JP2005292662A - Wave front compensating apparatus, wave front compensation method, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wave front compensation apparatus capable of precisely compensating wave front, to provide a wave front compensation method, and to provide a program and a recording medium. <P>SOLUTION: A wave front modulating device 40 modulates the phase of incident light to form a phase modulated light. A wave front detecting device 60 converts the phase modulated light into a multipoint spot image, photographs the multipoint spot image and sends out an image signal of the multipoint spot image to a control device 80. The control device 80 calculates the difference between the center of gravity of spots of the multipoint spot image and a reference center of gravity as a shift in the center of gravity and obtains a wave front equation, by applying a least square method to a relational equation between the shift of the center of gravity and a polynomial primary differential equation and calculating a polynomial weight coefficient. The control device 80 further calculates residual wave fronts for each control point, by substituting coordinates of respective controlling points for the wave front equation, obtains feedback control data and converts the feedback control data into a control signals by a look-up table. The control device 80 compensates a wave front 30 of the incident light and outputs an ideal wave front 70, by performing closed loop feedback of the control signals to the wave front modulating device 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wavefront compensation device, a wavefront compensation method, a program, and a recording medium.

  As a technique for removing wavefront aberration, a wavefront detection device for detecting wavefront aberration and a wavefront modulation device are provided, and the wavefront modulation device is subjected to open-loop feedback control or closed-loop feedback control based on the wavefront aberration detected by the wavefront detection device, 2. Description of the Related Art A wavefront aberration compensation device that compensates for wavefront aberration is known.

  As a wavefront aberration compensation device that performs open-loop feedback control, a phase modulation device that uses a Shack-Hartmann wavefront sensor as a wavefront detection device and an electrical address type spatial light phase modulation device as a wavefront modulation device is known. (For example, refer to Patent Document 1). An aberration correction pattern is created by inverting the sign of the wavefront aberration measured by the wavefront sensor. A distortion-corrected pattern is created by adding the aberration correction pattern to an arbitrary wavefront. At the time of addition, a 2π folding process is performed by a remainder calculation. In this way, the electrical address type spatial light phase modulator is subjected to open loop feedback control with a distortion corrected pattern.

  However, in such open loop feedback control, it is necessary to make the electrical address type spatial light phase modulation device inactive while the wavefront detection device is performing detection. For this reason, the wavefront aberration detected by the wavefront detection device is independent of the control signal applied to the electrical address type spatial light phase modulator. Therefore, wavefront compensation cannot be compensated accurately.

  On the other hand, in the wavefront aberration compensation device that performs closed-loop feedback control, the wavefront detection device performs detection while the electrical address type spatial light phase modulator is operating. For this reason, the wavefront aberration detected by the wavefront detection device depends on the control signal applied to the electrical address type spatial light phase modulator, and the wavefront can be compensated more accurately.

  As a wavefront aberration compensation device that performs closed-loop feedback control, a Shack-Hartmann type wavefront sensor is used as a wavefront detection device, and a low-resolution electric address type spatial light phase modulation device (for example, 69 control points) is used as a wavefront modulation device. 2. Description of the Related Art A wavefront aberration compensator using an electrical address type spatial light phase modulator is known (for example, see Non-Patent Document 1). Since the number of control points is small, the control signal is calculated using a control matrix measured in advance. The control matrix is a matrix describing the correspondence between the detection result of the wavefront detection device and the control signal of the wavefront modulation device. By applying the detection result of the wavefront detection device expressed in vector, the control signal of the wavefront modulation device in vector format can be obtained. However, if the number of control points increases, it becomes difficult to obtain a control matrix by measurement, and a low-resolution electric address type spatial light phase modulation device cannot perform fine and precise correction.

Therefore, a wavefront compensation device that performs closed-loop feedback control using a high-resolution electrical addressing spatial light phase modulation device (for example, an electrical addressing spatial light phase modulation device having 640 × 480 control points) as a wavefront modulation device has been proposed. Yes. A Shack-Hartmann type wavefront sensor is used as the wavefront detection device (see, for example, Non-Patent Documents 2 to 4). However, since a high-resolution electric address type spatial light phase modulator is used and the number of control points is large, it is impossible to measure the control matrix. For this reason, the phase incident on each lens of the wavefront sensor is inversely calculated based on the detection result of the wavefront sensor by the Fourier transform method. Here, the pitch of the lenses is larger than the pitch of the control points of the electrical address type spatial light phase modulator. For this reason, the control points are grouped, all the control points in each group correspond to one lens, and the same phase is given to all the control points in the group. That is, a high-resolution spatial light phase modulator is controlled at a low resolution.
International application WO03 / 036368 (pages 58-59, FIGS. 10, 15) Gourlay et al., "A real-time closed-loop liquid crystal adaptive optics system: first result," Optics Communications, vol 137, pp17-21. (1997) Olivier et al., "High-resolution wavefront control using liquid crystal spatial light modulators", Proceedings SPIE 3760-08 (1999) Thompson et al., "Performance of a high-resolution wavefront control system using a liquid crystal spatial light modulator," Proceeding SPIE 4124, pp170-177 (2000) Wilks et al., "High-Resolution Adaptive Optics Test-Bed for Vision Science", Proceedings SPIE Vol 4494, pp349-356. (2001)

  However, if the control points of the electrical address type spatial light phase modulator are grouped and the same phase is given to the control points in each group, the original spatial resolution of the electrical address type spatial light phase modulator is fully utilized. I can't. Thus, in the phase calculation method using Fourier transform, the original spatial resolution of the electrical address type spatial light phase modulation device cannot be fully utilized, and the wavefront cannot be corrected accurately.

