JP2001013453A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent performance from being lowered because of unstable control in an optical axis direction and the adjustment error of an optical axis even when a beam splitter having angle dependency is used in convergent luminous flux or divergent luminous flux. SOLUTION: The luminous flux emitted from a laser diode light source 21 is reflected from the polarized light separating plane 20a of a composite prism 23, transmitted and sent toward an opposed device from a lens group 25 having positive power after the spherical aberration thereof is corrected by a lens 22 having positive power and a lens 23 having a negative power. On the other hand, received light from the opposed device is made incident from the group 25 having the positive power, transmitted through the light intensity distribution correcting plane 20b of the prism 20 and received by a four-divided sensor 24 after the symmetry of light intensity distribution thereof is secured. By transmitting the received light through both of the planes 20a and 20b, the asymmetry of the light intensity distribution occurring when the received light is transmitted through the plane 20a is negated. Thus, the light intensity distribution of the beam spot of the received light on the light receiving surface of the sensor 24 can be made symmetric as for two orthogonally crossed axes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device having a beam splitter used for a spatial optical communication device, an optical pickup device, and the like.

[0002]

2. Description of the Related Art Conventionally, a spatial optical communication device equipped with an optical device using a beam splitter for splitting outgoing light and incident light in a convergent light beam or a divergent light beam of an optical system has been disclosed in Japanese Patent Application No. Hei. -133716. In this method, two communication devices having the same structure are installed facing each other with a space therebetween, and a light beam is projected into the atmosphere to perform two-way communication.

FIG. 12 shows a configuration diagram of a first conventional spatial optical communication device, in which a polarizing beam splitter 1 is disposed at a crossing point of a light projecting optical axis and a light receiving optical axis. A parallel light beam is incident on the polarization separation surface 1a at an incident angle of 45 °.
When the light is incident on the substrate, the most efficient polarization separation characteristics are exhibited. As shown in FIG. 13, on the light receiving side of the polarizing beam splitter 1, a light receiving beam splitter 2 having an elliptical mirror portion 2a at the center of the glass surface and reflecting 10% of the incident light beam is arranged. A laser diode light source 3 for emitting linearly polarized signal light having a polarization direction perpendicular to the paper surface; and a lens group 4 having a positive power.
And a lens group 5 having a positive power and an avalanche photodiode 6 constitute a light receiving section for signal detection, and a lens group 7 having a positive power, a quadrant sensor 8 and Constitute a light detecting unit for position detection.

An optical axis direction variable section 9 is disposed on the emission side of the projected light La from the polarization beam splitter 1, and the optical axis direction variable section 9 has an optical axis direction variable section 45 with respect to the optical axis O of the communication optical system. °
The optical axis direction variable mirror 10 is disposed with the inclination angle of the optical axis direction as a reference state. Further, a signal processing unit 12 for processing a position shift signal from the four-divided sensor 8 and an optical axis for sending an optical axis direction correction signal to the optical axis direction variable unit 9 based on the optical axis shift signal from the signal processing unit 12 A direction control unit 13 is provided.

With such a configuration, the light emitted from the laser diode light source 3 is converted into a substantially parallel light beam by the lens group 4 having a positive power, reflected by the polarization splitting surface 1a of the polarization beam splitter 1, and furthermore in the optical axis direction. Variable mirror 1
The light is reflected by 0, and is transmitted from the device A to the device B having the same configuration as the projection light La.

The light beam emitted from the device B enters the device A as received light Lb, is reflected by the optical axis direction variable mirror 10, passes through the polarization beam splitter 1, and reaches the light reception beam splitter 2. 10% of the light reflected by the light receiving beam splitter 2 is condensed on the four-divided sensor 8 by the lens group 7 having a positive power, while about 90% of the total received light amount
Is transmitted through the light receiving beam splitter 2 and is transmitted through the avalanche photodiode 6 by the lens group 5 having a positive power.
Focus on

The position shift signal of the light receiving beam spot T on the light receiving surface of the four-divided sensor 8 is sent to the optical axis direction control unit 13 as an optical axis shift signal via the signal processing unit 12, and the optical axis direction control unit An optical axis direction correction signal is sent from 13 to the optical axis direction variable section 9. Based on this optical axis direction correction signal, the motor of the mirror driving unit rotates, and the optical axis direction variable mirror 10 rotates around two rotation axes 10a and 10b as shown in FIG.

