Optical devices and optical apparatus

Abstract

To provide an optical device in which an arrangement pattern of parallel light in a plane vertical to an optical axis can be quickly and freely switched.SOLUTION: An optical device 1 comprises: an electro-optic crystalline body 10; a plurality of electric field formation portions 20; a first lens array 30; a light shielding member 40; and a second lens array 50. The electro-optic crystalline body 10 receives first parallel light L1 upon a principal plane 11, and outputs the first parallel light L1 from a rear surface 12. The plurality of electric field formation portions 20 is one-dimensionally or two-dimensionally arranged side by side. The plurality of electric field formation portions 20 form within the electro-optic crystalline body 10, electric fields in which intensities periodically varies, and can independently control the states of the electric fields respectively. The first lens array 30 condenses the first parallel light Li output from the electro-optic crystalline body 10 by each of a plurality of first lenses 31. The light shielding member 40 transmits or shields condensed light L2 in each of a plurality of areas 41 in accordance with a state of the electric field of the electric field formation portion 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical device and an optical apparatus.

Background Art

[0002] Patent Documents 1 to 7 disclose optical modulators. Those optical modulators have an electro-optic crystal and a plurality of electrodes that individually form an electric field inside the electro-optic crystal. The electro-optic crystal is, for example, a perovskite-type electro-optic crystal having a relative permittivity of 1000 or more. The electro-optic crystal is, for example, a KTN crystal, a KLTN crystal, or a PLZT crystal.

Prior Art Documents

Patent Documents

[0003] '

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0004] Optical devices using crystals that can rapidly and freely switch the arrangement pattern of parallel light in a plane perpendicular to the optical axis are useful. One example is a combination of such an optical device and a spatial light modulator. That is, a spatial light modulator is used when spatially modulating the phase of light. In addition to spatial light modulators equipped with electro-optic crystals as described in Patent Documents 1 to 7, there are also spatial light modulators equipped with a liquid crystal layer (liquid crystal type spatial light modulator). In a liquid crystal type spatial light modulator, an electric field is individually formed inside the liquid crystal layer by each of the multiple electrodes. However, in a liquid crystal type spatial light modulator, the response of the liquid crystal to the time change of the electric field inside the liquid crystal layer is delayed, which has the problem that the speed of switching the modulation pattern is impaired. Therefore, for example, by dividing the modulation region of a liquid crystal type spatial light modulator into multiple regions and sequentially inputting parallel light into each of the multiple regions using the optical device described above, it is possible to speed up the switching of the modulation pattern at the expense of resolution.

[0005] The present disclosure aims to provide an optical device that can quickly and freely switch the arrangement pattern of parallel light in a plane perpendicular to the optical axis, and an optical apparatus that can speed up the switching of modulation patterns. [Means for solving the problem]

[0006] [1] The optical device according to the present disclosure comprises a plate-shaped electro-optic crystal, a plurality of field forming sections, a first lens array, a light shielding member, and a second lens array. The electro-optic crystal has a main surface and a back surface, receives first parallel light on the main surface and outputs first parallel light from the back surface. The plurality of field forming sections are arranged in a one-dimensional or two-dimensional manner in a plane along the main surface or back surface of the electro-optic crystal. The plurality of field forming sections form an electric field within the electro-optic crystal whose strength changes periodically in a direction along the main surface or back surface of the electro-optic crystal, and the state of the electric field can be controlled independently for each section. The first lens array has a plurality of first lenses corresponding to the plurality of field forming sections, and focuses the first parallel light output from the back surface of the electro-optic crystal at each of the plurality of first lenses. The light shielding member has a plurality of regions corresponding to the plurality of field forming sections, and is configured to allow or shield the light focused by each of the plurality of first lenses in each of the plurality of regions, depending on the state of the electric field of the corresponding field forming section. The second lens array has multiple regions and multiple second lenses corresponding to each region, and converts the light that has passed through the light shielding member into second parallel light in each of the multiple second lenses.

[0007] In the optical device described in [1] above, when an electric field is formed inside the electro-optic crystal by a certain electric field forming part, a periodic change in refractive index instantaneously occurs in the region inside the electro-optic crystal corresponding to that electric field forming part. When a first parallel light passes through an electro-optic crystal in which a periodic change in refractive index is occurring, the phase distribution of the first parallel light changes. Therefore, when the first parallel light is focused by the first lens, the light is focused at multiple separate focal points. In contrast, when no electric field is formed inside the electro-optic crystal by each of the multiple electric field forming parts, no periodic change in refractive index occurs inside the electro-optic crystal. Even when the first parallel light passes through such an electro-optic crystal, there is no change in the phase distribution of the first parallel light. Therefore, when the first parallel light is focused by the first lens, the light is focused at a single focal point.

[0008] Each region of the light shielding member allows or blocks light focused by the corresponding first lens, depending on the state of the electric field in the corresponding electric field forming section. In one example, each region of the light shielding member blocks light when it is focused at multiple separated focal points, and allows light to pass through when it is focused at a single focal point. In another example, each region of the light shielding member allows light to pass through when it is focused at multiple separated focal points, and blocks light when it is focused at a single focal point. Therefore, it is possible to freely determine whether each portion of the first parallel light, corresponding to multiple electric field forming sections, passes through the light shielding member. The light that passes through the light shielding member from the light focused by the first lens array is converted into second parallel light by the corresponding second lens and output to the outside of the optical device. By switching the electric field forming sections that form the electric field, the arrangement pattern of parallel light in a plane perpendicular to the optical axis can be switched quickly and freely.

[0009] [2] In the optical device described in [1] above, each of the multiple field forming sections may have a first transparent electrode provided on the main surface and a second transparent electrode provided on the back surface. One or both of the first transparent electrode and the second transparent electrode may include a structure that is periodic in the above direction. In that case, a configuration in which a first parallel light passes through the electro-optic crystal while a periodic electric field is formed within the electro-optic crystal can be easily realized.

[0010] [3] In the optical device described in [2] above, one or both of the first transparent electrode and the second transparent electrode may be comb-shaped. In this case, the number of connection points between the first transparent electrode and / or the second transparent electrode, which include a periodic structure, and the wiring for applying voltage to the transparent electrode can be reduced, thus simplifying the structure for applying voltage to the transparent electrode.