  Therefore, the present invention provides a wavefront compensation device, a wavefront compensation method, a program, and the like that can accurately correct the wavefront by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulation device. And it aims at providing a recording medium.

  In order to achieve the above object, the invention according to claim 1 includes a modulation unit in which a plurality of control points are arranged two-dimensionally, and the phase of the readout light incident on the modulation unit is set for each control point. A multi-point spot image comprising a plurality of spots, and an electric address type spatial light phase modulation device to be modulated, and a plurality of lenses arranged two-dimensionally, and reading light whose phase is modulated by the electric address type spatial light phase modulation device A lens array for converting to, an image detecting means for detecting a light intensity distribution of the multi-point spot image, and calculating a plurality of spot centroids indicating centroid positions of the plurality of spots based on the detected light intensity distribution, Center-of-gravity difference calculating means for calculating a plurality of center-of-gravity differences indicating differences between the calculated plurality of spot centroids and a plurality of preset reference centroids, and using the least-squares method for the calculated plurality of centroid differences. And by fitting to a first-order differential expression of a predetermined polynomial, a weight coefficient calculating means for obtaining a weight coefficient of the predetermined polynomial, and a value corresponding to the coordinates of each control point using the calculated weight coefficient By substituting into the polynomial, a residual distortion computing means for obtaining residual distortion for each control point, and control for obtaining closed loop control data for the control point based on the residual distortion of each computed control point There is provided a wavefront compensator comprising data operation means and control means for controlling each control point of the electrical address type spatial light phase modulator based on the closed loop control data.

  In this way, by calculating the weighting coefficient of the polynomial, the wavefront of the readout light input to the lens array is fitted to the polynomial. By substituting a value corresponding to the coordinates of each control point into the polynomial, the residual distortion at each control point of the input wavefront is obtained. Closed loop control data is created based on the calculated residual distortion. By repeatedly controlling the electrical address type spatial light phase modulation device based on the closed loop control data, the electrical address type spatial light phase modulation device repeatedly executes phase modulation of the readout light and performs wavefront compensation.

  The invention according to claim 2 is the wavefront compensation device according to claim 1, wherein each control point of the electrical address type spatial light phase modulation device receives the input read light as the input control light. The phase modulation amount corresponding to the signal is modulated, and the control unit further includes a signal conversion unit, and the signal conversion unit calculates the phase modulation amount to be modulated by each control point based on the residual distortion of each control point. Determining, converting the determined phase modulation amount into a control signal using a preset look-up table, and controlling each control point of the electrical address type spatial light phase modulator based on the control signal It is a feature.

  The electrical addressing spatial light phase modulator is, for example, an electric addressing liquid crystal spatial light phase modulator (for example, PAL-SLM), an electrical addressing liquid crystal spatial light intensity modulator (for example, LCD), and a writing light source. It is preferable to comprise an address type liquid crystal phase modulation module. The electrical address type liquid crystal spatial light intensity modulator includes a modulation unit in which a plurality of control points are arranged two-dimensionally. The optical address type liquid crystal spatial light phase modulator is provided with a plurality of control points corresponding to the control points of the electric address type liquid crystal spatial light intensity modulator on a one-to-one basis. When the signal conversion means inputs a control signal to each control point of the electrical address type liquid crystal spatial light intensity modulator, the electrical address type liquid crystal spatial light intensity modulator modulates the intensity of the writing light at each control point according to the control signal. The optical address type liquid crystal spatial light phase modulator phase-modulates the read light incident on the modulation unit for each control point according to the write light intensity. Therefore, the optical address type liquid crystal spatial light phase modulator modulates the phase of the incident read light by a phase modulation amount corresponding to the control signal for each control point. According to such an electrical address type liquid crystal phase modulation module, the phase of the readout light can be modulated easily and accurately.

  The invention according to claim 3 is the wavefront compensation device according to claim 1, wherein the centroid difference calculating means evaluates the calculated spot centroids, and the weighting coefficient calculating means is The weighting factor is calculated based on a centroid difference calculated for a spot centroid other than the spot centroid evaluated as an invalid spot centroid among the plurality of spot centroids.

  According to a fourth aspect of the present invention, there is provided the wavefront compensation device according to the first aspect, wherein the control points are arranged in the modulation unit of the electrical address type spatial light phase modulation device. Is larger than the reading light incident on the modulation section.

