JP2022026416A - Spatial phase modulation device, optical scanner, object recognition device and spatial phase modulation method - Google Patents

Abstract

To make it possible to perform light phase modulation in a wide modulation width.SOLUTION: A spatial phase modulation plate 31 is provided in addition to a spatial phase modulation element 35. The spatial phase modulation plate 31 includes a plurality of blocks Ka, Kb (region) having different light path lengths (thicknesses Ha, Hb) and periodically arranged in a direction Gx. A light beam L entering the blocks Ka, Kb (periodic region part) is subjected to phase modulation (second phase modulation) of periodically changing the phase in the direction Gx with a modulation width Zp (second modulation width) corresponding to a difference between light path lengths of the blocks Ka, Kb. The light beam L is thus subjected to phase modulation by the spatial phase modulation element 35 and phase modulation by the spatial phase modulation plate 31, to periodically modulate the phase of the light beam L in the direction Gx with a modulation width Zt wider than a modulation width Zg. As a result, phase modulation of the light beam L can be executed with the wide modulation width Zt.SELECTED DRAWING: Figure 4B

Description

The present invention relates to a technique for performing phase modulation on light.

The planar light bulb described in Patent Document 1 includes a plurality of actuators arranged two-dimensionally. Each actuator is displaced by being driven by an electrode. Such a flat light bulb can perform phase modulation on the incident light by adjusting the displacement amount of each actuator to form unevenness.

Japanese Patent No. 4695603

By the way, as described in Patent Document 1, the displacement of the actuator is very small. Therefore, the unevenness is shallow with respect to the wavelength of light, and it is difficult to secure a sufficient modulation width for modulating the phase of light. Especially when trying to use light having a long wavelength, it was extremely difficult to secure the modulation width. Therefore, for example, in the case of diffracting light by phase modulation, if the phase modulation width is insufficient, the amount of zero-order light increases, and a required amount of diffracted light cannot be obtained. This situation also applies to other spatial phase modulation devices such as grating light bulbs, Elkos or digital mirror devices.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of performing phase modulation of light with a wide modulation width.

The spatial phase modulation device according to the present invention has a plurality of grid elements arranged in a predetermined arrangement direction, and by driving the grid elements in response to an input signal, the phase has a first modulation width corresponding to the input signal. A spatial phase modulation element that performs the first phase modulation that periodically changes in the arrangement direction on the light incident on the lattice element, and a periodic region portion in which a plurality of regions having different optical path lengths are periodically arranged in the arrangement direction. The second phase modulation that periodically changes the phase in the arrangement direction with the second modulation width according to the difference in the optical path length of each of the plurality of regions of the periodic region portion is executed on the light incident on the periodic region portion. The spatial phase modulation member is provided, and the first phase modulation and the second phase modulation are performed on the light, so that the phase of the light is periodic in the arrangement direction with a composite modulation width wider than the first modulation width. Will be changed.

The spatial phase modulation method according to the present invention is a first modulation according to an input signal by driving a lattice element of a spatial phase modulation element having a plurality of lattice elements arranged in a predetermined arrangement direction according to an input signal. The step of performing the first phase modulation that periodically changes the phase in the arrangement direction by the width on the light incident on the lattice element, and the periodic region portion in which a plurality of regions having different optical path lengths are periodically arranged in the arrangement direction. A second phase modulation that periodically changes the phase in the arrangement direction with a second modulation width corresponding to the difference in the optical path length of each of the plurality of regions of the periodic region portion of the spatial phase modulation member having the above is incident on the periodic region portion. The process of executing the light is provided, and the first phase modulation and the second phase modulation are performed on the light, so that the phase of the light is periodic in the arrangement direction with a composite modulation width wider than the first modulation width. Is modulated.

In the present invention (spatial optical modulation device and spatial optical modulation method) configured in this way, phase modulation is performed by a spatial phase modulation element having a plurality of lattice elements arranged in a predetermined arrangement direction. This spatial phase modulation element drives the grid element according to the input signal, so that the first phase modulation that periodically changes the phase in the array direction with the first modulation width corresponding to the input signal is incident on the grid element. Run to the light. However, as described above, it has been difficult to sufficiently secure the modulation width (first modulation width) of the phase modulation that can be executed by such a spatial phase modulation element. Therefore, in the present invention, a spatial phase modulation member is further provided in addition to the spatial phase modulation element. This spatial phase modulation member has a periodic region portion in which a plurality of regions having different optical path lengths are periodically arranged in the arrangement direction, and the phase is arranged in the second modulation width according to the difference in the optical path length of each region. The second phase modulation, which is periodically changed to, is performed on the light incident on the periodic region portion. In this way, the first phase modulation and the second phase modulation are performed on the light, so that the phase of the light is periodically modulated in the arrangement direction with a combined modulation width wider than the first modulation width. As a result, it is possible to perform phase modulation of light with a wide modulation width.

Further, the spatial phase modulation device may be configured so that the plurality of regions of the periodic region portion have different shapes from each other and have optical path lengths corresponding to the respective shapes. In such a configuration, the phase can be periodically changed in the arrangement direction with the second modulation width corresponding to the difference in the shape of each of the plurality of regions of the periodic region portion (second phase modulation). As a result, it becomes possible to perform phase modulation of light with a wide modulation width.

Further, the spatial phase modulation device may be configured so that the plurality of regions of the periodic region portion have different refractive indexes from each other and have optical path lengths corresponding to the respective refractive indexes. In such a configuration, the phase can be periodically changed in the arrangement direction with a second modulation width corresponding to the difference in the refractive index of each of the plurality of regions of the periodic region portion (second phase modulation). As a result, it becomes possible to perform phase modulation of light with a wide modulation width.

Further, the spatial phase modulation device may be configured so that the combined modulation width is less than 2π. This makes it possible to perform phase modulation with an appropriate modulation width.

Further, the spatial phase modulation device may be configured so that the period of the phase changed by the first phase modulation is an integral multiple of two or more of the period of the phase changed by the second phase modulation. In such a configuration, it is possible to perform phase modulation on light by adding the first modulation width by the first phase modulation and the second modulation width by the second phase modulation. Therefore, it is possible to perform phase modulation of light with a wide modulation width.

Further, the space phase modulation element and the space phase modulation member face each other, and the light passing through the space phase modulation member is reflected by the space phase modulation member and then passes through the space phase modulation member again to pass through the space phase modulation member again. Performs the first phase modulation on the light reflected by the space phase modulation element, and the space phase modulation member performs the second phase modulation on the light passing through the space phase modulation member and synthesizes the light. The spatial phase modulation device may be configured such that the modulation width is the sum of the first modulation width and the value obtained by multiplying the second modulation width by 2. In such a configuration, the spatial phase modulation member performs two second phase modulations on the light. Therefore, phase modulation is performed on the light with a combined modulation width corresponding to the sum of the first modulation width and the value obtained by multiplying the second modulation width by 2. As a result, it is possible to perform phase modulation of light with a wide modulation width.

Various specific configurations of the spatial phase modulation element can be assumed. For example, the spatial phase modulation element may be a grating light bulb, a planar light bulb, an Elkos or a digital mirror device.

The optical scanning device according to the present invention includes a light source that emits light, a spatial phase modulation device that can change the position where light is incident on an object by performing phase modulation on the light, and a spatial phase modulation device that is reflected by the object. The space phase modulation device includes a space phase modulation element and a space phase modulation member, and the space phase modulation element includes a plurality of lattice elements arranged in a predetermined arrangement direction. By driving the grid element according to the input signal, the first phase modulation that periodically changes the phase in the array direction with the first modulation width corresponding to the input signal is applied to the light incident on the grid element. The spatial phase modulation member has a periodic region portion in which a plurality of regions having different optical path lengths are periodically arranged in the arrangement direction, and the spatial phase modulation member has a periodic region portion according to the difference in the optical path length of each of the plurality of regions of the periodic region portion. 2 The second phase modulation that periodically changes the phase in the arrangement direction with the modulation width is executed on the light incident on the periodic region portion, and the first phase modulation and the second phase modulation are executed on the light. Therefore, the phase of light is periodically changed in the arrangement direction with a combined modulation width wider than the first modulation width. Therefore, it is possible to perform phase modulation of light with a wide modulation width, and by extension, it is possible to secure diffracted light while suppressing zero-order light and irradiate the object with light.

Further, the object recognition device of the present invention includes the above-mentioned optical scanning device and a control unit that calculates the positional relationship with the object based on the detection results by a plurality of photodetectors included in the optical scanning device. Therefore, the object can be appropriately recognized by irradiating the object with sufficiently secured diffracted light.

As described above, according to the present invention, it is possible to perform phase modulation of light with a wide modulation width.