[0011] [4] In any one of the optical devices described in [1] to [3] above, each of the multiple regions may be configured to allow light focused by each of the multiple first lenses to pass through when the electric field of the corresponding electric field forming unit is off, and to shield it when the electric field of the corresponding electric field forming unit is on. When the electric field of the electric field forming unit is on, a periodic refractive index distribution is generated within the electro-optic crystal, and the phase distribution of the first parallel light changes. When the first parallel light passes through the light shielding member, its phase distribution remains in the second parallel light, and the optical elements placed downstream of the optical device are affected by this phase distribution. In contrast, when the electric field of the electric field forming unit is off, the refractive index distribution within the electro-optic crystal does not change, and the phase distribution of the first parallel light does not change. Therefore, by allowing light focused by the first lens to pass through when the electric field of the electric field forming unit is off, the influence on the optical elements placed downstream of the optical device can be reduced.

[0012] [5] In any one of the optical devices described in [1] to [4] above, each of the multiple first lenses is a cylindrical lens that primarily has refractive power in the direction in which the strength of the electric field changes periodically, and each of the multiple regions may include a slit extending along the direction in which the cylindrical lens extends. In this case, it is sufficient to align the focusing position of the cylindrical lens with the slit only in the direction in which the cylindrical lens primarily has refractive power. Thus, the manufacturing of the optical device can be simplified.

[0013] [6] Any one of the optical devices described in [1] to [5] above may further include a wiring board on which an electro-optic crystal is mounted. The wiring board may have multiple terminals that are electrically connected to each of the multiple field forming units and that supply a driving voltage to each of the multiple field forming units. In this case, the driving voltage can be easily supplied to the multiple field forming units through the wiring board.

[0014] [7] In any one of the optical devices described in [1] to [6] above, the electro-optic crystal may include a KTN crystal.

[0015] [8] The optical device according to the present disclosure may include any one of the above [1] to [7] optical devices and a liquid crystal type spatial light modulator that receives the second parallel light output from the second lens array of the optical device and modulates the phase of the second parallel light for each pixel. The spatial light modulator may have a plurality of modulation regions respectively corresponding to a plurality of electric field forming portions of the optical device. According to this optical device, it is possible to increase the switching speed of the modulation pattern while sacrificing the resolution.

[0016] [9] The optical device of the above [8] may further include a control unit that controls the state of the electric fields of the plurality of electric field forming portions and the modulation pattern of the spatial light modulator. The control unit may control the plurality of electric field forming portions so that the second parallel light sequentially enters the plurality of modulation regions, and may update the modulation pattern after the second parallel light has finished entering the plurality of modulation regions.

Effect of the Invention

[0017] According to the present disclosure, it is possible to provide an optical device capable of quickly and freely switching the arrangement pattern of parallel light in a plane perpendicular to the optical axis, and an optical device capable of increasing the switching speed of the modulation pattern.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an optical device according to the first embodiment of the present disclosure. [Figure 2] FIGS. 2(a) and (b) are perspective views showing an enlarged electro-optic crystal and a plurality of electric field forming portions. [Figure 3] FIG. 3(a) is a schematic diagram showing the state in the electro-optic crystal when no electric field is formed. FIG. 3(b) is a schematic diagram showing the state in the electro-optic crystal when an electric field is formed. [Figure 4] FIGS. 4(a), (b), and (c) are schematic diagrams showing examples of switching of the second parallel light. [Figure 5] FIG. 5 is a perspective view showing an example of a method of supplying voltage to the first transparent electrode and the second transparent electrode. [Figure 6] FIG. 6 is a perspective view showing another example of a method for supplying voltages to the first transparent electrode and the second transparent electrode. [Figure 7] FIG. 7 is a diagram schematically showing the configuration of an optical device according to a second embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram schematically showing the configuration of an optical device according to a third embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram showing the optical modulation surface of the SLM. [Figure 10] FIG. 10 is a flowchart showing the operation of the optical device. [Figure 11] FIG. 11 is a timing chart showing an example of the operation of the optical device. [Figure 12] FIG. 12 is a diagram schematically showing the configuration of an optical device according to a fourth embodiment of the present disclosure. [Figure 13] FIG. 13 is a schematic diagram showing the states in an electro-optic crystal when (a) no electric field is formed and (b) an electric field is formed, in a form in which both the first transparent electrode and the second transparent electrode include a periodic structure. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of an optical device and an optical apparatus according to the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are assigned to the same elements, and redundant descriptions are omitted. (First Embodiment)

[0020] FIG. 1 is a cross-sectional view showing the configuration of an optical device 1 according to a first embodiment of the present disclosure. As shown in FIG. 1, the optical device 1 of the present embodiment includes a plate-shaped electro-optic crystal 10, a plurality of electric field forming portions 20, a first lens array 30, a light shielding member 40, and a second lens array 50.

[0021] The electro-optic crystal 10 includes, for example, at least one crystal from among KTN crystal, potassium niobate, lithium niobate, potassium tantalate, lithium tantalate, potassium dihydrogen phosphate, dipotassium phosphate, and barium titanate. The KTN crystal is a mixed crystal of potassium niobate and potassium tantalate and exhibits the optical Kerr effect as an electro-optic effect. In one example, the electro-optic crystal 10 consists of a KTN crystal. The electro-optic crystal 10 has a main surface 11 and a back surface 12. In one example, the main surface 11 and the back surface 12 are parallel to each other. The thickness direction of the electro-optic crystal 10 coincides with the normal direction of the main surface 11 and the back surface 12. The electro-optic crystal 10 receives a first parallel light L1 on the main surface 11, which has an optical axis along the normal direction of the main surface 11. The first parallel light L1 is, for example, laser light output from a laser diode, SLD (Super Luminescent Diode), or solid-state laser. The wavelength of the first parallel light L1 is, for example, between 300 nm and 3000 nm. This first parallel light L1 is transmitted through the electro-optic crystal 10 in the thickness direction of the electro-optic crystal 10. The electro-optic crystal 10 outputs the transmitted first parallel light L1 from its back surface 12. To maximize the transmittance of the first parallel light L1, the main surface 11 and the back surface 12 are polished.

