JP2580148B2 - Optical mixer - Google Patents

Description

The present invention relates to an optical device requiring uniform light, for example, an optical mixer suitable for use in an optical distance meter.

(Prior Art) Some optical devices require homogeneous light. For example, a lightwave distance meter that emits modulated light, reflects the modulated light by a corner cube, receives the reflected modulated light, and measures the distance by comparing the phases of the emitting side and the light receiving side. In this method, the distance is measured by comparing the phase on the light-emitting side with the phase on the light-emitting side. Therefore, in order to improve measurement accuracy, it is required that the emitted modulated light be uniform without phase unevenness. However, the modulated light emitted from the light emitting element as a light source has more or less phase unevenness.

Therefore, for example, the output optical system of
As shown in FIG. 14, one bent step index type fiber 1 (hereinafter, referred to as a step type fiber) as an optical mixer is provided, and modulated light emitted from the light emitting element 2 is transmitted through the relay lens 3 to the step type fiber. An image is formed on the incident end face 1a of the fiber 1 and propagated while being totally reflected inside the core of the step type fiber 1 as shown in FIG. When condensed and emitted as a parallel light beam, when the modulated light imaged so as to be focused on one point P of the incident end face 1a is propagated while undergoing total reflection, it is spread over the entire surface at the exit end face 1b. Due to the optical properties, the phase unevenness is made uniform in the direction of the angle of emission of the modulated light emitted from the objective lens 4. Objective lens 4
It is important that the modulated light emitted from the light source be uniform without phase unevenness over the entire surface a of the objective lens 4 and be uniform without phase unevenness even in the emission angle direction b.

(Problems to be Solved by the Invention) However, phase unevenness of the modulated light emitted from the light emitting element 2 includes positional phase unevenness based on the light emitting position of the light emitting element 2 and angular phase unevenness based on the emitting direction. is there. Conventional 1
In the configuration in which the phase unevenness of the modulated light is homogenized using the bent step type fiber 1, the positional phase unevenness is homogenized, and the phase unevenness in the emission angle direction b from the objective lens is homogenized. . However, since the rate of reduction of angular phase unevenness is small, the presence of angular phase unevenness causes
Phase unevenness occurs in the entire surface area a of the substrate. The reason for this is
For example, in a step-type fiber 5 having a linear and circular cross-section as shown in FIG. 16, light is propagated while rotating in the circumferential direction of the step-type fiber 5 by total internal reflection, as shown in FIG. The ring-shaped light beam having the incident angle c stored as the output angle c is output from the step-type fiber 5 and when the light beam including the angular phase unevenness is incident, the angular phase unevenness is not homogenized and the output angle differs. This is because the light is emitted in the direction and enters the objective lens 4. In addition, when the stepped fiber 1 is bent, the incident angle c is not stored as the output angle c due to the bending, and the angular phase unevenness can be homogenized, but is not sufficient.

As described above, in the conventional type in which the step type fiber 1 is bent, homogenization of the angular phase unevenness is not sufficient, and the light emitting element 2 having a small angular phase unevenness has been conventionally selected and used. Recently developed LEDs with higher brightness than conventional ones cannot use large angular phase unevenness as compared with conventional ones.In addition, semiconductor laser LDs have a small light-emitting area compared to LEDs, Angular phase unevenness rather than phase unevenness is regarded as a problem, and today, it is important to homogenize angular phase unevenness.

Accordingly, it is an object of the present invention to provide an optical mixer capable of obtaining light with uniform phase unevenness by achieving homogenization of positional phase unevenness and angular phase unevenness.

Configuration of the Invention (Means for Solving the Problems) The optical mixer according to the present invention focuses on the fact that the step-type fiber has at least the optical property of homogenizing the positional phase unevenness, and focuses on the angular phase unevenness. If it is possible to convert this light into light having uneven positional phase, it is possible to eliminate angular phase unevenness by propagating the light having angular phase unevenness converted into uneven positional phase through a step-type fiber. It is based on the idea that the characteristic is that it propagates the positional phase unevenness between the positional phase unevenness based on the light emitting position of the light emitted from the light emitting element and the angular phase unevenness based on the emitting direction. First to homogenize
A step-type fiber, an angle / position converting means for converting a difference in incident angle into a difference in emission position, and a difference in incident position into a difference in emission angle, and an angular phase unevenness converted into the positional phase unevenness. And a second-step type fiber that emits light that has been homogenized and that has homogenized the phase unevenness possessed by the light before being incident on the first-step type fiber.