The figure which shows an example of the spatial phase modulation device which concerns on this invention schematically. The perspective view which shows an example of the space phase modulation plate schematically. The plan view which shows the structure of the grating light bulb schematically. The side view which shows the structure of the grating light valve schematically. The side view which shows the operation of the space phase modulation device schematically. The side view which shows the operation of the space phase modulation device schematically. The figure which shows the phase modulation by the spatial phase modulation device shown in FIG. 4B schematically. The block diagram which shows the object recognition apparatus which concerns on this invention. The figure which shows the operation of a grating light bulb schematically. The perspective view which shows the structure of the transmission unit schematically. A ray diagram schematically showing the optical operation of the transmission unit in the orthogonal direction orthogonal to the scanning direction. A ray diagram schematically showing the optical operation of the transmission unit in the scanning direction. The figure which shows typically the structure and operation of the spatial phase modulation device which concerns on a modification. The figure which shows typically the phase modulation by the spatial phase modulation device which concerns on the modification of FIG. The perspective view which shows the deformation example of the space phase modulation plate schematically. The figure which shows the modification of the arrangement of a space phase modulation plate and a space phase modulation element. The perspective view which shows each component of the spatial phase modulation device which used the planar light valve as a spatial phase modulation element schematically. The perspective view which shows each component of the spatial phase modulation device which used the planar light valve as a spatial phase modulation element schematically. The perspective view which shows each component of the spatial phase modulation device which used the linear plane light valve as a spatial phase modulation element schematically. The perspective view which shows each component of the spatial phase modulation device which used the linear plane light valve as a spatial phase modulation element schematically. A ray diagram schematically showing the optical operation of a modified example of a projection optical system. The block diagram which shows an example of the modification of the object recognition apparatus.

FIG. 1 is a diagram schematically showing an example of a spatial phase modulation device according to the present invention. In the present specification, the directions Gx, the direction Gy, and the direction Gz that are orthogonal to each other are appropriately shown. The spatial phase modulation device 3 includes a spatial phase modulation plate 31 and a spatial phase modulation element 35 facing each other at intervals I in the direction Gz. The light beam L, which is the target of phase modulation, passes through the spatial phase modulation plate 31, is reflected by the spatial phase modulation element 35, and passes through the spatial phase modulation plate 31 again. As described above, when the optical beam L is incident on the spatial phase modulation plate 31, it reciprocates between the spatial phase modulation plate 31 and the spatial phase modulation element 35 and is emitted from the spatial phase modulation plate 31. The spatial phase modulation plate 31 and the spatial phase modulation element 35 can perform phase modulation on the light beam L incident on each of them. Therefore, for the optical beam L, two-degree phase modulation by the spatial phase modulation plate 31 and one-degree phase modulation by the spatial phase modulation element 35 can be performed.

FIG. 2 is a perspective view schematically showing an example of a spatial phase modulation plate. The spatial phase modulation plate 31 extends in the direction Gx, and FIG. 2 shows a part of the spatial phase modulation plate 31. The spatial phase modulation plate 31 has a flat plate portion 32 parallel to the direction Gx and the direction Gy. In a plan view from the direction Gz, the flat plate portion 32 has a rectangular shape that is long in the direction Gx and short in the direction Gy. Further, the spatial phase modulation plate 31 has a plurality of convex portions 33 arranged on the surface 321 of the flat plate portion 32 with a constant period Tp1 (in other words, an arrangement pitch) in the direction Gx. The flat plate portion 32 and the plurality of convex portions 33 are made of a material that can transmit light, such as glass or resin. These may be formed integrally or may be formed separately.

The convex portion 33 is a rectangular parallelepiped short in the direction Gx and long in the direction Gy, and projects from the surface 321 of the flat plate portion 32 in the direction Gz. The surface 331 of the convex portion 33 is a plane parallel to the direction Gx and the direction Gy. Further, the width Wk of the convex portion 33 in the direction Gx is one half of the period Tp1. Therefore, in the spatial phase modulation plate 31, N blocks Ka and Kb having different thicknesses Ha and Hb in the direction Gz are periodically arranged in the direction Gx with a period Tp1 (= N × Wk). "N" is an integer of 2 or more indicating the number of blocks Ka and Kb existing in the period Tp1, and is "2" in this example.

Block Ka and block Kb have equal widths Wk in the direction Gx. Further, in the direction Gz, the block Ka has a thickness Ha, and the block Kb has a thickness Hb thicker than the thickness Ha. The back surfaces of the blocks Ka and Kb are planes parallel to the direction Gx and the direction Gy, and are arranged flush with each other to form the back surface 322 of the flat plate portion 32. On the other hand, the positions of the surfaces 321 and 331 of the blocks Ka and Kb differ depending on the difference in the thickness Ha and Hb of the blocks Ka and Kb. That is, the surface 331 of the block Kb projects in the direction Gz from the surface 321 of the block Ka.

The light beam L to be modulated passes through the spatial phase modulation plate 31 in the direction Gz. On the other hand, in the spatial phase modulation plate 31, blocks Ka and Kb having different thicknesses are periodically arranged with a period Tp1, and the blocks Ka and Kb are phase-modulated in an amount corresponding to the respective thicknesses Ha and Hb. Is executed on the light beam L. As a result, the phase of the light beam L is modulated by the modulation width Zp corresponding to the difference between the thickness Hb and the thickness Ha, and the light beam L is diffracted.

That is, the block Ka has an optical path length corresponding to the thickness Ha, and the block Kb has an optical path length corresponding to the thickness Hb. That is, a periodic region portion having an optical path length that periodically changes in the period Tp1 in the direction Gx is composed of blocks Ka and Kb. As described above, since the plurality of blocks Ka and Kb have different optical path lengths (thickness Ha and Hb), there is a block between the light beam L passing through the block Ka and the light beam L passing through the block Kb. A phase difference is generated according to the difference in the optical path lengths of Ka and Kb. As a result, phase modulation is executed on the optical beam L with a modulation width Zp (phase difference) corresponding to the difference between the maximum optical path length and the minimum optical path length among the optical path lengths of each of the plurality of blocks Ka and Kb. ..

The spatial phase modulation element 35 is, for example, the grating light bulb shown in FIGS. 3A and 3B. Here, FIG. 3A is a plan view schematically showing the configuration of the grating light valve, and FIG. 3B is a side view schematically showing the configuration of the grating light valve.

The spatial phase modulation element 35 has a plurality of ribbons 351 arranged in the direction Gx with a period Tg. The ribbon 351 which is a "lattice element" has a rectangular shape which is short in the direction Gx and long in the direction Gy, as shown in the plan view of FIG. 3A. In the direction Gx, the width Wg of the ribbon 351 is equal to the period Tg in which the ribbon 351 is arranged, and is equal to the width Wk of the blocks Ka, Kb. The period Tg in which the ribbon 351 is arranged is 1/N of the period Tp1 in which N blocks Ka and Kb are arranged in the spatial phase modulation plate 31. That is, N ribbons 351 are arranged in one cycle Tp1, and N blocks Ka and Kb in one cycle Tp1 and N ribbons 351 have a one-to-one correspondence. Then, as shown in FIGS. 4A and 4B later, the ribbon 351 and the block Ka (or the block Kb) corresponding to each other face each other in the direction Gz.

The ribbon 351 has flexibility, and its surface functions as a reflecting surface that specularly reflects a light beam. In FIG. 3B, the non-bent ribbon 351 and the bent ribbon 351 (broken line) are shown together. In this way, the ribbon 351 is displaced in the direction Gz by bending. The spatial phase modulation element 35 bends the ribbon 351 by an electrostatic force corresponding to the input signal Sig from the outside, thereby displaces the ribbon 351 by the amount of displacement indicated by the input signal Sig. Thereby, as will be described later, the plurality of ribbons 351 can be displaced in a desired manner.

4A and 4B are side views schematically showing the operation of the spatial phase modulation device. As described with reference to FIG. 1, the light beam L incident on the spatial phase modulation plate 31 reciprocates between the spatial phase modulation plate 31 and the spatial phase modulation element 35, and then is emitted from the spatial phase modulation plate 31. To. That is, the optical beam L passes through the spatial phase modulation plate 31 from the opposite side of the spatial phase modulation element 35 toward the spatial phase modulation element 35 in the direction Gz. The light beam L that has reached the spatial phase modulation element 35 is reflected by the spatial phase modulation element 35 and heads toward the spatial phase modulation plate 31. Then, the light beam L passes through the spatial phase modulation plate 31 toward the opposite side of the spatial phase modulation element 35.

As described above, the plurality of blocks Ka and Kb and the plurality of ribbons 351 have a one-to-one correspondence. The light beam L that has passed through the block Ka is incident on the ribbon 351 corresponding to the block Ka. Further, the light beam L reflected by the ribbon 351 is incident on the block Ka corresponding to the ribbon 351. The same applies to the block Kb.

