JPH08152313A - Composite optical element and inclination angle measuring apparatus employing it - Google Patents

Abstract

PURPOSE: To increase the quantity of luminous flux to be received by providing a polarization separation plane for reflecting the predetermined polarization components of an incident light and passing the perpendicularly intersecting components, and an optical path for reflecting the transmitted components and returning the transmitted components to the separation plane. CONSTITUTION: Lights from a light source 101 enter into a collimator lens 102 to produce a collimated luminous flux L0 which enters into a righ-angle prism 103. A luminous flux L0 impinging normally on an incident plane 103a enters into an inclining plane 103b at an angle of about 45 deg. and the S polarization component LPR1 is reflected on a polarization separation plane 104 on the outside while the P polarization component LPT1 is transmitted through the plane 104. The luminous flux LPR1 leaves an outgoing plane 1O3c as a reference light while the luminous flux LPT1 enters, as a measuring light, into an optical member 105 from the bottom face 105a and passes through a reflection optical path including a measuring plane 109a and the separation plane 104 before leaving the outgoing plane 103c as a luminous flux LPT2 . The luminous flux LPR1 , LPT2 passes through a lens 106 to be imaged on the light receiving element in a detector 107 and the inclination angle of apparatus is determined based on the relative displacement in the position of condensation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a beam splitter which allows a light source having no polarization characteristics to pass at least one of reflected light and transmitted light a plurality of times repeatedly and to compare the respective amounts of light. The present invention relates to an optical element and an optical device using the same.

[0002]

2. Description of the Related Art An example of a conventional tilt angle measuring device is shown in FIG. In this device, the right-angle prism 303, the optical member 30
5 and a composite optical element having an optical path splitting surface 304, and the optical path splitting surface 304 is provided on the joint surface between the right-angle prism 303 and the optical member 305.

The right-angle prism 303 has an entrance surface 303a and an exit surface 303c which are orthogonal to each other, and these are the entrance and exit surfaces of the light flux in the above-mentioned composite optical element. An optical path splitting surface 304 is provided on the outer side of the inclined surface (bonding surface) 303b of the right-angled prism, and an optical member is arranged on the opposite side so as to be in contact with the bottom surface (bonding surface) 305a. That is, the conventional composite optical element shown in this figure is
The optical path splitting surface 304 is sandwiched between the inclined surface 303b of the right angle prism and the bottom surface 305a of the optical member.

Here, the optical path splitting surface 304 is constituted by a so-called half mirror that intensity-divides the incident light into a transmitted light and a reflected light, and a part of the light flux incident on the sloped surface 303b of the right-angled prism is partially converted. It has a function of reflecting at a predetermined ratio R and transmitting the rest (ratio T = 1-R).

The optical member 305 has a bottom surface (bonding surface) 305.
a, side surfaces 305b and 305c, and an upper surface 305d, and is joined to the optical path splitting surface 304 at the bottom surface 305a. Therefore, of the light flux L ₀ incident on the inclined surface 303 b of the right-angled prism, the light flux L ₀ transmitted through the optical path splitting surface 304
_T1 is introduced into the optical member 305 from the bottom surface 305a.
Each surface of the optical member 305 has a function as a reflecting surface (excluding 305d) for the light flux L _T1 incident on the optical member 305.

The bottom surface 305a and the top surface 305d and the side surfaces 305b and 305c are arranged so as to face each other in parallel. The optical member 305 having such a plurality of reflecting surfaces internally forms a return optical path for the incident light beam L _T1 . Specifically, the light flux that has passed through the optical path splitting surface 304 (the light flux that has entered the optical member 305 from the bottom surface 305a) L
Regressing _T1 with a return optical path consisting of multiple reflective surfaces,
It has a function of guiding the light to the optical path dividing surface 304 again and partially transmitting the light again (light flux L _T2 ).

The right angle prism 303 and the optical member 305 are
Both are made of members having substantially the same refractive index. The parallel light beam L _{0 that} is incident substantially perpendicularly to the incidence surface 303a of the right-angled prism has an incident angle of approximately 4 with respect to the inclined surface 303b.
The optical path splitting surface 3 which is incident at 5 ° and is provided outside the slope 303b
At 04, a part is reflected and the rest is transmitted. Optical path splitting surface 3
The light flux L _R1 reflected by 04 is the exit surface 3 of the rectangular prism.
The light is emitted almost vertically from 03c.

The luminous flux L _T1 transmitted through the optical path splitting surface 304 is
The light is introduced from the bottom surface 305a of the optical member to the optical member 305, traces a return optical path configured such that the incident angle and the reflection angle of each light flux L _T1 on each reflection surface are approximately 45 °, and again enters the optical path splitting surface 304. To do. At this time, the light is incident from the side opposite to the first time (the back surface side) at an incident angle of approximately 45 °. Here, the light flux L _T2 that has partially passed through the optical path splitting surface 304 again passes through the right-angle prism 303 and exit surface 303 c.
Is emitted vertically from. The emission direction at this time almost overlaps the emission optical path of the light flux L _R1 reflected by the optical path splitting surface 304.

The tilt angle measuring device using the conventional composite optical element as described above is composed of the composite optical elements (303 to 305).
And the measurement surface 309a and light source means (30
1 to 302) and light receiving means (306 to 307).

The measurement surface 309a is joined to the above-mentioned optical member at 305d on the upper surface of the liquid enclosure case 308.
It is composed of the liquid surface (surface) of the liquid 309 sealed in the hollow inside (joined at the bottom plate portion 308a). This functions as one of the reflecting surfaces in the returning optical path for the light flux L _T1 described above.

The light beam L _T1 follows the return optical path composed of the optical member side surface 305c, the measurement surface 309a, and the optical member side surface 305b, passes through the optical path splitting surface 304 again (light beam L _T2 ), and exits via the right-angle prism 303. The light is emitted vertically from 303c. The emission direction at this time is the liquid surface 309.
It changes depending on the height of a and the inclination with respect to the optical path splitting surface 304.

Here, the height of the liquid surface 309a is
With reference to a state (horizontal state) in which 9a faces the optical path dividing surface 304 in parallel, the emission direction of the light flux L _T2 is
The light flux L _R1 reflected by the optical path splitting surface 304 is adjusted so as to substantially overlap with the outgoing light path.

The transparent liquid 309 and the bottom plate 308a of the liquid-filled case are the right-angled prism 303 which constitutes a composite optical element.
The optical member 305 and the optical member 305 have substantially the same refractive index.

The light source means comprises a light source 301, a collimator lens 302 and the like. The light source 301 is a non-polarized light source having no polarization characteristic. Collimator lens 302
Are arranged in front of the entrance surface 303a of the rectangular prism, and are arranged so that the light beam emitted from the light source 301 becomes a parallel light beam L ₀ and is incident perpendicularly on the entrance surface 303a of the rectangular prism. .

