JP3533724B2 - Optical reflective encoder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot, a machine tool,
The present invention relates to an optical reflective encoder that measures a rotation angle, a position, and the like of an object such as a measuring instrument. 2. Description of the Related Art Conventionally, as shown in FIG. 2, for example, as shown in FIG. 2, an optical reflection type encoder converts light emitted from a laser diode 1 which is a light emitting element for emitting coherent laser light into parallel light or convergent light through a lens 2. Diverging light, beam splitter 3
And is reflected by the reflecting portion 51 of the slit pattern 5 formed on one surface 41a of the moving slit plate 4 made of a glass plate. The reflected light reflected by the moving slit plate 4 has the same light distribution as the slit pattern 5, the reflected light is changed by 90 ° by the beam splitter 3, transmitted through the index slit 6, and the light intensity is detected by the light receiving element 7. I do. In the prior art, the laser beam incident on the reflecting portion 51 of the slit pattern 5 is reflected as it is, but the laser beam incident from the slit portion 52 is reflected by the moving slit plate 4. The multiple reflection of light occurs between a surface having the slit pattern 5 and a surface having no slit pattern on the opposite side. As a result, as shown in FIG. 3B, there is a problem that interference fringes are generated between the patterns of the light reflected by the slit pattern 5 and erroneous detection occurs. The present invention does not generate interference fringes in reflected light,
It is an object of the present invention to provide an optical reflective encoder capable of performing highly accurate measurement. In order to solve the above problems, the present invention provides a light emitting device that emits coherent light, and a lens that converts light emitted from the light emitting device into parallel light or convergent divergent light. A beam splitter that transmits light emitted from the light emitting element and changes the optical path of the emitted light by 90 °, and a reflection part and a slit part on one surface that receives the light emitted from the light emitting element. A moving slit plate made of a glass plate on which a slit pattern is formed, and a reflected light from the slit pattern whose 90 ° direction is converted by the beam splitter to transmit the reflected light from the slit pattern so that the light intensity is sinusoidal with the movement of the moving slit plate. An optical reflective encoder including an index slit that changes in a wave shape and a light receiving element that converts light transmitted through the index slit into an electric signal. In da, the moving slit plate, the opposite surface of the surface forming the slit pattern, light Ranhan
It is provided with fine irregularities to be projected . By the above means, the light emitted from the light emitting element is reflected by the reflecting portion of the slit pattern formed on one surface of the movable slit plate. However, the outgoing light entering from the slit portion of the slit pattern enters the glass plate of the moving slit plate, and scatters irregularly on the uneven portion provided on the surface opposite to the surface on which the slit pattern is formed,
Since there is no multiple reflection inside the glass plate, interference fringes do not occur. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is a laser diode which is a light emitting element for emitting coherent laser light, 2 is a lens for converting light emitted from the laser diode 1 into parallel light or convergent divergent light, 3 is an optical path for transmitting incident light and reflecting light. At 90 °. Reference numeral 4 denotes a moving slit plate made of a glass plate coupled to a moving object, which is provided with a reflecting portion 51 and a slit portion 52 by vapor-depositing aluminum or chromium on one surface 41a for receiving light emitted from the laser diode 1. A slit pattern 5 is formed. On the surface 41b on the opposite side of the surface 41a on which the slit pattern 5 is formed, for example, a ground glass-like uneven portion 42 having fine unevenness is provided. The light reflected by the slit pattern 5 has the same light intensity distribution pattern as the slit pattern 5. Reference numeral 6 denotes an index slit, which transmits the reflected light from the slit pattern 5 whose direction has been changed by 90 ° by the beam splitter 3 and changes the light intensity in a sinusoidal shape as the moving slit plate 4 moves. Reference numeral 7 denotes a light receiving element that converts light transmitted through the index slit 6 into an electric signal.
When laser light is emitted from the laser diode 1, the light is converted into parallel light or convergent divergent light by the lens 2, and the laser light passes through the beam splitter 3, is reflected by the reflecting portion 51 of the slit pattern 5 of the movable slit plate 4, and is reflected by the beam splitter. The direction is changed by 90 ° at 3, the light passes through the index slit 6, and is incident on the light receiving element 7. The laser light entering from the slit portion 52 of the slit pattern 5 enters the moving slit plate 4 and the surface 41 of the moving slit plate 4 on the opposite side of the surface 41 a on which the slit pattern 5 is formed.
b, the light is irregularly reflected in the moving slit plate 4 when hitting the concave / convex portion 42 of FIG. As a result, as shown in FIG. 3A, multiple reflections disappear, and no interference fringes occur. As described above, according to the present invention, a slit pattern is provided on one surface of a moving slit plate made of a glass plate, and fine uneven portions are provided on the opposite surface. Provides a slit plate of an optical reflective encoder that can perform highly accurate measurement without causing interference fringes in the reflected light because it causes diffuse reflection and prevents multiple reflection of laser light entering from the slit part of the slit pattern. There is an effect that can be done.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of the present invention. FIG. 2 is a plan sectional view showing a conventional example. FIG. 3A shows a pattern of reflected light according to the embodiment of the present invention;
(B) It is explanatory drawing which shows the pattern of the reflected light of the prior art example. [Description of References] 1 laser diode, 2 lens, 3 beam splitter, 4 moving slit plate, 41a, 41b surface, 4
2 Uneven part, 5 slit pattern, 51 reflective part, 5
2 slit part, 6 index slit, 7 light receiving element

Claims (1)

(57) Claims 1. A light emitting element that emits coherent light, a lens that converts light emitted from the light emitting element into parallel light or convergent divergent light, and light emitted from the light emitting element. Through,
A beam splitter for changing the optical path of the outgoing light in a 90 ° direction, and a moving slit made of a glass plate having a slit pattern provided with a reflecting portion and a slit portion on one surface for receiving the outgoing light from the light emitting element A plate, an index slit that transmits reflected light from the slit pattern whose 90 ° direction has been converted by the beam splitter, and changes the light intensity in a sinusoidal shape with the movement of the moving slit plate, and transmits through the index slit. the optical reflective encoder that includes a light receiving element for converting light into an electric signal, the moving slit plate, the opposite surface of the surface forming a slit pattern, provided fine irregularities for irregularly reflecting light An optical reflection type encoder characterized by the above-mentioned.