In this way, the spatial phase modulation plate 31 performs the first phase modulation on the light beam L passing toward the spatial phase modulation element 35, and further passes toward the opposite side of the spatial phase modulation element 35. A second phase modulation is performed on the light beam L. The operation of the spatial phase modulation plate 31 is common to both the states of FIGS. 4A and 4B. On the other hand, the operation of the spatial phase modulation element 35 differs between FIGS. 4A and 4B.

In FIG. 4A, the displacement amount of the plurality of ribbons 351 of the spatial phase modulation element 35 is uniformly zero. Therefore, the spatial phase modulation element 35 functions as a mirror and does not perform phase modulation. Therefore, for the light beam L incident on the spatial phase modulation device 3, only two-degree phase modulation by the spatial phase modulation plate 31 is executed.

In FIG. 4B, the displacement amount of the ribbon 351 of the spatial phase modulation element 35 changes periodically with a period Tgm in the direction Gx. The period Tgm is M times the period Tp1 of the shape change composed of the blocks Ka and Kb (periodic region portion). “M” is an integer of 1 or more indicating the ratio (Tgm / Tp1) of the period Tgm of the displacement amount of the ribbon 351 to the period Tp1 of the shape change due to the blocks Ka and Kb. In this example, "M" is "6", which corresponds to 12 times the period Tg in which the ribbon 351 is arranged.

Specifically, during the period Tgm, the distance between the ribbon 351 and the spatial phase modulation plate 31 in the direction Gz increases from one side of the direction Gx (left side in FIG. 4B) to the other side (right side in FIG. 4B). The displacement amount of the ribbon 351 is controlled in the Q stage so as to be shortened. "Q" is an integer of 2 or more indicating the number of steps that change the displacement amount of the ribbon 351 during one cycle Tgm. In this example, "Q" is "6", which corresponds to "Tgm / Tp1". However, it is not always necessary for "Q" to match (Tgm / Tp1). As a result, in the period Tgm, the displacement amount (maximum) of the ribbon 351 located at one end and the displacement amount (minimum = zero) of the ribbon 351 located at the other end differ by the modulation width Zg.

Further, a group is composed of N adjacent ribbons 351 and the displacement amounts of the N ribbons 351 belonging to the same group are the same. On the other hand, for two groups adjacent to each other, the displacement amount of the ribbon 351 of the other side group is one step higher than the displacement amount of the ribbon 351 of the one side group (= Zg / (Tgm / Tp1). )) Only small. That is, the spatial phase modulation element 35 controls the displacement amount of the plurality of ribbons 351 so that the slope in which the displacement amount of the ribbon 351 changes in equal steps appears periodically. In this way, the plurality of ribbons 351 form a blazed diffraction grating having a period of Tgm. The light beam L to be modulated is incident on the ribbon 351 and the ribbon 351 performs phase modulation on the light beam L in an amount corresponding to the displacement amount. As a result, the phase of the light beam L is modulated by the modulation width Zg, and the light beam L is diffracted (blazed diffraction).

That is, among the plurality of ribbons 351 the ribbon 351 having the largest displacement amount and the ribbon 351 having the smallest displacement amount have a difference in optical path length according to the difference in the respective displacement amounts. Therefore, between the light beam L incident on the ribbon 351 having the maximum displacement amount and the light beam L incident on the ribbon 351 having the minimum displacement amount, the difference in the optical path length between the ribbons 351 is accommodated. A phase difference occurs. As a result, the optical beam L is phase-modulated with a modulation width Zg (phase difference) corresponding to the difference (difference in optical path length) between the maximum displacement amount and the minimum displacement amount among the displacement amounts of each of the plurality of ribbons 351. Is executed.

Therefore, the spatial phase modulation element 35 performs phase modulation on the optical beam L whose phase modulation is executed by the spatial phase modulation plate 31. Further, the spatial phase modulation plate 31 performs phase modulation again on the optical beam L whose phase modulation has been executed by the spatial phase modulation element 35. Therefore, for the optical beam L, two-degree phase modulation by the spatial phase modulation plate 31 and one-degree phase modulation by the spatial phase modulation element 35 are executed.

FIG. 5 is a diagram schematically showing phase modulation by the spatial phase modulation device shown in FIG. 4B. Each graph of FIG. 5 has the amount of phase to be modulated on the vertical axis and the position in the direction Gx on the horizontal axis. The column of "spatial phase modulation element" in FIG. 5 shows phase modulation by the spatial phase modulation element 35. The amount of phase modulation by the spatial phase modulation element 35 changes in the direction Gx, reflecting the shape of the blazed diffraction grating composed of the plurality of ribbons 351. That is, the phase modulation amount changes monotonically from 0 to 5π / 6 during one cycle of Tgm. In this way, the phase of the light beam L is modulated by the modulation width Zg (= 5π / 6) with the reflection by the spatial phase modulation element 35.

The column of "spatial phase modulation plate" in FIG. 5 shows phase modulation by the spatial phase modulation plate 31. The amount of phase modulation by the spatial phase modulation element 35 reflects the periodic shape composed of the blocks Ka and Kb, and changes in two stages between zero and π in the period Tp1. In this way, the phase of the light beam L is modulated by twice the modulation width Zp (= π) with the passage of the spatial phase modulation plate 31 twice.

The column of "spatial phase modulation device" in FIG. 5 shows phase modulation by the spatial phase modulation device 3. The spatial phase modulation device 3 executes phase modulation on the optical beam L, which is a combination of phase modulation by the spatial phase modulation plate 31 and phase modulation by the spatial phase modulation element 35. As shown in the same column, the spatial phase modulation device 3 has the characteristics of adding the blazed diffraction grating E1 that modulates the phase between 0 and π and the blazed diffraction grating E2 that modulates the phase between π and 2π. Has. As a result, the spatial phase modulation device 3 modulates the optical beam L with a modulation width Zt (= Zg + 2 × Zp).

As described above, in the present embodiment, phase modulation is executed by the spatial phase modulation element 35 having a plurality of ribbons 351 (lattice elements) arranged in the direction Gx (arrangement direction). The spatial phase modulation element 35 drives the ribbon 351 according to the input signal Sig, so that the phase is periodically changed in the direction Gx with the modulation width Zg (first modulation width) corresponding to the input signal Sig. (First phase modulation) is performed on the light beam L incident on the ribbon 351. However, it has been difficult to sufficiently secure the modulation width Zg of the phase modulation by the spatial phase modulation element 35. Therefore, in the present embodiment, a spatial phase modulation plate 31 (spatial phase modulation member) is further provided in addition to the spatial phase modulation element 35. In the spatial phase modulation plate 31, a plurality of blocks Ka and Kb (regions) having different optical path lengths (thickness Ha and Hb) are periodically arranged in the direction Gx. Then, phase modulation (second phase modulation) in which the phase is periodically changed in the direction Gx with a modulation width Zp (second modulation width) corresponding to the difference in the optical path length of each block Ka and Kb is performed by the blocks Ka and Kb (second phase modulation). It is executed on the light beam L incident on the periodic region portion). In this way, the phase modulation by the spatial phase modulation element 35 and the phase modulation by the spatial phase modulation plate 31 are executed for the optical beam L, so that the light has a modulation width Zt (composite modulation width) wider than the modulation width Zg. The phase of the beam L is periodically modulated in the direction Gx. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt.

Further, the plurality of blocks Ka and Kb (regions) constituting the periodic region portion have different thicknesses Ha and Hb (shapes), and have optical path lengths corresponding to the respective thicknesses Ha and Hb. In such a configuration, the phase can be periodically changed in the direction Gx with a modulation width Zp corresponding to the difference in the thickness Ha and Hb of each of the plurality of blocks Ka and Kb (second phase modulation). As a result, it becomes possible to execute the phase modulation of the optical beam L with a wide modulation width Zt.

It should be noted that the phase modulation does not need to be executed in excess of 2π. On the other hand, the modulation width Zt (composite modulation width) by the spatial phase modulation device 3 is less than 2π. As a result, phase modulation can be performed with an appropriate modulation width Zt that is just right.

Further, the phase period Tgm changed by the phase modulation by the spatial phase modulation element 35 is an integral multiple of 2 or more of the phase period Tp1 changed by the spatial phase modulation plate 31. In such a configuration, the optical beam L can be subjected to phase modulation by adding the modulation width Zg of the phase modulation by the spatial phase modulation element 35 and the modulation width Zp of the phase modulation by the spatial phase modulation plate 31. Therefore, the phase modulation of the optical beam L can be executed with a wide modulation width Zt.

Further, the spatial phase modulation element 35 and the spatial phase modulation plate 31 face each other. Then, the light beam L that has passed through the spatial phase modulation plate 31 is reflected by the spatial phase modulation element 35 and then passes through the spatial phase modulation plate 31 again. In such a configuration, the spatial phase modulation plate 31 performs two phase modulations on the light beam L. Therefore, phase modulation is performed on the optical beam L with a modulation width Zt corresponding to the sum of the modulation width Zg and the value obtained by multiplying the modulation width Zp by 2. As a result, the light beam L can be executed with a wide modulation width Zt.

