JP3198019B2 - Optical displacement detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a main scale having a reflection type first grating and an index scale having a transmission type second grating and four third gratings having a phase shift of 90 degrees. Displaceably disposed, the diffused light from the light emitting element is transmitted through the second grating to irradiate the first grating and
The detection light reflected by the grating and transmitted through the third grating is received by each light receiving element corresponding to each of the third gratings, and the electric signal output from each light receiving element is analyzed to determine the relative displacement of both scales. The present invention relates to an optical displacement detection device configured to be detectable.

[0002]

2. Description of the Related Art For example, FIGS. 10 to 13 show optical displacement detectors employing three types of optical gratings used for detecting displacement of various precision stages. 10, the main scale 10 having a reflection-type first grating 11 and the transmission-type second grating 21 and four third scales 21 having a phase shift of 90 degrees.
The index scale 20 having the gratings 25A, 25RA, 25B, 25RB can be relatively displaced in the X direction.

Light-emitting elements (eg, LEDs) as diffusion light sources
Reference numeral 35 denotes a first grating 1 that transmits diffused light through the second grating 21.
Irradiate 1 The detection light reflected from the first grating 11 passes through each of the third gratings 25A, 25RA, 25B, and 25RB, and the third gratings 25A, 25RA, 25B, and 25R.
The light is incident on the respective light receiving elements (for example, photodiodes) 41A, 41RA, 41B, 41RB arranged corresponding to each of B.

The scale pitches of the first grating 11, the second grating 21 and the third grating 25 are respectively set to P1, P2 and P3. Further, each third grating 25 is connected to each of the light receiving elements 4.
1 are arranged so as to have a phase difference of 90 degrees with respect to each other in the photoelectric conversion signals of the first and second photoelectric conversion signals. For example, the third grating 2
5A, each third grating 25B, 25RA, 2
The 5RBs are displaced by 1/4, 1/2, and 3/4 pitch.

Further, as shown in FIG. 13, for example, the detection circuit 60 includes respective light receiving elements 41A, 41RA, 41B, 41R.
Four amplifiers 61A, 61RA, 61 to which B is connected
B, 61 RB and the amplified photoelectric conversion signals Sa and Sra
And an operational amplifier 62A that generates and outputs an A-phase detection signal SA to a terminal 63A, and an operational amplifier 62B that similarly generates and outputs a B-phase detection signal SB to a terminal 63B.

The light emitting element 35, each light receiving element 41A,
41RA, 41B, 41RB and the detection circuit 60 are housed in the unit case 1 integrated with the index scale 20.

Accordingly, the index scale 20
If (1) is mounted on the movable body side of the stage, for example, and the main scale 10 is mounted on the stationary body side, the two detection signals SA and SB output from the detection circuit 60 and having a sine wave-like phase difference of 90 degrees are digitally output. If processed, the movable body (2
0) and the relative displacement between the stationary body (10) can be detected with high accuracy. Further, the direction of displacement can also be detected.

The reflection type optical displacement detecting device using three kinds of optical gratings has a gap d between a main scale 10 and an index scale 20 shown in FIG.
Can be increased, so that the pitch P1 of the first grating 11 can be reduced. Therefore, mounting (handling) to the object to be detected is easy, and high-resolution and high-precision displacement detection can be performed.

[0009]

Incidentally, such an optical displacement detection device is no exception, and furthermore, higher resolution, higher accuracy, higher detection speed, and smaller size, lighter weight, and lower performance in terms of performance. There is a strong demand for cost reduction and easy handling. In other words, it is considered that the conventional device has many room for improvement.

That is, the fact that the gap d can be increased means that the attenuation of the diffused light is large. That is, the light energy that can be received by each of the light receiving elements 41A, 41RA, 41B, and 41RB becomes a very small solid angle 39 having the diffusion light source (35) as the apex as shown by the two-dot chain line in FIG. Low utilization of light energy. However,
Since the response speed of the light receiving element (41) is proportional to the amount of received light energy, it has been a factor that hinders further increase in detection speed.

Regarding the prevention of attenuation of the light energy, each of the third gratings 25A, 25RA, 25B, 2
A four-set system in which four light-emitting elements (35) and light-receiving elements (41) are provided according to the number (4) of 5RBs has been proposed, but this cannot satisfy the demand for further miniaturization.
The work of matching the relative positions is also complicated.