(Embodiment) FIG. 1 shows a first embodiment in which an optical mixer according to the present invention is applied to an emission optical system of an optical distance meter. In FIG. 1, reference numeral 10 denotes a light emitting element, 11 denotes a relay lens, 12 denotes an optical mixer, and 13 denotes an objective lens. The optical mixer 12
First step fiber 14, second step fiber 15, graded index fiber 16
(Hereinafter referred to as graded fiber). The light emitting element 10 emits modulated light, and the modulated light is focused and focused on the incident end face 14a of the first step type fiber 14 by the relay lens 11. The input end face 16a of the graded fiber 16 is optically connected to the output end face 14b of the first step type fiber 14, and the input end face of the second step type fiber 15 is connected to the output end face 16b of the graded fiber 16. 15a is optically connected,
The exit end face 15b of the second step fiber 15 is located at the focal point of the objective lens 13. In addition, the first step type fiber 14, the graded type fiber 16,
An optical connector may be used for the optical connection of the step-type fibers 15, or the end faces of the fibers may be fused together. Further, an adhesive can be used.

The first step type fiber 14 homogenizes the positional phase unevenness during propagation between the positional phase unevenness based on the emission position of the modulated light emitted from the light emitting element 10 and the angular phase unevenness based on the emission direction. The modulated light A having a function and converging toward a point P _A shown in FIG. 2 is a modulated light emitted from a light emitting position P _A ′ of the light emitting element 10 toward a point P _B shown in FIG. It is assumed that the modulated light B to be focused is the modulated light emitted from the point P _B 'of the light emitting element 10. The modulated light A and the modulated light B have different phases due to positional phase unevenness based on the light emitting position of the light emitting element 10.

In other words, the modulated light A, A ₁ and the light flux with finely subdivided modulated light B in the angular _{direction, A 2, ..., B 1} , B 2, ..., and when the light flux A _1, A _2, ..., B _1, B _2, although ... can be regarded as the phase in each light beam is uniform, the light flux a _1, B _1, the light beam
A _2, B _2, ..., since there is a positional phase unevenness modulated light, different the phase with each other. The light fluxes A ₁ , A ₂ ,..., And the light fluxes B ₁ , B ₂ ,... Also have different angular phases due to the angular phase unevenness based on the emission direction of the modulated light emitted from the light emitting element 10.

Here, when focusing on the light beam A _1, B _1, the light beam A _1,
B ₁ propagates toward the emission end face 14b while being totally reflected by the first step type fiber 14 and rotating in the circumferential direction, and at the time of propagation, the widths of the light fluxes A ₁ and B ₁ expand, respectively. The light is emitted as a ring-shaped light beam that overlaps from the entire area of the emission end face 14b. The light flux A ₁ and the light flux B ₁ ,
The light flux A ₂ and the light beam B _2, ... since the overlap each other when emitted from the exit end face 14b, as a result, homogenized ring-shaped light flux C positioning phase irregularity is emitted from the exit end face 14b Will be. In that Figure 2, the region denoted by dots indicates a state of divergence of the light beam A _1.

However, in the first step type fiber 14, the light beam propagates while being totally reflected, so that the light beams A ₁ , A ₂ ,.
The incident angle α of B ₁ , B ₂ ,...
Focusing on A ₁ , A ₂ ,..., The light fluxes A ₁ , A ₂ ,.
Comrades are emitted without overlapping each other. This is the same for the light beams B ₁ , B ₂ ,...