FIGS. 15 and 16 show the scanning direction of the light receiving beam spot T on the light receiving surface of the four-divided sensor 8 at this time, and the rotation of the optical axis direction variable mirror 10 around the rotation axis 10a is the light receiving beam. The spot T is moved up and down on the light receiving surface of the four-divided sensor 8 as shown by the arrow in FIG. 15, and the rotation of the optical axis direction variable mirror 10 around the rotation axis 10b moves the light receiving beam spot T in FIG. As shown by an arrow, the light-receiving surface moves in the upper right 45 ° or upper left 45 ° direction.

By such a combination of spot movements, the center of the light-receiving beam spot T coincides with the center of the light-receiving portion effective area 8a of the four-divided sensor 8, that is, the cross point of the cross-shaped separation band 8b which is an insensitive area. Next, the inclination of the optical axis direction variable mirror 10 is adjusted to perform optical axis direction correction control.

By operating this optical axis direction correction control in two bidirectional optical communication devices A and B opposed to each other with a space therebetween, the central portions of the spreads of both transmission beams are opposed to each other. It is possible to maintain a state that always coincides with the beam inlet of the apparatus. At the same time, the light received by both devices can be collected within the effective light receiving area of the avalanche photodiode 6.

Here, the material of the polarizing beam splitter 1 is G, its refractive index is ng, the thin film layer made of a relatively high refractive index material is H, the thin film layer made of a low refractive index material is L, and their refractive indices are Are respectively nh and nl, the optical thickness of the thin film layer is nd, the design reference wavelength is λk, and the configuration of the dielectric multilayer film constituting the polarization splitting surface 1a of the polarization beam splitter 1 is G / H 1 of /L/.../H/L/H
The numerical values of the seven-layer film are as follows.

G; ng = 1.74 (S-TIH4; manufactured by OHARA Co., Ltd.) H; TiO ₂ , nh = 2.26, nd = 223 nm L; SiO ₂ , nl = 1.45, nd = 223 nm λk = 780 nm

The prism on which the dielectric multilayer film is deposited is joined to a prism of the same material (S-TIH4) with a light-transmitting adhesive having a refractive index of nb = 1.56 to form a polarizing beam splitter 1. I have.

FIG. 17 shows a polarization splitting characteristic when a parallel light beam is incident on the polarization splitting surface 1a of the polarizing beam splitter 1 at an incident angle of 45 °. Here, the reflectance of the S-polarized light component is represented by RS, and the transmittance of the P-polarized light component is represented by TP. In the range from wavelength 510 to 820 nm, these reflectances RS
And the transmittance TP are both close to 100%, and the polarization beam splitter 1 exhibits polarization separation characteristics with extremely good polarization separation properties.
It has become.

FIG. 18 shows a configuration diagram of a second conventional example. The afocal portion and a lens group having a positive power immediately before the light receiving element and the light emitting element are eliminated from the necessity of miniaturization or simplification. Then, a lens group 17 having a positive power is disposed in front of the polarizing beam splitter 1, and the F number = 2.0
Optical device.

FIG. 19 shows the angle dependence at 780 nm of the polarization splitting characteristic of the polarizing beam splitter 1 arranged in a convergent light beam or a divergent light beam, and the angle on the horizontal axis is the value in the glass of the polarizing beam splitter 1. Represents. When the incident angle 45 ° on the polarization separation surface 1a is set as the angle center, the transmittance of the P-polarized light component between the incident light beam on the tilt angle side smaller than -4 ° and the incident light beam on the tilt angle side larger than + 4 °. The asymmetry of TP is significant. Similarly, the incident angle is 45 °
With respect to the incident light beam at a tilt angle smaller than -7 ° with respect to
The asymmetry of the reflectance RS of the S-polarized light component is remarkable with the incident light beam on the tilt angle side larger than ゜. The polarization splitting characteristic of the polarization beam splitter 1 has such an angle dependence, and therefore, the light incident angle corresponding to the F number 2.0 is 37 ° to 5 °.
The range is up to 3 °.