Thus, since the light-emitting element 35 is a common one, the third gratings 25A and 25RA and the third
As shown in FIG. 12, the gratings 25B and 25RB must be separated from each other in the longitudinal direction of the index scale 20 (the left-right direction in FIG. 12) with the second grating 21 interposed therebetween. Therefore, miniaturization is hindered and light energy utilization is reduced. Also, the scale pitch P1
, The plane including the first grating 11 such as 10 μm or less, the second grating 21 and the third gratings 25A, 25RA, 25
It is extremely difficult to precisely adjust the parallelism with the plane including B and 25RB, that is, the inclination angle in the R direction shown in FIG. 14 within a few seconds. It is very difficult to handle and causes high costs.

Further, each of the light receiving elements 41A, 41RA and 4RA
1B, 41RB and each of the third gratings 25 that are spaced apart from each other.
A, 25RA and 25B, 25RB must be separated from each other. Therefore, problems in temperature characteristics and deterioration characteristics occur, which hinders high-accuracy detection and lowers reliability.

For example, when used in a high-vacuum sealed room at about 10 ⁻⁷ Torr, such as an electronic drawing apparatus for semiconductor manufacturing or an electron microscope, the temperature rises by several tens degrees or more with respect to normal temperature. However, each of the light receiving elements 41A, 41RA, 41B,
Generally, the temperature characteristic of the semiconductor forming 41RB is 1
It is usual to have a variation of at least about 5% within a single wafer, and it is necessary to expect about 10% between lots.

Therefore, each of the light receiving elements 41A on one side is
If there is a difference in the temperature characteristics between the light receiving element 41RA and each of the light receiving elements 41B and 41RB on the other side, an error will be generated as it is, which will hinder high-precision detection. In addition, the deterioration characteristics are not known until the end of the service life, that is, it is extremely difficult to initially select the deterioration characteristics.

Each of these light receiving elements 41A, 41RA, 41
Variations in the temperature characteristics and deterioration characteristics of B and 41RB become even more severe in the case of the above four-set system. Further, even if an expensive hermetic seal type in which a light emitting element (for example, LED) 35 as a diffusion light source is housed in a metal package and an inert gas such as helium is sealed is employed, the problem of variation due to temperature rise cannot be solved.

The above problem is caused by the four third gratings 25.
A, 25RA, 25B, 25RB, two thirds
This also occurs in a system having a grating (25A, 25RB) and one or more reference windows.

An object of the present invention is to increase the resolution in terms of performance,
High accuracy, high detection speed, small size and light weight in use,
It is an object of the present invention to provide an optical displacement detection device capable of greatly reducing costs and facilitating handling.

[0019]

The principle of detection of an optical displacement detector using three types of optical gratings is described in, for example, Prin.
chips of Optics, 6thediti
on (MAX BORN & EMIL WOLF, Pe
rgamon Press, 1980), p. 383, and is reviewed using FIG. 1 and based on the theory of Fresnel diffraction.

The second grating 2 on the same plane shown in FIG.
1 and each third grating 25A (25RA), 25RB (25
B) as a reference grating 100 and a gap d
(Z), the first grating 11 is arranged in parallel,
Consider a case where the first grating 11 is tilted by a small angle △ θ about a point d (Z) on the axis. And a diffusion light source (35)
Is transmitted through the reference grating 100 and reflected (diffused) by the first grating 11, and the light intensity distribution on the X-axis when the reflected light reaches the reference grating 100 is represented by a constant Light intensity distribution function [I (x), I (x
θ)].

When the first grating 11 is parallel to the reference grating 100, the light intensity distribution function [I (x)] becomes [Equation 1] and [Equation 2].

(Equation 1) Note that F = COS [πλd (Z) / 2 (P1) ² ], λ is the effective wavelength of the diffused light S, and P1 is the first grating 1
A pitch of 1, d (Z) is a gap.

(Equation 2)

Strictly speaking, the light intensity distribution function is obtained by superposing [Equation 1] and [Equation 2]. However, when constructing an actual device, it is more convenient to treat each formula independently. Thus, if the scale pitches of the first grid 11, the second grid 21, and the third grid 25 are P1, P2, and P3, and n, m, and q are integers (1, 2, 3,...), The conditions for configuring the detection device using the detection principle of Equation 1 are as follows:
This is expressed by [Equation 3] and [Equation 4].