For example, as shown in FIG. 3, the light beam B ₁ incident at the light beam A ₁ and the incident angle alpha ₁ which is incident at an incident angle alpha ₁ although overlap each other, the incident angle alpha ₁ is stored as an outgoing angle alpha ₁ Therefore, the light beam a _1, B ₁ is emitted from the exit end face 14b as a ring-shaped light flux C ₁ output angle alpha _1, the light beam incident at an incident angle alpha ₂ and the light flux a ₂ incident at an incident angle alpha ₂ as well B ₂ is overlapped with each other, exit end face as a ring-shaped light flux C ₂ output angle alpha ₂
Emitted from 14b, generally different ring-shaped light flux C ₁ of the emission angle, C _2, will be ... is emitted from the exit end face 14b, the light beams A _1, A _2, ... each other, the light beams B _1, Since B ₂ ,... Do not overlap each other, the light fluxes C ₁ , C ₂ ,... Have different phases from each other, and the light flux C as a whole is emitted while containing angular phase unevenness.

Here, the light beams C ₁ and C ₂ can be treated as parallel light beams each having a diameter equal to the diameter of the exit end face 14b rotated around the optical axis at angles α ₁ , α ₂ . This is due to the above-mentioned micro-division.

As shown in FIG. 4, the graded fiber 16 propagates the light while swelling, and functions as a lens. Considering the light beam C _1, the light beam C ₁ can be regarded as a parallel light flux incident angle alpha ₁ symmetrically to the optical axis. The light beam C ₁ minute parallel beam C _1-1, the C _1-2, and made of ..., the micro parallel beam C _1-1, C _1-2, ... the outgoing side plane orthogonal to the optical axis O is focused imaged to a point P ₁ in S, is emitted from the point P ₁ as radiation light C ₁ '. Here, C _1-1 ′ is a light beam corresponding to the minute parallel light beam C _1-1 , and C _1-2 ′ is a minute parallel light beam
This is a light beam corresponding to _C1-2 , and a difference in the incident position on the incident end face 16a appears as a difference in the outgoing angle. Also, the incident angle α ₂
When the parallel light flux C ₂ is considered, the parallel light flux C ₂ is focused and imaged at the point P ₂ in the emission-side plane S, and the emitted light is emitted from the point P _2.
The light is emitted as C ₂ ′, and the difference in the incident angle appears as the difference in the emission position.

As described above, the parallel light beams C ₁ and C ₂ are incident at α ₁ and α ₂ symmetrically with respect to the optical axis, and form an image in a ring shape around the optical axis in the exit plane S.

That is, it functions as an angle / position conversion unit that converts the difference in the incident angle into the difference in the outgoing position and the difference in the incident position into the difference in the outgoing angle. The synchrotron radiation C ₁ ′, C ₂ ′,.
Is determined by the diameter of the light beam incident on the graded fiber 16, and is approximately the same.

By the way, the phases of the light fluxes C ₁ , C ₂ ,... Are homogenized in each range, and therefore, the emitted light C ₁ ′, C ₂ ′,.
Has a uniform phase within each range, but the emitted light C ₁ ′, C ₂ ′,
... the phases of each other are different and not homogeneous. Such radiated light C ₁ ′, C ₂ ′,... Can be regarded as radiated light C ′ having no angular phase unevenness and positional unevenness. As shown in FIG. 5, such modulated light is incident on the incident end face 15a of the second step type fiber 15 as radiation light C 'and propagates through the second step type fiber 15. As in FIG. 14, the radiated lights C ₁ ′, C ₂ ′,... Incident at different positions spread over the entire area at the emission end face 15 b, so that the radiated lights C ₁ ′, C ₂ ′,. Then, the modulated light D is emitted from the emission end face 15b as the homogenized positional phase unevenness and angular phase unevenness. That is, the second step type fiber 15 functions to homogenize the angular phase unevenness of the light emitting element 10 converted into the positional phase unevenness by the graded type fiber 16.

In the above description, graded fiber 16
Explained that it was ideal. The effect of the angle / position conversion is due to the undulation cycle of the light beam, and a uniform effect cannot be obtained unless the distribution and length of the refractive index are managed.

