Wavefront control device and compensating optical device

Abstract

The wavefront control device of the present invention includes: an optical frequency comb generating unit that emits an optical frequency comb having a plurality of optical pulses arranged in numbered order on a time axis; and a wavefront synthesis unit that generates a synthesized wavefront of the optical pulses emitted from the optical frequency comb, which are distributed to different positions on a plane intersecting the travel direction of the optical frequency comb according to their relative phase with respect to the first optical pulse. The optical frequency comb generating unit includes a phase control unit that controls the repetition frequency and offset frequency of the optical frequency comb.

Description

Technical Field

[0001] This invention relates to a wavefront control device and a compensation optics device. This application claims priority based on Japanese Patent Application No. 2021-137394, filed on August 25, 2021, the contents of which are incorporated herein by reference. Background Technology

[0002] Traditionally, in determining the shape of an object, acquiring tomographic images, and analyzing structural features, compensating optics are used to correct and restore the captured image. The direct image acquired from the object being measured is distorted due to environmental and spatial fluctuations. This distorted image is corrected through wavefront control, thereby obtaining a clear image with high contrast on the imaging surface of a camera or similar device. Measurements using compensating optics involve wavefront measurement to determine the shape and state of the acquired wavefront, and wavefront control to control the wavefront based on information related to the measured wavefront.

[0003] Techniques for wavefront measurement include, for example, using a Shack-Hartmann wavefront sensor with a lens array, using a variable mirror with an adjustable reflector that can adjust the orientation of a reflector intersecting the optical axis of the incident light, or directly modulating the phase of the incident wavefront using a spatial light modulator (SLM). Measurement techniques based on these methods have been established, but the response speed for wavefront measurement is on the order of tens of Hz, and the response speed for wavefront control is on the order of tens of kHz. Therefore, a method for wavefront measurement and control at a higher speed than previously known has been investigated.

[0004] Phased arrays are a method for achieving high-speed wavefront measurement and control. Phased array antennas are implemented using multiple antennas arranged in an array and phase-controlled electromagnetic waves, and are used in weather radars and ultrasonic diagnostic machines that use radio waves as electromagnetic waves. By using phased array antennas, electromagnetic waves with individually controlled phases are emitted from multiple antennas, thus enabling simultaneous wavefront measurement and control. In recent years, optical phased arrays using light as the electromagnetic wave have been anticipated for applications in LiDAR (light detection and ranging), projectors, and biological fluorescence measurements.

[0005] For example, Patent Document 1 and Non-Patent Documents 1 and 2 disclose waveguide-type optical integrated circuit devices as examples of optical phased arrays. In these optical integrated circuit devices, phase adjustment units are provided in multiple branch waveguides formed from an input waveguide such as a planar optical wave circuit, with the same number of branch waveguides as the antenna. The light wave, whose phase is controlled by the phase adjustment units, is emitted from the exit end (antenna) of each of the multiple branch waveguides.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2020-112582

[0009] Non-patent literature

[0010] Non-patent literature 1: MCShin, et al., “Chip-scale blue light phased array”, Optics Letters, Vol.45, No.7, pp.1934-1937 (2020).

[0011] Non-patent literature 2: H. Abediasl, et al., “Monolithic optical phased array transceiver in a standard SOI CMOS process”, Optical Express, Vol. 23, No. 5, pp. 6509-6519 (2015). Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] Conventional optical phased arrays, as illustrated in Patent Document 1 and Non-Patent Documents 1 and 2, are constructed from waveguide-type optical integrated circuit devices. However, in waveguide-type optical integrated circuit devices, the same number of phase adjustment sections as the branch waveguides, i.e., the same number of phase adjustment sections as the number of antennas in the optical phased array, need to be controlled individually. As the number of antennas increases, the space occupied by multiple phase adjustment sections and the phase control devices connected to them increases. Parameters approximately twice the number of antennas need to be controlled and corrected independently, and as the number of antennas increases, the control of multiple antennas and the correction of the parameters of each antenna become complex. To suppress the degradation of the propagation characteristics of light waves in the waveguides of waveguide-type optical integrated circuit devices, monochromatic light is practically necessary. As described above, in order to broadband the light waves of the object being measured and controlled by the conventional waveguide-type optical phased array and to control them at high speed, the enlargement of integrated circuits and control devices and the increase in control parameters are unavoidable. Therefore, conventional waveguide-type optical phased arrays have low practicality.

[0014] This invention provides a wavefront control device and a compensation optical device that can perform wavefront control at high speed through simple control without relying on an increase in the number of antennas, and can realize the broadband of the light wave of the controlled object.

[0015] Methods for solving problems

[0016] The wavefront control device of this embodiment includes: an optical frequency comb generating unit that emits an optical frequency comb having a plurality of optical pulses arranged in numerical order on a time axis; and a wavefront synthesis unit that distributes the plurality of optical pulses incident from the optical frequency comb from the optical frequency comb generating unit to different positions on a plane intersecting the travel direction of the optical frequency comb according to their relative phase with respect to the first optical pulse, thereby generating a synthesized wavefront of the optical pulses emitted from the different positions. The optical frequency comb generating unit includes a phase control unit that controls the repetition frequency and offset frequency of the optical frequency comb.

[0017] In the wavefront control device of this embodiment, the wavefront synthesis unit includes a resonator structure having a pair of mirrors arranged opposite to each other. The reflecting surface of one of the mirrors reflects a portion of the incident optical frequency comb and transmits at least a portion of the remaining portion. The distance L between the reflecting surfaces of the pair of mirrors is represented by the following equation (1).

[0018] [Formula 1]

[0019] L = L rep / 2=c / 2f rep ... (1)

[0020] In equation (1), Lrep The distance between pulses of the optical frequency comb is represented by c, where c represents the speed of light, and f represents the distance between pulses. rep This indicates the repetition frequency of the optical frequency comb.

[0021] The wavefront control device of this embodiment may include an adjustment mechanism that adjusts the incident angle of the optical frequency comb incident on at least one of the pair of reflectors. When using the pair of reflectors, the synthesized wavefront can be controlled by changing the incident angle onto at least one reflector.

[0022] In the wavefront control device of this embodiment, the optical frequency comb generating unit may include a wavelength conversion unit that converts the wavelength of the optical frequency comb. The synthesized wavefront of the optical pulses may not be a single-cycle pulse, but rather the synthesized wavefront may be formed by interference between pulses that cycle any number of times.

[0023] The wavefront control device of this embodiment may include a feedback mechanism that feeds back the intensity information of the light wave having the synthesized wavefront to the phase control unit.

[0024] In the wavefront control device of this embodiment, the phase control unit sets the ratio of the repetition frequency to the offset frequency to a predetermined value.

[0025] In addition, the wavefront control device of this embodiment includes an intensity modulator that emits a portion of the optical pulses emitted from the optical frequency comb generating section to the wavefront synthesizing section.

[0026] The compensation optical device of this embodiment includes the wavefront control device and the imaging optical system. The imaging optical system is configured to illuminate the object being measured with light waves emitted from the wavefront synthesis section of the wavefront control device and having the synthesized wavefront, and is configured to receive light waves reflected or transmitted from the object being measured.

[0027] Invention Effects

[0028] According to the wavefront control device and the compensation optical device of the present invention, wavefront control can be performed at high speed with simple control without relying on an increase in the number of antennas, and broadbanding of the light wave of the controlled object can be achieved. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the wavefront control device according to the first embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the electric field distribution (upper section) on the time axis and the intensity distribution (lower section) on the frequency axis of the optical frequency comb.

[0031] Figure 3 It is used for explanation Figure 1 The diagram shows the principle of the wavefront synthesis unit in the wavefront control device.

[0032] Figure 4 It is used for explanation Figure 1 This diagram illustrates the wavefront synthesis process in the wavefront synthesis unit of the wavefront control device.

[0033] Figure 5 This is a schematic diagram of the wavefront measurement system according to the second embodiment of the present invention.

[0034] Figure 6 It means Figure 5 A schematic diagram illustrating an example of a two-dimensional wavefront distribution in a wavefront measurement system.

[0035] Figure 7 This is a schematic diagram of the wavefront control device according to the second embodiment of the present invention.

[0036] Figure 8 It means in Figure 7 A schematic diagram illustrating an example of the phase distribution of multiple optical pulses allocated to a predetermined surface in a wavefront control device.