(Equation 3)

(Equation 4)

The conditions for constructing the detection device using the detection principle of [Equation 2] are expressed by [Equation 5] and [Equation 6].

(Equation 5)

(Equation 6)

In [Equation 3] and [Equation 5], m = q = 1 is the most basic condition. From the above,
In a reflection type detection device using three types of optical gratings, there are two configuration conditions.

That is, when the detection principle of [Equation 1] is used, the light intensity depends on the gap d (Z), but since the S / N ratio of the detection signal is good, the pitch P1 of the first grating 11 is set to 2
It is suitable for a pitch of about 0 μm or more.

When the detection principle of [Equation 2] is used, the light intensity does not depend on the gap d (Z), and when the first grating 11 is displaced by one pitch, the third grating 25 has the first grating. Detection signals for two pitches of the grating 11 are output. Therefore, it is suitable when the pitch P1 of the first grating 11 is set to a pitch of about 20 μm or less.

Next, the light intensity distribution function [I (xθ)] when the first grating 11 is inclined by a small angle △ θ with respect to the reference grating 100 is obtained by [Equation 7] and [Equation 8]. .

(Equation 7)

(Equation 8)

[Equation 7] and [Equation 8] are represented by [Equation 1],
[−2 △ θd (Z)] is added to the last term in [Equation 2]. Therefore, [−2 △ θd
If (Z)] is constant, it can be said that there is no problem since the detector can be handled as an offset.

However, as in the conventional detecting device, the light receiving element 41A (41RA) is disposed around the point X1 on the X axis shown in FIG. 1 with a gap d (Z1), and the light receiving element 41RB (41B) Is arranged around the point X2 and with a gap d (Z2), the light energy received by the light receiving element 41A is [Equation 7],
Substituting d (Z1) into d (Z) in [Equation 8], and the light energy received by the light receiving element 41RB is d (Z) as d (Z).
It can be obtained by substituting 2).

Here, d (Z1) -d (Z2) = △ θ
Since (X1 + X2) holds, when the first grating 11 and the reference grating 100 are relatively displaced in the X direction, the light receiving element 4
The phase difference between the detection signals of 1A and 41RB is Δθ (X1
It can be seen that the larger the value of + X2), the larger the value. According to [Equation 7] and [Equation 8], it is clear that the smaller the pitch P1 of the first grating 11 is, the more the influence is exerted.

From the above reexamination, the light receiving elements 41A (41RA) and 41R are required to achieve higher precision and higher resolution.
It is understood that it is necessary to make the interval between the light receiving elements B (41B) smaller, make the light receiving effective area of each light receiving element smaller, and further improve the dimensional accuracy and assembly accuracy of each light receiving element itself. In this way, it is possible to simultaneously reduce the size, weight, and cost.

Thus, according to the present invention, it is possible to collect the third gratings at one place, dispose them close to the second grating, and form each light receiving element corresponding to the third grating by dividing a one-chip light receiving element into four parts. By greatly reducing the distance and the effective light receiving area, the temperature characteristics and the deterioration characteristics of each light receiving element are made uniform, so that high resolution and high accuracy on the performance surface and miniaturization on the use surface can be achieved. Reduce weight and cost.

However, when the light receiving effective area of each light receiving element is reduced, the light receiving energy is also reduced. Therefore, by using a single light-emitting element with a condensing lens structure and arranging the light-emitting element, diffused light is effectively used, and the light-receiving energy of each light-receiving element is increased. However, the light source is a diffused light and should not be a coherent light source such as a collimated light or a semiconductor laser. With such a light source, the light sources are independent (incoherent) on the second lattice plane.
This is because the above [Equation 1] and [Equation 2] do not hold because the line light source cannot be generated.

That is, the light emitting element is selected from an LED or the like formed by an infinite number of point light sources, which has a large light source itself. Thus, the detection energy can be increased because the light receiving energy of each light receiving element can be increased, and the resolution can be increased because the gap d can be increased and the graduation pitch of the first grating can be made finer. Since it is a four-division type light receiving element with a chip, it is one step smaller and lighter,
At the same time as the cost is reduced, installation and handling become very easy.