In general, the graded fiber 16 has a swell cycle that varies depending on the incident angle and the incident position.
Ideal position / angle conversion cannot be performed. The graded fiber 16 has a characteristic that the allowable incident angle is large at the center of the incident end face 16a, but the allowable incident angle is small at the peripheral part as compared with the central part. The coupling efficiency with the mold fiber 14 is small. Therefore, a second embodiment using a lens system as the angle / position conversion means will be described next with reference to FIGS.

In FIG. 6, reference numeral 17 denotes a lens system as angle / position conversion means. This lens system 17 includes a lens 18 and a lens 19
It consists of The lens 18 and the lens 19 are the same as the lens 18
The image of the exit end face 14b of the first step-type fiber 14 is in a positional relationship that is formed at the position of the front focus f ₁ of the lens 19 by. This positional relationship between the lenses 18 and 19 is generally known as the Koehler illumination method.

The input end face 15a of the second step type fiber 15 is disposed at a position where the light beam is focused. That is, as shown in FIG. 7, the exit end face 14 of the first step type fiber 14
b is a front focus f ₂ of the lens 19 are optically conjugate, side focal f ₁ of the lens 18 and the incident end face 15a of the second step-type fiber 15 is optically conjugate. This means that either the first step type fiber 14 or the second step type fiber 15 may be on the incident side.

The light fluxes C ₁ , C ₂ ,... Are parallel light fluxes having incident angles α ₁ and α ₂ symmetrical with respect to the optical axis as described in the first embodiment.
Focusing on the rear focal point f ₁ , respectively, and the front focal point of the lens 19
f ₂ , the input end face 15 of the second step type fiber 15
focused to different positions P _1, P ₂ of the outgoing side plane S including the a, emitted light C ₁ from the position _{P 1, P 2 ', C} 2', and is emitted as .... The positions P ₁ and P ₂ are incident angles α ₁ and α ₂ on the incident side plane including the exit end face of the first step type fiber 14, and the radiation direction depends on the incident position on the incident side plane. Luminous flux
C _1, C _2, ... overlap at the front focal position of the lens 19, C _1, part of the rays of C ₂ of overlapping each other are emitted on the output side plane S as collimated light. Therefore, the luminous fluxes C ₁ and C ₂ have the same spread angle.

Here, as shown in FIG. 8, the size of the image formed at the front focal point of the lens 19 is R, the core diameter of the first step type fiber 14 is d ₁ , and the front focal point f ₁ of the lens 18 and the exit end face 14 b the distance to the l _1, and the distance from the lens 18 to the imaging position and _{L, R = d 1 · L} / (f 1 + l 1) ... _{or, R = d 1 · f 1} / l 1 ... at the indicated It is.

The maximum incident angle θ ₂ of the light beam incident on the second step type fiber 15 is represented by θ ₂ = tan ⁻¹ (R / 2f ₂ ).

By this formula and the formula, the distance L from the lens 18 to the image forming position is obtained as L = f ₁ · (d ₁ + 2f ₂ · tan θ ₂ ) / d ₁ .

If the diameter of the light beam incident on the second step type fiber 15 is d ₂ , and the maximum opening angle determined by the numerical aperture NA of the first step type fiber 14 is θ ₁ , d ₂ = 2f ₂ · (f ₁ + l ₁ ) · Tan θ ₁ / L... Accordingly, the diameter d ₂ is obtained as d ₂ = d ₁ · tan θ ₁ / tan θ ₂ .

Here, the expression gives a conditional expression when the coupling efficiency between the first step type fiber 14 and the second step type fiber 15 is ideal. In addition, "ideal" means that there is no end face reflection and lens aberration and the coupling efficiency is 100%
Means that

For example, if the first step fiber 14 and the second step fiber 15 have the same core diameter and the same numerical aperture NA, the second step fiber
The maximum incidence angle of the light beam on the first step type fiber 14
Equal to the maximum exit angle of the light beam emitted from
It is necessary that the diameter of the light beam incident on the input end face 15a of the step type fiber 15 is equal to the size of the output end face 14b of the first step type fiber 14, which is represented by the following equation: θ ₁ = θ ₂ , d ₁ = given as d _2, a distance L from the lens 18 at that time to the image forming position 'is the _{formula, L' = f 1 · (} d 1 + 2f 2 · tanθ 1) / d 1 ... obtained as.

