JPH04351917A - Position detector - Google Patents

Abstract

PURPOSE:To obtain an extremely low-profile, high-resolution position detector such as a rotary encoder, a linear encoder and potentiometer. CONSTITUTION:An extremely low-profile microlens array 2 which consists of several semicylindrical lenses is mounted on a light emitting diode 1 so that the axial lines of the semicylindrical lenses can be perpendicular to the rotational direction of a rotary slit plate 3, and light flux passing through the opening 5 of the rotary slit plate 3 forms parallel beam perpendicular to the rotational direction of the rotary slit plate 3. A light receiving array 6 to which light flux passing through the rotary slit array 3 is illuminated outputs a signal such that the sine and cosine curves are formed with a secular change in the light receiving area through spindle-shaped windows 7, 8 for creating low- distortion sine and cosine waves to provide high resolution.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a rotary encoder,
It relates to position detection devices such as linear encoders and potentiometers.

0002

[Prior Art] Conventionally, each opening (window) of a rotating slit plate and a fixed slit plate constituting a rotary encoder as a position detecting device, for example, has a rectangular shape. The time variation of the common shape of both openings forms a triangle. therefore,
The signal generated by the rotary encoder is proportional to the shape of the light flux emitted from the light emitting diode, which passes through the opening formed by the intersection of both slit plates and is irradiated onto the light receiving sensor, so the electrical signal generated is also a triangular wave. become. now,
For simplicity, the shapes of the openings of the rotating slit plate and the fixed slit plate are both square or rectangular with the same dimensions. When the rotating slit plate rotates, the shape S of the common opening part becomes as shown in FIG. 3(A). It is shown by the formula.

0003

[Math 1]

[0004] In this way, the change in the shape S is represented by a linear function, and when plotted periodically, it becomes a triangular wave as shown in FIG. 3(B). In addition, in conventional encoders, in order to convert the light rays emitted from one light emitting diode into parallel rays within a two-dimensional range using one spherical optical lens, the thickness of the optical lens used must be adjusted. Usually it had to be about 100 m thick.

[0005]

[Problem to be solved by the invention] In the conventional configuration as described above, the electric signal generated from the sensor is a triangular wave, and in principle it is impossible to obtain an output with a low distortion sine or cosine wave curve suitable for a servo system. First, there was the problem that it was difficult to obtain high resolution. In addition, in order to obtain parallel rays within a two-dimensional range, the optical system used cannot be made thin;
Another problem was that the encoder could not be configured to be ultra-thin.

The present invention solves the above problem by using a plurality of semi-cylindrical diodes so that the light rays emitted from the light emitting diodes form one-dimensional parallel rays in a direction perpendicular to the moving direction of the slit plate. We have developed and adopted a microlens array consisting of lenses, and this one-dimensional parallel light beam passes through the opening of the slit plate and the time change in the light receiving area forms a low distortion sine and cosine wave curve suitable for servo systems. The purpose of this project is to develop and employ a light-receiving sensor array equipped with a window with a special pattern to provide a position detection device that is ultra-thin, has high precision, and has high resolution.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the position detection device of the present invention includes a light emitting diode, and a plurality of semi-cylindrical lenses each having an axis in a direction perpendicular to the moving direction of the slit plate. A microlens array consisting of a microlens array made of The light-receiving sensor array has a window having a dedicated pattern such that the time change of the light-receiving area forms a sine or cosine curve.

[0008]

[Operation] With the above configuration, one-dimensional parallel light rays formed in parallel in a direction perpendicular to the moving direction of the slit plate from the microlens array consisting of a plurality of semi-cylindrical lenses attached to the light emitting diode are transmitted to the slit plate. A one-dimensional parallel beam of light that is emitted toward the slit plate and passes through the opening of the slit plate is irradiated onto the light-receiving sensor array through a low-distortion sine and cosine wave generation window. Therefore, the time change of the light-receiving area on the light-receiving sensor array becomes a low-distortion sine and cosine wave curve.
Unlike the conventional triangular wave curve, the output of the light receiving sensor array is a low-distortion sine and cosine wave with reduced secondary and tertiary components relative to the sine and cosine fundamental waves, and high resolution is obtained. High-speed positioning control of servo motors, etc. becomes easier. Moreover, the microlens array attached to the light emitting diode is composed of multiple semi-cylindrical lenses that emit one-dimensional parallel light beams, so unlike conventional methods, the optical lens has to be thickened to produce two-dimensional parallel light beams. There is no need for such a configuration, and the overall structure can be made extremely thin.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the configuration of a rotary encoder as a position detection device according to an embodiment of the present invention.