The light receiving means comprises a condenser lens 306 and a photoelectric detector 307. The condenser lens 306 is disposed on the rear surface of the exit surface 303c of the right-angle prism, and emits light from the composite optical element (light flux L reflected from the optical path splitting surface 304).
_R1 and the light beam L _T2 which has been transmitted twice are condensed on the light receiving surface of the photoelectric detector 307. The photoelectric detector 307 is composed of a light receiving element such as a CCD line sensor and detects the focus position of each emitted light beam.

The light beam emitted from the light source 301 is converted into a substantially parallel light beam L ₀ via the collimator lens 302,
First, the rectangular prism 303 is introduced. The parallel light beam L _{0 that} is incident substantially perpendicularly to the incidence surface 303a of the right-angled prism is incident on the slope surface 303b at an incident angle of 45 °, and is partially reflected by the optical path dividing surface 304 provided outside the slope surface 303b. , The rest is transparent.

The light beam L _R1 reflected by the optical path splitting surface 304 is
The reference light is emitted almost vertically from the emission surface 303c of the rectangular prism. Light flux L _T1 transmitted through the optical path splitting surface 304
Is introduced as measurement light from the bottom surface 305a of the optical member to the optical member 305, travels through the optical splitting surface 304 again following the above-mentioned returning optical path (light flux L _T2 ), and the right angle prism 3
The light is vertically emitted from the emission surface 303c via 03.

Both the reference light L _R1 and the measurement light L _T2 are condensed on the light receiving element of the photoelectric detector 307 via the condenser lens 306. The respective focusing positions are P ₁ and P ₂ .

Here, a measurement surface 309a is included in the return optical path traced by the light flux L _T1 , and a state (horizontal state) in which the measurement surface 309a opposes the optical path dividing surface 304 in parallel is set as a reference. , The emission direction of the measurement light L _T2 is the reference light L
_Since it is adjusted so that it almost overlaps the exit optical path of _R1 ,
In the horizontal state, the _focus positions P ₁ and P ₂ of the light fluxes L _R1 and L _T2 substantially coincide with each other.

On the other hand, when the entire tilt angle measuring device is tilted, the liquid surface 309a is always kept horizontal, so that the liquid surface 309a is relatively tilted with respect to the device. This state is represented in the figure as a liquid surface 309b (dotted line). At this time, the return optical path that the measurement light L _T1 follows is the liquid surface 30.
After being reflected by 9b, it changes as shown by the dotted line in the figure (light flux L _T1 '), and the focus position on the photoelectric detector 307 is P.
Displaces to ₂ '.

[0021] At this time, since the converging position P ₁ of the light beam L _R1 is hardly changed, P ₂ from the condensing position P ₁ (P
The relative displacement of ₂ ') is determined by the tilt angle of the device as a parameter. Therefore, the reference light L _R1 and the measurement light L _T2
By detecting the relative displacement of each condensing position of
The tilt angle of the device can be determined.

[0022]

In the conventional composite optical element described above, a half mirror is used as an optical path splitting surface 304 for splitting the parallel light flux L ₀ from the light source 301 into the reference light L _R1 and the measurement light L _T1. It was If the reflectance of this half mirror is R% and the transmittance is T%, the emission intensity of the reference light L _R1 is reduced to R% of the incident light intensity, and the emission intensity of the measurement light L _T2 is reduced to T ² %. Become.

Therefore, when the simplest half mirror of R≈T≈50% is used, the emission intensity of the reference light L _R1 is reduced to 50% of the incident light intensity and the emission intensity of the measurement light L _T2 is reduced to 25%. And the reference light L _R1 on the photoelectric detector 307
And the measurement light L _T2 has a large difference in intensity, and the measurement light L _T2
There was a problem that the strength of _T2 could not be obtained sufficiently.

On the other hand, since the reference light L _R1 and the measurement light L _T2 are detected by the same photoelectric detector, the emitted light intensities R and T
It is preferable to use a half mirror in which R and T are determined so that ² becomes almost equal. If the absorption of light by the half mirror is negligible, the reflectance can be expressed as R = 1-T.
At this time, as a half mirror satisfying R = T ² , R≈
38% and T≈62% are preferable. In this case, the emission intensities of the reference light L _R1 and the measurement light L _T2 are both reduced to approximately 38% of the incident light intensity, and the intensities of the reference light L _R1 and the measurement light L _T2 on the photoelectric detector 307 are equal. However, for this reason, the transmittance T of the half mirror must be set to a large value in advance, and the reflectance R is inevitably set to be small.

As described above, in the conventional composite optical element, the parallel light flux L ₀ from the light source 301 having no polarization characteristic is
Since a so-called half mirror is used as the optical path dividing surface 304 for dividing the reference light L _R1 and the measurement light L _T1 , the reference light L
The total emission intensity of _R1 and the measurement light L _T1 is about 75 times the incident light intensity.
%, The loss (25%) is large, the amount of light received on the photoelectric detector 307 cannot be sufficiently secured, and the detection accuracy is poor.

The present invention has been made in view of the above problems, and provides a composite optical element capable of increasing the amount of received light of each outgoing light flux when applied to, for example, a tilt angle measuring device. That is the purpose.

[0027]

In order to achieve the above object, in the invention described in claim 1 of the present application, the first polarization component of the incident light beam is reflected and the polarization direction is orthogonal to the first polarization component. A polarization splitting surface that transmits the second polarization component, and a return optical path that reflects the second polarization component that has passed through the polarization splitting surface a plurality of times and guides it to the polarization splitting surface. An optical element having a plurality of reflecting surfaces forming an optical path for guiding the second polarized light component passing through the polarized light splitting surface onto an outgoing optical path of the first polarized light component reflected by the polarized light splitting surface; There is provided a composite optical element integrally including.

The invention described in claim 2 is a tilt angle measuring device using the composite optical element according to claim 1,
One of the plurality of reflecting surfaces forming the return optical path functions as a measurement surface, and when the first polarization component is reference light and the second polarization component is measurement light, the composite optical element On the emission optical path, a condenser lens system that condenses the reference light and the measurement light, and a photoelectric detector that detects a relative displacement amount of each condensing position of the reference light and the measurement light are provided. It is characterized by being present.

The invention described in claim 3 is the tilt angle measuring device described in claim 2, characterized in that it is provided with a light source means that is not polarized as the incident light beam.

In the invention described in claim 4, a polarization splitting surface that reflects the first polarization component of the incident light flux and transmits the second polarization component whose polarization direction is orthogonal to the first polarization component. And the second light transmitted through the polarization splitting surface.
While forming a return optical path that reflects the polarization component of to the polarization splitting surface, and the second polarization component that has passed through the return optical path and the polarization splitting surface is reflected by the polarization splitting surface. Provided is a composite optical element integrally provided with an optical element having a reflecting surface forming an optical path for guiding a polarization component onto an outgoing optical path.

[0031]

As shown in FIG. 2, the compound optical element according to the invention described in claim 1 is mainly composed of a polarization splitting surface 204 and an optical element 205 having a plurality of reflecting surfaces forming a return optical path. The polarization splitting surface is used as a means for splitting the optical path of incident light into transmitted light and reflected light.