However, since each of the third gratings is arranged close to the second grating and a diffusion light source is employed, the more the miniaturization is promoted, the more the diffused light from the light emitting element is directly incident on each light receiving element. The fear increases. Therefore, optical insulation means for preventing this is provided.

It should be noted that the above-described new idea can be similarly applied to a case where two third gratings and one or more reference windows are used instead of the four third gratings.

Here, the optical displacement detecting device according to the first aspect of the present invention comprises a main scale having a reflection-type first grating, and a transmission-type second grating and four transmission-type second gratings having a phase shift of 90 degrees. An index scale having a third grating is disposed so as to be relatively displaceable, and diffused light from the light emitting element is transmitted to the second scale.
The light transmitted through the grating, illuminates the first grating, is reflected by the first grating, and the detection light transmitted through the third grating is received by each light receiving element corresponding to each of the third gratings, and is output from each light receiving element. In the optical displacement detection device configured to detect the relative displacement between the two scales by analyzing the electrical signal, the third gratings are gathered at one location and the second grating is arranged in the longitudinal direction or the width direction of the index scale.
A light-emitting element with a single condensing lens, wherein the light-emitting elements are arranged in close proximity to a grating, each light-receiving element is formed by dividing a one-chip light-receiving element into four parts, and each light-receiving element is arranged corresponding to each of the third gratings. and permeable inclined disposed detection light reflected by the permeable and said first grating the respective third grating diffused light is second grating collected by the condenser lens so as to form a and the light emitting An optical insulating means is provided for preventing diffused light from the element from directly entering each of the light receiving elements.

The optical displacement detecting device according to claim 2 is
A main scale having a reflection-type first grating and an index scale having a transmission-type second grating, two third gratings having a phase shift of 90 degrees, and at least one reference window are arranged so as to be relatively displaceable. The diffused light from the light emitting element is transmitted through the second grating to irradiate the first grating and is reflected by the first grating, and the detection light transmitted through the third grating and the reference window is reflected by the third grating and the third grating. An optical displacement detection device configured to be able to detect relative displacement between the two scales by analyzing and processing an electric signal output from each light receiving element corresponding to each of the reference windows and output from each light receiving element. 3 grids and 1 reference window
And the light receiving elements are arranged close to the second grating in the longitudinal direction or the width direction of the index scale, and the number of the light receiving elements is reduced to one chip light receiving element by the total number of the third gratings and the number of the reference windows. The third grating and the reference window are formed separately, and the light emitting device is formed from a single light emitting device with a condensing lens, and the diffused light collected by the condensing lens is formed. Second
The detection light that can transmit through the grating and is reflected by the first grating is inclined so as to transmit through the third grating and the reference window, and diffused light from the light emitting element directly enters each light receiving element. An optical insulating means for preventing such a situation is provided.

[0039]

According to the first aspect of the present invention, the diffused light from the light emitting element is condensed by the lens, passes through the second grating on the index scale, and is incident on the first grating on the main scale with high light efficiency. You. At this time, since the light insulating means is provided, the diffused light does not directly enter each light receiving element.

The detection light reflected from the first grating is collected at one position on the index scale, passes through each of the third gratings arranged close to the second grating, and enters each light receiving element. Since each light receiving element is formed by dividing a one-chip light receiving element into four, there is no variation in temperature characteristics and deterioration characteristics.

Thus, if the index scale and the main scale are displaced relative to each other, by analyzing the photoelectric conversion signal from each light receiving element, the displacement can be obtained with high resolution.
High precision and high speed detection.

Also, since the second grating and each third grating are disposed close to each other in the longitudinal direction or the width direction of the index scale, the second grating and each third grating include a plane including the second grating and each third grating and the first grating. Since the parallelism with the plane can be adjusted relatively easily, the handling is easy, and the size and cost of the device can be reduced.

In the case of the second aspect of the present invention, two third gratings and at least one reference window are formed for the four third gratings in the case of the first aspect of the present invention. Is the same as that of the first aspect of the present invention. Therefore,
By supplementing the level adjustment of the photoelectric conversion signal output from the light receiving element corresponding to the reference window, the same operation as in the first aspect of the invention can be achieved.