FIG. 6 is a block diagram showing an object recognition device according to the present invention. The object recognition device 1 of FIG. 6 measures the distance to the surrounding object J by scanning the surroundings, and recognizes the existence range of the object J. The object recognition device 1 includes a transmission unit 2 that transmits a measurement light beam Lm to an object J, a reception unit 6 that receives the measurement light beam Lm reflected by the object J, and a transmission unit 2 and a reception unit 6. A control unit 9 for controlling the above is provided.

The transmission unit 2 comprises a wavelength sweep light source 21 that emits a light beam whose wavelength changes continuously, and a spatial phase modulation device 3 that performs phase modulation on the measured light beam Lm emitted from the wavelength sweep light source 21. Have. The measurement light beam Lm whose phase modulation is executed by the spatial phase modulation device 3 is transmitted to the object J.

The receiving unit 6 has a photodetector array 61 composed of a plurality of photodetectors arranged in a row, and the measurement light beam Lm reflected by the object J is detected by the photodetector array 61. More specifically, the receiving unit 6 superimposes the reference light beam Lr received from the transmitting unit 2 and the measurement light beam Lm reflected by the object J to generate a composite wave, and the photodetector array 61 generates the composite wave. Is detected. This combined wave includes a beat generated by the interference between the measurement light beam Lm and the reference light beam Lr.

The control unit 9 is a processor such as a CPU (Central Processing Unit) or an FPGA (Field).
Programmable Gate Array) etc. The control unit 9 controls the emission of the measured light beam Lm and the reference light beam Lr from the wavelength sweep light source 21. Further, the control unit 9 applies an input signal Sig to the spatial phase modulation element 35 of the spatial phase modulation device 3 to control the phase modulation by the spatial phase modulation element 35. Further, the control unit 9 calculates the distance to the object J based on the beat included in the combined wave of the measured light beam Lm and the reference light beam Lr detected by the photodetector array 61.

FIG. 7 is a diagram schematically showing the operation of the grating light bulb. In the mode M1, the displacement amounts of the plurality of ribbons 351 are equally zero, and the spatial phase modulation element 35 functions as a mirror. In the modes M2 and M3, the displacement amount of the ribbon 351 changes periodically in the direction Gx, and the spatial phase modulation element 35 functions as a blazed diffraction grating. That is, the spatial phase modulation element 35 reflects the measured light beam Lm at an angle corresponding to the period of the displacement amount of the ribbon 351. The displacement period of the ribbon 351 is different between the mode M2 and the mode M3, and the angle at which the measured light beam Lm light is reflected by the spatial phase modulation element 35 is different. Therefore, the spatial phase modulation element 35 can scan the measurement light beam Lm in the scanning direction by changing the period in which the plurality of ribbons 351 are displaced.

In particular, the spatial phase modulation device 3 includes a spatial phase modulation element 35 and a spatial phase modulation plate 31. Therefore, phase modulation is executed for the measured light beam Lm with a relatively wide modulation width Zt in which the modulation width Zg of the phase modulation by the spatial phase modulation element 35 and the modulation width Zp of the phase modulation by the spatial phase modulation plate 31 are combined. can. As a result, it is possible to suppress the amount of zero-order diffracted light generated and secure the amount of light of the measured light beam Lm scanned in the scanning direction.

FIG. 8 is a perspective view schematically showing the configuration of the transmission unit, FIG. 9A is a ray diagram schematically showing the optical operation of the transmission unit in the orthogonal direction orthogonal to the scanning direction, and FIG. 9B is a ray diagram schematically showing the optical operation of the transmission unit in the scanning direction. It is a ray diagram which shows the optical operation of a transmission unit schematically. In FIG. 9A, the configuration of the receiving unit is also shown.

First, the operation of the orthogonal direction Dr will be described. The wavelength sweep light source 21 emits a wavelength sweep light beam Lo whose wavelength continuously changes in response to a command from the control unit 9. From the viewpoint from the scanning direction Ds shown in FIG. 9A (in other words, in the orthogonal direction Dr), the wavelength sweep light beam Lo emitted from the wavelength sweep light source 21 is collimated by the cylindrical lens C. The wavelength sweep light beam Lo collimated in this way is split into a reference light beam Lr and a measurement light beam Lm by the beam splitter S1. As a result, a reference light beam Lr whose wavelength continuously changes is generated as in the case of the measurement light beam Lm. This reference light beam Lr is transmitted from the transmitting unit 2 to the receiving unit 6 and is used for generating a beat described later.

On the other hand, the measurement light beam Lm is imaged on the spatial phase modulation element 35 of the spatial phase modulation device 3 by the lens Fa1 from the viewpoint from the scanning direction Ds shown in FIG. 9A. In this example, the scanning direction Ds corresponds to the direction Gx and the orthogonal direction Dr corresponds to the direction Gy (FIGS. 3A, 3B, 9A, 9B). Therefore, the measurement light beam Lm is focused in the direction Gy and imaged in the center of each ribbon 351. As described above, the spatial phase modulation device 3 includes a spatial phase modulation plate 31. Therefore, the measured light beam Lm incident on the spatial phase modulation device 3 passes through the spatial phase modulation plate 31 and then is imaged on the spatial phase modulation element 35. Then, the measurement light beam Lm reflected by the spatial phase modulation element 35 passes through the spatial phase modulation plate 31 again and is emitted from the spatial phase modulation device 3.

Incidentally, as shown in FIG. 8, a polarizing beam splitter S2 and a quarter wave plate P are arranged between the lens Fa1 and the spatial phase modulation device 3. Therefore, the measurement light beam Lm emitted from the lens Fa1 is reflected by the polarization beam splitter S2 and bent at a right angle toward the spatial phase modulation device 3. The measured light beam Lm reflected by the polarizing beam splitter S2 is rotated by 1/4 wavelength as it passes through the 1/4 wave plate P, and then is incident on the space phase modulation element 35 of the space phase modulation device 3.

The measured light beam Lm incident on the spatial phase modulation element 35 is reflected by the spatial phase modulation element 35 toward the 1/4 wave plate P and the polarizing beam splitter S2. Therefore, the measurement light beam Lm is further rotated by a quarter wavelength as it passes through the 1/4 wave plate P, and then is incident on the polarizing beam splitter S2. Since the measurement light beam Lm is rotated by 1/2 wavelength by passing through the 1/4 wave plate P twice, the measurement light beam Lm incident on the polarization beam splitter S2 passes through the polarization beam splitter S2. The beam is directed to the projection optical system Fa23 composed of the lenses Fa2 and Fa3. In FIGS. 9A and 9B, for the sake of brevity, the folding of the light rays of the reflection type spatial phase modulation element 35 is not shown.

From the viewpoint from the scanning direction Ds shown in FIG. 9A, the measured light beam Lm reflected by the spatial phase modulation element 35 is collimated by the lens Fa2 and then imaged by the lens Fa3. The imaging point on which the measured light beam Lm is imaged by the lens Fa3 is located between the lens Fa3 and the object J. Therefore, the measurement light beam Lm is incident on the object J while spreading in the orthogonal direction Dr. In this way, the projection optical system Fa23 forms the measurement light beam Lm spreading in the orthogonal direction Dr and irradiates the object J with the object J.

Next, the operation of the scanning direction Ds will be described. The cylindrical lens C has no power in the scanning direction Ds, and the wavelength sweep light beam Lo emitted from the wavelength sweep light source 21 from the viewpoint from the orthogonal direction Dr shown in FIG. 9B (in other words, in the scanning direction Ds). Travels without being refracted by the cylindrical lens C and is incident on the lens Fa1 as a measurement light beam Lm.

From the viewpoint from the orthogonal direction Dr, the measured light beam Lm incident on the lens Fa1 is collimated by the lens Fa1 and then incident on the spatial phase modulation element 35 of the spatial phase modulation device 3. That is, the measurement light beam Lm is incident on the spatial phase modulation element 35 in a state of being collimated in the scanning direction Ds and imaged in the orthogonal direction Dr as described above. Therefore, the measurement light beam Lm extending parallel to the direction Gx is formed in the center of the direction Gy of the spatial phase modulation element 35.