That is, the distance between the lens 18, 19, L '+ by setting f _2, may be a first step-type fiber 14 coupling efficiency between the second stepped fiber 15 to an ideal state.

In the equation, the core diameter d ₁ and 2f ₂ · tan θ ₁ are:
d ₁ <2f ₂ · tan θ ₁ With ordinary lens on the lens 18 and 19, the difference between the core diameter d ₁ and 2f ₂ · tanθ ₁ is large,
The equation can be approximately transformed into the following equation: L ′ = 2f ₁ · f ₂ · tan θ ₁ / d ₁ .

Although outside position and angle conversion from some ideal state, from the viewpoint of coupling efficiency, coupling efficiency hardly changes between the front focus f ₂ of the lens 19 of the lens 19. Thus, the image of the exit end face 14b of the first step-type fiber 14 is set between the lens 19 and a front-side focal f _2, the lens
By setting the interval between 18 and 19 based on the approximate expression f ₂ (d ₁ + 2f ₁ · tan θ ₁ ) / d ₁ , good position-angle conversion can be achieved. It may be equal to the focal length f ₂ of the focal length f ₁ and the lens 19 of the lens 18.

By the way, in a general lens, the focal length is several mm or more, and the lens interval becomes large. However, as shown in FIG. 9, if a 0.25 pitch selfoc lens 20, 21 is used instead of a general lens, for example, Since the focal length can be suppressed to about 1 mm, the distance between the lenses can be reduced, and the overall length of the lens system 17 can be shortened, which is convenient.

FIG. 10 and FIG. 11 show a third embodiment of the optical mixer according to the present invention. When a semiconductor laser is used as the light emitting element, a speckle pattern is generated in the modulated light emitted from the fiber because the modulated light emitted from the semiconductor laser is coherent. The speckle pattern changes depending on the temperature, the strain of the step-type fiber, and the like. If the speckle pattern occurs in the optical distance meter, the measurement accuracy deteriorates, which is not preferable. In the third embodiment, an effect based on the occurrence of the speckle pattern is reduced, and an arm 23 is attached to an output shaft of a motor 22, and a roller 24 is rotatably supported at a tip of the arm 23. The first step type fiber 14 is wound around the roller 24, the motor 22 is rotated to change the contact position of the roller 24 with the first step type fiber 14, This is to cause the 14 to vibrate. The distortion position of the first step type fiber 14 changes due to its vibration, whereby the speckle pattern changes and is averaged. In the lightwave distance meter, measurement is performed by averaging processing.If the speckle pattern is changed in a time shorter than the time required for the averaging processing, the speckle pattern is averaged, and a measurement error based on the effect is reduced. Can be excluded.

By the way, in this embodiment, the vibration generating device is provided on the side of the first step type fiber 14, but may be provided on the side of the second step type fiber 15. However, it is desirable to provide a vibration generator on the side of the first step type fiber 14 because the first step type fiber 14 can be made longer than the second step type fiber 15. This is because a step-type fiber propagates by total internal reflection, so that the optical path difference differs depending on the incident angle. If the second step-type fiber 15 is lengthened, the optical path difference increases, and the step-type fiber 15 Although the phase difference based on the length appears in the emission angle direction, even if the phase difference based on the length appears when the first step type fiber 14 is lengthened, the phase difference in the emission angle direction is converted into the angle-position conversion. This is because the second step type fiber 15 homogenizes it.