The polarization splitting surface 204 mainly reflects the first polarization component L _PR1 of the incident light beam L ₀ to the composite optical element, and also has the second polarization component whose polarization direction is orthogonal to that of the first polarization component. What has a function of mainly transmitting the polarization component L _PT1 may be used. Generally, it is separated into P-polarized light and S-polarized light depending on the direction of the incident light and the separation surface.

The optical element 205 has a return optical path formed by a plurality of reflecting surfaces, reflects the light beam L _PT1 transmitted through the polarization separating surface 204 a plurality of times, and again returns to the polarization separating surface 2.
Lead to 04. Then, the luminous flux L _{PT1 passing} through the return optical path is
The light is transmitted again through the polarization splitting surface 204, and the _{retransmitted} light flux (twice transmitted light) L _PT2 is
The light beam L _PR1 reflected by the polarization splitting surface 204 is guided to the emission optical path.

By the way, generally, the reflectance and the transmittance on the polarization splitting surface 204 are different based on the difference in the polarization characteristics. The reflectance of the incident light beam L ₀ with respect to the P-polarized component (a component that oscillates parallel to the incident surface of light) and the S-polarized component (a component that oscillates perpendicularly to the incident surface) are R _P and R _S , and the transmittance is T.
_P and T _S , which are P-polarized light and S-light contained in the incident light beam L _0.
A light beam whose polarization component ratio is approximately 1: 1 (for example,
Assuming a light beam having no polarization characteristic such as white light), the reflectance R _A and the transmittance T _A of the polarization splitting surface 204 can be expressed by the following equations as the average of each component.

R _A = (R _P + R _S ) / 2 ……………… (1) T _A = (T _P + T _S ) / 2 ……………… (2)

In the equation (2), when the intensity of the incident light beam L ₀ is 1, the intensity of the light beam L _PT1 transmitted by the polarization splitting surface 204 decreases to T _A, and the intensity of the P-polarized component contained therein is The intensity of the T _P and S polarization components is T _S. The same applies to the light flux L _PR1 reflected by the polarization splitting surface 204 from Expression (1). It is assumed that the above-mentioned first polarization component represents the S polarization component here, and the second polarization component represents the P polarization component here.

Next, the light flux L transmitted through the polarization splitting surface 204
_{When PT1} is guided to the polarization splitting surface again by the returning optical path and is transmitted through the polarization splitting surface once more (total twice), the intensity (T ² ) _A of the light flux L _PT2 after the second transmission is the P polarization component. And S
Intensities T _P ² and T _S ² after two transmissions of each polarization component
Can be expressed as the average of

(T ² ) _A = (T _P ² + T _S ² ) / 2 (3)

Equation (3) represents that when the intensity of the incident light beam L ₀ is 1, the intensity of the light beam L _PT2 after being transmitted twice decreases to (T ² ) _A.

Here, one half of the difference between the intensity T _{P of the P-} polarized component and the intensity T _S of the S-polarized component contained in the intensity T _A of the light beam L _PT1 transmitted once through the polarization splitting surface 204 is _calculated. The amount standardized by T _A is defined as r as shown in equation (4).

R≡ (T _P −T _S ) / (2 · T _A ) ... (4)

However, the absolute value of r is an amount that satisfies the following conditional expression (5).

0 ≦ | r | ≦ 1 (5)

The absolute value of r takes the minimum value 0 because T _P =
When T _S (transmissivity has no polarization characteristic), that is, for a non-polarization separation film (half mirror, etc.). The absolute value of r increases as the difference between T _P and T _S increases, and takes a value close to 1. The polarization splitting surface has a difference between T _P and T _S.

In order to express the intensity (T ² ) _A of the light flux L _PT2 after the two transmissions of the formula (3) using the above defined amount r, first, T _P and T _S are expressed by using r From the expressions (2) and (4), the following expressions (6) and (7) are obtained.

T _P = T _A · (1 + r) ………… (6) T _S = T _A · (1-r) ………… (7)

Therefore, the expressions (3) and (T ² ) _A are expressed by the following expression (8).

(T ² ) _A = (T _A ) ² · (1 + r ² ) ... (8)

From the equation (8), the intensity (T ² ) _A of the light beam L _PT2 after passing twice is the minimum value (T _A ) ² when the non-polarization separation film is used and when the polarization separation surface is used. Has r,
That is, it can be seen that it increases depending on the square of the difference between T _P and T _S (the difference in transmittance due to the polarization characteristics of the polarization splitting surface). The rate of increase in the intensity (T ² ) _A of the light flux L _PT2 after two passes is
It is 100 · r ² (%).

[0050] Thus, in the composite optical element according to the present invention, T _P and T by the difference using the large polarization splitting surface 204 of the _S, the intensity of the light beam L _PT2 after two transmission (T
² ) Large _A can be secured.

As described above, in the polarization splitting surface 204, even if the transmittance T _A of the polarization splitting surface is not set to a large value in advance, if the difference between T _P and T _S is large, the light flux L after two passes is obtained.
_Since it is possible to increase the strength (T ² ) _A of _PT2 ,
The reflectance R _A of the polarization splitting surface (R _A = 1-T if there is no absorption)
_A ) does not become small either. That is, the intensity R _A of the light beam L _PR1 reflected once by the polarization splitting surface and the light beam L transmitted twice
It is possible to efficiently secure the strength (T ² ) _A of _PT2 together.

In the case of a film having the following polarization characteristics as the most ideal polarization separation surface, the intensity _RA of the light beam L _PR1 reflected once by the polarization separation surface and the light beam L transmitted twice are The intensity (T ² ) _A of _{PT 2} is 0.5 (half the intensity of the incident light flux).

R _p = 0, R _s = 1 and T _p = 1 and T _s = 0 (9)

As described above, a non-polarization separation film such as a half mirror is used as the separation surface, and the light flux L reflected once is L.
_When the intensity of _{R1 and} the intensity of the light beam L _T2 transmitted twice are equalized, these detected intensities are both 0.38 of the intensity of the incident light beam.
Becomes By comparison with this, it can be seen that by using the polarization splitting surface as in the present invention, an increase in light amount of about 32% can be obtained as compared with the conventional case.

In the above description, the light beam L _PT2 transmitted through the polarization splitting surface twice is used as the measurement light, but the number of times the light is transmitted through the splitting surface does not necessarily have to be two, and may be three or more depending on the configuration of the element. But it doesn't matter. The intensity (T ⁿ ) _A of the light flux L _PTn when the light is transmitted through the polarization splitting surface n times can be expressed by the following formula (10) according to the same idea as described above.

[0056]

[Equation 1]

The second and subsequent terms of the equation (10) become larger as the difference between T _P and T _S becomes larger, and the light quantity (T ⁿ ) _A of the light beam L _PTn after n times of transmission is _unpolarized by a half mirror or the like. Separation membrane n
It represents the rate of increase from the light amount (T _A ) ⁿ when the light is transmitted once. Therefore, it can be seen that even when the light is transmitted through the polarization splitting surface n times, the use of the polarization splitting surface as in the present invention makes it possible to obtain an increase in the amount of light as compared with the conventional case.

