a small output. Therefore, the rotary plate 13 rotates, and the difference in output when light passes through the lens and when it does not becomes large, making it possible to improve measurement accuracy.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention.

In this embodiment, as shown in FIG.
A rotating plate 13 having a microlens array 12 arranged thereon and fixed to the shaft 10, and a lens 11 of the rotating plate.
The light source 14 includes a light source 14 such as a laser diode or LED, a collimator lens 15, a fixed light shielding plate 16, and a photodetector 17 that detects the light transmitted through the lens 11.

An example of the method for manufacturing the microlens array 12, which is the main point of this embodiment, will be explained with reference to FIG.

First, as shown in FIG. 2a, 1000 Ti or Cr films are deposited on a Pyrex or polymethyl methacrylate (PM?lA) substrate 20 by vacuum evaporation, and then a lens is formed using lithography and etching techniques. A mask 21 is formed by removing a portion corresponding to . Next, as shown in Figure 2, a solution of methyl methacrylate (HMA) and cinnamic acid ester such as cinnamoyl chloride dissolved in 1-4 dioxic acid is applied onto the mask 21 to a thickness of about 4 μm using a spinner. A photoreactive film 22 is formed. After drying this at room temperature for about 20 minutes, as shown in Figure 2C, the wavelength 2
Ultraviolet light 23 of 80 to 350 nm is irradiated for 15 to 30 minutes. As a result, as shown in FIG. 2d, the portion hit by the light expands due to photopolymerization, and a lens 11 is formed. Finally 100
C. for 1 hour to stabilize the unexposed areas. Note that the shape of the lens 11 may be circular or rectangular.

In this embodiment configured as described above, the rotating plate 13 is connected to the shaft 1.
When rotating with 0, the light is condensed in the lens 11 portion and enters the photodetector 17, resulting in a large output. However, the light is blocked by the mask 21 in areas other than the lens 11, and even if it enters an adjacent lens, the light is not absorbed by the lens action. Since the focus is set at a position away from the detector 17, it does not cause malfunction.

Also, as a lens array with a diameter of 20 μm and a focal length of 50 to 10
Lenses with a diameter of 0 μm are placed on the circumference of a crane with a diameter of 25 μm.
When arranged as follows, approximately 3770 pulses can be output per rotation of the rotating plate, and the minimum detection angle is 0.096 degrees, allowing highly accurate measurement.

FIG. 3 is a diagram showing another embodiment of the present invention.

In this figure, the same parts as in FIG. 1 are designated by the same reference numerals.

This embodiment differs from the previous embodiment in that a second lens array 12' is also provided on the back surface of the rotary plate 13, and the imaging plane of the front lens 11 is placed almost at the focal point of the back ρ lens 11'. This is how it was structured.

In this embodiment configured in this way, the light emitted from the lens 11' on the back surface of the rotary plate becomes parallel light, so fluctuations in the amount of incident light due to warping of the rotary plate 13, etc. can be further reduced, resulting in stable detection. becomes possible.

Note that it is also possible to produce a disk having a microlens array by injection molding.

〔Effect of the invention〕

As described above, according to the present invention, by providing the rotating plate with a microlens array that functions as a slit and has a light condensing function, it is possible to manufacture it at low cost, increase the detection output, and also make it possible to Since the light that hits the lens or enters the adjacent lens does not form an image on the detection unit, there are fewer malfunctions and high accuracy is achieved, making it extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a diagram for explaining a method for manufacturing a microlens array used in an embodiment of the present invention. FIG. 3 is a diagram showing another embodiment of the present invention. 4 are diagrams showing a conventional rotary encoder. 1 and 3, 10 is an axis, 11 and 11' are lenses, 12 and 12' are microlens arrays, 13 is a rotating plate, 14 is a light source, 15 is a collimator lens, 16 is a light shielding plate, and 17 is a light shielding plate. It is a photodetector. Figure 1 shows an embodiment of the present invention. Figure 2 11 - Lens 2〇 - Substrate 21 - Mask 22 - Photoreactive film Showing another embodiment of the present invention Figure 3 11.11'---Lens 12 12'--Microlens array 13---Rotating plate 14--Light source 15--Collimator lens 16---Shading plate 17---Photodetector Conventional Optical rotary ~ Diagram showing encoder Fig. 4 7 - Slit 2 m - Rotating plate 3 m - Light source 4 - Collimator lens 5 - Photodetector 6.7 - Fixed slit

Claims (1)

[Claims] 1. A microlens array (12) consisting of a large number of lenses (11) is arranged along the circumference, and a rotary plate (13) fixed to a shaft (10), a light source (14) that enters light into the lens (11); and a photodetector (14) that detects the transmitted light from the lens (11).
17) An optical rotary encoder comprising at least the following. 2. Two sets of microlens arrays (12, 12') are provided on the front and back surfaces of the rotary plate (13), and the image of the front lens (11) is formed almost at the focal point of the back lens (11'). The optical rotary encoder according to claim 1, characterized in that the optical rotary encoder is configured such that a surface is arranged.