On the other hand, the spatial phase modulation element 35 displaces the plurality of ribbons 351 in a manner corresponding to a command from the control unit 9, and performs phase modulation on the measurement light beam Lm. Therefore, the measured light beam Lm incident on the spatial phase modulation element 35 is reflected by the spatial phase modulation element 35 at an angle corresponding to the displacement mode of the plurality of ribbons 351. In FIG. 9B, the measurement light beam Lm reflected to four different angles by the spatial phase modulation element 35 is also shown. Since the spatial phase modulation device 3 includes the spatial phase modulation plate 31, the amount of zero-order diffracted light generated can be suppressed and the amount of light of the measured light beam Lm scanned in the scanning direction can be secured, as described above. be. In this way, the measurement light beam Lm reflected by the spatial phase modulation element 35 is incident on the lens Fa2.

Incidentally, as described above, a polarizing beam splitter S2 and a quarter wave plate P are arranged between the lens Fa1 and the spatial phase modulation device 3. Therefore, the measurement light beam Lm is incident on the spatial phase modulation element 35 from the polarization beam splitter S2 via the 1/4 wave plate P. Further, the measurement light beam Lm is incident on the polarization beam splitter S2 from the spatial phase modulation element 35 via the 1/4 wave plate P. The details of the functions of the polarization beam splitter S2 and the quarter wave plate P are as described above.

From the viewpoint from the orthogonal direction Dr shown in FIG. 9B, the measured light beam Lm reflected by the spatial phase modulation element 35 is imaged by the lens Fa2 and then collimated by the lens Fa3. As shown in FIG. 9B, the projection optical system Fa23 composed of the lenses Fa2 and Fa3 narrows the width of the measurement light beam Lm emitted from the spatial phase modulation device 3. Further, as described above, the projection optical system Fa23 spreads the measurement light beam Lm in the orthogonal direction Dr. That is, the projection optical system Fa23 forms the measurement light beam Lm in a straight line that is wide in the orthogonal direction Dr and narrow in the scanning direction Ds, and irradiates the object J.

In such a configuration, when the angle at which the spatial phase modulation element 35 reflects the measurement light beam Lm is changed, the measurement light beam Lm extending linearly in the orthogonal direction Dr is scanned in the scanning direction Ds with respect to the object J. As shown in FIG. 9B, the projection optical system Fa23 widens the reflection angle of the light beam Lm measured by the spatial phase modulation element 35. As a result, a wide scanning range of the measurement light beam Lm is secured.

The above is the details of the transmission unit 2. Subsequently, the receiving unit 6 will be described. The measurement light beam Lm reflected by the object J does not return to the transmission unit 2 but is incident on the reception unit 6 provided separately from the transmission unit 2. The receiving unit 6 includes a photodetector array 61, a photosynthetic element array 63, a microlens array 65, and a camera lens 67. The measurement light beam Lm reflected by the object J is guided to the microlens array 65 by the camera lens 67. Then, the measurement light beam Lm transmitted through the microlens array 65 is incident on the photodetector array 61 via the photosynthetic element array 63.

The photodetector array 61 has a plurality of photodetectors 611 arranged in a row in the array direction A. On the other hand, the photosynthetic element array 63 has a plurality of photosynthetic elements 631 arranged in a row in the array direction A corresponding to the plurality of photodetectors 611, and the microlens array 65 corresponds to the plurality of photodetectors 611. It has a plurality of microlenses 651 arranged in a row in the array direction A. Needless to say, the number of photodetector arrays 61 is not limited to the number shown in FIG. 9A.

The array direction A corresponds to the orthogonal direction Dr, and the linear measurement light beam Lm reflected by the object J irradiates a plurality of microlenses 651 along the array direction A. Then, the measurement light beam Lm transmitted through the plurality of microlenses 651 reaches the plurality of photodetectors 611 via the plurality of photosynthetic elements 631.

More specifically, the microlens 651 forms an image of the incident measurement light beam Lm toward the corresponding photodetector array 61. Further, a reference light beam Lr divided from the wavelength sweep light beam Lo by the beam splitter S1 is transmitted to each photosynthesis element 631, and the photosynthesis element 631 is formed with measurement light formed toward the corresponding photodetector 611. The beam Lm and the reference light beam Lr are superposed and ejected toward the photodetector 611. In this way, the photodetector 611 detects the combined wave of the measurement light beam Lm and the reference light beam Lr. This combined wave includes a beat generated by the interference between the measurement light beam Lm and the reference light beam Lr, and the control unit 9 calculates the distance to the object J based on this beat.

Incidentally, as described above, the wavelength sweep that continuously changes the wavelength is executed for the measurement light beam Lm and the reference light beam Lr. This wavelength sweep is an operation of continuously changing the wavelength from a long wavelength to a short wavelength or continuously changing the wavelength from a short wavelength to a long wavelength. While the wavelength sweep is being performed, the spatial phase modulation element 35 makes the plurality of ribbons 351 stationary in a displacement mode according to the angle (scanning angle) at which the measured light beam Lm is reflected. Then, the change of the scanning angle is executed by changing the displacement mode of the plurality of ribbons 351 while the wavelength sweep is completed and the next wavelength sweep is started.

In this way, the optical scanning device (transmitting unit 2 and receiving unit 6) changes the input signal Sig to the spatial phase modulation element 35 of the spatial phase modulation device 3, and the measurement light beam is measured by the phase modulation by the spatial phase modulation element 35. Change the angle at which Lm is diffracted. As a result, the measurement light beam Lm is scanned by the object J. Further, the spatial phase modulation device 3 includes a spatial phase modulation plate 31. Therefore, as described above, it is possible to suppress the amount of zero-order diffracted light generated and secure the amount of light of the measured light beam Lm scanned in the scanning direction Ds. Further, in the object recognition device 1, it is possible to scan the object J with the measurement light beam Lm sufficiently secured in this way to appropriately recognize the object J.

In the embodiment described above, the object recognition device 1 corresponds to an example of the "object recognition device" of the present invention, and the transmission unit 2 and the reception unit 6 cooperate with each other to form the "optical scanning device" of the present invention. As an example, the wavelength sweep light source 21 corresponds to an example of the "light source" of the present invention, the spatial phase modulation device 3 corresponds to an example of the "spatial phase modulation device" of the present invention, and the spatial phase modulation plate 31 corresponds to the present invention. The spatial phase modulation element 35 corresponds to an example of the "spatial phase modulation element" of the present invention, and the ribbon 351 corresponds to an example of the "lattice element" of the present invention. The receiving unit 6 corresponds to an example of the "light receiving unit" of the present invention, the photodetector 611 corresponds to an example of the "photodetector" of the present invention, and the control unit 9 corresponds to an example of the "control unit" of the present invention. Direction Gx corresponds to an example of the "arrangement direction" of the present invention, object J corresponds to an example of the "object" of the present invention, and blocks Ka and Kb correspond to an example of the "periodic region portion" of the present invention. Each of the blocks Ka and Kb corresponds to an example of the "region" of the present invention, the input signal Sig corresponds to an example of the "input signal" of the present invention, and the modulation width Zg corresponds to the "first modulation width" of the present invention. The modulation width Zp corresponds to an example of the "second modulation width" of the present invention, and the modulation width Zt corresponds to an example of the "synthetic modulation width" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications can be made other than those described above as long as the present invention is not deviated from the gist thereof. For example, the configuration of the spatial phase modulation plate 31 may be modified. That is, in the spatial phase modulation plate 31, the number of "N", which is the number of blocks Ka and Kb having different thicknesses in the period Tp1, is two. However, the spatial phase modulation device 3 may be modified so that it has three or more blocks in the period Tp1, for example, as shown below.

FIG. 10 is a diagram schematically showing the configuration and operation of the spatial phase modulation device according to the modified example. In the spatial phase modulation plate 31 of the spatial phase modulation device 3, three blocks Ka, Kb, and Kc having different thicknesses in the direction Gz are periodically arranged in the direction Gx with a period Tp1 (= 3 × Wk). These blocks Ka, blocks Kb and blocks Kc have equal widths Wk in the direction Gx. In this way, a periodic region portion having an optical path length that periodically changes in the period Tp1 in the direction Gx is composed of blocks Ka, Kb, and Kc.

The light beam L to be modulated passes through the spatial phase modulation plate 31 in the direction Gz. On the other hand, in the spatial phase modulation plate 31, blocks Ka, Kb, and Kc having different thicknesses are periodically arranged with a period Tp1, and the blocks Ka, Kb, and Kc are phased in an amount corresponding to each thickness. Modulation is performed on the optical beam L. As a result, the phase of the light beam L is modulated by the modulation width Zp corresponding to the difference between the maximum thickness of the block Ka and the minimum thickness of the block Kc, and the light beam L is diffracted. That is, as described above with reference to FIG. 2, the modulation width Zp (phase difference) according to the difference between the maximum optical path length and the minimum optical path length among the optical path lengths of each of the plurality of blocks Ka, Kb, and Kc. ), Phase modulation is executed on the optical beam L.