A tilt angle measuring device according to a second aspect of the present invention uses the above-described composite optical element according to the first aspect, and the composite optical element is provided with a measurement surface. A light receiving means for detecting the light emitted from the element is provided.

As described above, the incident light beam L ₀ on the composite optical element has its optical path split on the polarization splitting surface based on the difference in polarization characteristics. That is, the first polarized component (eg, S polarized component) is reflected, and the second polarized component (eg, P polarized component) whose polarization direction is orthogonal to that of the first polarized component.
Is transmitted. Here, the reflected light flux L _PR1 is the reference light,
The transmitted light flux L _PT1 is used as measurement light.

The measuring surface provided in the composite optical element causes a relative angle change in accordance with the inclination of the apparatus. As an example, the measuring surface is composed of the liquid surface (surface) of the liquid as in the conventional example. It may be one that has been formed and functions as one of a plurality of reflecting surfaces that form the return optical path of the device. Also, not limited to this,
A mirror surface member floating on the liquid may be used as the measurement surface.

The measurement light L _PT1 transmitted through the polarization splitting surface passes through the return optical path composed of a plurality of reflection surfaces including the above-mentioned measurement surface, then passes through the polarization splitting surface again (L _PT2 ), and is emitted from the composite optical element. It The height (arrangement) of the measurement surface is adjusted so that the emission direction of the light flux L _PT2 is guided to the emission optical path of the reference light L _PR1 reflected on the polarization splitting surface.
That is, with respect to the height of the measurement surface, the emission direction of the measurement light L _PT2 at this time is the reference light L _PR1 with reference to the state (horizontal state) in which the liquid surface faces the polarization separation surface in parallel. It is adjusted so that it substantially overlaps with the outgoing optical path.

Therefore, the measurement light L transmitted through the polarization splitting surface
_PT1 passes through the return optical path including a plurality of reflecting surfaces including the measurement surface, passes through the polarization splitting surface again (measurement light L _PT2 ), and is guided to the outgoing light path of the reference light L _PR1 reflected by the polarization splitting surface.

The light receiving means is roughly composed of a condenser lens system, a photoelectric detector and the like. The condenser lens system is arranged on the optical path of the light emitted from the composite optical element, and collects the luminous flux (reference light L _PR1 and measurement light L _PT2 ) emitted from the composite optical element on the light receiving surface of the photoelectric detector. (Image). The photoelectric detector is composed of a light receiving element such as a CCD line sensor, and a light receiving surface is arranged on the emission optical path of the composite optical element with the optical axis of the condenser lens as the center. In the detector, the reference light L
Each _focus position P ₁₁ (reference point) of _PR1 and measurement light L _PT2 ,
P ₂₂ (measurement point) is detected at the same time, and the relative amount of mutual displacement is detected.

When the tilt angle measuring device is kept substantially horizontal, both the reference light L _PR1 and the measurement light L _PT2 emitted on substantially the same optical path are respectively located at the center positions on the photoelectric detector by the condenser lens. Since the light is focused, the reference point P ₁₁ and the measurement point P ₂₂ substantially coincide with each other. If the tilt angle measuring device tilts,
Since the reference light L _PR1 reflected by the polarization splitting surface is not affected at all, it remains focused on the reference point P ₁₁ (center position) whose position does not change from that in the horizontal state.

On the other hand, the measuring point P ₂₂ is displaced depending on the inclination angle of the apparatus from the horizontal state (P ₂₂ ′). That is,
The tilted state of the device appears as a relative displacement amount between the reference point P ₁₁ and the measurement point P ₂₂ (P ₂₂ ′) based on the change in the reflection angle on the measurement surface. Therefore, the tilt angle of the device can be obtained by detecting the relative displacement amount by the photoelectric detector.

By the way, the reference light L _PR1 and the measurement light L _PT2
Are detected using the same photoelectric detector, it is desirable to use an optical path splitting surface on the light receiving surface so that the respective intensities are substantially equal. As described above, in the present invention, since the polarization splitting surface is used as the optical path splitting surface for splitting the light flux L ₀ from the light source into the reference light L _PR1 and the measurement light L _PT2 , even if the mutual intensities are equal, Compared with the half mirror of the above, it is possible to increase the received light amount of each outgoing light flux on the photoelectric detector by about 32%,
Therefore, the detection accuracy of the tilt angle measuring device could be improved.

The tilt angle measuring apparatus according to the invention described in claim 3 is characterized by comprising a light source means which is not polarized as an incident light beam. The light source means comprises a light source and a collimator lens. The light source has no polarization characteristics,
For example, a non-polarized light source (for example, an LED that produces white light or the like)
Etc.) can be used. The collimator lens is arranged on the front surface of the composite optical element, and is arranged so that the light beam emitted from the light source is made into a parallel light beam L ₀ and is incident on the composite optical element.

The non-polarized light is, in other words, a light beam having a random polarization characteristic, and therefore P contained in the light beam.
The ratio of the polarization component to the S polarization component is approximately 1: 1. In this case, the emission intensity of the reference light L _PR1 is R _A (%) of the reflected light intensity using the above-mentioned formula (1), and the measurement light L _PT2 is (T ² ) _A (%) using the formula (3). It can be seen that it decreases to.

When a film having the following polarization characteristics is used as the most ideal polarization splitting surface, the intensity R _A of the reference light L _PR1 and the intensity (T ² ) _A of the measurement light L _PT2 are both The intensity is equal to 50% of the intensity of the incident light beam L ₀ , and a light amount increase of about 32% is obtained as compared with the intensity (38% of the intensity of incident light) when a non-polarization separation film such as a half mirror is used. I understand.

R _p = 0, R _s = 1 and T _p = 1 and T _s = 0

Therefore, the detection accuracy of the tilt angle measuring device could be improved. Further, as a light source, a general light source that produces white light can be applied as it is, so that the device according to the present invention can be formed by simply improving the conventional device,
Moreover, there is an advantage that the manufacturing cost can be suppressed.

According to a fourth aspect of the present invention, there is provided a return optical path that reflects the second polarized component at least once and guides it again to the polarization splitting surface. Also in the present invention, due to the action of the polarization splitting surface, it is possible to extract the light of the first and second polarization components that are guided to the outgoing optical path to have the same intensity and to have the intensity higher than that of the conventional light.

[0073]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 is a schematic sectional view showing a first embodiment of a tilt angle measuring device using a composite optical element according to the present invention.
This tilt angle measuring device is a composite optical element having a measuring surface,
The light source means and the light receiving means are roughly configured.

The composite optical element used in this example is composed of a right-angle prism 103, an optical member 105, an optical element containing a liquid 109 forming a measurement surface, and a polarization splitting surface 104. Is a right angle prism 103
And the optical member 105.