[0022] Multiple electric field forming units 20 are arranged in a one-dimensional or two-dimensional manner within the plane along the main surface 11 and / or back surface 12. Figure 1 shows an example where three electric field forming units 20 are arranged in a row, but the number of electric field forming units 20 and the number of rows are not limited to this. Multiple electric field forming units 20 form an electric field within the electro-optic crystal 10 whose strength changes periodically in the direction D1 along the main surface 11 and / or back surface 12 of the electro-optic crystal 10. The state of each of the multiple electric field forming units 20 is configured to be independently controllable.

[0023] Figures 2(a) and 2(b) are enlarged perspective views of the electro-optic crystal 10 and the multiple field-forming sections 20. Figure 2(a) is a perspective view of the electro-optic crystal 10 seen from the main surface 11 side, and Figure 2(b) is a perspective view of the electro-optic crystal 10 seen from the back surface 12 side. As shown in Figure 2(a), multiple (three in the illustrated example) first transparent electrodes 21 are provided on the main surface 11 of the electro-optic crystal 10. In the figure, the region where the first transparent electrodes 21 are located is indicated by halftone dots. As shown in Figure 2(b), a second transparent electrode 22 is provided on the entire back surface 12 of the electro-optic crystal 10. In the figure, the region where the second transparent electrode 22 is located is indicated by halftone dots. The constituent materials of the first transparent electrode 21 and the second transparent electrode 22 are, for example, tin-doped indium oxide such as tin oxide, or fluorine-doped tin oxide. The first transparent electrode 21 and the second transparent electrode 22 are formed on the surface of the electro-optic crystal 10, for example, by vacuum deposition.

[0024] Each of the multiple first transparent electrodes 21 includes a structure that is periodic in direction D1. A periodic structure is, for example, a structure in which regions where the first transparent electrode 21 is present and regions where the first transparent electrode 21 is absent are arranged periodically and alternately. In one example, the first transparent electrode 21 is comb-shaped with multiple comb teeth arranged in direction D1.

[0025] Each of the multiple electric field forming sections 20 is composed of a first transparent electrode 21 and a region of the second transparent electrode 22 facing the first transparent electrode 21. The electro-optic crystal 10 has a second-order electro-optic effect called the photo-Kerr effect, and when a voltage is applied between a first transparent electrode 21 and a second transparent electrode 22, an electric field is formed in the portion of the electro-optic crystal 10 between them, corresponding to the magnitude of the voltage. Figure 3(a) is a schematic diagram showing the state inside the electro-optic crystal 10 when no electric field is formed. Figure 3(b) is a schematic diagram showing the state inside the electro-optic crystal 10 when an electric field is formed. As shown in Figure 3(a), when no electric field is formed between the first transparent electrode 21 and the second transparent electrode 22, the refractive index distribution inside the electro-optic crystal 10 is uniform in direction D1. In contrast, as shown in Figure 3(b), when an electric field is formed between the first transparent electrode 21 and the second transparent electrode 22, the refractive index of region A1 where the electric field is formed changes instantaneously relative to other regions within the electro-optic crystal 10. As a result, in the region inside the electro-optic crystal 10 corresponding to the electric field forming portion 20, the refractive index changes periodically and instantaneously along direction D1, and the refractive index distribution forms a binary diffraction grating.

[0026] Refer again to Figure 1. The first lens array 30 is a microlens array positioned opposite the back surface 12 of the electro-optic crystal 10. The optical axis of the first lens array 30 is parallel to the optical axis of the first parallel light L1. The first lens array 30 has a plurality of (three in the illustrated example) first lenses 31. Each of the plurality of first lenses 31 corresponds to a plurality of electric field forming sections 20. The first lens array 30 focuses the first parallel light L1 output from the back surface 12 of the electro-optic crystal 10 at each of the plurality of first lenses 31. Each of the plurality of first lenses 31 is, for example, a convex lens. Each of the plurality of first lenses 31 may be a cylindrical lens having refractive power mainly in the direction of the periodic structure of the first transparent electrode 21 (direction D1 in the illustrated example).

[0027] When the first parallel light L1 passes through a region of the electro-optic crystal 10 where the refractive index undergoes a periodic change, the phase distribution of the first parallel light L1 changes. Therefore, when the first parallel light L1 is focused by the first lens 31, the light L2 after passing through the first lens 31 is focused to a plurality of focal points P1 that are separated from each other in the direction of the periodic structure of the first transparent electrode 21 (direction D1 in the illustrated example). In contrast, when the first parallel light L1 passes through a region of the electro-optic crystal 10 where the refractive index does not undergo a periodic change, there is no change in the phase distribution of the first parallel light L1. Therefore, when the first parallel light L1 is focused by the first lens 31, the light L2 after passing through the first lens 31 is focused to a single focal point P2. In the illustrated example, of the three electric field forming parts 20 arranged along direction D1, only the two electric field forming parts 20 located at both ends form an electric field, while the electric field forming part 20 located in the center does not form an electric field. Furthermore, if the first lens 31 is a cylindrical lens, the focal points P1 and P2 have a linear shape extending along the direction of extension of the cylindrical lens (in other words, a direction that intersects both the direction of the periodic structure of the first transparent electrode 21 and the direction of the optical axis of the first parallel light L1).

[0028] The light shielding member 40 is positioned opposite the back surface 12 of the electro-optic crystal 10, with the first lens array 30 in between. The light shielding member 40 is, for example, a metal mask. The light shielding member 40 has a plurality of regions 41, each corresponding to a plurality of electric field forming sections 20. Each of the regions 41 corresponds to a plurality of first lenses 31 and is optically coupled to each of the plurality of first lenses 31. The light shielding member 40 is configured to allow or shield the light L2 focused by each of the plurality of first lenses 31 in each of the plurality of regions 41, depending on the state of the electric field of the corresponding electric field forming section 20.