Further, the displacement amount of the ribbon 351 of the spatial phase modulation element 35 changes periodically with a period Tgm in the direction Gx. The period Tgm is M times the period Tp1 of the shape change composed of the blocks Ka, Kb, and Kc (periodic region portion) (M = 4 in this example). Specifically, during the period Tgm, the distance between the ribbon 351 and the spatial phase modulation plate 31 in the direction Gz increases from one side (left side in FIG. 10) to the other side (right side in FIG. 10) of the direction Gx. The displacement amount of the ribbon 351 is controlled in the Q stage so as to be shortened (Q = 4 in this example). As a result, in the period Tgm, the displacement amount (maximum) of the ribbon 351 located at one end and the displacement amount (minimum = zero) of the ribbon 351 located at the other end differ by the modulation width Zg. The spatial phase modulation element 35 in which the ribbon 351 is displaced in this way functions as a blazed diffraction grating. That is, in the same manner as described above with reference to FIG. 4B, the modulation width Zg (difference in optical path length) according to the difference between the maximum displacement amount and the minimum displacement amount among the displacement amounts of each of the plurality of ribbons 351 (difference in optical path length). (Phase difference), phase modulation is performed on the light beam L.

FIG. 11 is a diagram schematically showing phase modulation by the spatial phase modulation device according to the modification of FIG. 10. Each graph of FIG. 10 has the amount of phase to be modulated on the vertical axis and the position in the direction Gx on the horizontal axis. The column of "spatial phase modulation element" in FIG. 11 shows phase modulation by the spatial phase modulation element 35. The amount of phase modulation by the spatial phase modulation element 35 changes stepwise in the direction Gx, reflecting the shape of the blazed diffraction grating composed of the plurality of ribbons 351. That is, the phase modulation amount changes monotonically in four steps from 0 to π / 2 during one cycle of Tgm. In this way, the phase of the light beam L is modulated by the modulation width Zg (= π / 2) with the reflection by the spatial phase modulation element 35.

The column of "spatial phase modulation plate" in FIG. 11 shows the phase modulation by the spatial phase modulation plate 31. The amount of phase modulation by the spatial phase modulation element 35 changes in three stages between zero and 4π / 3 at period Tp1 reflecting the periodic shape composed of blocks Ka, Kb, and Kc. In this way, the phase of the light beam L is modulated by twice the modulation width Zp (= 4π / 3) with the passage of the spatial phase modulation plate 31 twice.

The column of "spatial phase modulation device" in FIG. 11 shows phase modulation by the spatial phase modulation device 3. The spatial phase modulation device 3 executes phase modulation on the optical beam L, which is a combination of phase modulation by the spatial phase modulation plate 31 and phase modulation by the spatial phase modulation element 35. As shown in the same column, the spatial phase modulation device 3 has a characteristic of adding blazed diffraction gratings E1, E2, and E3 that modulate the phase in different ranges. As a result, the spatial phase modulation device 3 modulates the optical beam L with a modulation width Zt (= Zg + 2 × Zp).

Also in such a modification, a spatial phase modulation plate 31 is further provided in addition to the spatial phase modulation element 35. In this spatial phase modulation plate 31, a periodic region portion having an optical path length that periodically changes in the direction Gx is composed of blocks Ka, Kb, and Kc, and the phase is oriented in the direction Gx with a modulation width Zp corresponding to the change in the optical path length. Phase modulation is performed on the light beam L incident on the blocks Ka, Kb, and Kc. In this way, the phase modulation by the spatial phase modulation element 35 and the phase modulation by the spatial phase modulation plate 31 are executed for the optical beam L, so that the phase of the optical beam L has a modulation width Zt wider than the modulation width Zg. It is periodically modulated in the direction Gx. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt.

Further, it is possible to change the dimensional relationship of the spatial phase modulation device 3. For example, by designing the distance I between the spatial phase modulation plate 31 and the spatial phase modulation element 35 as follows, the light beam L reflected by the ribbon 351 is placed on the block Ka (Kb, Kc) facing the ribbon 351. It may be configured to be efficiently incident.

That is, the diffraction angle θ by the spatial phase modulation element 35 is the following equation Λ · sin θ = m · Λ ... Equation 1
Given in. Here, Λ is the blaze period, λ is the wavelength of the light beam L, and m is the order of diffraction. The ± 1st order diffraction angle is generated at m = 1. Therefore, the interval I is the following equation I = ΔΛ ・ Λ / Λ ... Equation 2
By designing to satisfy the above conditions, the light beam L reflected by the ribbon 351 can be efficiently incident on the block Ka (Kb, Kc). Here, ΔΛ is the amount of deviation of the ribbon 351 from the block Ka (Kb, Kc) in the direction Gx, and the interval I is the amount of displacement I to the ribbon 351 having zero displacement and the direction Gz to the spatial phase modulation plate 31. The distance. In obtaining Equation 2 from Equation 1, it was approximated as tan θ = sin θ = θ. According to Equation 2, for example, if λ = 905 nm, Λ = 102 μm, and a gap of ΔΛ = 5.1 μm corresponding to 5% is allowed, the interval I (air gap) becomes 575 μm.

Further, in the above embodiment, the difference in the optical path lengths of the blocks Ka, Kb and the like is provided depending on the shapes (thickness Ha, Hb) of the blocks Ka and Kb. However, as shown in FIG. 12, the optical path length may be different depending on the difference in the refractive index of each of the blocks Ka and Kb.

FIG. 12 is a perspective view schematically showing a modified example of the spatial phase modulation plate. Here, the description will be centered on the differences from the above example, the common parts will be designated by corresponding reference numerals, and the description will be omitted as appropriate. The spatial phase modulation plate 31 shown in FIG. 12 is a flat plate having a rectangular shape that is long in the direction Gx and short in the direction Gy. In the spatial phase modulation plate 31, a plurality of blocks Ka and Kb having the same thickness H are arranged in the direction Gx. Block Ka and block Kb have equal widths Wk in the direction Gx. The refractive index na of the block Ka and the refractive index nb of the block Kb are different from each other. For example, the refractive index nb of the block Kb is larger than the refractive index na of the block Ka.

The light beam L to be modulated passes through the spatial phase modulation plate 31 in the direction Gz. On the other hand, in the spatial phase modulation plate 31, blocks Ka and Kb having different refractive indexes na and nb are periodically arranged with a period Tp1, and the blocks Ka and Kb correspond to the respective refractive indexes na and nb. Phase modulation is performed on the optical beam L in a large amount. As a result, the phase of the light beam L is modulated by the modulation width Zp corresponding to the difference between the refractive indexes na and nb of the blocks Ka and Kb, respectively, and the light beam L is diffracted.

That is, the block Ka has an optical path length corresponding to the product of the thickness H and the refractive index na (H × na), and the block Kb has an optical path length corresponding to the product of the thickness H and the refractive index nb (H × nb). Has. As described above, the plurality of blocks Ka and Kb have different optical path lengths (H × na, H × nb). As a result, a phase difference is generated between the light beam L that has passed through the block Ka and the light beam L that has passed through the block Kb, depending on the difference in the optical path lengths of the blocks Ka and Kb. As a result, phase modulation is executed on the optical beam L with a modulation width Zp (phase difference) corresponding to the difference between the maximum optical path length and the minimum optical path length among the optical path lengths of each of the plurality of blocks Ka and Kb. ..

In this modification, in the spatial phase modulation plate 31, a plurality of blocks Ka and Kb (regions) having different optical path lengths (H × na, H × nb) are periodically arranged in the direction Gx. Then, phase modulation (second phase) in which the phase is periodically changed in the direction Gx by the modulation width Zp (second modulation width) according to the difference in the optical path lengths (H × na, H × nb) of each block Ka and Kb. Modulation) is performed on the light beam L incident on the blocks Ka and Kb (periodic region portion). In this way, the phase modulation by the spatial phase modulation element 35 and the phase modulation by the spatial phase modulation plate 31 are executed for the optical beam L, so that the light has a modulation width Zt (composite modulation width) wider than the modulation width Zg. The phase of the beam L is periodically modulated in the direction Gx. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt.

Further, in this modification, the plurality of blocks Ka and Kb constituting the periodic region portion have different refractive indexes na and nb, and have optical path lengths corresponding to the respective refractive indexes na and nb. In such a configuration, the phase can be periodically changed in the direction Gx with a modulation width (second modulation width) corresponding to the difference in the refractive index na and nb of each of the plurality of blocks Ka and Kb (second phase modulation). ). As a result, it becomes possible to execute the phase modulation of the optical beam L with a wide modulation width Zt.

In this modification, a spatial phase modulation plate 31 having two blocks Ka and Kb having different refractive indexes from each other is shown. However, even when the spatial phase modulation plate 31 is configured to have three or more blocks (blocks Ka, Kb, Kc, etc.), the difference in optical path length can be similarly provided by the difference in the refractive index. Further, the thicknesses H of the blocks Ka, Kb, etc. do not necessarily have to be equal to each other, and may be different from each other.