12 and 13 are diagrams for explaining an embodiment in which the output optical system using the optical mixer according to the present invention is applied to a measurement system of an optical distance meter, and in FIG. 12, 25 denotes a chopper. , 26 is a reflection prism, 27 is a corner cube, 28 is a half mirror, 29 is an internal reference light path, 30, 31 are total reflection mirrors of the internal reference light path 29, 32 is a lens, 33 is a fiber, 34
Is a condensing lens, and 35 is a light receiving element, and the modulated light emitted from the light emitting element 10 and propagated through the emission optical system, and having uniform phase unevenness, is selected by the chopper 25 to be reflected by the reflection prism 26 and the objective lens 13. Then, the light is emitted toward the corner cube 27. The modulated light reflected by the corner cube 27 and returned is reflected by the reflecting prism 26 through the objective lens 13, guided through the fiber 33, and
The light is guided to 34 and enters the light receiving element 35.

FIG. 13 shows a distance measuring circuit of the lightwave distance meter. The distance measuring circuit has a control operation unit 36, an operation unit 37, a memory 38, a display unit 39, and an oscillator 40, and an oscillator 40 Generates a 15 MHz signal, which is supplied to a first switch 41, a frequency divider 42, a combiner 43, and a gate circuit 44. The frequency divider 42 divides the frequency of the 15 MHz signal of the oscillator 40 into a 75 kHz signal and a 3 kHz signal.
And a function of generating the

The first switch 41 is controlled by the control calculation unit 36, and outputs either the 15 MHz signal or the 75 KHz signal to the light emitting element 10 via the amplifier 45 by the control. As a result, the light emitting element 10 emits any one of the modulated lights of 15 MHz and 75 KHz. Where 15MH
The modulated light of z has a wavelength of 20 m, and the modulated light of 75 KHz has a wavelength of 4 m.
Km, and the modulated light of 15 MHz is used for precision measurement.
The 5 KHz modulated light is used for coarse measurement. Synthesizer 43 is 15
14.997MHz signal and 75KHz which are about 3KHz lower than MHz signal
A signal of 72 KHz, which is lower by about 3 KHz, is output to the second switch 46.

The second switch 46 controls the first operation under the control of the control operation unit 36.
When the switch 41 outputs a signal of 15 MHz to the light emitting element 10, a signal of 14.997 MHz is output toward the mixer 47, and the first switch 41 outputs a signal of 75 MHz to the light emitting element 10. Sometimes it has the function of outputting a 72 KHz signal to the mixer 47.

The light receiving output of the light receiving element 35 is input to the mixer 47 via an amplifier 48. The mixer 47 synthesizes the signal of the light receiving element 35 and the signal of the second switch 46 to generate a signal of 3 KHz.
Is output to the waveform shaper 49. The waveform shaper 49 shapes the 3 KHz signal of the mixer 35 and outputs the signal to the gate circuit 44. The gate circuit 44 receives 3 kHz from the frequency divider 42.
The rising (falling) signal of
Rise (fall) of 3KHz signal from waveform shaper 49
Is the stop signal, and the oscillator 40 existing within the cycle
And outputs a signal of 15 MHz toward the count 50.

The counter 50 counts a signal from the gate circuit 44 in accordance with a control signal from the control operation unit 36 to the chopper 25. In this example, a measurement point (an installation position of a corner cube) measured by 15 MHz modulated light is used. the count value D ₂ according to the distance to the measuring point measured by the counting value D ₁ and modulated light 75KHz according to the distance to, the count value D ₁ 'according to the distance of the internal reference optical path as measured by 15MHz modulated light A count value D ₂ ′ relating to the distance of the internal reference optical path measured by the 75 KHz modulated light is obtained. The counter 50 is provided by the control unit 36.
Reset at an appropriate timing by a signal from

The control operation unit 36 obtains the upper digit of the distance from the difference between the count values D ₂ and D ₂ ′ of the counter 50 to the measurement point by averaging processing, and also calculates the difference between the count values D ₁ and D ₁ ′ to the measurement point. Is obtained by an averaging process and displayed on the display 39, whereby the distance to the measurement point is measured.