The right-angle prism 103 has an entrance surface 103a and an exit surface 103c which are orthogonal to each other, and these are the entrance and exit surfaces of the light flux in the composite optical element. A polarization splitting surface 1 is provided outside the inclined surface (bonding surface) 103b of the right angle prism.
04 is provided, and the bottom surface (bonding surface) 105a of the optical member 105 is bonded to the opposite side of the switch 04.

The optical member 105 has a bottom surface (bonding surface) 105.
a, side surfaces 105b and 105c, and an upper surface 105d, and the bottom surface 105a is joined to the polarization splitting surface 104. Therefore, of the light flux L ₀ incident on the inclined surface 103 b of the right-angled prism, the light flux (P-polarized component) L _PT1 transmitted through the polarization splitting surface 104 is transmitted from the bottom surface 105 a to the optical member 1.
It is introduced in 05. The side surfaces 105b and 105c of the optical member 105 have a function as reflecting surfaces that form a return optical path for the light beam L _PT1 that has entered the optical member 105.

Right angle prism 103 and optical member 105
Is made of material such as glass or plastic,
In order to facilitate the design of the optical path and the like, it is preferable that the refractive indices are substantially equal to each other, and it is more preferable that they are the same substance.

The measuring surface 109a as one of the reflecting surfaces is
The liquid-filled case 108 (joined on the bottom plate portion 108a) joined on the upper surface 105d of the above-mentioned optical member.
Liquid surface (surface) of the liquid 109 enclosed in an appropriate amount inside the hollow of
It is composed of The liquid encapsulating case 108 is generally cylindrical in shape, and has a parallel flat bottom plate 108 a and a cylindrical ring 1.
It is made by joining with 08b.

At least the bottom plate portion 108 of the liquid-filled case.
a is made of a material such as glass or plastic. This material is also the right angle prism 103 and the optical member 1.
No. 05 and a substance having almost the same refractive index, and more preferably the same substance.

The liquid 109 is sealed in the liquid sealing case 108, and the liquid surface 109 a functions as one of a plurality of reflecting surfaces forming a return optical path for the light beam L _PT1 incident on the optical member 105. Then, when the entire apparatus is tilted, only the liquid level 109a is kept horizontal (conversely, only the liquid level is tilted relative to the entire apparatus (the state of the liquid level 109b in the figure). Therefore, the return optical path formed by the liquid surface 109b and each surface of the optical member 105 is deformed. In other words, the luminous flux L _PT2 through the return optical path
The emission direction of is changed. That is, since the inclination of the device can be recognized from the change in the emission direction (detection position) of the light beam L _PT2 via the return optical path, the liquid level 109 functions as a measurement surface in the device.

Since the liquid 109 is sealed in the liquid sealing case 108, its surface 1 which functions as a measuring surface.
09a is slightly curved due to surface tension. If the measurement surface is curved, the light flux L incident on the liquid surface 109a
_This will adversely affect the reflection performance of _PT1 . If the inner diameter Φ _C of the liquid-filled case is small, the influence is great, so it is necessary to make the inner diameter Φ _C as large as possible.

According to the experiment, at least 5 times the luminous flux diameter Φ _L of the luminous flux L _PT1 incident on the liquid surface 109a is required,
It is preferably 10 times or more. For example, when the luminous flux diameter Φ _L = 3 mm, the practical error is within the permissible range when the inner diameter Φ _C of the liquid-filled case is 15 mm or more. For this reason,
There is no big problem if it is 5 times or more, but 30 is preferable.
If it is equal to or larger than mm, an error hardly occurs.

The material of the liquid 109 is selected in consideration of various characteristics such as viscosity, refractive index, temperature characteristics of refractive index, freezing point and the like according to the purpose of use. Generally, any material may be used as long as it is optically homogeneous, transparent (high transmittance) to the wavelength used, and has a refractive index that reflects at the incident angle used, but generally silicone oil is used. . This is because silicon oil has a refractive index of about 1.4, which is close to that of glass (usually, a refractive index of 1.5), and various viscosities can be selected. Although the refractive index is as low as 1.33, alcohol or water may be used.

On the other hand, the polarization splitting surface 104 provided between the inclined surface 103b of the rectangular prism and the bottom surface 105a of the optical member is the first polarization component of the light beam L ₀ incident on the inclined surface 103b of the rectangular prism. (For example, S-polarized component)
A second polarization component (eg, P polarization component) L _{PT 1} that reflects L _PR1 and has a polarization direction orthogonal to the first polarization component
It has a function to let through.

Here, a specific structural example of the composite optical element will be described below. Right angle prism 103 and optical member 105
For example, when glass (refractive index n ₀ ≈1.52) is used, the polarization separation surface 104 has a high refractive index such as SiO ₂ (refractive index n _L ≈1.47) as the low refractive index material L. For example, TiO ₂ (n _H ≈2.2) is used as the substance H, and a seven-layer alternating layer film having a predetermined thickness starting with the low refractive index substance L layer is formed.

The light source means comprises a light source 101 and a collimator lens 102. The light source 101 is a non-polarized light source having no polarization characteristic such as an LED. The collimator lens 102 is disposed on the front surface of the incidence surface 103a of the right-angle prism, and is arranged so that the light flux emitted from the light source 101 becomes a parallel light flux L ₀ and is incident vertically on the incidence surface 103a of the right-angle prism. It is set up.

The light receiving means comprises a condenser lens 106 and a photoelectric detector 107. The condenser lens 106 is disposed on the rear surface (on the exit optical path of the composite optical element) of the exit surface 103c of the right-angle prism, and the exit light flux (the light fluxes L _{PR 1} and 2 reflected by the polarization splitting surface) from the composite optical element. The light flux L _PT2 that has been transmitted once is condensed (imaged) on the light receiving surface of the photoelectric detector 107.
To do.

The photoelectric detector 107 is composed of a two-dimensional light receiving element such as a CCD line sensor, and is arranged with the optical axis of the condenser lens 106 on the exit optical path of the composite optical element as the center of the light receiving surface. Therefore, the light-condensing positions P ₁₁ and P ₂₂ of the respective light fluxes L _PR1 and L _PT2 are detected at the same time, and the relative displacement amount between them is detected. Specifically, as shown in JP-A-5-256647, an illuminated L-shaped slit is used as a secondary light source to form an L-shaped image so that any inclination in the horizontal direction can be detected. Has become.