  The invention according to claim 5 is a wavefront compensation method for compensating the wavefront of readout light by performing closed-loop feedback control of an electrically addressed spatial light phase modulator having a plurality of control points arranged two-dimensionally. In addition, the readout light whose phase is modulated for each control point by the electrical address type spatial light phase modulation device is made up of a plurality of spots formed by passing through a lens array in which a plurality of lenses are two-dimensionally arranged. An image detection step for detecting a light intensity distribution of a spot image, and calculating a plurality of spot centroids indicating centroid positions of the plurality of spots based on the detected light intensity distribution, and calculating the plurality of spot centroids A center-of-gravity difference calculating step for calculating a plurality of center-of-gravity differences indicating differences from a plurality of preset reference center-of-gravity, and using the least-square method A weight coefficient calculation step for obtaining a weight coefficient of the predetermined polynomial by fitting to a first-order differential equation of a constant polynomial, and a value corresponding to the coordinates of each control point using the calculated weight coefficient Substituting into the polynomial, a residual distortion calculation step for obtaining a residual distortion for each control point, and a control for obtaining closed loop control data for the control point based on the residual distortion of each calculated control point A wavefront compensation method comprising: a data calculation step; and a control step of controlling each control point of the electrical address type spatial light phase modulation device based on the closed loop control data, wherein the steps are repeated. providing.

  In this way, by calculating the weighting coefficient of the polynomial, the wavefront of the readout light input to the lens array is fitted to the polynomial. By substituting a value corresponding to the coordinates of each control point into the polynomial, the residual distortion at each control point of the input wavefront is obtained. Closed loop control data is created based on the calculated residual distortion. By repeatedly controlling the electrical address type spatial light phase modulation device based on the closed loop control data, the electrical address type spatial light phase modulation device repeatedly executes phase modulation of the readout light and performs wavefront compensation.

  According to a sixth aspect of the present invention, there is provided a program for causing a computer to perform closed-loop feedback control of an electrical address type spatial light phase modulation device having a plurality of control points arranged two-dimensionally to compensate a wavefront of readout light. The readout light whose phase is modulated for each control point by the electrical address type spatial light phase modulation device is formed from a plurality of spots formed by transmitting a plurality of lenses in a two-dimensionally arranged lens array. Calculating a plurality of spot centroids indicating the positions of the centroids of a plurality of spots based on the light intensity distribution of the multi-point spot image, and indicating a difference between the calculated plurality of spot centroids and a plurality of preset reference centroids The center-of-gravity difference calculation procedure for calculating the center-of-gravity difference and the calculated plurality of center-of-gravity differences are fit into a first-order differential expression of a predetermined polynomial using the least square method. By assigning a value corresponding to the coordinates of each control point to the predetermined polynomial using the calculated weighting factor. A residual distortion calculation procedure for obtaining a residual distortion for each control point, a control data calculation procedure for obtaining closed loop control data for the control point based on the residual distortion of each calculated control point, and the electric address type spatial light There is provided a program characterized by having a control procedure for controlling each control point of the phase modulation device based on the closed-loop control data and a procedure for repeating each procedure.

  The computer executes the program according to claim 6 to perform wavefront compensation by performing closed-loop feedback control of the electrical address type spatial light phase modulator.

  The invention according to claim 7 provides a computer-readable recording medium in which the program according to claim 6 is recorded.

  According to an eighth aspect of the present invention, there is provided an electrically addressed spatial light phase in which a plurality of control points are arranged in a two-dimensional manner, and the read light is phase-modulated for each control point based on control data to generate a phase pattern. A modulation device, and a lens array in which a plurality of lenses are arranged in a two-dimensional manner, converting the phase pattern output from the electrical address type spatial light phase modulation device into a multipoint spot image composed of a plurality of spots, Wavefront detecting means for detecting the light intensity distribution of the multipoint spot image, and calculating a plurality of spot centroids indicating the positions of the centroids of the plurality of spots based on the detected light intensity distribution, and setting the plurality of spot centroids in advance. The phase pattern output from the electrical address type spatial light phase modulation device based on a plurality of center-of-gravity differences indicating a difference from a plurality of reference centroids corresponding to the ideal wavefront, Calculating a wavefront equation representing a phase difference with an ideal wavefront, substituting a value corresponding to the coordinates of the control point into the wavefront equation, and calculating a phase difference for each control point as a residual wavefront; and An aberration wavefront calculation storage means for adding a residual wavefront and an aberration wavefront for each control point and storing the result as a new aberration wavefront for each control point; and the new aberration wavefront and the ideal wavefront Wavefront synthesis means for adding each control point and creating feedback control data based on the result, and control means for outputting the feedback control data as the control data to the electrical address type spatial light phase modulator The wavefront compensator is characterized in that the electrical address type spatial light phase modulator repeats phase modulation of readout light based on the feedback control data input from the control means.

  If a value corresponding to the coordinates of each control point is substituted into the wavefront equation, the phase difference for each control point can be accurately calculated as a residual wavefront. Even if the lens pitch is larger than the control point pitch, that is, the spatial resolution of the wavefront detection means is lower than the spatial resolution of the electrical address type spatial light phase modulator, the spatial resolution of the electrical address type spatial light phase modulator is not impaired. The residual wavefront can be calculated accurately. The feedback control data is created based on the residual wavefront calculated precisely in this way, and the electric address type spatial light phase modulator is controlled based on the feedback control data to cause phase modulation of the readout light. The electric address type spatial light phase modulator is repeatedly closed-loop feedback controlled based on the feedback control data to sequentially correct distortion of the phase pattern output from the electric address type spatial light phase modulator.