Alternatively, as shown in FIG. 13, the arrangement relationship between the spatial phase modulation plate 31 and the spatial phase modulation element 35 may be changed so that the optical beam L passes through the spatial phase modulation plate 31 only once. good. FIG. 13 is a diagram showing a modified example of the arrangement of the spatial phase modulation plate and the spatial phase modulation element. In the example of the figure, the measured light beam Lm that has passed through the lens Fa1 passes through the spatial phase modulation plate 31 and then is incident on the spatial phase modulation element 35. Then, the measured light beam Lm reflected by the spatial phase modulation element 35 heads for the lens Fa2 without returning to the spatial phase modulation plate 31.

That is, for the optical beam L, phase modulation by the spatial phase modulation plate 31 and phase modulation by the spatial phase modulation element 35 are executed once. Therefore, the phase of the light beam L is periodically modulated in the direction Gx with a modulation width Zt wider than the modulation width Zg. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt. The order of incidence of the light beam L is not limited to the example of FIG. 13, and contrary to the example of FIG. 13, the light beam L is incident on the spatial phase modulation element 35 and then on the spatial phase modulation plate 31. It may be configured.

Further, the specific configuration of the spatial phase modulation element 35 is not limited to the above-mentioned grading light bulb. For example, a planar light bulb, an Elkos or a digital mirror device can be used as the spatial phase modulation element 35. 14A and 14B are perspective views schematically showing each component of a spatial phase modulation device using a planar light valve as a spatial phase modulation element, FIG. 14A shows a spatial phase modulation element, and FIG. 14B is a spatial phase modulation element. Shows the plate. Here, a case where the spatial phase modulation element 35 configured by the planar light bulb is used in the object recognition device 1 will be described as an example.

In the spatial phase modulation element 35 of FIG. 14A, a plurality of reflection elements 353 are arranged in a matrix in the direction Gx and the direction Gy. Needless to say, the number of reflecting elements 353 is not limited to the example of FIG. 14A. The surface of each reflecting element 353 functions as a reflecting surface that specularly reflects the light beam L. Each reflective element 353 includes a fixed member 354 and a movable member 355.

The fixing member 354 is a planar substantially rectangular member fixed to the substrate, and is provided with a substantially circular opening in the center. The movable member 355 is a substantially circular member provided in the opening of the fixing member 354. A fixed reflection surface is provided on the upper surface of the fixing member 354 (that is, the upper surface in the direction Gz in FIG. 14A). A movable reflective surface is provided on the upper surface of the movable member 355. The movable member 355 can move in the direction Gz.

In the reflecting element 353, the relative position between the fixed member 354 and the movable member 355 is displaced by the amount of displacement indicated by the signal Sig from the control unit 9. The control unit 9 can individually displace the movable member 355 of each reflection element 353, in other words, the plurality of movable members 355 of the spatial phase modulation element 35 can be displaced independently.

In the spatial phase modulation element 35, a plurality of reflecting element rows Rp are formed by a plurality of reflecting element trains 353 arranged in a row in the direction Gx, and the plurality of reflecting element trains Rp are arranged in the direction Gy. Then, similarly to the operation of the ribbon 351 described with reference to FIG. 7, the movable members 355 of the plurality of reflecting elements 353 arranged in one row in the direction Gx in the reflecting element row Rp are periodically displaced according to the mode and blazed diffraction. Make up the grating.

Further, as shown in FIG. 14B, in the spatial phase modulation plate 31, a plurality of blocks K are arranged in a matrix in the direction Gx and the direction Gy. Needless to say, the number of blocks K is not limited to the example of FIG. 14B. The plurality of blocks K have a one-to-one correspondence with the plurality of reflective elements 353. Then, similarly to the above, when the spatial phase modulation plate 31 and the spatial phase modulation element 35 face the direction Gz with an interval I, the corresponding block K and the reflection element 353 face each other in the direction Gz.

Then, the light beam L that has passed through the block K is incident on the reflecting element 353 corresponding to the block K. Further, the light beam L reflected by the reflecting element 353 passes through the block K again. In this way, one-degree phase modulation by the spatial phase modulation plate 31 and two-degree phase modulation by the spatial phase modulation plate 31 are executed on the optical beam L.

This point will be described corresponding to the column configuration of the spatial phase modulation element 35 described above. In the space phase modulation plate 31, the block sequence Rk is composed of a plurality of blocks K arranged in a row in the direction Gx, and the plurality of block rows Rk are arranged in the direction Gy. The plurality of block rows Rk of the spatial phase modulation plate 31 correspond one-to-one with the plurality of reflection element rows Rp of the spatial phase modulation element 35. Therefore, the light beam L that has passed through the block row Rk is incident on the reflecting element row Rp corresponding to the block row Rk. Then, the light beam L that has been blazed and diffracted by the reflecting element row Rp passes through the block row Rk again.

A projection optical system is provided for the spatial phase modulation device 3 provided with the spatial phase modulation element 35 and the spatial phase modulation plate 31. This projection optical system forms a rectangular light beam L (colimated light) having a size corresponding to a matrix of a plurality of blocks K possessed by the spatial phase modulation plate 31, and projects the light beam L (colimated light) onto the plurality of blocks K. Then, as described above, the light beam L passes through the block K, is reflected by the reflecting element 353, and passes through the block K again.

Also in such a modification, a spatial phase modulation plate 31 is further provided in addition to the spatial phase modulation element 35. In this spatial phase modulation plate 31, a periodic region portion having an optical path length that periodically changes in the direction Gx is formed by a block K, and the phase is periodically changed in the direction Gx with a modulation width Zp corresponding to the change in the optical path length. The changing phase modulation is performed on the light beam L incident on the block K. In this way, the phase modulation by the spatial phase modulation element 35 and the phase modulation by the spatial phase modulation plate 31 are executed for the optical beam L, so that the phase of the optical beam L has a modulation width Zt wider than the modulation width Zg. It is periodically modulated in the direction Gx. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt. As described above with reference to FIG. 12, the change in the optical path length of each block K of the spatial phase modulation plate 31 may be provided depending on the refractive index of the block K regardless of the thickness of the block K.

15A and 15B are perspective views schematically showing each component of a space phase modulation device using a linear plane light valve as a space phase modulation element, FIG. 15A shows a space phase modulation element, and FIG. 15B shows a space phase. The modulation plate is shown. Here, a case where the spatial phase modulation element 35 configured by the linear plane light bulb is used in the object recognition device 1 will be described as an example. In addition, the differences from the above-described embodiment will be mainly described, and the common parts are designated by corresponding reference numerals and the description thereof will be omitted as appropriate.

In the spatial phase modulation element 35 of FIG. 15A, a plurality of reflection elements 353 are arranged in a matrix in the direction Gx and the direction Gy. However, in the spatial phase modulation element 35 configured by the linear plane light valve, the displacement amount of the movable members 355 of the reflection elements 353 arranged in a row in the direction Gy is the same. That is, in the spatial phase modulation element 35, the reflecting element row Up is composed of a plurality of reflecting element rows 353 arranged in a row in the direction Gy, and the plurality of reflecting element rows Up are arranged in the direction Gx. Then, the displacement amount of the movable member 355 of the reflecting element 353 is controlled in the unit of the reflecting element row Up. By such control, for example, similarly to the operation of the ribbon 351 described with reference to FIG. 7, the movable members 355 of the plurality of reflecting elements 353 arranged in a row in the direction Gx are periodically displaced according to the mode to form the blazed diffraction grating. Configure. At this time, since the displacement amounts of the movable members 355 adjacent to each other in the direction Gy are the same, the spatial phase modulation element 35 constitutes one blazed diffraction grating as a whole.

Further, as shown in FIG. 15B, in the spatial phase modulation plate 31, a plurality of blocks K having a rectangular parallelepiped shape extending in each direction Gy are arranged in the direction Gx. The plurality of blocks K have a one-to-one correspondence with the plurality of reflecting element rows Up. Then, similarly to the above, when the spatial phase modulation plate 31 and the spatial phase modulation element 35 face each other in the direction Gz with an interval I, the corresponding blocks K and the reflecting element train Up face each other in the direction Gz. In other words, the block K faces each reflecting element 353 belonging to the corresponding reflecting element row Up from the direction Gz.

Then, the light beam L that has passed through the block K is incident on the reflecting element 353 corresponding to the block K. Further, the light beam L reflected by the reflecting element 353 passes through the block K again. In this way, one-degree phase modulation by the spatial phase modulation plate 31 and two-degree phase modulation by the spatial phase modulation plate 31 are executed on the optical beam L.