The projected light L from the laser diode light source 3
When a part of a is reflected by each lens surface in the lens group 17 having positive power, and the reflected light returns to the avalanche photodiode 6 after passing through the polarization splitting surface 1a, the crosstalk in the signal communication is reduced. If it returns to the four-divided sensor 8, it may cause a malfunction in the optical axis direction correction control.

In order to minimize this return light flux,
The transmitted light beam used as the received light Lb is a P-polarized light beam,
Since the light La emitted from the laser diode light source 3 is converted into an S-polarized light beam, when the light is incident on the polarization separation surface 1a of the polarization beam splitter 1, the most efficient polarization separation effect is exhibited. Therefore, communication is performed by disposing two optical devices having the same structure in which the optical system having the configuration shown in FIG.

[0019]

However, in the above-mentioned conventional example, when the four-divided sensor 8 is used as a light-receiving element for position detection, if the light receiving beam spot T is too small, the insensitive area of the four-divided sensor 8 is not used. The light receiving beam spot T falls into the cross-shaped separation band 8b, and the output disappears, or the detection output changes rapidly when crossing the cross-shaped separation band 8b, and the control becomes unstable. On the other hand, if the light receiving beam spot T is too large, the sensitivity becomes poor, and the control cannot follow the fluctuation of the high frequency component.

In order to solve such inconvenience in the optical axis direction correction control, it is desirable that the light receiving beam spot T has an appropriate spread. In general, the position of the surface is set. Therefore, in the conventional optical device, the light receiving beam spot T having an asymmetric light intensity distribution is received on the light receiving surface of the four-divided sensor 8, and when the light intensity distribution is asymmetric, the light receiving beam spot T The detection sensitivity of the optical axis shift differs depending on the direction crossing the cross-shaped separation band 8b, and this becomes an unstable element of the optical axis direction correction control.

In order to adjust the optical axis of the position detecting optical system and the optical axis of the light projecting optical system when assembling such an optical device, a corner cube reflector or a mirror is generally used. A reflective tool such as a corner reflector of a type is used. The light reflected by such a reflection tool has a light intensity distribution that is inverted with respect to the light intensity distribution of the incident light, with the optical axis passing through the intersection of the three reflection surfaces constituting the reflection tool as the axis of symmetry. The optical axis at the time and the optical axis at the time of actual use are different, and this becomes a position detection error and causes an optical axis adjustment error.

An object of the present invention is to solve the above-mentioned problems,
Even if the light branching means is used in a convergent light beam or a divergent light beam,
It is an object of the present invention to provide an optical device having a small and simple configuration that can avoid instability of optical axis direction control and performance degradation due to an optical axis adjustment error.

[0023]

An optical device according to the present invention for achieving the above object comprises a light projecting means, a light receiving means,
In an optical device having a lens group having a positive power and a light branching unit arranged at a position where a light projecting optical axis and a light receiving optical axis intersect, a light intensity distribution correcting unit between the light branching unit and the light receiving unit A light transmittance distribution or a light reflectance distribution in a cross section perpendicular to the optical axis of the received light transmitted or reflected by the light intensity distribution correcting means through the lens group having the positive power and the light branching means. , With respect to two orthogonal axes.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a configuration diagram of an optical device according to a first embodiment, which detects an optical axis shift of the own device,
An optical device used in a spatial optical communication device having an optical axis direction correction mechanism for correcting an optical axis deviation of a communication optical system based on the optical axis deviation detection information. In the optical device of the present embodiment, the light branching member and the light intensity distribution correcting member are created by the same manufacturing method, and when the light branching surface of the light branching member is inclined by an angle + θ with respect to the optical axis, the light intensity increases. The light intensity distribution correction surface of the member for the distribution correction is arranged to be inclined by an angle -θ with respect to the optical axis.