[0037] Figure 9 This is a schematic diagram of a first modified example of the wavefront control device of the present invention.

[0038] Figure 10 This is a schematic diagram of a second modified example of the wavefront control device of the present invention.

[0039] Figure 11 This is a schematic diagram of a third variation of the wavefront control device of the present invention.

[0040] Figure 12 This is a schematic diagram illustrating the wavefront synthesis in the wavefront synthesis section of a third variation of the wavefront control device of the present invention. Detailed Implementation

[0041] Hereinafter, embodiments of the wavefront control device and compensation optical device of the present invention will be described with reference to the accompanying drawings.

[0042] [First Implementation Method]

[0043] like Figure 1As shown, the wavefront control device 11 of the first embodiment of the present invention includes an optical frequency comb generating unit 21 and a wavefront combining unit 22. The optical frequency comb generating unit 21 generates an optical frequency comb (hereinafter, sometimes referred to as an optical comb) LC1 and emits the generated optical frequency comb LC1 toward the wavefront combining unit 22. The optical frequency comb generating unit 21 includes at least an optical frequency comb generator 30 and a phase control unit 50, and also includes an optical fiber 42, an optical fiber collimator 44, and a plane mirror 46.

[0044] The optical frequency comb generator 30 generates one optical frequency comb LC1, which is emitted from the output end. For example... Figure 2 As shown, the optical frequency comb LC1 is on the time axis, i.e. Figure 2 Multiple optical pulses LP1, LP2, ..., LP are arranged at intervals on the upper horizontal axis. n LP n+1 A series of light pulses, LP1, LP2, ..., LP3. n is an arbitrary natural number representing the time-axis number of the light pulses. Hereinafter, multiple light pulses may be referred to as LP1, LP2, ..., LP4. n LP n+1 ... are uniformly recorded as multiple optical pulses LPn. The optical frequency comb LC1 has multiple optical pulses LPn arranged in numerical order along the time axis. Each optical pulse LPn contains information about its longitudinal modes along the frequency axis. Each optical pulse LPn has a predetermined frequency distribution. The frequency of each optical pulse LPn changes continuously along the time axis.

[0045] Multiple optical pulses LPn repeat at a constant time T rep Oscillation. In the context of... Figure 2 If the optical frequency comb LC1 on the time axis shown in the upper paragraph undergoes a Fourier transform and is observed on the frequency axis, then... Figure 2 As shown in the lower section, multiple frequency modes arranged at intervals were observed. That is, the optical frequency comb LC1 has multiple frequency modes arranged at intervals along the frequency axis. Figure 2 The lower horizontal axis contains multiple frequency modes FM1, FM2, ..., FM... arranged at intervals. m FM m+1 ... m is an arbitrary natural number representing the frequency axis number of the spectrum. Hereinafter, multiple frequency modes will sometimes be referred to as FM1, FM2, ... FM... m FM m+1 ... are uniformly recorded as multiple frequency modes FMm. Adjacent frequency modes FM on the frequency axis... m FM m+1 The distance between the centers is the repetition frequency f. rep Repeat time T rep It is represented by equation (2).

[0046] [Formula 2]

[0047] T rep =1 / f rep ...(2)

[0048] Multiple optical pulses LPn are each composed of the overlap of multiple longitudinal modes propagating inside the resonator of the light source, etc. The optical frequency comb LC1, which is the optical pulse train, consists of a carrier wave (or carrier) that is the overlapping longitudinal mode wave and a beam that constitutes its envelope (or envelope). Because the velocity of the carrier wave and the velocity of the beam are different, a phase difference occurs over time. This phase difference occurs at predetermined repetition times T along the time axis. rep In a repeatedly emitted light pulse train, the light pulses LP that are adjacent to each other on the time axis n LP n+1 Between them, a phase difference Δφ is generated, which is expressed by equation (3). n+1 .

[0049] [Formula 3]

[0050] Δφ n+1 =φ n+1 -φ n ...(3)

[0051] In the spectral distribution of the optical frequency comb LC1, the frequency mode FM m With repetition frequency f rep The interval is virtually extended to the remaining frequency when the frequency is 0 (zero), which is called the offset frequency f. ceo Or carrier envelope offset (CEO). The offset time T of the optical frequency comb LC1. ceo It is expressed by equation (4).

[0052] [Formula 4]

[0053] T ceo =1 / f ceo ...(4)

[0054] On the time axis, at predetermined repetition times T rep In a light pulse train that repeatedly emits light pulses, the phase shift, i.e., the phase difference Δφ, is... n+1 The period is offset by time T ceo One cycle. The center frequency fn of the nth frequency mode of the optical frequency comb LC1 uses the repetition frequency f. rep and offset frequency f ceo As shown in equation (5).

[0055] [Formula 5]

[0056] f n =n×f rep +f ceo...(5)

[0057] By controlling the repetition frequency f in the MHz to GHz range of the optical frequency comb LC1 rep and offset frequency f ceo It can freely set and control the phase relationship of multiple optical pulses LPn. The repetition frequency f rep and offset frequency f ceo It achieves stability with the level of precision of an atomic clock, and accurately locks to each predetermined value with high precision.

[0058] The optical frequency comb generator 30 is configured to emit an optical comb and to independently control the repetition frequency f of the emitted optical comb, as described later. rep and offset frequency f ceo Each of these components. The structure of the optical frequency comb generator 30 can be appropriately modified as long as it can emit and control the optical comb as described above. Although not shown, the optical frequency comb generator 30 can be constructed, for example, as a resonator of a mode-locked fiber laser (MLLD) equipped with erbium-doped (Er) fiber, a polarization controller, and a delay controller. The optical frequency comb generator 30 can also be constructed, for example, as a linear waveguide for insertion / splitting made of quartz on a glass substrate and a ring waveguide connected between the linear waveguides. The optical frequency comb generator 30 can also be constructed on a silicon (Si) substrate using a ring resonator made of silicon nitride. The optical frequency comb generator 30 can also be constructed as a ring microresonator with a flange at the front end of a protrusion on a Si substrate. The optical frequency comb generator 30 can also be constructed using a resonator made of crystal.

[0059] like Figure 1 As shown, the phase control unit 50 is connected to the optical frequency comb generator 30 and controls the repetition frequency f of the optical frequency comb LC1 emitted from the optical frequency comb generator 30. rep and offset frequency f ceo The phase control unit 50 is connected, for example, to the function generator (not shown) included in the optical frequency comb generator 30. The function generator provides a high-frequency signal to the resonator that generates the optical frequency comb LC1 in the optical frequency comb generator 30, directly affecting the repetition frequency f of the optical frequency comb LC1. rep and offset frequency f ceo The phase control unit 50 is provided for operating the high-frequency signal output of the function generator, and is, for example, a computer connected to the function generator. Regarding the repetition frequency f controlled by the phase control unit 50... rep and offset frequency f ceo The details of the control will be described later.

[0060] like Figure 1As shown, the incident end of optical fiber 42 is connected to the optical frequency comb generator 30. An optical fiber collimator 44 is connected to the exit end of optical fiber 42. The optical fiber collimator 44 collimates the optical frequency comb LC1 propagating in optical fiber 42 and emits it toward the reflecting surface 46a of the plane mirror 46. The plane mirror 46 reflects the optical frequency comb LC1 incident on the reflecting surface 46a toward the wavefront synthesizer 22. An adjustment mechanism 146 capable of rotating the reflecting surface 46a is provided on the plane mirror 46. The adjustment mechanism 146 is, for example, a rotary table having a rotating shaft extending vertically through the top-view center of the reflecting surface 46a and a motor that rotates the rotating shaft. When the reflecting surface 46a is rotated in the direction of the arrow by the adjustment mechanism 146, the angle of the optical frequency comb LC1 emitted from the reflecting surface 46a toward the wavefront synthesizer 22 changes.

[0061] The wavefront synthesizer 22 assigns the positions P1 of the multiple optical pulses LPn contained in the incident optical frequency comb LC1 in the traveling direction of the optical frequency comb LC1 (i.e., the positions on the optical path of the optical frequency comb LC1, and the positions of the exit surface 46b of the plane mirror 46) to each optical pulse LP. n phase φ n Corresponding, mutually distinct positions. Assigned to mutually distinct positions PO. n Light pulse LP n phase φ n They interfere with each other, thus forming a predetermined wavefront. Optical pulse LP n phase φ n The repetition frequency f of the optical frequency comb rep With offset frequency f ceo Ratio control. This means that the wavefront, which is the longitudinal mode, can be manipulated as the transverse mode using a frequency that is the longitudinal mode. The phase φ of multiple optical pulses LPn on the time axis. n The relationship is transformed into the relationship of the positions of each of the multiple light pulses LPn irradiating at position P1. The multiple light pulses LPn, which are assigned to different positions at the predetermined position P1, are combined on the wavefront side which is closer to the emission side than position P1 to form a combined wavefront WP.