The tilt angle measuring device of this embodiment has the above-mentioned structure and operates as follows. Light source 101 without polarization characteristics
The light emitted from (for example, LED) is collimated by the collimator lens 10
It is converted into a substantially parallel light beam L ₀ via 2 and is first introduced into the rectangular prism 103. Incident surface 10 of right angle prism
The parallel light flux L _{0 that} is incident substantially perpendicularly to 3a is incident on the inclined surface 103b of the right-angle prism at an incident angle of approximately 45 °, and the optical path is split based on the polarization characteristics by the polarization splitting surface 104 provided outside thereof. To be done. That is, the first polarization component (mainly S polarization component) L _PR1 is reflected and the second polarization component (mainly P polarization component) L _PT1 whose polarization direction is orthogonal to the first polarization component is transmitted. It

Light flux L _PR1 reflected by the polarization splitting surface 104
Is emitted as a reference light substantially perpendicularly from the exit surface 103c of the rectangular prism. The light beam L _PT1 transmitted through the polarization splitting surface 104 is introduced as measurement light from the bottom surface 105a of the optical member to the optical member 105, passes through the return optical path composed of a plurality of reflecting surfaces including the above-described measurement surface 109a, and is then polarized again. The _light passes through the separation surface 104 (L _PT2 ) and is emitted almost vertically from the emission surface 103c of the rectangular prism.

The height of the measurement surface 109a is adjusted so that the emission direction of the light beam L _PT2 at this time is guided to the emission direction of the reference light L _PR1 reflected by the polarization splitting surface 104. That is, the height of the measurement surface is such that the liquid surface 109a faces the polarization separation surface 104 in parallel (horizontal state).
With reference to, the emission direction of the measurement light L _PT2 at this time is
The reference light L _PR1 is adjusted so as to substantially overlap with the outgoing light path.

Therefore, the measurement light (mainly the P-polarized component) L _PT1 transmitted through the polarization splitting surface 104 is transmitted through the return optical path composed of a plurality of reflecting surfaces including the measurement surface and the polarization splitting surface 104 (second time). The (light flux L _PT2 ) and the reference light (mainly S-polarized component) L _PR1 reflected by the polarization splitting surface 104 are guided to the emission optical path.

Reference light L _PR1 emitted on almost the same optical path
The measurement light L _PT2 and the measurement light L _PT2 are both condensed on the light receiving element of the photoelectric detector 107 via the condenser lens 106, and the relative displacement amounts of the respective condensing positions P ₁₁ and P ₂₂ are detected by the photoelectric detector 107. .

When the tilt angle measuring device is kept horizontal, the reference point P ₁₁ and the measurement point P ₂₂ substantially coincide with each other. But,
When the tilt angle measuring device is tilted, the measuring point P ₂₂ ′ is displaced with respect to the reference point P ₁₁ whose position is the same as when the device is horizontal, depending on the tilt angle of the device from the horizontal position. That is, the tilted state of the device appears as a relative displacement amount between the reference point P ₁₁ and the measurement point P ₂₂ ′. Therefore, the tilt angle of the device can be obtained by detecting the relative displacement amount by the photoelectric detector 107.

Since the reference light L _PR1 and the measurement light L _PT2 are detected by the same photoelectric detector 107, it is desirable to use the polarization splitting surface 104 such that the respective intensities on the light receiving surface are substantially equal. . When a film having the following polarization characteristics is used as the most ideal polarization splitting surface 104, the reference light L _PR1 and the measurement light L emitted from the element are used.
The intensity of _PT2 is 50% of the intensity of the incident light beam L ₀ .

R _p = 0, R _s = 1 and T _p = 1 and T _s = 0

Therefore, when the polarization splitting surface is used, the amount of light received on the photoelectric detector 107 should be increased by about 32% as compared with the conventional case using a non-polarizing film such as a half mirror (38%). You can

Generally, it is difficult to obtain a film that completely satisfies T _s = 0 because of the characteristics of the film. Here, when the film (11) having the following conditions, which has more realistic polarization characteristics than the previous film, is used, the reference light L emitted from the element is used.
The intensity of _PR1 and the measurement light L _PT2 are both 44% of the intensity of the incident light flux L ₀ .

R _p = 0.08, R _s = 0.8, T _p = 0.92, T _s = 0.2 (11)

Polarizing film used here (polarization separating surface 104)
Is the SiO ₂ (refractive index n _L ≈
1.47) and TiO ₂ (n _H as the high refractive index substance H)
.Apprxeq.2.2) is used to form a seven-layer alternating layer film having a predetermined thickness starting with the low refractive index substance L layer.

Even in this case, the amount of light received on the photoelectric detector 107 can be increased by about 16% as compared with the conventional case (38%) using a non-polarizing film such as a half mirror.

Here, when it is desired to increase the amount of light received on the photoelectric detector 107 by about 10% or more, compared to the conventional case (38%) using a non-polarization separation film such as a half mirror, the light amount is increased. The following conditional expression (12) may be given to the second term of the expression (8).

0.1 ≦ r ² ≦ 1 (12)

Therefore, r satisfies the following conditional expression (13).

0.316 ≦ | r | ≦ 1 (13)

On the other hand, there is no absorption of the light beam on the polarization splitting surface 104 (R _A = 1-T _A ), and the reference light L _PR1 and the measurement light L
_When the light quantities of _PT2 are set to be equal (R _A = (T ² ) _A ), the following equation is obtained using equation (8).

1-T _A = T _A ² (1 + r ² ) ... (14)

From the equation (14), r can be expressed by the following equation (15) using the transmittance T _A of the polarization splitting surface. Equation (15)
In combination with the formula (13), an effective polarizing film can be set.

R = ± √ ((1−T _A ) / T _A ² −1) (15) where 0 ≦ | r | ≦ 1

Although the case where the light _amounts of the reference light L _PR1 and the measurement light L _PT2 are equal to each other has been shown above as an example, the same method can be used to compare T _P and The polarization splitting surface 104 with a difference in T _S is
An increase in the amount of light can be obtained as compared with using a half mirror.

As in the conventional example, the light source means may be a slit or pinhole illuminated by a relay system (not shown).

The optical path lengths from the collimator lens 102 to the condenser lens 106 are the reference light L _PR1 and the measurement light L _PT2.
Is different, or the case where the incident light beam L ₀ is a parallel light beam (that is, the light source 101 is arranged at the focal point of the collimator lens 102) is optimal so as not to be affected by the angular characteristics of the film. However, it is of course effective to use the convergent light and the divergent light in terms of increasing the light amount.

The light source 101 is circularly polarized light if the component ratio of P-polarized light and S-polarized light is approximately 1: 1 or 45 degrees relative to the incident surface.
The same effect can be obtained with linearly polarized light inclined at an angle of 0 °, and some effect can be obtained with linearly polarized light having an angle of inclination with respect to the incident surface other than 45 °, but a non-polarized light source is cheaper and easier to obtain. Can be kept at low cost.

Next, a tilt angle measuring device using the composite optical element according to the second embodiment of the present invention will be shown. This device is shown in FIG.
As shown in FIG. 3, it is roughly composed of a composite optical element having a measuring surface, a light source means, and a light receiving means.

The composite optical element according to the present embodiment is composed of a right-angle prism 403, an optical member 405, an optical element containing a liquid 409 forming a measurement surface, and a polarization splitting surface 404. The polarization splitting surface 404 is the right angle prism 40.
3 and the optical member 405.