  The invention according to claim 9 is the wavefront compensation device according to claim 8, wherein the wavefront equation is a polynomial, and the calculation means is a relationship between the centroid difference and a first-order differential expression of the polynomial. The least squares method is applied to the equation to calculate the weighting coefficient of the polynomial, thereby obtaining the wavefront equation.

  According to a tenth aspect of the present invention, closed-loop feedback control is performed on an electrical address type spatial light phase modulator having a plurality of control points arranged in a two-dimensional manner, and the electrical address type spatial light phase modulator is controlled by the electrical address type spatial light phase modulator. A wavefront compensation method for compensating a wavefront of readout light phase-modulated on a point-by-point basis according to control data, wherein the readout light output from the electrical addressing spatial light phase modulation device has a plurality of lenses arranged two-dimensionally. A wavefront detection step for detecting a light intensity distribution of a multi-point spot image formed by a plurality of spots formed by transmitting through the arranged lens array, and the center of gravity positions of the plurality of spots based on the detected light intensity distribution Calculating a plurality of spot centroids, and indicating a difference between the plurality of spot centroids and a plurality of reference centroids corresponding to preset ideal wavefronts. A wavefront equation representing a phase difference between the wavefront of the readout light output from the electrical address type spatial light phase modulator and the ideal wavefront based on a heart difference is calculated, and the value corresponding to the coordinates of the control point in the wavefront equation And calculating the phase difference for each control point as a residual wavefront, adding the residual wavefront and the aberration wavefront for each control point, and adding the result to a new aberration for each control point. Aberration wavefront calculation storage step for storing as a wavefront, a wavefront synthesis step for adding the new aberration wavefront and the ideal wavefront for each control point, and creating feedback control data based on the result, and the feedback control data Is provided as the control data to the electrical address type spatial light phase modulation device, and a wavefront compensation method is provided which includes a step of repeating the steps.

  If a value corresponding to the coordinates of each control point is substituted into the wavefront equation, the phase difference for each control point can be accurately calculated as a residual wavefront. Even if the lens pitch is larger than the control point pitch, the residual wavefront can be accurately calculated without impairing the spatial resolution of the electrical address type spatial light phase modulator. The feedback control data is created based on the residual wavefront calculated precisely in this way, and the electric address type spatial light phase modulator is controlled based on the feedback control data to cause phase modulation of the readout light. The electric address type spatial light phase modulator is repeatedly closed-loop feedback controlled based on the feedback control data to sequentially correct distortion of the phase pattern output from the electric address type spatial light phase modulator.

  The invention according to claim 11 is the wavefront compensation method according to claim 10, wherein the wavefront equation is a polynomial, and the calculation step is a relationship between the centroid difference and a first-order differential expression of the polynomial. The least squares method is applied to the equation to calculate the weighting coefficient of the polynomial, thereby obtaining the wavefront equation.

  According to a twelfth aspect of the present invention, an electrical address type spatial light phase modulation device having a plurality of control points arranged two-dimensionally is closed-loop feedback controlled by a computer, and the electrical address type spatial light phase modulation is performed. A program for compensating the wavefront of readout light that has been phase-modulated based on control data for each control point by the apparatus, wherein the readout light output from the electrical address type spatial light phase modulation device is in a two-dimensional form. Calculating a plurality of spot centroids indicating centroid positions of the plurality of spots based on a light intensity distribution of a multi-point spot image formed of a plurality of spots formed by transmitting through the lens array arranged in And the electric address type based on a plurality of center-of-gravity differences indicating differences between a plurality of reference centroids corresponding to a preset ideal wavefront Calculating a wavefront equation representing a phase difference between the wavefront of the readout light output from the inter-phase optical phase modulator and the ideal wavefront, and substituting a value corresponding to the coordinates of the control point into the wavefront equation for each control point A calculation procedure for calculating the phase difference of the residual wavefront as a residual wavefront, and adding the residual wavefront and the aberration wavefront for each control point, and storing the result as a new aberration wavefront for each control point A procedure, a wavefront synthesis procedure for adding the new aberration wavefront and the ideal wavefront for each control point, and generating feedback control data based on the result, and using the feedback control data as the control data as the electrical address There is provided a program characterized by having a control procedure for outputting to a type spatial light phase modulation device and a procedure for repeating each procedure.

  The computer executes the program according to claim 12 to perform wavefront compensation by performing closed-loop feedback control of the electrical address type spatial light phase modulator.

  The invention according to claim 13 is the program according to claim 12, wherein the wavefront equation is a polynomial, and the calculation procedure is a relational expression between the centroid difference and a first-order differential expression of the polynomial. The least square method is applied to calculate the weighting coefficient of the polynomial, thereby obtaining the wavefront equation.

  The invention according to claim 14 provides a computer-readable recording medium in which the program according to claim 12 is recorded.