[0062] The wavefront synthesizer 22 is, for example, composed of an MPC optical system 60 that constitutes a multipass cavity (MPC). The MPC optical system 60 includes a concave mirror 62 and a plane mirror 64. The concave mirror 62 is positioned so that the optical frequency comb LC1 reflected by the plane mirror 46 of the optical frequency comb generator 21 can be directly incident upon it. The concave mirror 62 is positioned in front of the reflecting surface 46a of the plane mirror 46 in the direction of travel of the optical frequency comb LC1. The plane mirror 64 is positioned in front of the concave mirror 62, incident on the wavefront synthesizer 22 and passing through the concave mirror 62 in the direction of travel of the optical frequency comb LC1. A plano-convex lens 66 is positioned in front of the plane mirror 64, incident on the wavefront synthesizer 22 and passing through the concave mirror 62 in the direction of travel of the optical frequency comb LC1.

[0063] The concave mirror 62 has a reflecting surface 62a that mirrors almost entirely the incident optical frequency comb LC1. The plane mirror 64 has a reflecting surface 64a that mirrors a portion of the incident optical frequency comb LC1 and transmits at least a portion of the remaining portion. The reflecting surface 64a is opposite to the reflecting surface 62a in the direction of travel of the optical frequency comb LC1 (i.e., on the optical axis). In the MPC optical system 60, the concave mirror 62 and the plane mirror 64 constitute a resonator. The concave mirror 62, the plane mirror 64, and the plano-convex lens 66 are each formed of a material capable of transmitting the optical frequency comb LC1, such as quartz or optical glass. The reflecting surfaces 62a and 64a are formed of dielectric multilayer films or metal vapor-deposited films, respectively, taking into account the wavelength of the optical frequency comb LC1, to exhibit the aforementioned transmission characteristics.

[0064] The distance L between the reflecting surface 62a of the concave mirror 62 and the reflecting surface 64a of the plane mirror 64 is expressed as in equations (6) and (7).

[0065] [Formula 6]

[0066] L = L rep / 2... (6)

[0067] L rep =c / f rep ... (7)

[0068] In equation (7), c represents the speed of light, and L... rep This indicates the inter-pulse distance of the optical frequency comb LC1. For example... Figure 3 As shown, the optical frequency comb LC1 incident on the MPC optical system 60 initially passes through the concave mirror 62 and travels along the path direction D1 toward the reflecting surface 64a of the plane mirror 64. Within the optical frequency comb LC1, time-series optical pulses LP... n+1 In light pulse LP n Then repeat at intervals T rep And continuous. Therefore, the light pulse LP nFirst, the light is incident on reflecting surface 64a, and after a repetition time T... rep After that, the light pulse LP n+1 The incident light is incident on the reflecting surface 64a. A portion of the optical frequency comb LC11 incident on the reflecting surface 64a is reflected by the mirror and travels in the loop direction D2 having a component opposite to the outgoing direction D1. At least a portion of the remaining portion of the optical frequency comb LC12 incident on the reflecting surface 64a is transmitted through the plane mirror 64.

[0069] Optical frequency comb LC11 is reflected by the reflective surface 62a of concave mirror 62 and travels again in the path direction D1 as optical frequency comb LC2, incident on the reflective surface 64a of plane mirror 64. A portion of optical frequency comb LC2 incident on reflective surface 64a is reflected again and travels in the return direction D2. At least a portion of the remaining portion of optical frequency comb LC2 incident on reflective surface 64a is transmitted through plane mirror 64. Optical frequency comb LC21 is reflected by the reflective surface 62a of concave mirror 62 and travels again in the path direction D1 as optical frequency comb LC3 (not shown), incident on the reflective surface 64a of plane mirror 64. Similarly, optical frequency comb LCk branches into optical frequency combs LCk1 and LCk2 at the reflective surface 64a of plane mirror 64, just like optical frequency combs LC1 and LC2. k represents a natural number greater than 3. As k increases, the amount of light from optical frequency comb LCk decreases. In the MPC optical system 60, the branching from the optical frequency comb LCk to the optical frequency combs LCk1 and LCk2 is repeated as described above until the amount of light from the optical frequency comb LCk is approximately eliminated.

[0070] like Figure 4 As shown, the exit surface 64b of the plane mirror 64, opposite to the reflecting surface 64a, is a surface that intersects the traveling direction (optical axis) of the optical frequency comb LC1 and the central axis AX of the resonator, and is positioned at a predetermined position P1 in the traveling direction of the optical frequency comb LC1. The central axis AX passes through the centers of the concave mirror 62 and the plane mirror 64. Multiple optical frequency combs LCp2 are incident on different positions of the exit surface 64b, transmitted through the exit surface 64b, and incident on... Figure 4 The plano-convex lens 66 is omitted. p represents a natural number. Multiple optical frequency combs LCp2 are respectively positioned on the exit surface 64b along the circumferential direction centered on the central axis AX, with phase φ. n They are launched from corresponding but different positions.

[0071] like Figure 3 As shown, for example, at a certain moment, at least the optical pulse LP of the optical frequency comb LC12. n+1 And the optical pulse LP of the L22 optical frequency comb n It can simultaneously reach position P2, which is ahead of position P1 in the direction of travel of optical frequency comb LC1. At position P2, multiple optical pulses LPn, according to their respective phases φ nThey were assigned to different locations. Figure 4 As shown, in the exit surface 64b of the plane mirror 64, multiple light pulses LPn travel along the circumferential direction centered on the central axis AX, with phase φ. n Corresponding and distinct positions PO n The light is distributed. When multiple light pulses LPn are distributed through the focusing function of the reflecting surface 62a of the concave mirror 62, the radius of the annular distribution centered on the central axis AX is the shortest at the exit surface 64b of the plane mirror 64.

[0072] The MPC optical system 60 is a passive optical system, thus eliminating the need for mechanical actuation. In the MPC optical system 60, multiple light pulses LPn are distributed approximately simultaneously at different positions PO on the exit surface 64b of the plane mirror 64, based solely on the phenomenon of the optical frequency comb LC1 reciprocating between the concave mirror 62 and the plane mirror 64 and branching at the reflecting surface 64a of the plane mirror 64. n In detail, solely due to the aforementioned phenomena at the speed of light, with light pulses LP... n The projected objects pass through different positions PO on the exit surface 64b of the plane mirror 64. n In this manner, the timing of the optical frequency comb LC1 reaching the output surface 64b is staggered.

[0073] like Figure 4 As shown, the exit surface 64b of the plane mirror 64 simultaneously emits light with phases φ1, φ2, ..., φ1. n φ n+1 Multiple light waves LW1, LW2, ..., LW n LW n+1 ... Hereafter, light waves LW1, LW2, ..., LW... will sometimes be referred to as... n ... are uniformly recorded as light waves LWn. Sometimes the positions PO1, PO2, ..., PO are... n ...and so on are uniformly recorded as light waves PON. Multiple light waves LWn interfere with each other, such as... Figure 1 As shown, the emitted light wave LL has a synthetic wavefront WP.

[0074] The positions PON of the emitted multiple optical pulses LPn are determined by the phase difference Δφ between them from the optical frequency comb LCp2. n+1 The incident position of the optical frequency comb LCp2 on the exit surface 64b, as described above, varies according to the angle between the travel direction of the optical frequency comb LCp2, which undergoes multiple reflections between the concave mirror 62 and the plane mirror 64, and the central axis AX. The curvature of the reflecting surface 62a of the concave mirror 62 is designed taking into account the incident position of the optical frequency comb LCp2 on the exit surface 64b. As will be described later, the incident position of the optical frequency comb LCp2 on the exit surface 64b is determined by the phase φ of the light pulse LPn of the optical frequency comb LC1. nThe relationship is used to set and control.

[0075] Here, the inter-pulse phase difference Δφ n+1 As shown in equation (3).