[0029] In the illustrated example, each region 41 of the light shielding member 40 shields the light L2 when it is focused at a plurality of separate focal points P1, in other words, when the electric field of the corresponding electric field forming unit 20 is ON, and allows the light L2 to pass through when it is focused at a single focal point P2, in other words, when the electric field of the corresponding electric field forming unit 20 is OFF. Therefore, each region 41 of the light shielding member 40 in the illustrated example has a single optical aperture 42 corresponding to a single focal point P2. When light L2 is focused at a single focal point P2, the light L2 passes through the optical aperture 42. Also, when light L2 is focused at a plurality of separate focal points P1, the light L2 is shielded by the light shielding member 40 outside the optical aperture 42. The optical aperture 42 may be an opening formed in the light shielding member 40, or it may be made of a transparent material such as glass. Alternatively, the light shielding member 40 may be configured by providing a light-shielding film on the surface of a transparent plate such as glass, excluding the optical aperture 42. If the first lens 31 is a cylindrical lens, the optical aperture 42 may be a slit extending along the extending direction of the cylindrical lens. If the wavelength of the first parallel light L1 is λ and the period of the electric field formed by the electric field forming unit 20 is X, then the width of the optical aperture 42 is, for example, (λF) / X. However, in practice, the width of the optical aperture 42 may differ from (λF) / X due to the influence of the light intensity distribution and modes of the first parallel light L1.

[0030] In another example, each region 41 of the light shielding member 40 may allow light L2 to pass through when it is focused at a plurality of separate focal points P1, and may shield the light L2 when it is focused at a single focal point P2. In this case, each region 41 of the light shielding member 40 has an optical aperture corresponding to the plurality of focal points P1. The configuration of the optical aperture in this case may be the same as that of the optical aperture 42 described above.

[0031] The second lens array 50 is a microlens array and is positioned opposite the surface of the light shielding member 40 that is opposite to the surface facing the first lens array 30. In other words, the light shielding member 40 is located between the first lens array 30 and the second lens array 50. The optical axis of the second lens array 50 is parallel to the optical axis of light L2. The second lens array 50 has a plurality of (three in the illustrated example) second lenses 51. Each of the plurality of second lenses 51 corresponds to a plurality of regions 41 of the light shielding member 40 and is optically coupled to the optical aperture 42 of each of the plurality of regions 41. The second lens array 50 converts the light L2 that has passed through the light shielding member 40 into second parallel light L3 in each of the plurality of second lenses 51. Of the light L2 focused by the first lens array 30, the light L2 that has passed through the light shielding member 40 is converted into second parallel light L3 by the corresponding second lens 51 and output to the outside of the optical device 1. Each of the multiple second lenses 51 is, for example, a convex lens. If each of the multiple first lenses 31 is a cylindrical lens, then each of the multiple second lenses 51 is also a cylindrical lens that has refractive power mainly in the direction of the periodic structure of the first transparent electrode 21 (direction D1 in the illustrated example).

[0032] The spacing between the electro-optic crystal 10, the first lens array 30, the light shielding member 40, and the second lens array 50 may be equal to or different from the focal lengths of the first lens array 30 and the second lens array 50.

[0033] According to the optical device 1 of this embodiment described above, by independently controlling whether or not each of the multiple field-forming units 20 forms an electric field within the electro-optic crystal 10, it is possible to freely determine, on a portion-by portion, whether or not multiple portions of the first parallel light L1 corresponding to each of the multiple field-forming units 20 pass through the light-shielding member 40. Furthermore, by switching the field-forming units 20 that form the electric field, the arrangement pattern of the second parallel light L3 in a plane perpendicular to the optical axis can be freely switched at high speeds, for example, on the order of kHz.

[0034] Figures 4(a), (b), and (c) are schematic diagrams illustrating examples of switching the second parallel light L3. Figure 4(a) shows the emission position of the second parallel light L3 when light L2 passes only through the outermost region 41 of the three regions 41 shown in Figure 1, and light L2 is blocked in the other two regions 41. Figure 4(b) shows the emission position of the second parallel light L3 when light L2 passes only through the central region 41 of the three regions 41 shown in Figure 1, and light L2 is blocked in the other two regions 41. Figure 4(c) shows the emission position of the second parallel light L3 when light L2 is blocked only in the central region 41 of the three regions 41 shown in Figure 1, and light L2 passes through the other two regions 41. Note that light L2 may also pass through all of the multiple regions 41. Thus, according to the optical device 1 of this embodiment, the arrangement pattern of the second parallel light L3 in a plane perpendicular to the optical axis can be freely switched.

[0035] As shown in the illustrated example, when the number of electric field forming units 20 is 3, a total of 7 arrangement patterns can be realized: 3 arrangement patterns of the second parallel light L3 that pass through only one region 41, 3 arrangement patterns of the second parallel light L3 that pass through two regions 41, and 1 arrangement pattern of the second parallel light L3 that passes through all regions 41. When the number of electric field forming units 20 is m, the number of possible arrangement patterns is expressed by the following formula (1).

number

[0036] As in this embodiment, each of the multiple electric field forming sections 20 may have a first transparent electrode 21 provided on the main surface 11 and a second transparent electrode 22 provided on the back surface 12. One or both of the first transparent electrode 21 and the second transparent electrode 22 may include a periodic structure. In that case, a configuration in which a first parallel light L1 passes through the electro-optic crystal 10 while a periodic electric field is formed within the electro-optic crystal 10 can be easily realized.

[0037] As in this embodiment, one or both of the first transparent electrode 21 and the second transparent electrode 22 may be comb-shaped. In that case, the number of connection points between the first transparent electrode 21 and / or the second transparent electrode 22, which include a periodic structure, and the wiring for applying voltage to these transparent electrodes (for example, terminal 62 shown in Figure 5) can be reduced, thus simplifying the structure for applying voltage to the transparent electrodes.

