JPS623617A - Optical scale - Google Patents

Abstract

PURPOSE:To obtain an optical scale which can be attached to an object to be examined with a high precision in an easy assembling process, by forming a mark part, where light-transmissive parts and light-nontransmissive parts are formed alternately on a translucent member, and a junction part into one body. CONSTITUTION:The light from a light source 1 is converted to parallel rays of light by a collimator lens 2 and is made incident on an optical scale 3 from above. The light incident on the flat face of the scale 3 is transmitted through the scale, but the light incident on the slope is reflected totally twice and is not transmitted through the scale 3. Consequently, the light and drakness distribution is moved in the direction of an arrow when the scale 3is rotated in the same direction. For example, a master die having the same shape as a scale shown in the figure is worked, and an inverted die is obtained by Ni electroforming or the like, and this die is used as the molding die to transfer the ruggedness to plastic materials or the like, thereby producing the scale 3. Thus, a flange part 11 which is used to attach the scale to the object to be examined is formed easily with a high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical scale, and particularly to an optical scale suitable for use in an optical encoder or the like.

[Prior art]

Conventionally, optical encoders have been widely used in information devices such as electronic typewriters to detect the position and speed of movable parts such as carriages. Such optical encoders are usually fixed to a movable part, project light onto an optical scale on which an optical code is recorded, and photoelectrically convert the modulated light, thereby encoding the position information of the movable part. It was designed to be extracted as a converted electrical signal.

Optical scales include (I) a metal plate with slits etched into it ([) silver, copper, etc. on a transparent substrate such as glass or plastic;
The metal layer used was one in which a metal such as chromium or aluminum was vapor-deposited and only the metal layer was removed in the form of a slit by etching.

However, in these methods, the slit width that can be etched is limited to at least twice the thickness of the metal, making it difficult to record fine symbols. In addition, the manufacturing process is complicated, and expensive photosensitive resin is used for etching, resulting in high costs.

Furthermore, conventional optical scales have been attached to the test object in a manner as shown in FIG. FIG. 5 shows an example of an optical encoder configured using a conventional optical scale, in which 21 is a light source, 22 is a conventional optical scale in which a marking part is formed by etching a metal plate, and 30 is a collimator lens. , 23 is a fixed optical grating manufactured by etching a metal plate, 24 is a light receiving element, and 25 is a waveform shaping circuit, which shapes the signal from the light receiving element 24 to form a signal waveform as shown in S in the figure. It is to be formatted as follows. 26 is a rotating shaft whose position is to be detected by an encoder; 27 is a mounting plate glued to the shaft 26 in order to attach the optical scale 21 to the shaft 26; and 28 is a mounting plate for fixing the optical scale 21 to the mounting plate 27. It is a holding plate for
29 is a screw used at that time. Light source 21. Optical grating 23. The light receiving element 24 is fixed to a case (not shown) made of plastic or metal, and the case is connected to the rotating shaft 2.
6 via a bearing or the like.

Here, the gap between the optical scale 22 and the fixed optical grating 23 is minute because it greatly affects the performance of the optical encoder, and the optical scale 22 must be rotated without changing the gap. For this purpose,
High component precision and adhesion precision were required for the mounting plate 27, etc., and the work process was complicated.

On the other hand, an optical scale with a novel structure that can be manufactured easily and inexpensively has been proposed by the present applicant in Japanese Patent Application No. 58-250551.

[Summary of the invention]

The present invention is a further improvement of the aforementioned prior application by the present applicant, and its purpose is to provide an optical scale that can be attached to a test object with high precision through a simple assembly process.

The above-mentioned object of the present invention is to provide a sign portion in which a light-transmitting part and a light-non-transmitting part consisting of an inclined surface whose angle of incidence is set to be equal to or greater than a critical angle with respect to an incident light beam are alternately formed in a light-transmitting member. This is achieved by an optical scale formed by integrally molding the joint part for attaching the member to the test object.

〔Example〕

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

FIG. 1 is a perspective view showing an example of an optical encoder configured using the optical scale of the present invention. In the figure,
1 is a light source, 2 is a collimator lens, and 3 is a rotary type optical scale based on the present invention, which is fixed to a rotating shaft 7 and rotates in accordance with this drive. Further, this optical scale 3 is provided with a marking part 8 in which light-transmitting parts and non-light-transmitting parts are formed alternately, and a flange part 11 for joining this optical scale to a rotating shaft. 4 is a fixed optical grating made of a transparent member; 5 is a light-receiving element that converts the light transmitted through the optical grating 4 into an electrical signal; 6 is a waveform shaping circuit that shapes the waveform of the signal from the light-receiving element 5 to produce the signal as shown in the figure. The signal waveform is shaped as shown by S on the right side.

FIG. 2 shows the configuration of the optical scale 3, (A)
is a view seen from the bottom, and (B) is a schematic cross-sectional view at Ax in (A). The optical scale 3 is formed by integrally molding a convex marker portion 8 and a flange portion 11 using a transparent member such as glass or plastic. Further, light transmitting portions 9 and light non-transmitting portions 10 are regularly and alternately formed in this marker portion 8, and the irradiated light is modulated as shown in FIG.