  According to the wavefront compensation device of the first aspect of the present invention, the control point pitch of the electrical address type spatial light phase modulation device and the lens pitch of the lens array are not consistent, and the lens pitch is the control point pitch. Even if the lens array is larger, that is, the spatial resolution of the lens array is smaller than that of the electrical address type spatial light phase modulator, the residual distortion at each control point of the input wavefront can be calculated with high accuracy. Therefore, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  According to the wavefront compensation device of the second aspect of the present invention, even if the electrical address type spatial light phase modulation device has a non-linear modulation characteristic, the lookup table reflects this modulation characteristic. The control signal level of the type spatial light phase modulator can be adjusted accurately. For this reason, precise control becomes possible.

  The wavefront compensator according to claim 3 of the present invention can continue to operate stably even if it is used in a complicated environment and a specific spot centroid is generated.

  According to the wavefront compensation device of the fourth aspect of the present invention, since the readout light continues to fall within the control point region even if the incident position and size of the readout light fluctuate due to the distortion of the readout light, the wavefront compensation device Wavefront compensation can continue to be performed stably.

  According to the wavefront compensation method of the fifth aspect of the present invention, each control of the input wavefront can be performed even if the control point pitch of the electrical address type spatial light phase modulation device and the lens pitch of the lens array are not consistent. Since the residual distortion at the point can be calculated with high accuracy, the wavefront compensation can be performed precisely by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  If the computer executes the program according to the sixth aspect of the present invention, the wavefront compensation can be performed precisely by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  If the program according to claim 6 is recorded and stored in a computer-readable recording medium according to claim 7 of the present invention and the program is transplanted to an arbitrary computer, the arbitrary computer changes to claim 6. By executing the described program, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  According to the wavefront compensation apparatus of the eighth aspect of the present invention, the control point pitch of the electrical address type spatial light phase modulator and the lens pitch of the lens array are not consistent, and the lens pitch is the control point pitch. Even if the lens array is larger, that is, the spatial resolution of the lens array is smaller than the spatial resolution of the electrical address type spatial light phase modulator, the residual wavefront at each control point of the input wavefront can be calculated with high accuracy. For this reason, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  According to the wavefront compensation device of the ninth aspect of the present invention, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulation device.

  According to the wavefront compensation method of claim 10 of the present invention, even if the control point pitch and the lens pitch of the electrical address type spatial light phase modulator are not consistent, the residual at each control point of the input wavefront. Since the difference wavefront can be calculated with high accuracy, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  According to the wavefront compensation method of the eleventh aspect of the present invention, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulation device.

  If the computer executes the program according to the twelfth aspect of the present invention, the wavefront compensation can be accurately performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  If the computer executes the program according to the thirteenth aspect of the present invention, the wavefront compensation can be performed precisely.

  If the program according to claim 12 is recorded and stored in a computer-readable recording medium according to claim 14 of the present invention and the program is transplanted to an arbitrary computer, the arbitrary computer changes to claim 12. By executing the described program, the wavefront compensation can be precisely performed by fully utilizing the phase modulation capability of the spatial resolution inherent in the electrical address type spatial light phase modulator.

  A wavefront compensation device, a wavefront compensation method, a program, and a recording medium according to this embodiment of the present invention will be described with reference to FIGS. 1 to 16 (e).

  As shown in FIG. 1, the wavefront compensation apparatus 1 according to the present embodiment includes a wavefront modulation device 40, a beam sampler 50, a wavefront detection device 60, and a control device 80. The wavefront compensation device 1 is an optical device for modulating an incident wavefront 30 of incident light (readout light) to a desired wavefront 70 and outputting the modulated wavefront.

  The wavefront modulation device 40 is an electrical address type phase modulation type liquid crystal spatial light modulation device including a modulation unit 40s. The wavefront modulation device 40 performs phase modulation on the readout light incident on the modulation unit 40s from the readout light source (not shown), and emits the phase-modulated readout light from the modulation unit 40s. The reading light source is made of, for example, a He—Ne laser, and generates reading light having a high degree of spatial coherence. The readout light from the readout light source is linearly polarized light having a wavefront 10 with a substantially uniform phase distribution and a polarization plane parallel to the paper surface of FIG.

  A beam diameter conversion collimating means (not shown) is provided on the optical path from the readout light source to the wavefront modulation device 40. The readout light emitted from the readout light source has a substantially circular cross section orthogonal to the optical axis. To a parallel beam having a beam diameter of. An optical element and an optical device (not shown) are provided on the optical path from the readout light source to the wavefront modulation device 40 in addition to the beam diameter conversion collimating means.

  The readout light usually has a distorted wavefront 30 when entering the wavefront modulation device 40. This is due to the disturbance factor 20 existing on the optical path from the readout light source to the wavefront modulation device 40. The disturbance factor 20 includes design errors, manufacturing errors, alignment errors, fluctuations due to the thermal effect of the medium through which the readout light passes, and optical elements and optical devices existing on the optical path from the readout light source to the wavefront modulation device 40, and And light emission fluctuation of the light source for reading. The wavefront modulation device 40 performs phase modulation on the readout light having the distorted wavefront 30 and emits the phase-modulated readout light.