Further, a projection optical system is provided as described above, and the projection optical system forms a rectangular light beam L having a size corresponding to the entire plurality of blocks K included in the spatial phase modulation plate 31. It is projected onto these plurality of blocks K. Further, an imaging optical system is provided for the spatial phase modulation device 3. This imaging optical system condenses the light beam L emitted from the reflecting element train Up at one place in the direction Gy, thereby forming the light beam L on a line extending in the direction Gx. As a result, it is possible to secure a large amount of light of the light beam L emitted from the spatial phase modulation device 3.

Also in such a modification, a spatial phase modulation plate 31 is further provided in addition to the spatial phase modulation element 35. In this spatial phase modulation plate 31, a periodic region portion having an optical path length that periodically changes in the direction Gx is formed by a block K, and the phase is periodically changed in the direction Gx with a modulation width Zp corresponding to the change in the optical path length. The changing phase modulation is performed on the light beam L incident on the block K. In this way, the phase modulation by the spatial phase modulation element 35 and the phase modulation by the spatial phase modulation plate 31 are executed for the optical beam L, so that the phase of the optical beam L has a modulation width Zt wider than the modulation width Zg. It is periodically modulated in the direction Gx. As a result, it is possible to perform phase modulation of the optical beam L with a wide modulation width Zt. As described above with reference to FIG. 12, the change in the optical path length of each block K of the spatial phase modulation plate 31 may be provided depending on the refractive index of the block K regardless of the thickness of the block K.

It is also possible to make changes different from these modifications. For example, in each of the above-described embodiments, the modulation width Zt (composite modulation width) by the spatial phase modulation device 3 is less than 2π. However, the spatial phase modulation device 3 may be configured so as to have a modulation width Zt (composite modulation width) of 2π or more.

Further, in each of the above-described embodiments, the spatial phase modulation plate 31 is a transmission type that performs phase modulation on the light beam L passing through the spatial phase modulation plate 31. However, the spatial phase modulation plate 31 may be a reflection type that performs phase modulation on the light beam L reflected by the spatial phase modulation plate 31.

Further, the projection optical system Fa23 has widened the scanning angle of the measurement light beam Lm by forming an image of the measurement light beam Lm in front of the object J. However, the projection optical system may be configured as shown in FIG. Here, FIG. 16 is a ray diagram schematically showing the optical operation of a modified example of the projection optical system. In the figure, the measurement light beams Lm projected on four different scanning angles are also shown. The projection optical system Fb14 is composed of four lenses Fb1 to Fb4 that widen the angle of the measurement light beam Lm.

Further, the polarization beam splitter S2 and the 1/4 wave plate P are not essential configurations. Therefore, the transmission unit 2 may be configured without providing the polarization beam splitter S2 and the 1/4 wave plate P.

Further, the method of generating the reference light beam Lr is not limited to the above example. For example, the reference light beam Lr may be generated by a beam splitter that splits the reference light beam Lr from the measurement light beam Lm from the viewpoint from the orthogonal direction Dr shown in FIG. 9B.

Further, the configuration of the object recognition device 1 may be modified as shown in FIG. FIG. 17 is a block diagram showing an example of a modification of the object recognition device. The object recognition device 1 of FIG. 17 differs from the above in that the light source 22 included in the transmission unit 2 emits a light beam L having a constant wavelength without sweeping the wavelength.

The spatial phase modulation device 3 irradiates the light beam L to the target position on the object J by performing phase modulation on the light beam L emitted from the light source 22 (beam steering). On the other hand, the photodetector 62 included in the receiving unit 6 detects the light reflected at the target position on the object J. Then, the control unit 9 performs measurement by the so-called ToF (time of flight) method. That is, the control unit 9 calculates the distance to the target position on the object J based on the time (detection result) from the emission of the light beam L from the light source 22 to the detection by the photodetector 62. In the object recognition device 1, the positional relationship between the object recognition device 1 and the object J can be obtained by calculating the distance to the target position while changing the target position by the spatial phase modulation device 3. ..

The present invention is applicable to all phase modulation techniques for performing phase modulation on light.

1 ... Object recognition device 2 ... Transmission unit (optical scanning device)
21 ... Wavelength sweep light source (light source)
3 ... Spatial phase modulation device 31 ... Spatial phase modulation plate (spatial phase modulation member)
35 ... Spatial phase modulation element 351 ... Ribbon (lattice element)
6 ... Receiver unit (light receiving unit, optical scanning device)
611 ... Photodetector 9 ... Control unit Gx ... Direction (arrangement direction)
J ... Objects Ka, Kb. Kc ... Block (periodic area, area)
Lm ... Measurement light beam (measurement light)
Lr ... Reference light beam (reference light)
Sig ... Input signal Zg ... Modulation width (first modulation width)
Zp ... Adjusting width (second modulation width)
Zt ... Modulation width (composite modulation width)

Claims (10)

It has a plurality of lattice elements arranged in a predetermined arrangement direction, and by driving the lattice elements in response to an input signal, the phase is periodically set in the arrangement direction with a first modulation width corresponding to the input signal. A spatial phase modulation element that performs the first phase modulation to be changed on the light incident on the lattice element, and
A plurality of regions having different optical path lengths have a periodic region portion that is periodically arranged in the arrangement direction, and the phase is set by a second modulation width according to the difference in the optical path length of each of the plurality of regions of the periodic region portion. A spatial phase modulation member that performs a second phase modulation periodically changing in the arrangement direction on the light incident on the periodic region portion is provided.
By performing the first phase modulation and the second phase modulation on the light, the phase of the light changes periodically in the arrangement direction with a combined modulation width wider than the first modulation width. Spatial phase modulation device to be. The spatial phase modulation device according to claim 1, wherein the plurality of regions of the periodic region portion have different shapes from each other and have optical path lengths corresponding to the respective shapes. The spatial phase modulation device according to claim 1, wherein the plurality of regions of the periodic region portion have different refractive indexes from each other and have optical path lengths corresponding to the respective refractive indexes. The spatial phase modulation device according to any one of claims 1 to 3, wherein the combined modulation width is less than 2π. The spatial phase modulation device according to any one of claims 1 to 4, wherein the period of the phase changed by the first phase modulation is an integral multiple of two or more of the period of the phase changed by the second phase modulation. The spatial phase modulation element and the spatial phase modulation member face each other and
The light that has passed through the spatial phase modulation member is reflected by the spatial phase modulation member, and then passes through the spatial phase modulation member again.
The spatial phase modulation element performs the first phase modulation on the light reflected by the spatial phase modulation element.
The spatial phase modulation member performs the second phase modulation on the light passing through the spatial phase modulation member.
The spatial phase modulation device according to any one of claims 1 to 5, wherein the combined modulation width is the sum of the first modulation width and a value obtained by multiplying the second modulation width by 2. The spatial phase modulation device according to any one of claims 1 to 6, wherein the spatial phase modulation element is a grating light valve, a planar light valve, an Elkos, or a digital mirror device. A light source that emits light and
A spatial phase modulation device capable of changing the position where the light is incident on an object by performing phase modulation on the light.
A light receiving unit for detecting the light reflected by the object by a photodetector is provided.
The spatial phase modulation device includes a spatial phase modulation element and a spatial phase modulation member.
The spatial phase modulation element has a plurality of lattice elements arranged in a predetermined arrangement direction, and by driving the lattice elements in response to an input signal, the phase is adjusted with a first modulation width corresponding to the input signal. The first phase modulation that periodically changes in the arrangement direction is performed on the light incident on the lattice element, and the light is subjected to the first phase modulation.
The spatial phase modulation member has a periodic region portion in which a plurality of regions having different optical path lengths are periodically arranged in the arrangement direction, and corresponds to a difference in the optical path length of each of the plurality of regions of the periodic region portion. A second phase modulation that periodically changes the phase in the arrangement direction with the second modulation width is performed on the light incident on the periodic region portion.
By performing the first phase modulation and the second phase modulation on the light, the phase of the light changes periodically in the arrangement direction with a combined modulation width wider than the first modulation width. Optical scanning device. The optical scanning apparatus according to claim 8,
An object recognition device including a control unit that calculates a positional relationship with an object based on detection results by a plurality of photodetectors included in the optical scanning device. By driving the grid element of the spatial phase modulation element having a plurality of grid elements arranged in a predetermined arrangement direction according to the input signal, the phase is shifted in the arrangement direction with the first modulation width corresponding to the input signal. A step of performing a first phase modulation that is periodically changed on the light incident on the lattice element, and
The second modulation width according to the difference in the optical path length of each of the plurality of regions of the periodic region portion of the spatial phase modulation member having the periodic region portion in which the plurality of regions having different optical path lengths are periodically arranged in the arrangement direction. The present invention comprises a step of performing a second phase modulation that periodically changes the phase in the arrangement direction on the light incident on the periodic region portion.
By performing the first phase modulation and the second phase modulation on the light, the phase of the light is periodically modulated in the arrangement direction with a combined modulation width wider than the first modulation width. Spatial phase modulation method.

Images