[0076] [Formula 7]

[0077] Δφ n+1 =φ n+1 -φ n ... (3)

[0078] If the repetition frequency f is completely controlled rep and offset frequency f ceo Then the phase difference between pulses Δφ n+1 For all n being constant, the phase difference Δφ becomes constant.

[0079] In the aforementioned wavefront control device 11, for multiple light waves LW n LW n+1 phase φ n φ n+1 Equation (9) holds true.

[0080] [Formula 8]

[0081]

[0082] According to equation (9), the light wave LW n LW n+1 phase difference Δφ n+1 The repetition frequency f of the optical frequency comb LC1 alone rep and offset frequency f ceo These two parameters determine the phase difference Δφ. n+1 For (Δφ) n+1 -Δφ n If the repetition frequency f rep and offset frequency f ceo If fully controlled, the phase difference Δφ n+1 It is constant regardless of n. Based on equations (5) and (9), by using the repetition frequency f rep and offset frequency f ceo The control is set to their respective predetermined values, which can control the adjacent optical pulses LP on the time axis of the optical frequency comb LC1. n LP n+1 The phase difference Δφ between them. A light wave LL with a composite wavefront WP is emitted from the exit surface 64b of the plane mirror 64 positioned at position P1. This composite wavefront WP depends on the repetition frequency f controlled by the phase control unit 50. rep and offset frequency f ceoThe phase difference Δφ. At this time, the synthesized wavefront WP depends on the repetition frequency f controlled by the phase control unit 50. rep and offset frequency f ceo The phase difference Δφ. Multiple phases φ emerge from the exit surface 64b of the plane mirror 64 of the MPC optical system 60. n φ n+1 ...light waves LW n LW n+1 Thus, the respective exit points of light waves LWn serve as the exit ends of the optical antenna and the exit points of multiple light waves after phase modulation in the optical phased array.

[0083] Multiple optical frequency combs (LCp2) are transmitted through a plane mirror 64 and incident on a plano-convex lens 66 positioned in front of the plane mirror 64 in the direction of travel of the multiple optical frequency combs (LCp2). The plano-convex lens 66 has a convex surface 66a and a flat surface 66b. The plano-convex lens 66 is configured as an auxiliary means to adjust the optical axes of the multiple optical frequency combs (LCp2) exiting from the plane mirror 64, adjust the beam diffusion direction, and cause the multiple optical frequency combs (LCp2) to interfere with each other. In the case where the multiple optical frequency combs (LCp2) interfere with each other, a compound lens such as a camera lens can also be configured as an auxiliary means instead of the plano-convex lens 66. If it is not necessary to adjust the optical axis or the beam diffusion direction to cause the multiple optical frequency combs (LCp2) to interfere with each other, the plano-convex lens 66 can be omitted.

[0084] As explained above, the wavefront control device 11 of the first embodiment includes an optical frequency comb generating unit 21 and a wavefront synthesis unit 22. The optical frequency comb generating unit 21 emits an optical frequency comb LC1 having a plurality of optical pulses LPn arranged in numerical order on the time axis. The optical frequency comb generating unit 21 is equipped with a function to control the repetition frequency f of the optical frequency comb LC1. rep and offset frequency f ceo The phase control unit 50. The wavefront synthesis unit 22 takes multiple light pulses LPn from the optical frequency comb LC1 incident from the optical frequency comb generation unit 21 and sets them on the plane 66b (the plane intersecting the travel direction of the optical frequency comb) of the plano-convex lens 66 according to the first light pulse LP1 (in Figure 2 The relative phase φ (omitted) n Assigned to different locations PO n The wavefront synthesizer 22 generates light pulses LP emitted from different positions. n The composite wavefront WP of each other.

[0085] In the wavefront control device 11 of the first embodiment, if the phase control unit 50 in the optical frequency comb generation unit 21 controls the two parameters of the optical frequency comb LC1: repetition frequency f... rep and offset frequency f ceoBy controlling each pulse to a predetermined value, multiple light pulses LPn, which are arranged in numerical order on the time axis before incident on the wavefront combining unit 22, can be distributed at the speed of light to the plane 66b, i.e., the transverse mode, of the plano-convex lens 66. In the wavefront control device 11 of the first embodiment, at the time point of distributing the multiple light pulses LPn, regardless of the number of pulses distributed, each light pulse LPn can be distributed. n Having only the repetition frequency f rep and offset frequency f ceo Controlled phase φ n The state of information. In the wavefront control device 11 of the first embodiment, waves with phase φ can be emitted from the plane 66b of the plano-convex lens 66. n Light pulse LP n The composite wavefront WP is formed by mutual interference. In waveguide-type optical phased arrays and conventional electromagnetic phased arrays, which are existing methods of wavefront control, the light waves and electromagnetic waves are branched into a number (i.e., a number of distributions) or more for phase control of the light waves and electromagnetic waves, or multiple wave sources are prepared to control the phases of multiple light waves and electromagnetic waves respectively. In the wavefront control device 11 of the first embodiment, it is completely different from waveguide-type optical phased arrays and conventional electromagnetic phased arrays. It controls only two control parameters of one optical frequency comb LC1: repetition frequency f. rep and offset frequency f ceo Control the distribution of light pulses LP to the plane 66b of the plano-convex lens 66. n phase φ n Therefore, it is possible to make the optical pulse LP n The assigned position PO n Each of the two devices functions as an optical antenna and controls the synthesized wavefront WP. In the wavefront control device 11 of the first embodiment, it is not necessary to perform phase control on each of the distributed multiple optical signals (i.e., optical pulses LPn) as in conventional wavefront control methods, and it is not necessary to configure a phase control unit for each of the multiple optical signals. In the wavefront control device 11 of the first embodiment, it is not necessary to calibrate the multiple phase control units with each other. Therefore, according to the wavefront control device 11 of the first embodiment, the repetition frequency f can be controlled without relying on an increase in the number of antennas. rep and offset frequency f ceo Such simple control operation enables high-speed wavefront control. The wavefront control device 11 according to the first embodiment can be miniaturized without relying on an increase in the number of antennas.

[0086] In the wavefront control device 11 of the first embodiment, a single optical frequency comb LC1 is used as the optical signal for the optical antenna. For example... Figure 2As illustrated in the following paragraph, the optical frequency comb LC1 has a wide-bandwidth spectral distribution. In the wavefront control device 11 of the first embodiment, multiple frequency modes FM constituting the spectral distribution of the optical frequency comb LC1 can be controlled with high precision. m Their respective frequencies f m That is, the repetition frequency f rep and offset frequency f ceo According to the wavefront control device 11 of the first embodiment, the phase φ of the plurality of optical pulses LPn forming the composite wavefront WP is allocated at position P1. n (i.e., the phase φ of each optical antenna) n Previously, the optical frequency comb generating unit 21 was able to control the repetition frequency f with high precision, at the level of an atomic clock. rep and offset frequency f ceo According to the wavefront control device 11 of the first embodiment, since the optical frequency comb LC1 has multiple frequency modes FM... m The resulting broad spectral distribution makes it easy to broadband the light waves of the controlled object.

[0087] In the wavefront control device 11 of the first embodiment, by performing wavelength conversion on the optical frequency comb LC1 emitted from the optical frequency comb generator 30 in the optical frequency comb generation unit 21, further broadbanding of the light wave of the controlled object can be easily achieved. For example, as Figure 1 As shown, a wavelength conversion section 70 can also be configured midway along the optical fiber 42 of the optical frequency comb generator 21. The wavelength conversion section 70 can be assembled into the optical frequency comb generator 30, or it can be disposed in the region where the optical frequency comb LC1 passes between the fiber collimator 44 and the plane mirror 46. The wavelength conversion section 70 is made of, for example, a material or crystal capable of converting the spectral distribution of the optical frequency comb LC1, which has a spectral distribution encompassing the near-infrared wavelength region, into a visible wavelength region or an ultraviolet wavelength region, when the optical frequency comb LC1 is incident. The structure of the wavelength conversion section 70 can also be appropriately modified. However, the phase φ of each optical pulse LPn in the optical frequency comb LC1 emitted from the wavelength conversion section 70 is maintained. n The relationship between the wavefront control device 11 in the first embodiment and the wavefront conversion unit 70 further enables wavefront control and compensation optics for ultrashort light pulses, for example, from the deep ultraviolet wavelength region to the terahertz (THz) region.