[0044]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) This first embodiment is shown in FIGS. That is,
The present optical displacement detection device has a third optical displacement detector as shown in FIGS.
The gratings 25A, 25RA, 25B, 25RB are gathered at one location and the second in the width direction of the index scale 20.
The light receiving elements 41A, 41RA,
41B and 41RB are formed by dividing the one-chip light-receiving element 41 shown in FIG. 7 into four parts, the light-emitting element 30 is inclined and disposed as a single condensing lens structure shown in FIG. Provided, each of the third gratings 25A, 25RA, 25
B, 25 RB are made extremely close to each other, and the condensing lens 3 is diffused from the light emitting element 30 while reducing the effective light receiving area.
2 to facilitate effective use of the diffused light collected .

Parts common to those in the conventional example (FIGS. 10 to 14) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

In FIGS. 3 and 6, each third grating 25A,
25RA, 25B, 25RB are collected at one location and are in the width direction of the index scale 20 (vertical direction in FIG. 6).
Are arranged close to the second grating 21.

Therefore, in comparison with the case of the conventional example (FIG. 12), each of the third gratings 25A (25RA) and 25RB
(25B) can be minimized and the effective light-receiving area can be minimized, so that the displacement can be detected with high accuracy and high resolution from the theory of Fresnel diffraction.

Each of the third gratings 25A, 25RA, 25
B, 25RB, each light receiving element 41A, 41
Each of the RAs 41B and 41RB has a configuration in which a one-chip light receiving element (photodiode) is divided into four as shown in FIG. Therefore, variations in temperature characteristics and deterioration characteristics between the light receiving elements can be minimized. In addition, the relative positional relationship between the light receiving elements can be accurately maintained on the same plane. It is clear from the comparison with the conventional example (FIG. 10).

As shown in FIG. 5, the light emitting element 30 is an LED.
The holder 2 is formed with a condenser lens 31 and a condenser lens 32 and is inclined. Condensing lens with emitted diffused light
The diffused light collected by the laser beam is transmitted through the second
The detection light incident on the grating 11 and reflected from the first grating 11 is applied to each of the third gratings 25A, 25RA, 25B, 25R.
B and the corresponding light receiving elements 41A, 41RA, 4
It is tilted and held at an angle that allows the light to enter 1B and 41RB. Therefore, the light energy can be significantly and effectively used while suppressing the excessive diffusion of the diffused light, and the light receiving energy amount of each of the light receiving elements 41A, 41RA, 41B, 41RB can be increased, so that the response is further improved, that is, the detection speed is increased. Can be achieved.

As shown in FIG. 5, the light isolating means 50 scatters the light from the light emitting element 30 into the light receiving elements 41A and 41A.
1RA, 41B, and 41RB are means for preventing direct incidence on the light emitting element 30 and the light receiving element 41 in the case of the first embodiment. It is attached to one lower end of the holder 2 so that the optical insulating surface 51 is interposed therebetween. However, the optical insulating surface 51 may be formed integrally with the holder 2 itself. Further, the light insulating means 50 may be configured by coating with a light blocking agent or the like.

According to the first embodiment having such a structure, the diffused light from the light emitting element 30 (31) shown in FIG. 5 is collected by the condenser lens 32 and is spread on the index scale 20 in accordance with the inclined arrangement angle. The light passes through the second grating 21 and is efficiently incident on the reflective first grating 11 on the main scale 10.

At this time, the light isolating means 50 (51) optically insulates the light receiving elements 41A, 41RA, 41B, 41.
The diffused light does not directly enter the RB. That is, no disturbance light is given to each of the light receiving elements 41A, 41RA, 41B, 41RB. In addition, since the guide surface 3 of the holder 2 can also suppress unnecessary diffusion, the effective use of light energy can be enhanced from this point as well.

The detection light reflected from the first grating 11 is collected at one position in the width direction on the index scale, and each of the third gratings 25 A, 25 A,
Each of the light receiving elements 41A, 41RA, 41B, 41RB that transmits through 25RA, 25B, 25RB and corresponds to each of them.
Is incident on. These light receiving elements 41A, 41RA, 41
Since B and 41RB are formed by dividing the one-chip light receiving element 41 into four parts, there is no variation in temperature characteristics and deterioration characteristics. Further, a predetermined relative positional relationship is accurately maintained on the same plane.