  The beam sampler 50 is an optical element that transmits and reflects incident light at a predetermined ratio. Here, the beam sampler 50 divides the light output from the wavefront modulation device 40 and incident on the beam sampler 50 into transmitted light and reflected light.

  Light reflected by the beam sampler 50 out of the light phase-modulated by the wavefront modulation device 40 is incident on the wavefront detection device 60. The wavefront detection device 60 is for converting the wavefront of incident light into a multipoint spot image signal, detecting it, and outputting it to the control device 80.

  Note that a relay lens system (not shown) is disposed between the beam sampler 50 and the wavefront modulation device 40 and at least one between the beam sampler 50 and the wavefront detection device 60.

  The control device 80 is for performing closed-loop feedback control of the wavefront modulation device 40. As a result of the closed loop feedback control, the distortion of the phase pattern emitted from the wavefront modulation device 40 is gradually corrected, and light having a wavefront 70 close to the ideal wavefront is generated. Of the light having the wavefront 70 close to the ideal wavefront, the portion that has passed through the beam sampler 50 is subjected to any subsequent processing. For example, a Fourier lens for spatially Fourier-transforming light transmitted through the beam sampler 50 is disposed at the subsequent stage of the beam sampler 50, and a processing target (not shown) is disposed on the Fourier plane of the Fourier lens. The surface of the processing target can be processed in a desired pattern by spatially Fourier-transforming the light that has been phase-modulated by the wavefront compensator 1 and has a wavefront 70 approximately approximate to an ideal wavefront by a Fourier lens. it can.

  Next, the wavefront modulation device 40 will be described with reference to FIG. In this example, the wavefront modulation device 40 includes an electric address type liquid crystal phase modulation module “SLM X7550” (trade name, manufactured by Hamamatsu Photonics Co., Ltd.), is computer-controllable, has high spatial resolution, and has a phase of 2π or more. Modulation is possible.

  More specifically, the wavefront modulation device 40 includes a writing light source 510, a collimating lens 520, a liquid crystal display (hereinafter referred to as LCD) 530, a relay lens 540, and a parallel alignment type nematic liquid crystal spatial light modulator (PAL-SLM (Parallel)). -Aligned nematic-Liquid-cristal Spatial Light Modulator): hereinafter referred to as PAL-SLM) 550. The optical axis of the collimating lens 520 and the optical axis of the relay lens 540 coincide with each other.

  The writing light source 510 is for generating writing light having a uniform intensity distribution. The writing light source 510 is constituted by, for example, a laser diode (LD). The collimating lens 520 is a lens for collimating the writing light from the writing light source 510 to generate parallel light.

  The LCD 530 is a transmissive electric address type intensity modulation type liquid crystal spatial light modulator. The LCD 530 is electrically addressed by a control signal input from the control device 80. The LCD 530 modulates the intensity of the writing light from the collimating lens 520 to generate intensity modulated light having a pattern intensity distribution indicated by the control signal.

  The LCD 530 includes a light incident layer 530a, a light transmission layer 530b, a pixel structure layer 530c, a twisted nematic liquid crystal layer 530d, and a counter electrode layer 530e. Each of the incident layer 530a and the light transmission layer 530b includes a transparent glass substrate and a polarizing plate provided on the outer surface thereof. The pixel structure layer 530c, the twisted nematic liquid crystal layer 530d, and the counter electrode layer 530e are provided between the light incident layer 530a and the light transmission layer 530b.

  The pixel structure layer 530c includes a plurality of transparent pixel electrodes. The pixel structure layer 530c includes transparent pixel electrodes having a predetermined number of pixels. For example, if the LCD 530 is a VGA (Video Graphics Array) type, the pixel structure layer 530c includes a transparent pixel electrode of 640 × 480 pixels. If the LCD 530 is an XGA (Extended Graphics Array) type, the pixel structure layer 530c includes a transparent pixel electrode of 1024 × 768 pixels. The plurality of transparent pixel electrodes are arranged at a predetermined pitch in a two-dimensional matrix on a virtual plane orthogonal to the collimating lens 520. Each pixel electrode has a predetermined size (width) P1 (Pl = 40 (μm) in the case of the VGA type). Each pixel electrode defines one pixel of the LCD 530.

  The LCD 530 having the above configuration is arranged such that the light incident layer 530a faces the collimator lens 520 and the light transmission layer 530b faces the relay lens 540. The pixel structure layer 530c is connected to the control device 80.

  When the transparent pixel electrode of the pixel structure layer 530c is electrically addressed by a control signal input from the control device 80, the alignment state of the liquid crystal molecules in the twisted nematic liquid crystal layer 530d changes corresponding to the signal level of the control signal. To do. When the writing light from the collimating lens 520 is incident on the twisted nematic liquid crystal layer 530d through the polarizing plate of the light incident layer 530a, the polarization state changes according to the alignment state of the liquid crystal molecules. The light whose polarization state has changed is emitted through the polarizing plate of the light transmission layer 530b, thereby being converted into intensity-modulated light. In this way, the LCD 530 outputs intensity modulated light having an intensity distribution corresponding to the control signal input from the control device 80.