[0088] In the wavefront control device 11 of the first embodiment, the wavefront synthesis unit 22 includes an MPC optical system (resonator structure) 60 having a concave mirror 62 and a plane mirror 64 (a pair of reflectors) arranged opposite to each other. The reflecting surface 62a of the concave mirror 62 mirror-reflects almost all of the incident optical frequency comb LCp. The reflecting surface 64a of the plane mirror (one reflector) 64 reflects a portion of the incident optical frequency comb LCp and transmits at least a portion of the remaining portion. The inter-surface distance L between the reflecting surfaces 62a of the concave mirror 62 and the reflecting surface 64a of the plane mirror 64 is represented by equation (1) (i.e., equation (6)), and is determined by the repetition frequency f of the optical frequency comb LC1. rep control.

[0089] According to the wavefront control device 11 of the first embodiment, the optical frequency comb LC1 incident on the MPC optical system 60, which is a passive optical system, can reciprocate between the reflecting surfaces 62a and 64a, and the optical frequency comb LCp2, whose numbered light pulses LPn are staggered from the reflecting surface 64a at the same time and in the same position in the same direction of travel, can be controlled without mechanical drive. The wavefront control device 11 of the first embodiment can control the multiple light pulses LPn of the optical frequency comb LC1 according to the phase φ on the exit surface 64b of the plane mirror 64 and the plane 66b of the planar lens 66. n They were assigned to different positions.

[0090] The wavefront control device 11 of the first embodiment includes an adjustment mechanism 146. The adjustment mechanism 146 adjusts the incident angle of the optical frequency comb LC1 incident on the reflecting surface 64a of the plane mirror 64 (at least one of the plane mirrors) of the concave mirror 62 and the plane mirror 64 (a pair of reflecting mirrors). By adjusting the angle of the reflecting surface 46a of the plane mirror 46 using the adjustment mechanism 146, the angle of the optical frequency comb LC1 incident on the plane mirror 64 can be changed, thereby controlling the synthesized wavefront WP.

[0091] In the wavefront control device 11 of the first embodiment, the reflecting surface 62a of the concave mirror 62 is a concave curved surface relative to the flat reflecting surface 64a of the plane mirror 64 and the plane 66b of the planar lens 66. Therefore, the optical frequency comb LC1 emitted from the optical frequency comb generation unit 21 is incident on the MPC optical system 60 in a manner approximately orthogonal to the reflecting surface 64a. In the wavefront control device 11 of the first embodiment, the optical frequency comb LCp resonates between the concave mirror 62 and the plane mirror 64, focusing light from the reflecting surface 62a towards the reflecting surface 64a. According to the wavefront control device 11 of the first embodiment, in the focusing region R of the reflecting surface 64b... 64 In this process, multiple optical pulses LPn can be distributed at appropriate intervals and configurations to form a synthetic wavefront WP.

[0092] According to the wavefront control device 11 of the first embodiment, by using the free-space type MPC optical system 60, multiple light pulses LPn can be directed at the exit surface 64b of the plane mirror 64 according to the phase φ. n They were assigned to different positions.

[0093] In the wavefront control device 11 of the first embodiment, the resonator length of the MPC optical system 60, i.e., the distance L between the reflecting surfaces, depends on the repetition frequency f of the optical frequency comb LC1. rep For example, in fiber lasers equipped with erbium-doped (Er) fiber with an excitation wavelength of around 1550 nm, ytterbium-doped (Yb) fiber with an excitation wavelength of around 1050 nm, or thulium-doped (Tm) fiber with an excitation wavelength of around 2000 nm, the repetition frequency f of the generated optical frequency comb... rep The frequency is approximately 10MHz to 1000MHz. When using a fiber laser with doped fiber having an excitation wavelength in the near-infrared region as the optical frequency comb generator 30, the distance L between the reflecting surfaces of the MPC optical system 60 is approximately several tens of centimeters to 1 meter. When using, for example, a microresonator with a resonant wavelength of approximately 1550nm as the optical frequency comb generator 30, the repetition frequency f of the generated optical frequency comb is... rep The frequency is approximately 10 GHz to 100 GHz. Under these conditions, the inter-reflective surface distance L of the MPC optical system 60 can be reduced to approximately several centimeters to 10 centimeters. This is achieved by using a repetition frequency f. rep The high-performance optical comb source, serving as the optical frequency comb generator 30, enables the miniaturization of the MPC optical system 60 and the wavelength control device 11, for example, enabling the realization of a wavelength control device that can be placed in the size of a palm.

[0094] [Second Implementation]

[0095] like Figure 5 As shown, the compensation optical device 12 of the second embodiment of the present invention includes the wavefront control device 11 and the imaging optical system 13 of the first embodiment. Hereinafter, in the description of the second embodiment, structures identical in structure to the wavefront control device 11 of the first embodiment will be labeled with the same reference numerals as those in the first embodiment. In the description of the second embodiment, content common to the description of the wavefront control device 11 of the first embodiment will be omitted.

[0096] exist Figure 5The diagram only shows a schematic structure of the exit surface 64b of the plane mirror 64 in the wavefront synthesis section 22 of the wavefront control device 11. The imaging optical system 13 is positioned in front of the direction of travel D3 of the light wave LL formed by the exit surface 64b. The imaging optical system 13 includes a beam splitter 102, condenser lenses 104 and 106, and a camera 110. In the compensation optical device 12, the camera 110 is used to perform wavefront measurement, and a clear image of the measured object S is captured during the wavefront compensation phase. Alternatively, a similar device can be used... Figure 5 The wavefront is measured using different devices such as the illustrated compensation optical device 12, and the wavefront-compensated image is captured using the camera 110.

[0097] In the compensating optical device 12, the object to be measured, S, is positioned in front of the light wave LL from the exit surface 64b in the direction of travel D3. A beam splitter 102 and a condenser lens 104 are sequentially positioned between the plane mirror 64 and the object to be measured in the direction of travel D3. The condenser lens 104 is positioned between the beam splitter 102 and the object to be measured in the direction of travel D3. The beam splitter 102 transmits the light wave LL emitted from the exit surface 64b and incident along the direction of travel D3. The condenser lens 104 is positioned at a focal distance behind the measurement position PX on the surface or inside the object to be measured, relative to the distance in the direction of travel D3.

[0098] Beam splitter 102 has a reflecting surface 102a. The reflecting surface 102a transmits light waves LL incident from the travel direction D3. The reflecting surface 102a also specularly reflects light waves LW incident approximately parallel to and in the opposite direction to the travel direction D3, and reflects them towards the travel direction D4, which intersects the travel direction D3. A condenser lens 106 and a camera 110 are sequentially arranged in front of beam splitter 102 near the travel direction D4.

[0099] In the compensation optical device 12, the light wave LL emitted from the exit surface 64b of the plane mirror 64 is transmitted through the beam splitter 102 and travels along the direction of travel D3. The wavefront WP1 of the light wave LL in the imaging optical system 13 is the same wavefront WP0 that propagates and reaches the wavefront of the imaging optical system 13. This composite wavefront WP is generated by combining multiple light pulses LPn emitted from each optical antenna of the exit surface 64b. The light wave LL transmitted through the beam splitter 102 is focused by the condenser lens 104 onto the measurement position PX. The light wave LW reflected from the measurement position PX contains information about the light wave LL and information about the measured object S. That is, the wavefront WP2 of the light wave LW is the wavefront that changes due to the optical properties of the measured object S acting on the wavefront WP1. In the case that the wavefront WP1 is an ideal plane wave, the wavefront WP2 is scattered by the measured object S and becomes a disordered wavefront, resulting in a distorted image captured by the imaging camera 110. If a known wavefront is generated by the wavefront control device 11 and the wavefront WP2 is captured as a reflected image, the optical characteristics of the measured object S can be determined. If a wavefront WP1 with compensated optical characteristics is generated by the wavefront control device 11, the wavefront WP2, which is the object light, is adjusted, and the image of the measured object S obtained by the camera 110 becomes clear. The light wave LW reflected from the measured object S is incident on the condenser lens 104, collimated, and travels approximately parallel to and opposite to the direction of travel D3. The light wave LW is incident approximately parallel to and opposite to the direction of travel D3 relative to the beam splitter 102, and is mirror-reflected by the reflecting surface 102a in the direction of travel D4. The light wave LW reflected by the reflecting surface 102a travels along the direction of travel D4, is focused by the condenser lens 106, and is received by the camera 110.