[0038] As in this embodiment, each of the multiple regions 41 of the light shielding member 40 may be configured to allow light L2 focused by each of the multiple first lenses 31 to pass through when the electric field of the corresponding electric field forming section 20 is in the off state, and to shield it when the electric field of the corresponding electric field forming section 20 is in the on state. When the electric field of the electric field forming section 20 is in the on state, a periodic refractive index distribution is generated within the electro-optic crystal 10, and the phase distribution of the first parallel light L1 changes. When the light L2 formed by focusing the first parallel light L1 passes through the light shielding member 40, its phase distribution remains in the second parallel light L3, and the optical elements placed downstream of the optical device 1 are affected by this phase distribution. In contrast, when the electric field of the electric field forming section 20 is in the off state, the refractive index distribution within the electro-optic crystal 10 does not change, and the phase distribution of the first parallel light L1 does not change. Therefore, each of the multiple regions 41 of the light shielding member 40 is configured to allow the light L2 focused by the first lens 31 to pass through when the electric field of the electric field forming unit 20 is in the off state, thereby reducing the influence on optical elements placed downstream of the optical device 1.

[0039] As mentioned above, each of the multiple first lenses 31 may be a cylindrical lens that primarily has refractive power in the direction in which the strength of the electric field changes periodically, and each of the multiple regions 41 may include a slit extending along the extending direction of the cylindrical lens. In that case, it is sufficient to align the focusing position of the cylindrical lens with the slit only in the direction in which the cylindrical lens primarily has refractive power. Thus, the manufacturing of the optical device 1 can be simplified.

[0040] In addition, an acoustic optic deflector (AOD), which is an acousto-optic element, is a device that has a similar function to the optical device 1 of this embodiment. However, with an AOD, the optical system becomes complex and high adjustment technology is required because the optical axis changes. The optical device 1 of this embodiment only needs to be positioned so that the main surface 11 of the electro-optic crystal 10 is perpendicular to the optical axis of the first parallel light L1, and since the optical axis does not change, it is useful in combination with other devices (for example, a spatial light modulator).

[0041] Here, Figure 5 is a perspective view showing an example of a method for supplying voltage to the first transparent electrode 21 and the second transparent electrode 22. As shown in Figure 5, the optical device 1 may further include a wiring board 60 on which the electro-optic crystal 10 is mounted. In the illustrated example, the wiring board 60 faces the main surface 11 of the electro-optic crystal 10. For simplification, the first lens array 30, the light shielding member 40, and the second lens array 50 are omitted from the illustration in Figure 5.

[0042] The wiring board 60 has an optical aperture 61, a plurality of terminals 62, and a terminal 63. The optical aperture 61 is formed at a position opposite the electro-optic crystal 10 and allows the first parallel light L1 to pass through. The optical aperture 61 may be an aperture formed in the wiring board 60, or it may be made of a transparent material such as glass. Alternatively, the wiring board 60 itself may be made of a transparent material such as glass. In that case, the optical aperture 61 is unnecessary. Each of the plurality of terminals 62 is electrically connected to each of the plurality of first transparent electrodes 21. In the illustrated example, each of the plurality of terminals 62 is conductively bonded to each of the plurality of first transparent electrodes 21 by conductive paste 64. A conductive adhesive such as solder may be used instead of conductive paste 64. The plurality of terminals 62 each supply a driving voltage to the plurality of first transparent electrodes 21. Terminal 63 is electrically connected to the second transparent electrode 22. In the illustrated example, terminal 63 is electrically connected to the second transparent electrode 22 via bonding wire 65. Terminal 63 is set to, for example, the reference potential (ground potential).

[0043] The wiring board 60 is connected to another wiring board 67 via a connector-equipped wiring 66A. The wiring board 67 is equipped with multiple electric field forming units 20 and multiple switching elements 68, each corresponding to a plurality of switching elements 68. The wiring board 67 is also connected to a computer's I / O connection terminal (not shown) via a connector-equipped wiring 66B. The computer inputs a signal S1 that controls the operation of the multiple switching elements 68. The wiring board 67 is also connected to a DC power supply (not shown) via a connector-equipped wiring 66C. The DC power supply provides a DC power supply voltage V1 that is applied to the multiple electric field forming units 20. Each switching element 68 is connected to a corresponding terminal 62 via a connector-equipped wiring 66A. When each switching element 68 receives a signal S1 from the computer, it supplies the DC power supply voltage V1 to its corresponding terminal 62. This DC power supply voltage V1 is applied to the first transparent electrode 21 connected to that terminal 62.

[0044] In the example shown in Figure 5, the wiring board 60 is mounted on a single electro-optic crystal 10, but as shown in Figure 6, the wiring board 60 may be mounted on multiple electro-optic crystals 10. In that case, by arranging the multiple electro-optic crystals 10 in a direction intersecting the direction of arrangement (direction D1) of the multiple field-forming portions 20 in each electro-optic crystal 10, the multiple field-forming portions 20 can be arranged in a two-dimensional manner.

[0045] As described above, the optical device 1 may further include a wiring board 60 on which the electro-optic crystal 10 is mounted. In that case, a drive voltage can be easily supplied to the multiple field forming units 20 through the wiring board 60. (Second Embodiment)

[0046] Figure 7 is a schematic diagram showing the configuration of an optical device 70A according to a second embodiment of the present disclosure. The optical device 70A of this embodiment comprises the optical device 1 of the first embodiment, a light source 71, a mirror 72, an objective lens 73, a mirror 74, a condensing lens 75, an imaging unit 76, a control unit 77, and an I / O controller 78.

[0047] Optical device 1 is optically coupled to light source 71 and receives first parallel light L1 from light source 71. Light source 71 includes, for example, a laser diode, SLD, or solid-state laser. Mirror 72 is, for example, a half-mirror or dielectric mirror and transmits the second parallel light L3 output from optical device 1. Objective lens 73 focuses the second parallel light L3 that has passed through mirror 72 toward the illumination target surface B1 of object B. Illumination target surface B1 receives the light L4 focused by objective lens 73 and generates light L5. For example, light L5 is scattered light on illumination target surface B1. Alternatively, if the second parallel light L3 and light L4 are excitation light, light L5 is fluorescence output from the excited object B. Light L5 is converted into parallel light L6 by objective lens 73. Parallel light L6 is separated from the second parallel light L3 by reflection at mirror 72. The parallel light L6 is reflected by the mirror 74 and then focused towards the imaging unit 76 by the focusing lens 75. The imaging unit 76 captures the light L7 focused by the focusing lens 75 and generates imaging data.