In the optical device of this embodiment, the composite prism 20 having the polarization splitting surface 20a and the light intensity distribution correcting surface 20b is provided at the intersection of the light projecting optical axis and the light receiving optical axis. It is arranged so that the intersection between the polarization splitting surface 20a and the light intensity distribution correction surface 20b is located closer to the light projection side than the light receiving optical axis.

The composite prism 20 has three triangular prisms joined in a rectangular parallelepiped shape, and a polarization splitting surface 20a, which is a light splitting surface, and a light intensity distribution correction surface 20b are formed at the joint by a dielectric multilayer film. The polarization splitting surface 20a is inclined at an angle of + 45 ° with respect to the light receiving optical axis, and the light intensity distribution correction surface 20b is inclined at an angle of -45 ° with respect to the light receiving optical axis.

A laser diode light source 21 as a light emitting element, a lens 22 having a positive power, and a lens 2 having a negative power
3 is disposed, and a spherical aberration that increases on the light projecting side due to an optical path difference caused by a difference in prism length between the light projecting side and the light receiving side is corrected by the lens 22 and the lens 23 having negative power. are doing.

A light-receiving portion comprising a four-divided sensor 24 as a position detecting light-receiving element is disposed on the light-receiving optical axis side. A lens group 25 having a positive power for optimization is arranged.

With such a configuration, the light beam emitted from the laser diode light source 21 is corrected for spherical aberration by the lens 22 having a positive power and the lens 23 having a negative power. The reflected light is transmitted and transmitted from the lens group 25 having positive power to the opposing device. On the other hand, the light received from the opposing device is incident from the lens group 25 having a positive power, passes through the light intensity distribution correction surface 20b of the composite prism 20, and the symmetry of the light intensity distribution is ensured.
4 receives light.

As described above, the received light Lb is applied to the polarization separation surface 20.
a and the light intensity distribution correction surface 20b, the asymmetry of the light intensity distribution generated when the light passes through the polarization separation surface 20a is canceled out, and the light receiving beam spot T on the light receiving surface of the four-divided sensor 24 is canceled out. The light intensity distribution of
It can be symmetric about two orthogonal optical axes.

In the above-described embodiment, the compound prism 20 in which the light splitting member and the light intensity distribution correcting member are integrated is used. However, the same two beam splitters as in the conventional example are used, and the two polarization splitting surfaces are used. To make a right angle,
Further, the same effect can be obtained even if the crossing position is arranged so as to be located on the light projecting side with respect to the light receiving optical axis to be joined or separated. Therefore, by applying such an optical device to a spatial optical communication device or an optical pickup device having an optical axis direction correction mechanism, downsizing or simplification can be performed while maintaining optical axis direction correction performance.

FIG. 2 is a block diagram of a modification of the first embodiment, in which a parallel plate-shaped polarizing beam splitter 26 and a light intensity distribution correcting member 27 made of a parallel plate glass manufactured by the same method are used. And the polarizing beam splitter 26
A lens group 28 having a positive power is disposed on the light-projecting side.

The polarization splitting surface 26a formed on the polarization beam splitter 26 has an angle of +24 with respect to the light receiving optical axis.
When the light intensity distribution correcting member 27 is inclined at an angle of °, the light intensity distribution correcting member 27a formed on the light intensity distribution correcting member 27 is inclined at an angle of −24 ° with respect to the light receiving optical axis. Furthermore, the polarization separation surface 26
a and the light intensity distribution correction surface 27a are arranged such that the crossing position is located closer to the light emitting portion than the light receiving optical axis. With the optical device having such a configuration, the same effect as that of the embodiment of FIG. 1 can be obtained.