[0100] exist Figure 5 In the compensation optical device 12 shown, for example, when the wavefront WP2 of the light wave LW reflecting the optical characteristics of the measured object S travels approximately parallel to and opposite to the direction of travel D3, the phase control unit 50 of the wavefront control device 11 controls the repetition frequency f of the optical frequency comb LC1. rep and offset frequency f ceo This is to obtain a wavefront that is approximately orthogonal to the direction of travel D3 and is approximately flat.

[0101] The compensation optical device 12 of the second embodiment described above includes the wavefront control device 11 and the imaging optical system 13 of the first embodiment. The imaging optical system 13 is configured to illuminate the measured object S with light waves LL emitted from the wavefront control device 11, and is configured to receive light waves LW reflected or transmitted from the measured object S. According to the compensation optical device 12 of the second embodiment, the phase control unit 50 of the wavefront control device 11 controls only two control parameters of the optical frequency comb LC1: repetition frequency f.rep and offset frequency f ceo This allows for free control of the wavefront WP1 of the light wave LL irradiating the object S being measured. According to the compensation optical device 12 of the second embodiment, the wavefront WP2 can be freely controlled. In the compensation optical device 12 of the second embodiment, information obtained from the light wave LW received in the imaging optical system 13 and the repetition frequency f of the optical frequency comb LC1 controlled by the phase control unit 50 can be used to... rep and offset frequency f ceo The optical properties of the object S at the measurement location PX are measured in relation to the relationship between the two.

[0102] In the compensation optical device 12 of the second embodiment, for example, only two control parameters of the optical frequency comb LC1 can be controlled by the phase control unit 50 of the wavefront control device 11: the repetition frequency f. rep and offset frequency f ceo So that the object S being measured is reflected or transmitted ( Figure 5 The wavefront WP2 of the reflected light wave LW becomes a flat wavefront orthogonal to the optical axis. Therefore, due to factors such as air fluctuations and heat in the imaging optical system 13, disturbances sometimes occur on the wavefront WP1 of the light wave LL and the wavefront WP2 of the light wave LW that are not causally related to the optical characteristics at the measurement position PX of the measured object S. In this case, the wavefront WP2 can be flattened, allowing for the acquisition of high-contrast images and high-precision measurement data by the imaging camera 110. The phase φ of multiple lights... n The light is emitted from multiple positions PON, which function as optical antennas, to form a wavefront WP0. According to the compensation optical device 12 of the second embodiment, it is not necessary to control the phase φ of multiple beams separately as in the past. n The compensation optical device 12 according to the second embodiment can compensate for the wavefront WP2 of the light wave LW.

[0103] In the compensation optics device 12 of the second embodiment, by providing a wavelength conversion unit 70 in the optical frequency comb generation unit 21 of the wavefront control device 11, wavelength conversion can be performed on the optical frequency comb LC1 at the position where the wavelength conversion unit 70 is located. Therefore, regardless of the wavelength of the optical frequency comb LC1 at the position where the wavelength conversion unit 70 is located, compensation optics can be achieved for ultrashort pulses, for example, from the deep ultraviolet wavelength region to the THz region. By using the compensation optics of the compensation optics device 12 of the second embodiment, for example, more efficient direct fluorescence measurement can be achieved, or it can be applied to multiphoton absorption measurement and multiphoton microscopy.

[0104] In addition to achieving the purpose of compensating optics as described above, the compensation optical device 12 of the second embodiment can also be used to evaluate the transverse mode characteristics of light waves. Figure 5 In the structure shown, a light emitting section, which constitutes a complex optical system (not shown) such as an optical communication system or optical functional device, can also be configured to replace the object S being measured, and the emitted light can be measured. Figure 5 In the structure shown, the emitted light can also interfere with the wavefront generated by the wavefront control device 11. For example... Figure 6 As shown in the upper section, the light wave LL emitted from the exit surface 64b of the plane mirror 64 at position P1 forms a phase in a two-dimensional plane intersecting the optical axis, which is controlled by the phase control unit 50 via a repetition frequency f. rep and offset frequency f ceo Controlled phase φ n The corresponding wavefront distribution. Figure 6 The lower section shows several two-dimensional wavefront distributions WD1, WD2, ..., WD n Examples of the pattern "、...", such as Figure 6 As shown, when the phase control unit 50 controls and changes the repetition frequency f rep and offset frequency f ceo When the wavefront WP0 of the light wave LL emitted from the exit surface 64b of the plane mirror 64 changes (i.e., the two-dimensional wavefront distribution of the composite wavefront WP), the light intensity of the light wave LL changes. Based on this, without compensating for the wavefront of the light wave LW reflected or transmitted from the light exit section of the complex optical system, and by directly receiving light and measuring the light intensity of the light wave LW, it can be determined how the original light wave LL is affected by the complex optical system. This reveals how the light wave LW is generated through a combination of simple wavefronts, enabling accurate evaluation of the transverse mode characteristics of complex optical systems. When the two-dimensional wavefront distribution WD1, WD2, ..., WD... n When generated sequentially and interfering sequentially with wavefronts emitted from the exit section of a complex optical system, the content of each transverse mode can be determined based on the interference intensity.

[0105] The compensation optical device 12 of the second embodiment is suitably used as a wavefront resolver or a two-dimensional beam splitter for evaluating transverse modes.

[0106] [Third Implementation Method]

[0107] like Figure 7As shown, in the wavefront control device 15 of the third embodiment of the present invention, a feedback mechanism 150 is provided in the wavefront control device 11 of the first embodiment. The feedback mechanism 150 includes a beam splitter 152 and a photodiode (PD) 154. The beam splitter 152 is disposed in the region through which the optical frequency comb LCp2 passes between the plane mirror 64 and the plano-convex lens 66 of the wavefront combining section 22, and is disposed on the central axis AX between the plane mirror 64 and the plano-convex lens 66. The beam splitter 152 has a reflecting surface 152a.

[0108] In the wavefront control device 15, the optical frequency comb LCp2, emitted from the exit surface 64b via the reflecting surface 64a of the plane mirror 64, is incident on the beam splitter 152. A portion of the optical frequency comb LCp2 incident on the beam splitter 152 is reflected by the reflecting surface 152a towards the travel direction D3, which is approximately orthogonal to the outgoing direction D1 and the return direction D2. At least a portion of the remaining portion of the optical frequency comb LCp2 incident on the beam splitter 152 is transmitted through the reflecting surface 152a and incident on the plano-convex lens 66. In the exit surface 64b of the plane mirror 64, multiple optical pulses LPn are generated according to the phase φ. n They were assigned to different locations (PO) n A light wave LL with a composite wavefront WP is emitted from the exit surface 64b of the plane mirror 64.

[0109] Photodiode 154 receives the optical frequency comb LCp2 reflected by the reflective surface 152a of beam splitter 152 in the direction of travel D3. Photodiode 154 is electrically connected to the phase control unit 50 of optical frequency comb generation unit 21 via wired or wireless means. Photodiode 154 outputs an electrical signal corresponding to the amount of light received from optical frequency comb LCp2 to phase control unit 50 in real time.

[0110] exist Figure 7 The diagram only shows the repetition frequency control unit 161, offset frequency control unit 162, frequency dividers 165 and 166, and mixer 170 in the optical frequency comb generation unit 21 of the wavefront control device 15. The repetition frequency control unit 161 receives electrical signals from the feedback mechanism 150 and the phase control unit 50, and synchronously controls the repetition frequency f of the optical frequency comb LC1 with the distance L between the reflecting surfaces of the MPC optical system 60. rep The offset frequency control unit 162 generates and controls the offset frequency f of the optical frequency comb LC1. ceo The repetition frequency f controlled by the repetition frequency control unit 161 repThe signal is input to frequency divider 165, where it is divided by (1 / α). The output from offset frequency control unit 162 is input to frequency divider 166, where it is divided by (1 / β). The outputs from frequency dividers 165 and 166 are input to mixer 170, and then fed back from mixer 170 to offset frequency control unit 162. Offset frequency control unit 162 controls the offset frequency f according to the returned input signal. ceo The offset frequency control unit 162 controls the repetition frequency f of the MPC optical system 60 in a stable manner. rep If the phase control unit 50 operates relative to the repetition frequency f rep Control offset frequency f ceo If the action is performed in a certain manner, the repetition frequency f can be controlled according to equation (10). rep and offset frequency f ceo The frequency ratio.