When the index scale 20 and the main scale 10 are relatively displaced in the X direction, the photoelectric conversion signals from the light receiving elements 41A, 41RA, 41B, and 41RB are detected by the detection circuit 60 shown in FIG. By obtaining the phase detection signal SA and the B-phase detection signal SB, digitally processing and analyzing them, the displacement can be detected with high accuracy, high resolution, and high speed.

The second grating 21 and each third grating 25A,
Since the 25RA, 25B, and 25RB are arranged close to each other in the width direction of the index scale 20 as shown in FIGS. 3 and 6, the plane including the second grating 21 and the third gratings (25) and the first The degree of parallelism with the plane including the grid 11 can be adjusted and mounted more easily than in the case of the conventional example (FIGS. 12 and 13). Therefore, it is easy to handle, and the size and cost of the detection device can be significantly reduced.

Thus, according to the first embodiment, the third gratings 25A, 25RA, 25B, 25RB are gathered at one location and are arranged close to the second grating 21 in the width direction of the index scale 20, Light receiving elements 41A, 41R
A, 41B and 41RB are formed by dividing the one-chip light-receiving element 41 into four parts, the light-emitting element 30 is inclined and disposed as a single structure with a condensing lens, and the optical insulation means 50 is provided. 25A, 25RA, 25B, and 25RB are remarkably close to each other, and the effective use of the diffused light from the light emitting element 30 can be promoted while reducing the effective light receiving area. Accuracy, high-speed detection, small size and light weight in use, low cost, and easy handling are greatly improved.

Each of the third gratings 25A, 25RA, 25
Since the B and 25 RBs are gathered at one place and are arranged close to each other in the width direction of the index scale 20, the size of the device in the displacement direction can be further reduced as compared with the conventional example (FIG. 12). The degree of parallelism with respect to the plane including one grid 11 can be more easily and quickly established.

Each of the light receiving elements 41A, 41RA, 41
Since B and 41RB are formed by dividing the one-chip light-receiving element 41 into four parts, variations in temperature characteristics and the like can be minimized, so that higher-precision detection can be performed, reliability can be improved, and the distance between each light-receiving element can be improved. The arrangement on the same plane and the work of adjusting the relative positional relationship can be greatly reduced, and it can be obtained at low cost.

Further, since the light emitting element 30 is held at a predetermined inclination angle by the holder 2, a stable operation for a long time can be guaranteed.

Further, since the light insulating means 50 has an L-shaped folded plate structure, the structure is simple and can be realized at low cost.

Since the effective utilization of the diffused light from the light emitting element 30 can be increased, the gap d is increased,
The resolution of the grating 11 can be further improved by miniaturizing the scale.

(Second Embodiment) In this second embodiment, as shown in FIG. 8, the second grating 21 and each of the third gratings 25A and 25R are provided.
A, 25B, and 25RB are rotated 90 degrees as compared with the case of the first embodiment (FIG. 6), that is, the conventional example (FIG. 1).
It is configured to be arranged in a state corresponding to the case of 2).

Therefore, also in the case of the second embodiment, the first
The same operation and effect as the embodiment can be obtained.
Also, the size in the relative displacement direction can be reduced to about ／ from the comparison with the conventional example (FIG. 12).

(Third Embodiment) A third embodiment is shown in FIG. The difference from the first embodiment (FIG. 6) is that each third grating 25
1 where the scales of A and 25B are perpendicular to the scale of the second grid 21
The number of reference windows 26 is changed.
Other configurations are the same as those of the first embodiment.

According to the third embodiment having such a configuration, when each of the light receiving elements 41A, 41RA, 41B, 41RB is connected to the detection circuit 60 shown in FIG. 13, the sinusoidal A-phase and B-phase detection signals SA, SB Is 1/2 the level in the first embodiment. Therefore, by compensating for the decrease in the signal level, the same operation and effect as in the first embodiment can be obtained.

The reference window 26 is connected to the light receiving element 4
It is only necessary that the level of each photoelectric conversion signal output from the 1RA and 41B or the value of the output current can be made constant. Therefore, a transparent window without a scale may be used in consideration of amplification processing later. Further, since the output current values of the respective light receiving elements 41RA and 41B are substantially the same, it is possible to construct a dedicated structure using one of the light receiving elements 41RA and 41B.

