JP2003149005A - Light receiving / emitting composite unit and displacement detection device using the same - Google Patents

Abstract

(57) [Problem] To provide a low-cost, high-reliability light receiving / emitting composite unit suitable for reduction in size and weight, and a displacement detection device using the unit. SOLUTION: In the composite light receiving and emitting unit 1, a light source 3 including a light emitting element 3a, a light branching unit 4 for returning light to the unit, lenses 8_1 to 8_3, diffraction optical elements 5_1 and 5_2 for polarization separation, The light receiving unit 6 including the light receiving elements 6_1 to 6_4 for detecting the diffracted light is formed as an integral structure. And, as an external optical system ET for the unit 1, a test portion including a reflection type diffraction grating RG,
Reflecting members R1a and R1b for reflecting the light emitted from the unit 1 toward the reflective diffraction grating RG, and polarizing members WP1a and WP1b for receiving the diffracted light from the reflective grating RG and changing the polarization state. Reflection members R2a and R2b for reflecting and returning light passing through each polarizing member
Are arranged to constitute a grating interference type displacement detecting device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical unit that uses a semiconductor laser as a light source and obtains a signal by using polarized light. In particular, it is a so-called "lattice interference type displacement detection" that detects displacement by using interference of diffracted light. It relates to the structure of the device.

[0002]

2. Description of the Related Art Displacement detecting devices used in the field of semiconductor manufacturing include, for example, a solid scale having a graduation recorded,
There is known a device (so-called linear encoder) including a detection unit that electrically detects a displacement amount of the scale in a linear movement direction.

A device (a hologram encoder or the like) for detecting displacement by utilizing interference of diffracted light obtained by a diffraction grating is given as a device for enabling detection with high accuracy and high resolution.

FIG. 4 shows an example a of the structure of a conventional displacement detecting device, which is composed of three parts: a light irradiation part b, an optical path control and inspection part c, and a light receiving part d.

In the light irradiation section b, a semiconductor laser LS is used as a light source, and a first converging lens L1 and a first polarization beam splitter PBS1 are arranged. Regarding the optical path control and the portion to be inspected c, the first reflection mirrors R1a and R1b, the reflection type diffraction grating RG, the second converging lenses L2a and L2b, the first λ / 4 wavelength plate (quarter wavelength). Plates WP1a and WP1b, and second reflecting mirrors R2a and R2b are arranged.

Regarding the light receiving section d, a semi-transmissive mirror HM,
Second polarization beam splitter PBS2, third polarization beam splitter PBS3, second λ / 4 wave plate WP
2, and photodetectors PD1 to PD4 are arranged.

The light emitted from the semiconductor laser LS is the first
After being converted into convergent light by the converging lens L1, the light is polarized and separated by the polarization beam splitter PBS1 into two lights (refer to the light beams LFa and LFb), one of which is subjected to the optical path change by the reflection mirror R1a to undergo the reflection-type diffraction. It reaches the grating RG, and the other reaches the reflection type diffraction grating RG after undergoing an optical path change by the reflection mirror R1b. Here, "polarization separation" means to separate the incident light beam into a P polarization component and an S polarization component.

In the reflection type diffraction grating RG attached to the portion to be inspected (linear scale, etc.), the same sign (the same sign)
For each light beam diffracted at least higher than the first order, the λ / 4 wave plate WP1a arranged at the angular position corresponding to the diffraction angle after passing through the second converging lenses L2a and L2b, WP1b and reflection mirror R2
After the respective polarization directions are rotated by 90 degrees by a and R2b, they reach the first polarization beam splitter PBS1 by following the same optical path as the forward path in the opposite direction.

Since the light reaching the polarization beam splitter PBS1 is in a state in which its polarization direction is rotated by 90 degrees with respect to the original direction, the light is emitted in a direction different from the incident direction on the outward path and is half emitted. It goes to the transmission mirror HM. The light amount of the light flux reaching the semi-transmissive mirror HM is 2
One of the split and split lights is the polarization beam splitter P
It reaches BS3, and the other light reaches the polarization beam splitter PBS2 after passing through the λ / 4 wave plate WP2.