FIG. 3 is a partial plan view of BB' in FIG. 2(A). The above-mentioned light transmitting section 9 is made of a flat surface, such as 9a, which has an angle of incidence smaller than the critical angle with respect to the incident light. In addition, the light non-transmissive portion 10 is configured so that the incident light L
For example, if the angle between the inclined surfaces 10a and 10b is 90'', then the inclined surfaces 10a and 10b are Assume that the combined horizontal width w1 (indicating the width of the projected image of the inclined surface on the plane perpendicular to the optical axis of the incident light) and @W2 of each of the flat surfaces 9a are the same. As shown, the light incident on the inclined surface 10a has an incident angle of 45 degrees, so it is totally reflected and reflected at a right angle, and then it enters the other inclined surface 10b at an angle of 45'', where it is totally reflected again. It is reflected at right angles and returns to the original incident side. Furthermore, the light incident on the inclined portion lOb also returns to the incident side in the same manner as above. However, the light incident on the flat surface 9a is transmitted as is, which means that only the flat surface plays the role of a slit. Therefore, this optical scale 3 has exactly the same width as the slits and the light shielding parts arranged at the same pitch. Furthermore, the above-described fixed optical grating 4 is also formed with concavities and convexities similar to those of the optical scale 3.

Next, FIGS. 1 and 4 (A) show the operation of an optical encoder using the optical scale of the present invention.

This will be explained using (B). Figure 4 shows optical scale 3.
．． (A) is a schematic cross-sectional view of the fixed optical grating 4 and the light receiving element 5;
(B) shows a state in which the phases of the marks formed on the optical scale 3 and the fixed optical grating 4 match, and (B) shows a state in which the phases are shifted by 1/2 period.

In Fig. 1, the light from the light source l is transmitted through the collimator lens 2.
The light is made into parallel light and enters the optical scale 3 from above. As described above, the light incident from above is transmitted through the optical scale 3 through its flat surface.

Further, the light is reflected from the two caps on the inclined surface and does not pass through the optical scale 3. Therefore, the light transmitted through the optical scale 3 produces a regular brightness/darkness distribution of light. Here, the optical scale 3 rotates in the direction of the arrow shown in the figure together with its rotation axis 7, and its brightness distribution also moves in the same direction. Here, the symbols formed on the fixed optical grating 4 and the optical scale are the same, that is,
Since the brightness distribution of the fixed optical grating 4 and the brightness and darkness distribution of the incident light have the same pitch, the phase of the unevenness of both is 4th.
When they match as shown in Figure (A), all the light that has passed through the optical scale 3 passes through the fixed optical grating 4, so the amount of light that enters the light receiving element 5 becomes maximum. Also, the phase of the unevenness is the fourth
When the period is shifted by 1/2 as shown in Figure (B), the inclined surfaces and flat surfaces of the optical gratings correspond to each other, so all the light that passes through the optical scale 3 is transmitted to the inclined surface of the fixed optical grating 4. The light is reflected from the two caps and returns to the incident side, and the amount of light incident on the light receiving element 5 is minimized.

Between the time when the amount of light is maximum and the time when it is minimum, there is a gap between the flat surface of the optical scale 3 and the fixed optical grating 4.
The light-receiving element 5 receives a light amount corresponding to the proportion of the area of the matched portion. Therefore,
The signal from the light-receiving element 5 has a sinusoidal waveform, and this signal is shaped by the waveform shaping circuit 6 into a pulse-like signal such as S in FIG.

The optical scale of the present invention is produced by processing a mask mold having the same shape as the scale, for example as shown in FIG. [Produced by making an inverted mold by casting or the like, and then using this as a molding die to transfer the unevenness to a material such as plastic. Therefore, the flange portion 11, which is a joint portion for attaching the scale to the test object (rotary shaft 7 in the embodiment), can also be easily formed with high precision. In addition, in FIG. 1, when attaching the optical scale 3 to the rotating shaft 7, first add a thickness corresponding to the gap intersection to the part between the optical scale 3 and the fixed optical grating 4 that does not affect the light receiving element 5. Sandwich the spacer, then pour the adhesive between the flange part 11 and the shaft 7 while holding down the optical scale 3 and rotating it, until the adhesive is completely applied.
After completely drying, pull out the spacer. By this step, the gap between the optical scale 3 and the fixed optical grating 4 is adjusted to the correct thickness of the spacer, and since it is glued while rotating, there is almost no change in the gap. do not have. Here, it is convenient to use a urethane sheet or the like as the spacer, since the optical scale will not be easily scratched. In addition, a flat part is provided on the outer periphery of the marking part 8 of the optical scale 3 as a place for inserting the spacer, and a part of the fixed optical grating 4 facing this is also formed flat, and these flat parts are used as a reference. This will make the work easier.

The present invention is not limited to the above embodiments, and can be applied in various ways. For example, when used in an optical encoder, reflected light may be detected instead of transmitted light. Furthermore, it goes without saying that the present invention can be applied not only to rotary type optical scales but also to linear type optical scales.

〔Effect of the invention〕

As explained above, since the optical scale of the present invention has a joint part to the test object integrally molded, it can be easily attached to the test object, and the mounting has the effect of increasing the accuracy.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of an optical encoder configured using the optical scale of the present invention, and FIGS. 2(A) and (B)
3 is a schematic diagram showing an embodiment of the optical scale of the present invention, FIG. 3 is a partial sectional view of the optical scale of FIG. 2, and FIG.
Figures (A) and (B) are sectional views of essential parts explaining the operation of the optical encoder shown in Figure 1, respectively, and Figure 5 is a perspective view showing an example of the configuration of an optical encoder using a conventional optical scale. be. 3-111 optical scale, 8-111 labeled part, 9-111 light transmitting part, 9a---1 flat surface, 10---1 light non-transmitting part, 10a, 10b--- One inclined surface, ti---flange part.

Claims (1)

[Claims] (1) A sign part in which a light-transmitting part and a light-non-transmitting part consisting of an inclined surface whose angle of incidence is set to be greater than a critical angle with respect to an incident light beam are alternately formed on a light-transmitting member, and the member. An optical scale with an integrally molded joint for attaching it to the test object.