[0067]

According to the first aspect of the present invention, each of the third gratings is gathered at one place and arranged close to the second grating in the longitudinal direction or the width direction of the index scale, and each light receiving element is a one-chip light receiving element. Are divided into four parts, the light-emitting elements are arranged in a slanted manner as a single structure with a condensing lens, and optical insulating means are provided so that the third gratings are remarkably close to each other and the effective light receiving area is reduced. collection in the diffused light from the light emitting element
Since it is configured to promote the effective use of diffused light collected by the optical lens, high resolution, high accuracy,
Significant improvements in detection speed, reduction in size and weight in use, cost reduction, and ease of handling can be achieved.

According to the second aspect of the present invention, the first aspect is provided.
In the present invention, two third gratings and at least one reference window are formed instead of the four third gratings, and the other configuration is the same as that of the first embodiment. Therefore, if the decrease in the level of the detection signal is complemented,
The same effect as in the case of the invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the technical basis of the present invention.

FIG. 2 is a side view showing the first embodiment of the present invention.

3 is a plan view based on the line AA of FIG. 2;

FIG. 4 is a plan view based on the line BB of FIG. 2;

FIG. 5 is a cross-sectional view also taken along line CC of FIG. 2;

FIG. 6 is a view for explaining the arrangement positional relationship between a light emitting element, a second grating, each third grating, and each light receiving element.

FIG. 7 is a diagram for explaining each light receiving element formed by dividing a one-chip light receiving element into four parts.

FIG. 8 is a diagram for explaining a second embodiment.

FIG. 9 is a diagram for explaining a third embodiment.

FIG. 10 is a side view for explaining a conventional example using three types of optical gratings.

FIG. 11 is a plan view based on the line of sight DD in FIG. 10;

FIG. 12 is a plan view based on the line EE of FIG. 10;

FIG. 13 is a circuit diagram for explaining an example of a detection circuit.

FIG. 14 is also an external perspective view for explaining the parallelism adjustment and its problems.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unit case 10 Main scale 11 1st grating 20 Index scale 21 2nd grating 25A, 25RA, 25B, 25RB 3rd grating 26 Reference window 30 Light emitting element 31 LED 32 Condensing lens 41 1 chip light receiving element 41A, 41RA, 41B, 41RB light receiving element 50 light insulating means 51 light insulating surface 60 detection circuit

Claims (2)

(57) [Claims] 1. A main scale having a reflection-type first grating and an index scale having a transmission-type second grating and four third gratings having a phase shift of 90 degrees are disposed so as to be relatively displaceable. The diffused light from the light emitting element is transmitted through the second grating, irradiates the first grating, is reflected by the first grating, and the detection light transmitted through the third grating is each light receiving element corresponding to each of the third gratings. In the optical displacement detecting device configured to detect the relative displacement of both scales by analyzing and processing the electric signal output from each light receiving element, the third gratings are collected at one location and the index The light receiving elements are arranged close to the second grating in the longitudinal direction or the width direction of the scale, each of the light receiving elements is formed by dividing one chip light receiving element into four parts, and each light receiving element is arranged corresponding to each of the third gratings. The permeable and the detection light reflected by the first grating respective third grating diffused light collected by the condenser lens is a second grid to form a device from a single condensing lens-mounted light emitting element An optical displacement detecting device, which is provided with an optical insulating means that is disposed so as to be capable of transmitting light and that prevents diffused light from the light emitting element from directly entering each of the light receiving elements. 2. A main scale having a reflection-type first grating, an index scale having a transmission-type second grating, two third gratings having a phase shift of 90 degrees, and at least one reference window. Arranged for relative displacement,
The diffused light from the light emitting element is transmitted through the second grating to irradiate the first grating and is reflected by the first grating, and the detection light transmitted through the third grating and the reference window is transmitted to the third grating and the reference window. In the optical displacement detection device configured to be able to detect the relative displacement of both scales by analyzing the electric signal received from each corresponding light receiving element and output from each light receiving element, the third grating and The reference windows are gathered at one location and disposed close to the second grating in the longitudinal direction or the width direction of the index scale. And the light-emitting elements are formed from a single light-emitting element with a condensing lens. Diffuse light collected by Atsumarikore lens is permeable inclined disposed detection light reflected by the permeable and said first grating the respective third grating and reference window a second grid as well as, and An optical displacement detecting device, comprising: an optical insulating means for preventing diffused light from the light emitting element from directly entering each of the light receiving elements.