With respect to the mounting posture of the polarization beam splitter PBS3, the polarization beam splitter PBS3 is arranged so that it is rotated around the optical axis with an angle of about 45 degrees with respect to the polarization direction of the reaching light beam.

The light beams polarized and separated by the polarization beam splitter PBS2 reach the photodetectors PD1 and PD2, respectively, and the light intensity is converted into an electric quantity. The light beams polarized and separated by the polarization beam splitter PBS3 reach the photodetectors PD3 and PD4, respectively, and the light intensity is converted into an electric quantity.

The operating principle of this example is as follows.

Two light beams LFa and LFb having different polarization directions (or polarization states) separated by the polarization beam splitter PBS1 are reflected and diffracted by the reflection type diffraction grating RG to become diffracted light of the same sign, and λ / 4 wave plates WP1a, WP1b and reflection mirror R
By 2a and R2b, a light beam whose polarization direction is rotated by about 90 degrees from the forward path is returned to the polarization beam splitter PBS1 and mixed.

At this time, since the two mixed light fluxes are bisected by the semiconductor laser LS having the same polarization component, the two lights interfere with each other even if they have different polarization directions.

Now, when the reflection type diffraction grating RG is moved in the direction in which the gratings are arranged relatively to other optical systems (for example, the direction indicated by arrow A in FIG. 4), the polarization beam splitter PBS is used.
The lights mixed in 1 interfere with each other, and an intensity change occurs at a pitch according to the diffraction order for each polarization direction. By separating the intensity change due to this interference into multiple polarization components,
The photodetectors PD1 to PD4 can detect light intensity distributions having different phases. That is, by detecting this change in light intensity, the movement amount of the reflection type diffraction grating RG can be detected with a resolution obtained by multiplying the reciprocal number of the diffraction order and the reciprocal number of the diffraction number with respect to the diffraction grating pitch by one half. You can Further, since the intensity changes obtained by the photodetectors PD1 to PD4 have a shape very close to a sine wave, it is possible to obtain high resolution by the method of interpolating the detected waveform.

In such a displacement detecting device using interference of diffracted light, for example, a reflection type diffraction grating is formed by a hologram or the like, and the obtained sine wave signal is divided to obtain nm (nanometer) order. It is also possible to achieve resolution.

[0017]

However, in the conventional displacement detecting device, it is necessary to assemble the individually manufactured light emitting components, light receiving components, or optical components while individually adjusting them in the manufacturing process. , There was a problem shown below.

When assembling the apparatus, it is necessary to make a precise adjustment for variations in finishing accuracy or characteristics of each part, which complicates the process and makes it difficult to reduce the cost.

A large space is required for adjusting, fastening and fixing each component, and it is difficult to reduce the shape of the device.

Since the adhesive must be used for the main fixing after the precise adjustment, the adhesion state is easily influenced by the surrounding environment change, etc., and the adjustment part is displaced due to the environmental change or the change over time. There is a risk that

Therefore, the present invention provides a highly reliable light emitting and receiving composite unit suitable for low cost, small size and light weight, and a displacement detecting device using the interference of diffracted light while mounting the unit. Is an issue.

[0022]

In order to solve the above-mentioned problems, a light emitting / receiving composite unit according to the present invention returns a light emitting element and light emitted from the light emitting element to the unit through an external optical system. A plurality of light receiving elements for detecting the returned light are arranged on the same substrate or member,
An optical branching part for the returning light (or an optical branching part including the same), a lens for converging or diverging the outgoing light and the returning light, and a polarization component in an arbitrary direction is separated from the polarization state of the returning light to be directed in different directions. Diffraction member for diffracting,
It has an integrally formed structure.