FIG. 3 shows the configuration of the second embodiment. This embodiment is also used in a spatial optical communication device having an optical axis direction correcting mechanism. As in the first embodiment, a laser diode light source 21 is used as a light emitting element of the light projecting unit, and a four-division sensor 24 is used as a light receiving element for detecting the position of the light receiving unit. A polarization beam splitter 30 having a polarization splitting surface 30a similar to that of the conventional example is used in a light branching unit as a branching unit for separating the projected light La from the received light Lb. A lens group 31 having a positive power is disposed on the exit side of the light source, and a light intensity distribution correction member 32 made of a disc-shaped parallel glass is disposed between the four-split sensor 24 and the polarization beam splitter 30. Number = 2.
0 optical device.

FIGS. 4 (a) and 4 (b) are explanatory diagrams for correcting the asymmetry of the light intensity distribution by the light intensity distribution correcting means. A light transmittance distribution in a cross section of a divergent light beam or a condensed light beam having an F number of 2.0, which crosses the converged light beam L1 between the polarization beam splitter 30 and the four-split sensor 24 having an angle dependence will be described. .

In FIG. 4A, an arbitrary point P1 on the optical axis between the four-split sensor 24 and the polarization beam splitter 30 is included.
The section inclined by 5 ° is referred to as section S1. An axis passing through a line at which the plane including the paper surface and the cross section S1 intersect is defined as a W axis.
The iso-transmittance line N1 when the section S1 is rotated by 90 ° about the W axis as a rotation axis and viewed from the front is a concentric circle centered on the intersection P3 of a perpendicular from the condensing point P2 on the light receiving side to the section S1. . The effective ray range A1 in the plane of the cross section S1 is indicated by an ellipse.
The angle dependence of the transmittance of the P-polarized light component of the incident light in the cross section S1 is represented by the transmittance distribution along the W axis, with the light incident angle from the small circle side to the large circle side of the equal transmittance line N1 taken along the horizontal axis. The graph shown corresponds to the transmittance distribution curve TP in FIG.

In FIG. 4B, a section passing through the point P1 and perpendicular to the optical axis is defined as a section S2. The point P in this section S2
An axis passing through 1 and perpendicular to the optical axis is defined as a Y axis. The uniform transmittance line N2 when the section S2 is rotated by 90 ° about the Y axis as a rotation axis and viewed from the front is an intersection P4 of a perpendicular from the intersection P3 to the section S2.
Is the intersection of the major axis and the minor axis of the ellipse, and a concentric ellipse having a shape obtained by multiplying the concentric isotransmittance line N1 by sin 45 ° in the Y-axis direction.

Here, in a plurality of ellipses, a group of ellipses in which the major axis and the minor axis are overlapped and the intersection of the major axis and the minor axis is one point is called "concentric ellipse". The effective ray range A2 in the plane of the cross section S2 is indicated by a circle. P of incident light in the plane of section S2
The transmittance distribution curve TP in FIG. 19 is a graph showing the transmittance distribution, with the angle dependence of the transmittance of the polarized light component as the horizontal axis, the ray angle from the upper ray to the lower ray along the Y axis.
Is equivalent to

The light intensity distribution correcting means is for correcting such asymmetry of the light intensity distribution. In the second embodiment, a light intensity distribution correcting member is provided between the four-division sensor 24 and the polarization beam splitter 30. 32 are arranged. In addition,
Although the case where the transmitted light from the light branching unit is used as the received light Lb has been described, the same principle can be applied to the case where the reflected light from the light branching unit is used as the received light Lb.

FIG. 5A is a front view of the light intensity distribution correcting member 32 of the present embodiment. The light intensity distribution correcting member 32 has a concentric elliptical shape shown in FIG. A symmetrical transmittance line N3 can be drawn with respect to an axis perpendicular to the Y axis through the intersection P5 between the transmittance line N2 and the optical axis,
As shown in FIG. 5B, the light intensity distribution correction in which the transmittance continuously changes so that the transmittance distribution C1 of the P-polarized component along the Y axis and the transmittance distribution C2 symmetrical with respect to the optical axis. Face 3
2a is formed.