[0111] [Formula 9]

[0112]

[0113] An optical frequency comb LC1 that satisfies the relationship of equation (10) is emitted from the optical frequency comb generating unit 21 of the wavefront control device 15. Figure 8 The results show the phase distribution of multiple light pulses LPn distributed on the exit surface 64b of the plane mirror 64 of the wavefront synthesizer 22 by numerical calculation. Figure 8 The X and Y axes represent two directions that are contained within the exit surface 64b and are orthogonal to each other, with the origin at the position where the exit surface 64b intersects the central axis AX. Figure 8 The vertical axis represents the phase φ n .like Figure 8 As shown, a phase distribution is formed on the exit surface 64b along the circumferential direction centered on the central axis AX. Multiple phases φ of the phase distribution formed around the central axis AX... n The light waves continuously increase and decrease in the circumferential direction, forming a virtual inclined surface. The light wave LL generated from the light pulse LPn is emitted in a direction approximately orthogonal to the inclined surface.

[0114] Phase control unit 50 controls the repetition frequency f of optical frequency comb LC1. rep and offset frequency f ceo It can freely and quickly control the phase distribution of multiple optical pulses LPn on the output surface 64b. The phase control unit 50 controls the repetition frequency f of the optical frequency comb LC1. rep And by controlling the ratio parameter (α / β) of equation (10), multiple phases φ can be controlled simultaneously. n It can freely and with high precision set the tilt of the phase distribution of multiple light pulses LPn on the emitting surface 64b and the emission direction of the light wave LL.

[0115] In the wavefront control device 15 of the third embodiment, similarly to the wavefront control device 11 of the first embodiment, multiple light pulses LPn are distributed by the MPC optical system 60 having a concave mirror 62 and a plane mirror 64, thus forming a phase distribution in the circumferential direction centered on the central axis AX in the exit surface 64b. By controlling (α / β) using the phase control unit 50, the radius of the phase distribution of the multiple light pulses LPn centered on the central axis AX in the exit surface 64b can be controlled.

[0116] The wavefront control device 15 of the third embodiment includes a feedback mechanism 150. The feedback mechanism 150 is located between the plane mirror 64 and the planar lens 66 of the MPC optical system 60 in the wavefront synthesis section 22, and directs the output light from the plane mirror 64 to the exit surface 64b according to the phase φ. n Optical pulses LP of multiple optical frequency combs LCP2 assigned to different locations n The intensity information is fed back to the phase control unit 50 of the optical frequency comb generation unit 21. The phase control unit 50 processes the received optical pulses LP from the multiple optical frequency combs LCp2. n Intensity information and the previously known optical pulse LP of the optical frequency comb LC1 n The intensity information is compared. By using the phase control unit 50, it is possible to confirm in real time whether an optical pulse LP caused by environmental changes such as air fluctuations, resulting in the optical frequency comb LCp2, is generated. n Fluctuations or disturbances in the phase distribution. In the optical pulse LP determined to be optical frequency comb LCp2... n When the phase distribution fluctuates or becomes disordered, the phase control unit 50 controls only two parameters of the optical frequency comb LC1 in the optical frequency comb generation unit 21; the repetition frequency f rep and offset frequency f ceo This eliminates fluctuations or disturbances in the phase distribution. According to the wavefront control device 15 of the third embodiment, the repetition frequency f of the optical frequency comb LC1 can be adjusted. rep Synchronizing with the resonator length of the MPC optical system 60 stabilizes the optical antenna.

[0117] By feeding back the environmental instabilities of various optical antennas, including the MPC optical system 60, to the repetition frequency f of the optical comb. rep and offset frequency f ceo It can improve environmental stability to the same level as atomic clocks, achieving very robust wavefront control.

[0118] The wavefront control device 15 of the third embodiment can be applied to ultra-precise three-dimensional measurements based on spot scanning on a plane intersecting the travel direction of the light wave LL and the central axis AX. The wavefront control device 15 of the third embodiment can also be applied to ultra-precise three-dimensional measurements based on the determination of absolute distance in the depth direction approximately parallel to the travel direction of the light wave LL and the central axis AX. For example, the wavefront control device 15 of the third embodiment can be used to perform a three-dimensional scan of a spherical object S, and the shortest distance to the sphere can be calculated through surface measurement. Based on this result, Avogadro's constant, for example, based on the shape of a silicon sphere, can be determined. For example, by using the wavefront control device 15 of the third embodiment to perform depth direction measurement while performing spot scanning, three-dimensional LiDAR can be realized.

[0119] In the wavefront control device 15 of the third embodiment, the beam splitter 152 of the feedback mechanism 150 is disposed between the plane mirror 64 and the planar lens 66 of the MPC optical system 60. Figure 7 As shown by the double-dotted line, the beam splitter 152 can also be configured, for example, in the region through which the optical frequency comb LCp reflected by the reflecting surface 64a of the plane mirror 64 passes.

[0120] In the wavefront control device 15 of the third embodiment, since the MPC optical system 60 with a concave mirror 62 and a plane mirror 64 is used, the phase components of the multiple light pulses LPn rotate relative to time in the circumferential direction centered on the central axis AX at the exit surface 64b of the plane mirror 64. To stop the rotational change, it is only necessary to give the phase distribution of the multiple light pulses LPn a reverse distribution that reverses the phase distribution of the multiple light pulses LPn.

[0121] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to specific embodiments. Various modifications and alterations to the embodiments of the present invention can be made within the scope of the spirit of the present invention as described in the claimed scope. The contents of the first to third embodiments are appropriately combined. For example, the compensation optical device 12 of the second embodiment may also include the wavefront control device 15 of the third embodiment instead of the wavefront control device 11 of the first embodiment.

[0122] For example, the wavefront synthesizing unit of the wavefront control device of the present invention may also have a passive optical antenna structure other than that of the MPC optical system. Examples of first and second modifications of the wavefront control device of the present invention can be cited. Figure 9 The wavefront control device 17 shown and Figure 10 The wavefront control device 18 shown is shown.

[0123] like Figure 9As shown, the optical frequency comb generation unit 21 of the wavefront control device 17 includes an optical frequency comb generator 30, a phase control unit 50, an optical fiber 42, and an optical fiber coupler 180. The wavefront synthesis unit 22 of the wavefront control device 17 includes multiple output waveguides 182 to replace the MPC optical system 60 of the wavefront control devices 11 and 15. The incident end of the optical fiber coupler 180 is connected to the exit end of the optical fiber 42. The exit end of the optical fiber coupler 180 is connected to the incident end of the multiple output waveguides 182. The multiple output waveguides 182 are composed of output waveguides with different optical path lengths. The difference in optical path length between the output waveguides 182 is equal to the difference in optical pulse LP between adjacent optical pulses on the time axis of the optical frequency comb LC1. n LP n+1 The optical path length difference during propagation via the output waveguide 182. At position P1, where multiple output waveguides 182 are configured, an optical frequency comb LC1 with staggered numbers of emitted optical pulses LPn at the same time. In the wavefront control device 17 of the first modified example, similar to wavefront control devices 11 and 15, it is possible to control the multiple optical pulses LPn of the optical frequency comb LC1 according to phase φ without mechanical drive. n The output waveguides 182 are distributed to the emitting ends of multiple output waveguides 182 located in different positions. According to the wavefront control device 17 of the first modified example, the same effect as the wavefront control devices 11 and 15 can be obtained.