Further, the displacement detecting apparatus according to the present invention is such that the light emitting and receiving composite unit manufactured in such an integrated structure, the test portion including the diffraction grating as an external optical system for the unit, and the light receiving and emitting composite unit. A polarizing member for receiving the diffracted light after being emitted from the diffraction grating and changing the polarization state, and a reflecting member for reflecting the light passing through the polarizing member and returning it in the opposite direction (direction toward the diffraction grating). And are provided.

Therefore, according to the present invention, the light emitting element, the light receiving element, the light branching portion for the returning light to the unit, the lens, and the diffractive member are integrally structured, so that the position adjustment of each portion becomes easy and the cost is low. It is possible to manufacture a highly reliable light emitting and receiving combined unit suitable for size reduction, size reduction, and weight reduction, and a displacement detection device using the same.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a configuration example of a displacement detecting device using a light emitting and receiving combined unit (or a light transmitting and receiving unit) according to the present invention, which is applied to a grating interference type displacement detecting device. It is a thing.

As can be seen from the structural comparison with FIG.
Most of the components of the optical system are housed in the light emitting / receiving composite unit 1, and the two light beams LFa and LFb that have been polarized and separated in the unit and then emitted to the outside are as follows.
The first reflecting member (reflecting mirror R1) that constitutes the external optical system ET.
a, R1b) to reach the respective optical paths.
It should be noted that these first reflecting members are necessary for reflecting the light emitted from the combined light emitting and receiving unit 1 toward the reflection type diffraction grating RG, for example, the hologram grating having a high diffraction efficiency (volume phase hologram or the like). It is something.

Each light that reaches the reflection type diffraction grating RG used for a detected part such as a linear scale is injected into the grating at a short distance (the difference in the optical path length in the grating is reduced to reduce the wavelength of the original signal). Error is less likely to occur.), After being diffracted by the first or higher order, the polarization members (λ / 4 wavelength plates WP1a and WP) are respectively passed through the converging lenses L2a and L2b.
1b) and the second reflecting member (reflecting mirrors R2a, R2b). That is, the light beam LFa reaches the reflecting mirror R2a via the λ / 4 wavelength plate WP1a after being diffracted by the reflection type diffraction grating RG, and the light beam LFb is diffracted by λ after the diffraction by the reflection type diffraction grating RG. / 4 wave plate WP1b
To reach the reflecting mirror R2b. Incidentally, regarding these λ / 4 wave plates WP1a and WP1b, the reflection type diffraction grating R
It has a role of changing the polarization state by receiving the diffracted light by G, and rotates the polarization direction by 90 degrees as described above. Further, the reflecting mirrors R2a and R2b have a role of reflecting the light whose polarization state has been changed and returning it in the opposite direction, and each reflected light follows the forward path in the reverse direction, and the light receiving and emitting composite unit. Reach 1 (return light to the unit).

FIG. 2 shows an example of the structure of the combined light emitting and receiving unit 1 and shows the main part of the internal structure.

The light emitting / receiving composite unit 1 has a light source 3, a light branching portion 4, lens groups 8_1 to 8_3, and a diffractive member 5 (5_1, 5) for the housing member (or sealing member) 2 thereof.
5_2), the light receiving portions 6 (6_1 to 6_4), and the λ / 4 wavelength plate 11 are arranged to form an integrated structure.

The light source 3 is used as a measuring light source (or a light emitting section) in the application to the above displacement detecting device. The light emitting element 3a (for example, a semiconductor laser is used) is fixed on the semiconductor substrate 7 having a reflection surface 7a for the light emitted by the element. That is,
The reflecting surface 7a serves as an optical path changing means for changing the light emitted from the light emitting element 3a in the direction along the set optical axis of the light source 3 (vertical direction in the same figure), and functions to raise the light upward in the figure. To do. The semiconductor substrate 7 is fixed to the inner bottom surface of the housing member 2.