  The relay lens 540 is a lens for transmitting the intensity-modulated light output from the LCD 530 to the PAL-SLM 550. In this example, the relay lens 540 transmits the intensity pattern displayed on the LCD 530 to the PAL-SLM 550 at a one-to-one imaging magnification.

  The PAL-SLM 550 is a reflection type optical address type phase modulation type liquid crystal spatial light modulator. The PAL-SLM 550 is optically addressed by the intensity-modulated light transmitted by the relay lens 540, phase-modulates the readout light, and generates phase-modulated light having a phase distribution corresponding to the intensity pattern of the intensity-modulated light. The PAL-SLM 550 has high spatial resolution and can modulate the phase by 2π or more.

  The PAL-SLM 550 includes a writing side transparent substrate 550a, a reading side transparent substrate 550b, a transparent electrode 550c, a photoconductive layer 550d, a mirror layer 550e, a liquid crystal layer 550f, and a transparent electrode 550g.

  The readout side transparent substrate 550b is formed of a transparent member such as glass. The transparent electrodes 550c and 550g are connected to an AC power source (not shown). The photoconductive layer 550d is made of, for example, amorphous silicon. The liquid crystal layer 550f is composed of a nematic liquid crystal in a horizontal alignment state. The liquid crystal molecules change the refractive index by rotating in a predetermined plane (in this example, in a plane parallel to the paper surface of the drawing) in accordance with a change in voltage applied to the liquid crystal layer 550f. The read light modulation section 40s includes a read side transparent substrate 550b, a transparent electrode 550g, and a liquid crystal layer 550f.

  In the PAL-SLM 550 configured as described above, the writing-side transparent substrate 550a faces the relay lens 540, and the reading-side transparent substrate 550b faces the reading light incident side and the beam sampler 50. The readout light is incident obliquely on the readout side transparent substrate 550b, propagates in the liquid crystal layer 550f, is reflected by the mirror layer 550e, propagates again in the liquid crystal layer 550f, and exits obliquely from the readout side transparent substrate 550b. The beam sampler 50 is reached.

  When intensity-modulated light emitted from the LCD 530 enters and forms an image on the photoconductive layer 550d via the relay lens 540, the voltage applied to the liquid crystal layer 550f changes. The liquid crystal layer 550f produces an ECB (Electrically Controlled Birefringence) effect in which the liquid crystal molecules rotate and the birefringence changes when the applied voltage changes. The readout light incident on the readout side transparent substrate 550b is phase-modulated by the ECB effect when propagating through the liquid crystal layer 550f. The phase-modulated light is reflected by the mirror layer 550e, propagates again through the liquid crystal layer 550f, is further phase-modulated, and then exits as phase-modulated light.

  Here, the pixels of the LCD 530 are projected onto the PAL-SLM 550 by the relay lens 540 and form virtual pixels (hereinafter referred to as “pixels of the PAL-SLM 550”) in the liquid crystal layer 550f of the modulation unit 40s. The pixels of the PAL-SLM 550 are arranged on the pixels of the LCD 530 on a virtual plane (hereinafter referred to as “modulator side two-dimensional plane (X, Y)”) orthogonal to the optical axis of the relay lens 540 in the liquid crystal layer 550f. Correspondingly, they are arranged in a two-dimensional matrix. 1 and 2, the X direction of the modulation device side two-dimensional plane (X, Y) is a direction penetrating the paper surface, and the Y direction is a direction parallel to the paper surface. Here, the number of pixels of the PAL-SLM 550 is equal to the number of pixels of the LCD 530. Since the imaging magnification of the relay lens 540 is 1, the pixel size of the PAL-SLM 550 is equal to the pixel size P1 of the LCD 530, and the pixel pitch of the PAL-SLM 550 is equal to the pixel pitch of the LCD 530. Thus, all the pixels of the PAL-SLM 550 are arranged on the modulation device side two-dimensional plane (X, Y) with the same size and pitch as the all pixels of the LCD 530.

  3A shows a cross section A of the liquid crystal layer 550f along the two-dimensional plane (X, Y) on the modulator side, that is, the liquid crystal layer 550f along the line III (a) -III (a) in FIG. Section A is shown schematically. Although not shown, all the pixels of the PAL-SLM 550 are arranged in a two-dimensional matrix in the cross section A of the liquid crystal layer 550f. Now, when the readout light is incident on the liquid crystal layer 550f, a substantially circular readout light incidence region B is formed in the cross section A. In particular, when an undistorted (plane wave) parallel beam (hereinafter referred to as reference light) is incident on the liquid crystal layer 550f as the readout light, the reference light incident area B0 is formed as the readout light incident area B as shown in FIG. It is formed at a substantially central position in the cross section A. In the present embodiment, a circular control point region C is set in a part of the cross section A. Outside the control point region C, a non-control point region D surrounding the control point region C is set. The control point area C has a larger size than the reference light incident area B0, and is set to a position that completely includes the reference light incident area B0. In other words, the control point region C includes the reference light incident region B0 and the annular region E surrounding the reference light incident region B0. The control point area C is an area for performing phase distortion correction. That is, the pixels located in the control point region C (hereinafter referred to as control points) function to perform phase modulation of the readout light. On the other hand, the non-control point region D is a region where phase distortion correction is not performed. That is, the pixels located in the non-control point region D do not perform phase modulation.