The right-angle prism 403 has an entrance surface 403a and an exit surface 403c which are orthogonal to each other, and these are the entrance and exit surfaces of the light flux in the composite optical element. The polarization splitting surface 4 is provided on the outer side of the inclined surface (bonding surface) 403b of the right angle prism.
04 is provided, and the optical member 405 is provided on the opposite side.
Are joined.

The optical member 405 in this embodiment is the first
Unlike the embodiment, the bottom plate portion 40 of the liquid sealing case 408 is
It is configured to also serve as 8a. That is, on the upper surface of the polarization splitting surface 404, a liquid enclosing case 408 similar to that of the first embodiment is provided, and an appropriate amount of the liquid 409 is enclosed in the hollow inside thereof. This liquid 409 is the same as that of the first embodiment, and its surface causes a measurement surface (reflection surface) 409.
a is configured.

In this embodiment, a return optical path is formed with only the measurement surface 409a as a reflecting surface. That is, of the light flux L ₀ incident on the inclined surface 403b of the rectangular prism, the light flux L _PT1 transmitted through the polarization splitting surface 404 is guided to the measurement surface 409a, which is the surface of the liquid, via the bottom plate portion 408a. The light beam L _PT1 is reflected by the measurement surface 409a and is returned to the polarization splitting surface 404 again.

The polarization splitting surface 404 is a polarization splitting film that splits the optical path based on the polarization characteristics as in the first embodiment.
First polarization component of the light beam L ₀ (primarily S-polarized light component) L
_It has a function of reflecting _PR1 and transmitting a second polarization component (mainly a P polarization component) L _PT1 whose polarization direction is orthogonal to that of the first polarization component.

In the light source means of this embodiment, the light source 401 having no polarization characteristic is arranged at the focal position of the collimator lens 402, and a parallel light flux is obtained as the incident light flux L ₀ . The parallel light flux L ₀ is first introduced into the right-angle prism 403 substantially perpendicular to the incident surface 403a. Further, the incident light beam L ₀ is directed to the inclined surface 403 of the rectangular prism.
It is incident on b at an incident angle of about 45 °, and the polarization splitting surface 404 provided on the outside thereof splits the optical path based on the polarization characteristics.

The light flux L _PR1 reflected by the polarization splitting surface 404
Is emitted as a reference light substantially vertically from the emission surface 403c of the rectangular prism. On the other hand, the light flux L _PT1 transmitted through the polarization splitting surface 404 is introduced into the optical member 405, that is, the bottom plate portion 408a of the liquid sealing case 408, as measurement light,
After having been reflected by the measurement surface 409a described above, it is guided again to the polarization splitting surface 404 and transmitted there (L _PT2 ).

Here, the measurement surface 409a is the deflection separation surface 40.
4 in a state where they are parallel to each other (horizontal state), the second transmission position of the measurement light L _PT2 is from the first transmission position to the bottom plate portion 405 of the liquid enclosure case and the enclosure liquid 409. The position is shifted by twice the total thickness d.
Therefore, the twice transmitted measurement light L _PT2 and the reflected reference light L _{PR 1}
The exit position from the exit surface 403c of the rectangular prism is
Both are ejected almost vertically while being shifted by √2 · d.

Two light beams L _PT2 and L to be emitted from different positions on the emission surface 403c of the rectangular prism.
_PR1, since the incident light beam L ₀ is a parallel light beam, a horizontal state is injected parallel to each other in (a device when being kept horizontally). Then, the condensing lens 406 condenses the reference point P ₁₁ and the measurement point P ₂₂ together at the center position on the photoelectric detector 407.

The reference point P ₁₁ and the measurement point P ₂₂ substantially coincide with each other in the horizontal state, which is the reference position. But,
When the device is tilted, the measurement point P ₂₂ ′ is displaced with respect to the reference point P ₁₁ whose position is the same as when the device is horizontal, depending on the tilt angle of the device from the horizontal position. That is, the tilted state of the device appears as a relative displacement amount between the reference point P ₁₁ and the measurement point P ₂₂ ′. Therefore, the tilt state of the device can be obtained by detecting this relative displacement amount by the photoelectric detector 407.

Therefore, by using the composite optical element according to the second embodiment, it is possible to construct a tilt angle measuring device having a structure simpler than that of the first embodiment and having substantially the same effect as that of the first embodiment. You can

Next, the case where the composite optical element according to the third embodiment of the present invention is used in a lightwave distance measuring apparatus will be described. The optical distance measuring device guides the intensity-modulated light (transmitted light) emitted from the light source to the reflector, the internal optical reference, and the received light reflected by the reflector to the light receiving element. It is composed of a receiving optical system. In this device, the distance to the reflector is measured by measuring the phase difference between the received light and the internal reference light.

A schematic configuration diagram of this apparatus is shown in FIG. In this drawing, an optical element including right-angle prisms 504 and 505, a corner cube prism 506, a mirror 507 and the like, and a polarization splitting surface 503 provided on a joint surface between the optical members 504 and 505 are used to combine the composite of the present embodiment. The optical element is constructed.

The right-angle prism 504 has an entrance surface 504a and an exit surface 504c which are orthogonal to each other, and these are the entrance and exit surfaces of the light beam in the composite optical element. Similarly, the right-angled prism 505 has two surfaces 505a, 5a which are orthogonal to each other.
Has 05c. These two right-angle prisms constitute one light wave separation member with their respective inclined surfaces 504b and 505b facing each other and the polarization separation surface 503 sandwiched therebetween.

In the light wave separation members (503 to 505), the normal line of the incident surface 504a thereof is the optical axis 500 of the transmission lens 502.
It is provided with a small angle θ with respect to. Therefore, the parallel light flux L ₀ emitted from the light source 501 (which is disposed on the focal plane of the transmission lens 502) and passed through the transmission lens 502 is refracted at the incident surface 504 a, and the polarization splitting surface 5
It is incident on 03. The polarization separation surface 503 is a polarization film having the same function as in the first and second embodiments, and the incident light beam L ₀
Is split based on the polarization component. That is, the first polarization component L _PR1 is reflected, and the second polarization component L _PT1 having a polarization component orthogonal to the first polarization component is transmitted.

The first polarization component L _PR1 is emitted as internal reference light from the emission surface 504c of the composite optical element (504 to 507) and guided to the reception optical system. One of the second polarization components L _PT1 is guided as transmission light to the reflector arranged at the measured point. Here, the reflector is a target such as a corner cube prism 506. The light beam reflected by this target is the received light L including the information of the measured point.
_It becomes _PT1 , goes through the mirror 507, and again the polarization splitting surface 50
Returned to 3.

The received light L transmitted through the polarization splitting surface 503 again.
_PT2 has an exit surface 504c similar to the internal reference light L _PR1.
The light is emitted and guided to the receiving optical system. In the receiving optical system, the two light fluxes (L _PR1 , L _PT2 ) are received by the receiving lens 50.
The light is condensed at 8, and reaches the light receiving element 509 arranged at the focal plane position of the receiving lens 508.