A light receiving portion 6 is housed in the housing member 2, and a plurality of light receiving elements 6_1 to 6_4 are provided in the semiconductor substrate 6 for detecting light passing through the diffractive member 5 (5_1, 5_2).
It is formed in a. Although not shown in the drawing, the light emitting element 3a or the semiconductor substrate 6a or 7 is electrically connected to an electrode member for wiring that leads from the housing member 2 to the outside by, for example, wire bonding. .

The housing member 2 on which the semiconductor substrates 6a and 7 are arranged and fixed is provided with a cover member 8 for covering and sealing the opening, whereby the light source 3, the light receiving portion 6, and the diffractive member 5 are packaged. Be converted. The cover member 8 includes
For example, a transparent plastic material is used and a plurality of lenses 8_1 to 8_3 are formed. That is, the lens 8_1 is a converging lens arranged on the optical axis of the light source 3, and light emitted from the light emitting element 3a and then reflected by the reflecting surface 7a is transmitted to the lens through the λ / 4 wavelength plate 11. Incident,
The light that has passed through the lens is emitted to the outside of the unit via the polarization separation film described below. The lenses 8_2 and 8_3 are provided to converge (or diverge) the return light from the external optical system ET shown in FIG.

On the cover member 8, the λ / 4 wave plate 11 is arranged near the lens 8_1. Then, the compound prism 9 that constitutes the light branching unit 4 and includes the λ / 4 wavelength plate 10, and further, the polarization splitting arranged near the lenses 8_2 and 8_3 to split the polarization component of the split return light. The diffractive optical elements 5_1 and 5_2 are fixed.

That is, on the inner surface side of the cover member 8, λ /
The four-wave plate 11 and the diffractive optical elements 5_1 and 5_2 are fixed, and the diffractive optical elements 5_1 and 5_2 form the diffractive member 5. The diffractive optical element 5_1 is provided for the lens 8_2, and the light diffracted by the element is detected by the light receiving elements 6_1 and 6_2. In addition, the diffractive optical element 5_2
Is provided for the lens 8_3, and the light diffracted by the element is detected by the light receiving elements 6_3 and 6_4.

A composite prism 9 is mounted and fixed on the upper surface of the cover member 8, and is provided with a polarization splitting film 9a, a light splitting film 9b for splitting a returning light beam, and a total reflection surface 9c. That is, the polarization splitting film 9a and the light splitting film 9b constitute the light splitting unit 4, and the polarization splitting film 9a is arranged at the position corresponding to the lens 8_1 and on the optical axis of the light source 3, and The light branching film 9b is arranged at a position corresponding to the lens 8_2. The total reflection surface 9c is arranged at a position corresponding to the lens 8_3.

As described above, the lens and the diffractive optical element are arranged between the composite prism 9 and the light receiving portion 6.

Immediately behind the light branching film 9b (total reflection surface 9c
A λ / 4 wave plate 10 (corresponding to the WP2) is disposed on the side), and the return light, which has passed through the wave plate, reaches the total reflection surface 9c.

In this example, the return light flux returning to the unit 1 through the external optical system ET is converted into the light branching film 9b.
However, the number of branches is not limited to this, and it may be configured such that at least two branches are introduced to the diffractive optical element for polarization separation. Further, the position of the diffractive optical element may be any position as long as it is between the light branching film 9b and the total reflection surface 9c and the light receiving section 6.

The operation of this structure is as follows.

First, the light emitted from the light emitting element 3a is reflected by the reflecting surface 7a of the semiconductor substrate 7 and undergoes an optical path change.
Then, the reflected light becomes circularly polarized light by the λ / 4 wavelength plate 11, becomes convergent light by the converging lens 8_1 arranged in the cover member 8, and reaches the polarization separation film 9a of the composite prism 9.