By constructing the optical device such that the light intensity distribution correcting member 32 has its effective ray range A3 coincident with the effective ray range A2 in FIG. 4B, the light receiving surface of the four-divided sensor 24 is formed. When the received light Lb is received, the received light beam spot T on the light receiving surface can have a light intensity distribution symmetric with respect to two orthogonal axes.

As shown in FIGS. 6 (a) and 6 (b), in the light intensity distribution which becomes the concentric elliptical transmittance boundary line N4, the transmittance distribution C3 of the P-polarized light component along the Y axis is stepwise. The light intensity distribution correction member 32 may be formed so as to change in shape.

Further, as shown in FIG. 7, the center of the concentric ellipse is located at a distance equal to the distance from the intersection P5 between the light intensity distribution correction surface 32a and the optical axis to the center P6 of the concentric ellipse, and is perpendicular to the Y axis. The light intensity distribution correction member 32 in which the light transmittance changes stepwise may be formed so as to draw the same transmittance line as the transmittance boundary line N4 at two locations in the vertical direction.

When such a light intensity distribution correcting member 32 is applied to an optical device, the light receiving surface of the four-divided sensor 24 has not only a light intensity distribution but also a spot shape that is symmetrical with respect to two orthogonal axes. It can be a beam spot T.

FIG. 8 shows the configuration of the third embodiment.
The third embodiment is a light intensity distribution correcting member 32 for canceling the asymmetry of the light intensity distribution when the incident light is transmitted through the light intensity distribution correcting surface 32a. The third embodiment is directed to the light intensity distribution correcting surface. A light intensity distribution correcting member 3 made of rectangular parallel glass that cancels the asymmetry of the light intensity distribution in the light emitted from the polarizing beam splitter 30 when the incident light is reflected.
3 are used. This light intensity distribution correction member 33 has four
The four-split sensor 24 is arranged between the split sensor 24 and the polarization beam splitter 30 at an angle of 45 ° with respect to the optical axis, and on the reflected light side of the light intensity distribution correction member 33.

FIG. 9 (a) is a front view of the light intensity distribution correcting member 33, and FIG. 9 (b) shows its transmittance or reflectance characteristics. The reflectance from the light intensity distribution correcting member 33 changes continuously. Here is an example. The light intensity distribution correction member 33 is a light intensity distribution correction surface 3.
With respect to an axis perpendicular to the W axis passing through the intersection P7 of 3a and the optical axis,
An isoreflectance line N5 symmetrical to the concentric isotransmittance line N1 in FIG. 4A can be drawn. The center P8 of the concentric ellipse describing the constant reflectance line N5 has a symmetrical positional relationship with the intersection P3 with respect to the point P1. Then, the transmittance distribution C4 of the P-polarized light component along the W axis becomes a transmittance distribution C5 symmetric with respect to the optical axis. Thus, the light intensity distribution correction member 33 is formed with the light intensity distribution correction surface 33a so that the reflectance changes continuously.

By constructing an optical device such that the light intensity distribution correcting member 33 has an effective ray range A4 corresponding to the effective ray range A1 in FIG.
When the light receiving light beam Lb is received on the light receiving surface of No. 4, the light receiving beam spot T can have a light intensity distribution symmetric with respect to two orthogonal axes.

As shown in FIGS. 10 (a) and 10 (b), the light intensity distribution correcting member 33 is provided with a P-polarized light component along the W axis by a reflectance distribution C4 which is a concentric reflectance boundary line N6. May be formed so that the reflectivity distribution C6 of the first step changes stepwise.