As described above, the normal line of the incident surface 504a is inclined by the minute angle θ with respect to the optical axis 500 of the transmitting lens 502. Therefore, the internal reference light L _PR1 and the received light L _PT2 split by the polarization splitting surface 503 can be emitted on different optical _paths , as shown in the figure.

That is, as shown in FIG. 6, the light wave separation members (603 to 605) are inclined, and the incident angle of the light beam L ₀ with respect to the normal line 601 (the one-dot chain line in the figure) of the incident surface 604a is a minute angle. When θ, the light flux L ₀ is refracted at the incident surface 604a and enters the polarization splitting surface 603. When the transmission light L _PT1 transmitted through the polarization splitting surface 603 reaches the surface 605c, it is refracted and emitted from the light wave splitting member in the same manner as above. The optical axis 600 at this time is the optical axis 6 of the light beam L _0.
02 (dotted line in the figure), but the position is shifted by δ.

This shift amount δ is determined by the light wave separation member (603
˜605) depending on the thickness t, the refractive index n, and the tilt angle θ. These relational expressions can be expressed by the following expression (16).

Δ≈ ((n−1) / n) · t · tan θ ……………… (16)

Therefore, the optical path of the received light L _PT2 also has an inclination angle θ.
Depending on the above, only the parallel shift by the above δ does not change the direction. However, the emission direction of the internal reference light L _PR1 reflected by the polarization splitting surface 503 is as shown in FIG.
The angle is only twice the tilt angle θ (that is, 2 · θ) with respect to the emission direction of _PT2 . Therefore, the reflected light L _PR1 is split into an optical path different from that of the received light L _PT2, and the internal reference light L _PR1 for canceling various errors in the signal processing system.
Can be formed as.

The internal reference light L _PR1 is emitted in a direction different from that of the received light L _PT2 as described above, but is guided to the light receiving element 507 via the mirror 511 similarly to the received light L _PT2 .
Then, in the light receiving element 507, the phase difference between the received light L _PT2 and the internal reference light L _PR1 is measured, and as a result, the distance to the target is measured.

Here, the received light L _PT2 and the internal reference light L _PR1
The switching between and is performed by the shutter 513. The shutter 513 is a shutter that is rotatable about a rotation axis 513a that is eccentric from the optical axis of the receiving lens 508 and that has an opening radius that differs depending on the rotation angle.

The amount of received light changes depending on the state of the atmosphere where the optical path is placed and mainly on the distance to the target. A rotating light amount adjuster 512 is used to balance the light amount between the received light amount and the fixed internal light amount.
The light quantity adjuster 512 is rotatable about a rotation axis 512a that is decentered from the optical axis of the receiving lens 508, and the concentration gradients in the radial portions corresponding to the optical paths of the respective light fluxes (L _PR1 , L _PT2 ) are respectively set according to the rotation angle. It is attached in the opposite direction.

As shown in the figure, the shutter 513 and the light quantity adjuster 512 are arranged in the vicinity of the light-converging point where the light flux is thin, that is, the light receiving element 509, so that the received light flux and the internal reference light flux do not interfere with each other. .

Although the most commonly used corner cube prism 506 is shown as the target, any object may be used as long as it reflects the amount of light necessary for distance measurement.

Here, if the polarization splitting surface 503 having the same structure as that described in the first and second embodiments is used, efficient light amount division can be performed for the same reason as described above, and highly accurate distance measurement can be performed. You can

Further, similarly to the above, the division ratio of the transmitted light and the reflected light may be determined in an optimum value in combination with the light amount adjuster 512 so that the light amount condensed on the light receiving element 509 is balanced.

Needless to say, the same use can be made in the parts equivalent to those of the first and second embodiments, such as the material of the right angle prisms (504, 505) and the characteristics of the light source 501.

[0145]

As described above, the present invention uses the polarization splitting surface having a large transmittance difference due to the polarization characteristic as the optical path splitting element in the composite optical element, and thereby the light flux and the light beam reflected once by the polarization splitting surface are provided. It was possible to efficiently and largely secure the intensity of the light flux that was transmitted once. Since the tilt angle measuring device using such a composite optical element can efficiently divide the light flux from the light source having no polarization characteristic into the light quantity, the amount of light received on the photoelectric detector is increased, and as a result, the detection accuracy is improved. , Signal processing became easier.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a tilt angle measuring device including a composite optical element according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a composite optical element for explaining the operation of the present invention.

FIG. 3 is a schematic cross-sectional view of a tilt angle measuring device including a composite optical element according to a conventional technique.

FIG. 4 is a schematic cross-sectional view of a tilt angle measuring device including a composite optical element according to a second embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of an optical distance measuring device including a composite optical element according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating optical path division of the third embodiment.

[Explanation of symbols]

101, 301, 401, 501: Light source 102, 302, 402: Collimator lens 103, 203, 303, 403, 504, 505, 6
04, 605: Right angle prism 104, 204, 404, 503, 603: Polarization splitting surface 304: Optical path splitting surface 105, 205, 305, 405: Optical member 106, 306, 406: Condensing lens 107, 307, 407: Photoelectric Detectors 108, 308, 408: Liquid-encapsulated cases 109, 309, 409: Liquid 502: Transmission lens 508: Reception lens 507, 511: Reflection mirror 506: Corner cube prism 509: Light receiving element 512: Light intensity controller 513: Shutter

Claims (4)

[Claims] 1. A polarization splitting surface that reflects a first polarization component of an incident light beam and transmits a second polarization component whose polarization direction is orthogonal to the first polarization component; and the polarization splitting surface. A return optical path that reflects the transmitted second polarization component a plurality of times and leads to the polarization splitting surface is formed, and the second polarization component that passes through the return optical path and the polarization splitting surface is converted into the polarization splitting surface. 2. A composite optical element comprising: an optical element having a plurality of reflecting surfaces that form an optical path that guides the first polarized component reflected on the exit optical path. 2. A tilt angle measuring device using the composite optical element according to claim 1, wherein one of a plurality of reflecting surfaces forming the return optical path functions as a measuring surface, and When the polarized light component of the reference light is the reference light and the second polarized light component is the measurement light, a condenser lens system that collects the reference light and the measurement light on the emission optical path of the composite optical element; An inclination angle measuring device, comprising: a photoelectric detector that detects a relative displacement amount of light and the measurement light at each condensing position. 3. The tilt angle measuring device according to claim 2, further comprising a light source unit that does not polarize the incident light flux. 4. A polarization splitting surface that reflects a first polarization component of an incident light beam and transmits a second polarization component whose polarization direction is orthogonal to the first polarization component; and the polarization splitting surface. Forming a return optical path that reflects the transmitted second polarization component and leads to the polarization splitting surface,
An optical element having a reflection surface that forms an optical path that guides the second polarization component that has passed through the return optical path and the polarization splitting surface onto the outgoing optical path of the first polarization component that is reflected by the polarization splitting surface. And a single integrated optical element.