The light beams LFa and LFb separated into linearly polarized light components by the polarization separation film 9a are diffracted by the reflection type diffraction grating RG of the external optical system ET shown in FIG. The polarization direction is rotated by about 90 degrees and becomes return light, which enters the composite prism 9 (the light of the light beam LFb enters from the upper side of FIG. 2 and the light of the light beam LFa enters from the left side of FIG. 2), and the polarized light is separated again. Return to the membrane 9a.

Since the respective return light beams have a phase difference of 90 degrees with respect to the polarization states which are incident from the light source 3 and are separated, the light branching film 9b and the total reflection surface 9c while mixing.
Head to. Further, the λ / 4 wave plate 10 arranged in the compound prism 9 has a function of further adding phase information by changing linearly polarized light into circularly polarized light.

With respect to the light beam split by the light branching film 9b and the total reflection surface 9c, the converging lens 8_2 of the cover member 8,
After it becomes convergent light by 8_3, it is separated into polarization components by the corresponding diffractive optical elements 5_1 and 5_2 and diffracted at different angles. Then, the diffracted light reaches the corresponding light receiving elements 6_1 to 6_4.

Incidentally, the diffractive optical elements 5_1 and 5 for separating polarized light
_2 can be manufactured by using, for example, a semiconductor lithography technique as a diffractive optical element having a grating period shorter than the emission wavelength of the light source 3, and in this example, the number of branches is 4, For example, the polarization direction is 0 degree,
The light fluxes set at 45 degrees, 90 degrees, and 135 degrees (intervals of 45 degrees) are separated and reach the light receiving elements 6_1 to 6_4, respectively.

With respect to the respective light fluxes incident on the respective light receiving elements 6_1 to 6_4, since the information on the movement amount relating to the reflection type diffraction grating RG due to the interference of the higher order diffracted light is included as the change in the light receiving amount, The amount of movement of the diffraction grating RG can be obtained by appropriately performing known arithmetic processing on the detection signal received by each light receiving element and converted into an electric signal.

In this example, when a semiconductor laser is used as the light emitting element 3a, the light emitted from the semiconductor laser is linearly polarized light parallel to the mounting surface. The λ / 4 wavelength plate 11 is used so that the polarization separation film 9a can perform polarization separation with an appropriate amount of light, but the present invention is not limited to this, and the configuration shown in FIG. 3 (the semiconductor substrate 7 on which the light emitting element 3a is mounted is shown. The posture can be rotated by an angle θ of approximately 45 degrees in the mounting surface of the housing member 2).

FIG. 3 is a plan view seen from the optical axis direction of the light source and the light receiving portion. In the light emitting and receiving composite unit 1, the light emitting element 3a (semiconductor laser) and the cover member 8 and the composite prism 9 are removed. The positional relationship between the semiconductor substrate 7 on which the reflecting surface 7a is mounted and the semiconductor substrate 6a forming the light receiving unit 6 is shown.

When the combined light emitting and receiving unit 1 is viewed from the optical axis directions of the light source 3 and the light receiving portion 6, the straight line "LN1" is
A straight line (light emitting axis) including the light emitting direction (emission direction) of the light emitting element 3a is shown (the set optical axis of the light source is a direction orthogonal to the paper surface). The straight line “LN2” is the semiconductor substrate 6
A straight line passing through each center of the light receiving elements 6_1 to 6_4 (indicated by broken line rectangles in the figure) formed in a (light receiving center, that is, the intersection of the optical axis of each element and the light receiving surface) is shown. It extends in the longitudinal direction of the semiconductor substrate 6a. The angle “θ” represents the angle formed by the straight line LN1 and the straight line LN2, and is an angle of 45 degrees (or almost 45 degrees).

According to this arrangement, the emitted light deflected from the light emitting element 3a on the reflecting surface 7a (raised in the optical axis direction of the light source 3 by changing the optical path) is substantially in accordance with the mounting angle of the semiconductor substrate 7. Polarization separation film 9a with a polarization angle of 45 degrees
Since the light is separated into the P-polarized component and the S-polarized component having almost the same light amount, it is possible to prevent uneven separation of the light flux.