Effect of the Invention As described above, the optical mixer according to the present invention has a positional phase unevenness between a positional phase unevenness based on a light emitting position of light emitted from a light emitting element and an angular phase unevenness based on an emitting direction. First-step type fiber that homogenizes the beam during propagation, angle / position conversion means for converting the difference in the incident angle into the difference in the outgoing position, and the difference in the incident position into the difference in the outgoing angle; And a second-step type fiber that homogenizes the angular phase non-uniformity converted into and emits light having the phase non-uniformity retained by the light before entering the first-step type fiber. There is an effect that the phase unevenness can be homogenized.

[Brief description of the drawings]

FIGS. 1 to 5 illustrate a first embodiment in which an optical mixer according to the present invention is applied to an emission optical system of a lightwave distance meter, and FIG. 1 shows an emission optical system of a lightwave distance meter. 2, FIG. 2 is a cross-sectional view showing the propagation state of the first step type fiber of FIG. 1, FIG. 3 is a side view of the first step type fiber of FIG. 2, and FIG. FIG. 5 shows a propagation state of a graded fiber, FIG. 5 is a cross-sectional view showing a propagation state of a second step type fiber in FIG. 1, and FIGS. 6 to 8 show an optical mixer and a light wave distance meter according to the present invention. FIG. 6 is a view showing an emission optical system of the optical distance meter, and FIGS. 7 and 8 are lenses of FIG. FIG. 9 is a diagram for explaining the operation of the system, FIG. 9 is a diagram for explaining a modification of the lens system, FIG. 10 and FIG. FIG. 12 is a view for explaining a third embodiment in which the optical mixer according to the present invention is applied to an output optical system of a lightwave distance meter. FIGS. 12 and 13 show an output optical system using the optical mixer according to the present invention. FIG. 12 is a view for explaining an embodiment applied to a measurement system of a distance meter, FIG. 12 is a diagram showing an example of a measurement system of the light wave distance meter, FIG. 13 is a circuit diagram of the light wave distance meter, FIG. 14 is a diagram showing an emission optical system of a conventional lightwave distance meter, and FIG.
FIG. 14 is a diagram showing the propagation state of light in the step-type fiber shown in FIG. 14, FIG. 16 is a diagram showing the propagation state of light propagating in the linear step-type fiber, and FIG. 17 is its FIG. It is a figure which shows the emission state of the light beam emitted from the shown step type fiber. 10 light emitting element 14 first step type fiber 15 second step type fiber 16 graded fiber 17 lens system A, B modulated light

Claims (6)

(57) [Claims] 1. A first-step type fiber for homogenizing positional phase unevenness during propagation between positional phase unevenness based on a light emitting position of light emitted from a light emitting element and angular phase unevenness based on an emitting direction. And an angle / position converting means for converting the difference in the incident angle into the difference in the emission position, and the difference in the incident position into the difference in the emission angle; and homogenizing the angular phase unevenness converted into the positional unevenness, An optical mixer, comprising: a second-step fiber that emits light having uniform phase unevenness possessed by light before being incident on the first-step fiber. 2. The optical mixer according to claim 1, wherein said angle / position conversion means is a graded fiber. 3. The first step-type fiber according to claim 1, wherein said angle-position conversion means is a first step type fiber.
A lens system having a lens and a second lens disposed so that the front focal point substantially coincides with the position where the image of the emission end face is formed, and the focal position of the second lens portion is located on the emission side plane. 2. The optical mixer according to claim 1, wherein the input end face of the second step type fiber is set substantially at the output side plane. 4. The apparatus according to claim 3, wherein an interval L from the first lens to a position where an image of the emission end face is formed is substantially set in accordance with the following condition. Light mixer. L = f ₁ · (d ₁ + 2f ₂ · tan θ ₂ ) / d ₁ where f ₁ is the rear focal point of the first lens, f ₂ is the front focal point of the second lens, and d ₁ is the first step type fiber. Core diameter, θ
₂ is the maximum incident angle to the second step-type fiber of the light flux emitted from the second lens. 5. The optical mixer according to claim 3, wherein a selfoc lens is used as said first lens and said second lens. 6. The first step type fiber and the second step type fiber.
The optical mixer according to any one of claims 1 to 5, wherein a vibration is applied to at least one of the step-type fibers.