[0124] like Figure 10 As shown, the optical frequency comb generating unit 21 of the wavefront control device 18 includes an optical frequency comb generator 30, a phase control unit 50, and an optical fiber 42. The wavefront synthesis unit 22 of the wavefront control device 18 replaces the MPC optical system 60 of the wavefront control devices 11 and 15 with an arrayed-waveguide grating (AWG) 190. The AWG 190 includes an input waveguide 191 connected to the output end of the optical fiber 42, an input-side planar waveguide 192, an arrayed waveguide group 193, an output-side planar waveguide 194, and multiple output waveguides 195. The optical frequency comb LC1 emitted from the optical fiber 42 is diffracted via the input waveguide 191 and the input-side planar waveguide 192, and then incident on the arrayed waveguide group 193, propagating through an independent optical path in each waveguide of the arrayed waveguide group 193. The optical path length difference between the individual waveguides of the array waveguide group 193 depends on the adjacent optical pulses LP on the time axis of the optical frequency comb LC1. n LP n+1The optical path length difference during propagation in the output waveguide 182. The optical frequency comb LC1 emitted from the array waveguide group 193 undergoes multiple interferences in the output-side planar waveguide 194 and is focused onto the incident end of the output waveguide 195 with different wavelengths. At position P1 at the exit end of the multiple output waveguides 195, the optical frequency comb LC1 emits optical pulses LPn with staggered numbers n at the same time. In the wavefront control device 18 of the second variation, similar to the wavefront control devices 11 and 15, it is possible to control the multiple optical pulses LPn of the optical frequency comb LC1 according to the phase φ without mechanical drive. n The output waves are distributed to the exit ends of multiple output waveguides 195 located in different positions. According to the wavefront control device 18 of the second modification, the same effect as the wavefront control devices 11 and 15 can be obtained.

[0125] As a third variation of the wavefront control device of the present invention, examples can be listed below. Figure 11 The wavefront control device 81 shown is as follows. Figure 11 As shown, in the wavefront control device 81, an intensity modulator (IM) 160 is provided in the wavefront control device 15 of the third embodiment. The intensity modulator 160 is disposed on the travel path of the optical frequency comb LC1 between the optical frequency comb generator 30 and the fiber collimator 44, and is disposed midway in the optical fiber 42 of the optical frequency comb generation unit 21. The intensity modulator 160 performs interval rejection on predetermined optical pulses among the multiple optical pulses LPn of the optical frequency comb LC1 emitted from the optical frequency comb generator 30 and incident through the optical fiber 42. Figure 11 In the example, the optical pulse LC1 is part of the optical frequency comb LC1. n+1 ~LC n+8 Light pulse LC n+3 LC n+6 LC n+7 The light pulses are removed at intervals by the intensity modulator 160. When a predetermined light pulse is removed from the plurality of light pulses LPn of the optical frequency comb LC1 at intervals by the intensity modulator 160, such as... Figure 12 As shown, the relative arrangement of the optical pulses on the exit surface 64b of the wavefront synthesizer 22 changes. When the predetermined optical pulses of the optical frequency comb LC1 are periodically rejected by the intensity modulator 160, based on the reference... Figure 8The principle explained is that the phase distribution formed on the exit surface 64b of the plane mirror 64 is different from the phase distribution formed by the optical frequency comb LC1, which is based on predetermined light pulses without interval rejection. The light wave LL generated from the optical frequency comb LC1 is emitted in a direction approximately orthogonal to the inclined surface of the phase distribution formed on the exit surface 64b. The predetermined light pulses of the optical frequency comb LC1 are interval rejected by the intensity modulator 160, thereby generating a new light wave LL that is different from the light wave LL based on the optical frequency comb LC1, which is based on predetermined light pulses without interval rejection.

[0126] In the wavefront control device 81 of the third variation, the synthesized wavefront WP is formed by the interference of multiple remaining light pulses LPn after the predetermined light pulses of the optical frequency comb LC1 emitted from the plane 66b of the plano-convex lens 66 in the wavefront synthesis section 22 are periodically eliminated. For example, as Figure 11 As shown, when the light pulse LC n+3 LC n+6 LC n+7 When rejected by the intensity modulator at 160 intervals, the light pulse LC n+1 LC n+2 LC n+4 LC n+5 and LC n+8 The synthesized wavefront WP generated by interference exits from the plane 66b of the plano-convex lens 66. The two-dimensional wavefront distribution of the wavefront WP0 of the light wave LL, i.e., the synthesized wavefront WP, is based on the light pulses remaining after predetermined light pulses are periodically removed. The predetermined light pulses periodically removed by the intensity modulator 160 are calculated and appropriately set based on the synthesized wavefront WP output from the wavefront synthesis unit 22. Thus, in order to obtain the synthesized wavefront WP and the two-dimensional wavefront distribution as a specific transverse mode, the intensity modulator 160 periodically removes predetermined light pulses corresponding to a specific transverse mode from the multiple light pulses LPn of the incident optical frequency comb LC1.

[0127] As described above, the wavefront control device 81 of the third modification includes an intensity modulator 160 that emits a portion of the optical pulses LCn from the optical frequency comb LC1 emitted from the optical frequency comb generator 21 to the wavefront synthesis unit 22. The portion of the optical pulse emitted from the intensity modulator 160 is obtained by inverse operation based on the desired transverse mode of the synthesized wavefront WP generated by the wavefront synthesis unit 22. According to the wavefront control device 81 of the third modification, higher-order transverse modes can be generated and effectively utilized by controlling a phase distribution with high degrees of freedom. In the wavefront control device 81 of the third modification, the phase distribution exhibiting higher-order transverse modes can be calculated, and the phase distribution can be controlled using the intensity modulator 160. In the wavefront control device 81 of the third modification, multiple phases φ emitted from multiple positions Pon that function as optical antennas can be appropriately detected. nThe correspondence is as follows. Furthermore, if interference occurs not only with the synthesized wavefront WP formed by the pulse train after interval elimination, but also with other synthesized wavefronts WP formed subsequently, more complex higher-order transverse modes can be formed. In this case, although not illustrated, by placing a resonator with the same resonator length as the MPC optical system 60 in front of the plano-convex lens 66 in the direction of travel of the synthesized wavefront WP, and using this resonator for pulse stacking, complex higher-order transverse modes can be formed as described above. The resonator placed in front of the MPC optical system 60 can be a spatial optical system like the MPC optical system 60, or it can be composed of an array of waveguides, a fiber bundle consisting of a large number of optical fibers, etc.

[0128] Symbol Explanation

[0129] 11, 15... Wavefront control device

[0130] 12··· Compensation optical device,

[0131] 13···Imaging Optical System,

[0132] 21···Optical Frequency Comb Generation Section,

[0133] 22··· Wavefront synthesis section.

Claims

1. A wavefront control device, characterized in that, have: An optical frequency comb generating unit emits an optical frequency comb having multiple optical pulses arranged in a numbered sequence along a time axis; and The wavefront synthesizer distributes the plurality of light pulses from the optical frequency comb incident from the optical frequency comb generator to different positions on a plane intersecting the travel direction of the optical frequency comb according to their relative phase with respect to the first light pulse, thereby generating a synthesized wavefront of the light pulses emitted from the different positions. The optical frequency comb generating unit includes a phase control unit that controls the repetition frequency and offset frequency of the optical frequency comb.

2. The wavefront control device according to claim 1, characterized in that, The wavefront synthesizer includes a resonator structure having a pair of mirrors arranged opposite to each other. The reflective surface of one of the pair of mirrors reflects a portion of the incident optical frequency comb and transmits at least a portion of the remaining portion. The distance L between the reflecting surfaces of the pair of mirrors is expressed by the following equation (1): L=L rep / 2=c / 2f rep …(1) In equation (1), L rep The distance between pulses of the optical frequency comb is represented by c, where c represents the speed of light, and f represents the distance between pulses. rep This indicates the repetition frequency of the optical frequency comb.

3. The wavefront control device according to claim 2, characterized in that, The wavefront control device includes an adjustment mechanism that adjusts the incident angle of the optical frequency comb incident on at least one of the pair of reflectors.

4. The wavefront control device according to any one of claims 1 to 3, characterized in that, The optical frequency comb generating unit includes a wavelength conversion unit that converts the wavelength of the optical frequency comb.

5. The wavefront control device according to any one of claims 1 to 3, characterized in that, The wavefront control device includes a feedback mechanism that feeds back the intensity information of the light wave having the synthesized wavefront to the phase control unit.

6. The wavefront control device according to any one of claims 1 to 3, characterized in that, The phase control unit sets the ratio of the repetition frequency to the offset frequency to a predetermined value.

7. The wavefront control device according to any one of claims 1 to 3, characterized in that, The wavefront control device includes an intensity modulator that emits a portion of the optical pulses emitted from the optical frequency comb generator to the wavefront synthesizer.

8. A compensating optical device, characterized in that, have: The wavefront control device according to any one of claims 1 to 3; and Imaging optical systems The imaging optical system is configured to illuminate the object being measured with light waves emitted from the wavefront synthesis section of the wavefront control device and having the synthesized wavefront, and is configured to receive light waves reflected or transmitted from the object being measured.

Images