In addition to the light receiving circuit, the semiconductor substrate 6a on which the light receiving elements 6_1 to 6_4 are formed is integrated with a detection signal amplification circuit (current-voltage conversion amplification circuit or the like) and an arithmetic circuit related to the detection signal. By forming the same, it is possible to realize the advantages of integration, for example, the detection accuracy is improved by improving the S / N ratio (signal-to-noise ratio), and the size and cost of the entire device can be reduced.

Note that the above-described structure is merely an example of the present invention. For example, the semiconductor substrates 6a and 7 are arranged and fixed on the inner bottom surface of the housing member 2, but have the same function. The present invention is not limited to this structure as long as it is based on the gist of the present invention, and the converging lenses 8_1 to 8_3 and the like formed integrally with the cover member 8 may be replaced with equivalent optical components. There are various embodiments such as the structure described above.

The above-described combined light emitting and receiving unit 1 and the displacement detecting device using the same have the following advantages.

First, in the conventional displacement detecting device, as shown in FIG. 4, from the light source LS to the polarization beam splitter PB.
In the optical path to S1 and the optical path from the beam splitter to the photodetectors PD1 to PD4, individual optical components are arranged. Therefore, for example, each component is fixed to a base portion such as an optical base. It is necessary to keep in mind that it is troublesome to adjust the positional relationship of each part,
According to the present invention, there is no such inconvenience.

That is, as in the present invention, when an optical component (optical element or the like) is packaged and integrally formed in a semiconductor encapsulation structure, a polarization separation for separating a polarization component related to a return light beam is performed. The diffractive optical elements 5_1 and 5_2 can be placed in the optical path, the light emitting element 3a and the light receiving elements 6_1 to 6_4 can be arranged in a plane, and the integrally formed optical parts can be moved or the mounting posture thereof can be changed. It can be easily manufactured by fixing after being adjusted. In particular, a semiconductor element is precisely arranged and fixed in a connected semiconductor encapsulation component, for example, which has a reference part on or on a silicon wafer,
After fixing, the electronic parts (light emitting element, light receiving element, etc.) are energized to operate, and then the optical parts are placed at a predetermined position to detect the state and amount of light flux reaching the light receiving element from the light emitting element before the optical Fine adjustment of the position of parts and then fixing can be easily realized using existing technology (for example,
Head device for optical discs (optical pickup, etc.)
It is realized by the optical system in. ). Therefore, the adjustment and the assembly process can be easily performed using the semiconductor manufacturing equipment.

By integrally forming the components in the semiconductor encapsulation structure in this manner, adjustment becomes extremely easy, and
It is possible to reduce the size and weight of the shape and mass, and at the same time, it is possible to guarantee the high reliability that has been proven in semiconductor manufacturing.

Furthermore, by using a diffractive optical element for separating polarized light, a compact structure can be realized.

[0057]

As is apparent from the above description, according to the first and third aspects of the invention, the light emitting element and the light receiving element, the optical branching portion for the returning light to the unit,
Since the lens and the diffractive member are integrally structured, precise position adjustment is facilitated, and it is not necessary to take a large space for arranging parts, which is suitable for downsizing. Further, by confining each part in the same housing member, it becomes difficult to be affected by environmental changes and changes over time, so that it is possible to prevent the occurrence of misalignment and improve the reliability of the unit.

According to the inventions of claims 2 and 4,
By disposing the diffractive member between the light branching portion and the light receiving element, a compact structure can be realized and the polarization component of the return light can be separated.

According to the inventions of claims 5 and 6,
Polarization separation (separation into P-polarized light and S-polarized light) can be performed with a substantially uniform light amount.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a grating interference type displacement detection device using a combined light emitting and receiving unit according to the present invention.

FIG. 2 is a diagram showing an example of a configuration of a combined light emitting and receiving unit according to the present invention.

FIG. 3 is a plan view for explaining an arrangement example of a light source and a light receiving section in the combined light emitting and receiving unit.