[0048] In the illustrated example, two second parallel beams L3 are focused and irradiated onto the target surface B1. In this case, on surfaces other than the irradiated surface B1, which is the focusing surface, interference fringes are formed by the interference of the two beams L4. These interference fringes can be used as structured illumination. Alternatively, three second parallel beams L3 that are not aligned in a line may be focused and irradiated onto the target surface B1. In that case, the three beams L4 interfere with each other, forming a grid of light spots. These grid of light spots can also be used as structured illumination.

[0049] The I / O controller 78 is electrically connected to the optical device 1 and applies a drive voltage to a plurality of electric field forming units 20 of the optical device 1. The I / O controller 78 is electrically connected to the control unit 77 and controlled by the control unit 77. The I / O controller 78 includes, for example, a wiring board 67 and a plurality of switching elements 68 as shown in Figure 5. The control unit 77 provides, for example, the signal S1 shown in Figure 5 to the I / O controller 78. The control unit 77 is a computer such as a personal computer, a smart device such as a smartphone or tablet terminal, or a cloud server. The computer as the control unit 77 has an HDD, a storage device such as flash memory or RAM, and a processor (CPU). The control unit 77 may be configured as a microcontroller or an FPGA (Field-Programmable Gate Array).

[0050] According to the optical device 70A of this embodiment, by including the optical device 1, the arrangement pattern of the second parallel light L3 in a plane perpendicular to the optical axis can be switched quickly and freely. Therefore, the shape of the irradiation area of ​​the light L4 irradiated onto the target surface B1 can be switched quickly and freely. (Third embodiment)

[0051] Figure 8 is a schematic diagram showing the configuration of an optical device 70B according to the third embodiment of this disclosure. The optical device 70B of this embodiment comprises the optical device 1 of the first embodiment, a light source 71, a mirror 72, an objective lens 73, mirrors 74a, 74b and 74c, a condensing lens 75, an imaging unit 76, a control unit 79, an SLM controller 80, and a spatial light modulator (SLM) 81.

[0052] The first parallel light L1 output from the light source 71 is a coherent laser beam with spatially aligned phase. The optical device 1 is optically coupled to the light source 71 and receives the first parallel light L1 from the light source 71. Mirrors 74a and 74b reflect the second parallel light L3 output from the optical device 1, thereby directing the second parallel light L3 to the SLM 81. The SLM 81 is a liquid crystal type SLM. The SLM 81 has multiple pixels and receives the second parallel light L3, modulating the phase of the second parallel light L3 pixel by pixel. The SLM 81 may be reflective or transmissive. Mirror 72 is, for example, a half mirror or a dielectric mirror, and transmits the modulated second parallel light L3 output from the SLM 81. The objective lens 73 focuses the second parallel light L3 that has passed through mirror 72 toward the illumination target surface B1 of the object B. The illuminated surface B1 receives light L4 focused by the objective lens 73 and generates light L5. For example, if the second parallel light L3 and light L4 are excitation light, light L5 is fluorescence emitted from the excited object B. Light L5 is converted into parallel light L6 by the objective lens 73. After being reflected by the mirror 74, the parallel light L6 is focused toward the imaging unit 76 by the focusing lens 75. The imaging unit 76 captures the light L7 focused by the focusing lens 75 and generates imaging data.

[0053] The SLM controller 80 is electrically connected to the SLM 81 and provides the SLM 81 with a signal indicating a modulation pattern. The SLM controller 80 is also electrically connected to the optical device 1 and applies a drive voltage to the multiple field-forming units 20 of the optical device 1. Furthermore, the SLM controller 80 is electrically connected to the imaging unit 76 and provides the imaging unit 76 with a trigger signal indicating the imaging timing. The SLM controller 80 is electrically connected to the control unit 79 and controlled by the control unit 79. The SLM controller 80 includes, for example, a wiring board 67 and multiple switching elements 68 as shown in Figure 5. The control unit 79 controls the state of the electric fields of the multiple field-forming units 20 and the modulation pattern of the SLM 81. The control unit 79 provides, for example, the signal S1 shown in Figure 5 to the SLM controller 80. The control unit 79 is a computer such as a personal computer, a smart device such as a smartphone or tablet terminal, or a cloud server. The computer acting as the control unit 79 includes an HDD, a storage device such as flash memory or RAM, and a processor (CPU). The control unit 79 may be configured using a microcontroller or an FPGA (Field-Programmable Gate Array).

[0054] The SLM81 has multiple modulation regions, each corresponding to one of the multiple field forming sections 20 of the optical device 1. A separate modulation pattern is presented in each modulation region. The modulation pattern may be, for example, a two-beam interference pattern necessary for structured illumination, or a multi-beam interference pattern showing a lattice pattern. In this case, multiple (e.g., 5×5 or 1×5) light points distributed in two dimensions are formed on the illuminated surface B1. The arrangement and number of light points formed may differ for each modulation region. In this way, by presenting a separate modulation pattern in each modulation region, the illumination pattern on the illuminated surface B1 changes in accordance with the switching of the arrangement pattern of the second parallel light L3.

[0055] For the sake of explanation, let's assume that the optical device 1 has 3 rows and 3 columns (a total of 9) of electric field forming units 20. Figure 9 shows the optical modulation surface of the SLM81 in this case. As shown in Figure 9, the SLM81 has the same number of modulation regions M(1) to M(9) as the electric field forming units 20. The modulation regions M(1) to M(9) are arranged in 3 rows and 3 columns, similar to the electric field forming units 20. The modulation regions M(1) to M(9) correspond one-to-one with the 9 electric field forming units 20. Second parallel light L3, which has passed through the corresponding electric field forming unit 20 and is output from the optical device 1, is incident on each of the 9 modulation regions M(1) to M(9) and modulated. The control unit 79 controls the voltage applied to the 9 electric field forming units 20 so that the second parallel light L3 is sequentially incident on the modulation regions M(1) to M(9) and modulated. Then, after the second parallel light L3 has finished incident on the modulation regions M(1) to M(9), the control unit 79 updates the modulation pattern of the SLM 81 via the SLM controller 80. Subsequently, the control unit 79 controls the voltage applied to the nine electric field forming units 20 again, so that the second parallel light L3 is sequentially incident on the modulation regions M(1) to M(9) and modulated. The optical device 70B repeats this operation.