FIG. 11 shows a configuration of a modification of the third embodiment. Instead of the prism-shaped polarizing beam splitter 30 whose light incident surface is perpendicular to the optical axis, a polarization splitting surface 26a is shown.
Are used. A parallel-plate-shaped polarization beam splitter 26 in which is inclined at an angle larger than 45 ° and a light intensity distribution correction member 34 manufactured on the same principle as the light intensity distribution correction member 33 are used. Since the angle dependence of the polarization splitting characteristic of the parallel plate-shaped polarization beam splitter 26 is more remarkable than the prism-shaped polarization beam splitter 30 in many cases, the effect of applying the light intensity distribution correction member 34 is more significant. growing.

[0050]

As described above, in the optical device according to the present invention, the light transmission distribution or the light reflectance distribution in the section perpendicular to the optical axis of the received light transmitted or reflected by the light intensity distribution correcting means is orthogonal. By symmetrical with respect to two axes, even if the transmittance or reflectance from the light branching unit has an angle dependency, a light intensity distribution with good symmetry with respect to two orthogonal axes on the light receiving surface of the light receiving optical system. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical device according to a first embodiment.

FIG. 2 is a configuration diagram of a modified example.

FIG. 3 is a configuration diagram of a second embodiment.

FIG. 4 is an explanatory diagram of the asymmetry of the light intensity distribution.

FIG. 5 is an explanatory diagram of a light intensity distribution correction member.

FIG. 6 is an explanatory diagram of another light intensity distribution correction member.

FIG. 7 is an explanatory diagram of still another light intensity distribution correction member.

FIG. 8 is a configuration diagram of a third embodiment.

FIG. 9 is an explanatory diagram of a light intensity distribution correction member.

FIG. 10 is an explanatory diagram of another light intensity distribution correction member.

FIG. 11 is a configuration diagram of an optical device according to a modification.

FIG. 12 is a configuration diagram of a communication optical system of a first conventional optical space communication device.

FIG. 13 is a front view of the light receiving beam splitter.

FIG. 14 is a perspective view of an optical axis direction variable mirror.

FIG. 15 is an explanatory diagram of a scanning direction of a light receiving beam spot.

FIG. 16 is an explanatory diagram of a scanning direction of a light receiving beam spot.

FIG. 17 is a graph showing the wavelength dependence of the polarization splitting characteristic of the polarization beam splitter.

FIG. 18 is a configuration diagram of a communication optical system of a second conventional example.

FIG. 19 is a graph showing the angle dependence of the polarization splitting characteristic.

[Explanation of symbols]

20, composite prism 20a, 26a, 30a polarization separation surface 20b, 27a, 32a, 33a, 34a light intensity distribution correction surface 21 laser diode light source 22, 23, 25, 27, 31 lens 24 quadrant sensor 26, 30 polarization beam splitter 27, 32, 33, 34 Light intensity distribution correction member

Claims (4)

[Claims] 1. An optical apparatus comprising: a light projecting unit; a light receiving unit; a lens group having a positive power; and a light branching unit disposed at a position where a light projecting optical axis and a light receiving optical axis intersect. A light intensity distribution correction means is provided between the branching means and the light receiving means, and is perpendicular to the optical axis of the received light transmitted or reflected by the light intensity distribution correction means via the lens group having the positive power and the light branching means. An optical device, wherein a light transmittance distribution or a light reflectance distribution in a simple cross section is symmetric with respect to two orthogonal axes. 2. The optical device according to claim 1, wherein said light splitting means is a polarization beam splitter. 3. The light intensity distribution correcting means has a light distribution correcting surface similar to the light splitting surface of the light splitting means, and when the light splitting surface is inclined by an angle + θ with respect to an optical axis,
The optical device according to claim 1, wherein the light intensity distribution correction surface is inclined by an angle −θ with respect to an optical axis. 4. A light transmittance distribution or a light reflectance distribution of the light intensity distribution correction surface, wherein a line group forms a concentric ellipse or a concentric circle when an iso-transmittance line or a transmittance boundary line is drawn. 2. The method according to claim 1, wherein the shape changes continuously or stepwise in the normal direction of the ellipse or concentric circle, and the intersection of the two symmetry axes of the concentric ellipse or the center of the concentric circle is located outside the effective ray range. An optical device according to claim 1.