FIG. 4 is a diagram showing a configuration example of a conventional grating interference type displacement detection device.

[Explanation of symbols]

1 ... Receiving and emitting combined unit, 1, ET ... Displacement detection device, 3
... light source, 3a ... light emitting element, 4 ... light branching part, 5, 5_1,
5_2 ... Diffraction member, 6 ... Light receiving part, 6_1 to 6_4 ...
Light receiving element, 8_1 to 8_3 ... Lens, 9a ... Polarization separation film, ET ... External optical system, RG ... Diffraction grating, R2a, R2
b ... Reflecting member, WP1a, WP1b ... Polarizing member

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 31/12 H01L 31/12 GF term (reference) 2F065 AA02 AA09 DD02 FF16 FF48 FF49 GG06 HH09 HH12 HH14 JJ01 JJ05 JJ08 JJ23 LL00 LL04 LL12 LL33 LL36 LL42 LL47 LL51 2F103 BA04 BA06 BA37 CA03 CA04 CA08 DA01 DA12 EA03 EA15 EB02 EB12 EB16 EB28 EB32 EB36 EB37 EC01 EC11 EC12 EC13 EC14 EC15 ED01 ED07 FA01 FA11 GA01 GA02 GA15 2H049 AA07 AA34 AA55 BA05 BA07 BB03 BC23 5F089 BA02 BB02 BC07 BC16 BC25 GA03 GA05 GA10

Claims (6)

[Claims] 1. A light emitting element and a plurality of light receiving elements for detecting return light emitted from the light emitting element and returned to a unit through an external optical system are arranged on the same substrate or member. Along with the optical branching portion for the return light, a lens for converging or diverging the emitted light and the return light, and a diffraction component for separating a polarization component in an arbitrary direction from the polarization state of the return light and diffracting it in different directions. A light emitting and receiving composite unit having a structure in which members are arranged and these members are integrally formed. 2. The light emitting and receiving composite unit according to claim 1, wherein the diffractive member is arranged between the light branching portion and the light receiving element. 3. A light-emitting element and a plurality of light-receiving elements for detecting return light emitted from the light-emitting element and returned to the unit through an external optical system are arranged on the same substrate or member. At the same time, an optical branching portion for the return light, a lens for converging or diverging the emitted light and the return light, and diffraction for separating a polarization component in an arbitrary direction from the polarization state of the return light and diffracting it in different directions A light receiving and emitting composite unit having a structure in which members are arranged and the members are integrally formed, a test portion including a diffraction grating, and diffracted light by the diffraction grating after being emitted from the light receiving and emitting composite unit. A displacement detecting device comprising: an external optical system including a polarizing member for receiving the light and changing the polarization state thereof and a reflecting member for reflecting the light passing through the polarizing member and returning the light in the opposite direction. 4. The displacement detecting device according to claim 3, wherein the diffractive member is arranged between the light branching portion and the light receiving element. 5. The combined light emitting and receiving unit according to claim 1, wherein the light emitted from the light emitting element reaches the polarization splitting film after the light path is changed in a direction along the set optical axis, When viewed from the optical axis direction of the light receiving section including the light source including the light emitting element and the light receiving element, a straight line including the emission direction of the light related to the light emitting element and a straight line passing through the center of each light receiving element forming the light receiving section Is arranged so as to form an angle of about 45 °. 6. The displacement detecting device according to claim 3, wherein the light emitted from the light emitting element in the light emitting / receiving composite unit is changed in optical path in a direction along the set optical axis before reaching the polarization separation film. When the light receiving and emitting composite unit is viewed from the optical axis direction of the light source including the light emitting element and the light receiving section including the light receiving element, the straight line including the light emitting direction of the light emitting element and the light receiving section are formed. A displacement detecting device characterized in that it is arranged so that a straight line passing through the center of each light-receiving element that constitutes it forms an angle of approximately 45 °.