[0056] Figure 10 is a flowchart illustrating the operation of the optical device 70B. As shown in Figure 10, first, the control unit 79 sets the modulation pattern of the SLM 81 through the SLM controller 80 (step ST1). This modulation pattern includes individual modulation patterns for each of the multiple modulation regions M(1) to M(9). Next, the control unit 79 controls the nine field forming units 20 through the SLM controller 80 to inject the second parallel light L3 into the modulation region M(1) (step ST2). Then, the control unit 79 provides a trigger signal to the imaging unit 76 through the SLM controller 80 indicating the imaging timing (step ST3). After that, the process returns to step ST2, injecting the second parallel light L3 into the modulation region M(2), and performing step ST3 again. In this way, the second parallel light L3 is sequentially injected into all modulation regions M(1) to M(9), and step ST3 is performed each time. After the second parallel light L3 has been incident on all modulation regions M(1) to M(9) (step ST4: YES), the process returns to step ST1 and the modulation pattern of the SLM81 is updated. This modulation pattern includes the individual modulation patterns for each of the multiple modulation regions M(1) to M(9). Then, steps ST2 to ST4 are repeated again. After all the pre-prepared modulation patterns have been presented (step ST5: YES), the optical device 70B terminates its operation.

[0057] The effects obtained by the optical device 70B of this embodiment are as follows. In a liquid crystal type SLM81, an electric field is individually formed inside the liquid crystal layer by each of the multiple electrodes. However, there is a problem that the speed of switching modulation patterns is impaired because the response of the liquid crystal is delayed to the time change of the electric field inside the liquid crystal layer. In this embodiment, the optical modulation surface of the SLM81 is divided into multiple modulation regions M(1) to M(9), and the optical device 1 is used to sequentially input the second parallel light L3 into each of the multiple modulation regions M(1) to M(9). This makes it possible to speed up the switching of modulation patterns at the expense of resolution. As a result, the optical device 70B can be applied to observation of high-speed phenomena or to optical tweezers or atomic trapping techniques that require a high frame rate, by controlling holographic light at a high rate.

[0058] In the above explanation, the modulation pattern of the SLM81 is updated after the second parallel light L3 has been injected into all modulation regions M(1) to M(9). However, the modulation pattern of the SLM81 may be divided into two or more regions (for example, three regions), and the modulation pattern may be updated for each region. Figure 11 is a timing chart showing an example of such operation. In Figure 11, line G1 represents the period during which the second parallel light L3 is injected into modulation regions M(1) to M(9). In the section where line G1 is high level, the second parallel light L3 is injected into one of the modulation regions, and the number i near line G1 represents the number of the modulation region M(i) into which the second parallel light L3 is injected. Line G2 represents the period during which the modulation patterns of modulation regions M(1) to M(3) are presented. In the section T1 where line G2 is high level, the modulation patterns of modulation regions M(1) to M(3) are presented. Line G3 represents the period during which the modulation pattern of modulation region M(4) to M(6) is presented. In section T2, where line G3 is at a high level, the modulation pattern of modulation region M(4) to M(6) is presented. Line G4 represents the period during which the modulation pattern of modulation region M(7) to M(9) is presented. In section T3, where line G4 is at a high level, the modulation pattern of modulation region M(7) to M(9) is presented.

[0059] Furthermore, because the response of the liquid crystal layer is delayed, for example, when presenting the modulation pattern of modulation regions M(1) to M(3) in section T1, the application of voltage to the electrodes of modulation regions M(1) to M(3) begins at timing t1, which is before section T1. Then, after ending the application of voltage to the electrodes at the end of section T1, the presentation of the modulation pattern completely ends at timing t2, which is after section T1. The same applies when presenting the modulation pattern of modulation regions M(4) to M(6) in section T2, and when presenting the modulation pattern of modulation regions M(7) to M(9) in section T3.

[0060] In this way, by dividing the modulation pattern of the SLM81 into two or more regions and updating the modulation pattern for each region, it becomes possible to repeatedly inject the second parallel light L3 into the modulation regions M(1) to M(9) without being affected by the response time of the liquid crystal layer, as shown in the timing chart of Figure 11. Therefore, the switching of the modulation pattern can be made even faster. (Fourth Embodiment)

[0061] Figure 12 is a schematic diagram showing the configuration of the optical device 70C according to the fourth embodiment of this disclosure. The optical device 70C of this embodiment further includes an SLM controller 82 and an SLM 83 in addition to the configuration of the optical device 70B of the third embodiment. Furthermore, the imaging unit 76 of this embodiment has a rolling shutter method that sequentially detects light from multiple light incident regions aligned in one direction.

[0062] The SLM controller 82 is electrically connected to the SLM 83 and provides the SLM 83 with a signal indicating a modulation pattern. The SLM controller 82 is electrically connected to the control unit 79 and controlled by the control unit 79. The control unit 79 controls the modulation pattern presented to the SLM 83 through the SLM controller 82. The modulation pattern presented to the SLM 83 causes the focused images of light L7 by the focusing lens 75 to form at multiple positions. The focused images of light L7 at each position are identical to each other. Since the imaging unit 76 has a rolling shutter system, the imaging unit 76 sequentially captures the focused images of light L7 formed at each position with equal time differences. This allows the focused images of light L7 to be captured at a rate faster than the imaging unit 76's original frame rate.

[0063] The optical devices and optical apparatuses described herein are not limited to the embodiments described above, and various other modifications are possible. For example, in the first embodiment described above, the first transparent electrode 21 has a structure that is periodic in direction D1, and the second transparent electrode 22 is formed over the entire surface of the back surface 12. The present invention is not limited to this form, and may also include a structure in which the first transparent electrode 21 is formed over the entire surface of the main surface 11, and the second transparent electrode 22 is periodic in direction D1. In that case, the second transparent electrode 22 may be comb-shaped.