In FIG. 1, 1 is a light emitting diode, and 2 is an ultra-thin microlens array consisting of a plurality of semi-cylindrical lenses attached to the light emitting diode 1. It is attached to the light emitting diode 1 so that its axis is perpendicular to the direction of rotation of the rotating slit plate 3, and through this microlens array 2, a light beam parallel to the direction perpendicular to the direction of rotation of the rotating slit plate 3 is mounted. A one-dimensional parallel beam 4 is formed and radiated towards the rotating slit plate 3. Reference numeral 5 denotes an opening formed in the rotating slit plate 3, which is configured to have a slit (approximately rectangular shape) with a pitch of 0.9°, for example, so as to allow the one-dimensional parallel light ray 4 emitted from the microlens array 2 to pass through. ing.

Reference numeral 6 denotes a light-receiving sensor array disposed opposite to the light-emitting diode 1 via the rotating slit plate 3; 7 and 8 are formed on the surface of the light-receiving sensor array 6, and the time change of the light-receiving area is suitable for a servo system. These are spindle-shaped windows with a special pattern for forming low-distortion sine and cosine curves, and these low-distortion sine and cosine wave generation windows 7 and 8 have a pitch of 0.9 in correspondence with the openings 5 of the rotating slit plate 3. 90 degrees, and are formed as sine and cosine wave curves with a phase shift of 90 degrees.

FIG. 2 shows the shapes of the low distortion sine and cosine wave generation windows 7 and 8 formed in the light receiving sensor array 6, each formed at a position corresponding to the center side of the rotating slit plate 3. It is formed by a combination of a small circular arc part, a large circular arc part formed at a position corresponding to the circumferential side of the rotary slit plate 3, and a diagonal line part connecting both ends of these parts, and the whole has a spindle shape. has been done. In addition, the chord length a of the small circular arc portion, the arc length b of the large circular arc portion, and the distance c between both chords depend on the diameter of the rotating slit plate 3 and the radial position of the rotating slit plate 3 to which the windows 7 and 8 correspond. These windows 7 and 8 are arranged with a respective pitch λ of 0.9°, and in order to provide a 90° positional shift for sine and cosine outputs, windows 7 and 8 are arranged with a pitch of λ/4. 0.225°
They are arranged with a deviation of .

Due to the low distortion sine and cosine wave generation windows 7 and 8 having such a shape, the sine and cosine wave outputs of the light receiving sensor array 6 are such that the second and third order components with respect to the fundamental sine and cosine waves are -50d.
It is possible to output low distortion sine and cosine waves of B or less. Therefore, each sine and cosine wave output due to 400 pulses generated in one rotation of the rotating slit plate 3 is electrically divided into two
If divided into 56 parts, high-speed positioning control of a DC servo motor or the like can be easily performed with a high resolution of 102,400 pulses/rotation.

In the above explanation, the rotary encoder was mainly used as an example, but by using other position detection devices, for example, a linear slit plate instead of a rotating slit plate, an ultra-small and ultra-thin linear encoder can be used. Of course, it can be applied to encoders, potentiometers, etc.

[0015]

As described above, according to the present invention, a microlens array consisting of a plurality of semi-cylindrical lenses is used, and the axis of the semi-cylindrical lenses is perpendicular to the moving direction of the slit plate. By arranging the microlens array in this manner, the light flux passing through the opening of the slit plate can be obtained as a one-dimensional parallel light beam that is uniformly formed in a direction perpendicular to the direction of movement of the slit plate. 2 as before
Compared to optical lenses that obtain parallel rays within a dimensional range, it can be configured to be ultra-thin. Furthermore, the output signal of the light-receiving sensor array is obtained through a low-distortion sine-cosine wave generation window in which the time change of the light-receiving area forms a sine and cosine wave curve, so the resolution is high and a high-resolution encoder can be easily installed. can get. Therefore, as an example of application, it can be used for high-resolution DC servo motor control, and its range of application is wide.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a rotary encoder as a position detection device according to an embodiment of the present invention.

2 is a plan view of a low distortion sine and cosine wave generation window of the light receiving sensor array in the rotary encoder of FIG. 1; FIG.

FIG. 3 is a diagram illustrating the conventional temporal change in the common shape of the openings of both the rotating slit plate and the fixed slit plate, which is caused by the rotation of the rotating slit plate.

[Explanation of symbols]

1 Light emitting diode 2 Microlens array consisting of a semi-cylindrical lens 3 Rotating slit plate 4 One-dimensional parallel light ray 5 Rotating slit plate opening (approximate rectangle)
6 Light receiving sensor array

Claims (1)

[Claims] 1. The light emitting diode is attached to a light emitting diode, and the axis thereof is arranged in the perpendicular direction so that the light beam passing through the opening of the slit plate forms a parallel light beam in a direction perpendicular to the moving direction of the slit plate. The microlens array consisting of a plurality of semi-cylindrical lenses and the light receiving area irradiated with the light beam passing through the aperture of the slit plate change over time as a sine,
A position detection device characterized by comprising a light receiving sensor array having a window for generating low distortion sine and cosine waves forming a cosine curve.