[0064] Alternatively, the structure may include both the first transparent electrode 21 and the second transparent electrode 22 being periodic in direction D1. In that case, both the first transparent electrode 21 and the second transparent electrode 22 may be comb-shaped. Figure 13 is a schematic diagram showing the state inside the electro-optic crystal 10 in such a configuration when (a) no electric field is formed and (b) an electric field is formed. As shown in Figure 13(b), even in such a configuration, when an electric field is formed between the first transparent electrode 21 and the second transparent electrode 22, the refractive index of the region A1 in which the electric field is formed changes instantaneously with respect to other regions within the electro-optic crystal 10. As a result, in the region inside the electro-optic crystal 10 corresponding to the electric field forming portion 20, the refractive index changes periodically and instantaneously along direction D1. Furthermore, when the structure includes both the first transparent electrode 21 and the second transparent electrode 22 being periodic in direction D1, the spread of the electric field in direction D1 can be suppressed compared to when the first transparent electrode 21 or the second transparent electrode 22 is formed over the entire surface of the main surface 11 or the back surface 12. Therefore, a more orderly periodic refractive index distribution can be formed.

[0065] Furthermore, in the above embodiment, the direction of the period in the periodic structure of the plurality of first transparent electrodes 21 coincides with each other among the plurality of first transparent electrodes 21. However, the embodiment is not limited to this form, and the direction of the period in the periodic structure of at least one first transparent electrode 21 may differ from the direction of the period in the periodic structure of the other first transparent electrodes 21.

[0066] Furthermore, in the above embodiment, a comb shape is exemplified for the shape of the first transparent electrode 21 and / or the second transparent electrode 22. The electric field forming section that forms an electric field of periodically changing strength within the electro-optic crystal 10 is not limited to this form. For example, the electric field forming section may have a plurality of transparent electrodes arranged in two dimensions, in which case a voltage may be selectively applied to a portion of the plurality of transparent electrodes in order to form an electric field of periodically changing strength.

[0067] Furthermore, although the above embodiment illustrates a configuration in which the electric field forming section is composed of transparent electrodes, the electric field forming section may also be composed of opaque electrodes (e.g., metal electrodes). In that case, the electrodes may have a structure (e.g., an opening) through which the first parallel light L1 can pass. [Explanation of symbols]

[0068] 1…Optical device, 10…Electro-optic crystal, 11…Main surface, 12…Back surface, 20…Field forming section, 21…First transparent electrode, 22…Second transparent electrode, 30…First lens array, 31…First lens, 40…Light shielding member, 41…Region, 42…Optical aperture, 50…Second lens array, 51…Second lens, 60…Wiring board, 61…Optical aperture, 62,63…Terminals, 64…Conductive paste, 65…Bonding wire, 66A,66B,66C…Wiring with connector, 67…Wiring board, 68…Switching element, 70A,70B,70C…Optical Device, 71...light source, 72...mirror, 73...objective lens, 74,74a,74b,74c...mirror, 75...focusing lens, 76...imaging unit, 77,79...control unit, 78...I / O controller, 80,82...SLM controller, 81,83...spatial light modulator (SLM), A1...region, B...object, B1...irradiation target surface, D1...direction, L1...first parallel light, L2,L4,L5,L7...light, L3...second parallel light, L6...parallel light, M(1)~M(9),M(i)...modulation region, P1,P2...focusing point, S1...signal, V1...DC power supply voltage.

Claims

1. A plate-shaped electro-optic crystal having a main surface and a back surface, the main surface receiving first parallel light and the back surface outputting the first parallel light, A plurality of electric field forming units are arranged in a one-dimensional or two-dimensional manner within a plane along the main surface or the back surface of the electro-optic crystal, forming an electric field within the electro-optic crystal whose strength periodically changes in the direction along the main surface or the back surface, and each of the states of the electric field can be controlled independently. A first lens array having a plurality of electric field forming sections and a plurality of first lenses corresponding to each of the first lenses, which focuses the first parallel light output from the back surface of the electro-optic crystal, A light shielding member having a plurality of regions corresponding to each of the plurality of electric field forming portions, configured to allow or shield the light focused by each of the plurality of first lenses in each of the plurality of regions, according to the state of the electric field of the corresponding electric field forming portion, A second lens array having a plurality of second lenses corresponding to each of the plurality of regions, which converts the light that has passed through the light shielding member into second parallel light in each of the plurality of second lenses, An optical device equipped with the following features.

2. Each of the aforementioned plurality of electric field forming units is: The first transparent electrode provided on the main surface, The second transparent electrode provided on the back surface, It has, The optical device according to claim 1, wherein one or both of the first transparent electrode and the second transparent electrode have a structure in which they are periodic in the aforementioned direction.

3. The optical device according to claim 2, wherein one or both of the first transparent electrode and the second transparent electrode are comb-shaped.

4. The optical device according to claim 1 or 2, wherein each of the plurality of regions is configured to allow light focused by each of the plurality of first lenses to pass through when the electric field of the corresponding electric field forming section is in the off state, and to shield it when the electric field of the corresponding electric field forming section is in the on state.

5. Each of the aforementioned plurality of first lenses is a cylindrical lens that has refractive power mainly in the aforementioned direction. The optical device according to claim 1 or 2, wherein each of the plurality of regions includes a slit extending along the extending direction of the cylindrical lens.

6. The wiring board further comprises the aforementioned electro-optic crystal, The optical device according to claim 1 or 2, wherein the wiring board is electrically connected to each of the plurality of electric field forming units and has a plurality of terminals for supplying each of the plurality of electric field forming units with a drive voltage.

7. The optical device according to claim 1 or 2, wherein the electro-optic crystal includes a KTN crystal.

8. The optical device according to claim 1 or 2, A liquid crystal spatial light modulator receives the second parallel light output from the second lens array of the optical device and modulates the phase of the second parallel light pixel by pixel, Equipped with, The spatial light modulator is an optical device having a plurality of modulation regions corresponding to the plurality of electric field forming portions of the optical device.

9. The system further comprises a control unit that controls the state of the electric field in the plurality of electric field forming units and the modulation pattern of the spatial light modulator, The optical apparatus according to claim 8, wherein the control unit controls the plurality of electric field forming units so that the second parallel light is sequentially incident on the plurality of modulation regions, and updates the modulation pattern after the second parallel light has finished incident on the plurality of modulation regions.

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