The control point located at the center of the reference light incident area B0, that is, the intersection of the optical axis of the reference light and the liquid crystal layer 550f is particularly called the control point origin, and its two-dimensional coordinates are ( _Xcontour , _Ycontour ). Represented by Further, the two-dimensional coordinates of each pixel of the PAL-SLM 550 are represented by (X, Y). Among the all pixels of the PAL-SLM 550, the two-dimensional coordinates of the control points are expressed in particular as (X _cont , Y _cont ). The two-dimensional coordinates _{(X, Y), (X} cont, Y cont), (X contorg, Y contorg) X _{in, Y, X cont, Y cont} , X contorg, Y contorg the modulation apparatus 2 dimensional plane An integer indicating on the (X, Y) the pixel is located at a position shifted ±± from the origin (0, 0) of the modulation device side two-dimensional plane (X, Y) in the X and Y directions. It is.

FIG. 3B shows an enlarged partial region F in the cross section A shown in FIG. In the region F, a part of the boundary between the reference light incident region B0 and the annular region E and a part of the boundary between the annular region E and the non-control region D are included. As shown in FIG. 3B, pixels (X, Y) are arranged in the region F. In particular, control points (X _cont , Y _cont ) are arranged in the reference light incident area B 0 and the annular area E.

When the readout light has no distortion, the readout light incident area B has the position and size indicated by B0 in FIG. 3A as described above. On the other hand, when the readout light has a distortion, the size and position of the readout light incident area B vary depending on the distortion. For example, the reading light incident area B has a size and a position indicated by B1, or has a size and a position indicated by B2, as shown in FIG. 3C, depending on the distortion of the reading light. It becomes like. In the present embodiment, as described with reference to FIG. 3A, the control point region C is set sufficiently wide with respect to the readout light incident region B (B0) formed when the readout light is not distorted. doing. For this reason, even if the position and size of the readout light incident area B change to the sizes and positions of B1 and B2 shown in FIG. 3C, the control point area C continues to include the readout light incident area B. Thus, it is ensured that the readout light always enters the control point region C and continues to be phase-modulated by the control points (X _cont , Y _cont ) regardless of the presence or absence of distortion of the readout light.

  Next, the wavefront detection device 60 will be described with reference to FIG.

  The wavefront detection device 60 is a Shack-Hartmann wavefront detector (Shack-Hartmann wavefront sensor (SHS)). The wavefront detection device 60 is disposed at a position for receiving the reflected light from the beam sampler 50 (FIG. 1). The wavefront detection device 60 includes a lens array 610 and an image sensor 620. The lens array 610 is a plurality of two-dimensionally arranged on a plane orthogonal to the optical axis of the reflected light from the beam sampler 50 (hereinafter referred to as “measurement device side two-dimensional plane (x, y)”). It is composed of a small lens 612. In this example, the plurality of small lenses 612 are arranged in a matrix. The diameter of the small lens 612 is larger than the pixel size P1 of the PAL-SLM 550 in this example. 1 and 4, the x direction of the two-dimensional plane (x, y) on the measurement device side is a direction that penetrates the paper surface, and the y direction is a direction parallel to the paper surface.

  The image sensor 620 includes, for example, a CCD camera, a high-speed vision sensor, a CMOS sensor, or other light intensity distribution detection device. The light receiving surface 620 s of the image sensor 620 is disposed on the focal plane of the lens array 610 so as to be orthogonal to the optical axis of the lens array 610. A plurality of pixels (hereinafter referred to as “measurement points”) are two-dimensionally arranged on the light receiving surface 620s.

As shown in FIG. 4, when the readout light output from the wavefront modulation device 40 enters the lens array 610 through the beam sampler 50, the wavefront 630 is divided into small wavefronts 631 for each small lens region 601 by the lens array 610. Then, a condensing spot array is formed on the light receiving surface 620s. The image sensor 620 captures an image of the condensing spot array formed on the light receiving surface 620s. The image sensor 620 includes an analog-to-digital conversion unit (not shown), converts a captured analog image signal into a digital image signal, and outputs the digital image signal to the control device 80. In addition, it is located in the position nearest to the optical axis of reference light among the multipoint spot images obtained when the reference light without distortion enters the PAL-SLM 550 and reaches the wavefront detection device 60 without being modulated by the PAL-SLM 550. A measurement point located on the intersection of the center of gravity of the spot (center spot) and the light receiving surface 620s is referred to as a measurement point origin. The two-dimensional coordinates of the measurement point origin are represented as (x _sensor , y _sensor ). The measurement point origin (x _sensor , y _sensor ) is at a substantially conjugate position with respect to the control point origin (X _contour , Y _contour ). The two-dimensional coordinates of the measurement points arranged on the light receiving surface 620s are represented as (x _sens , y _sens ). Here, two-dimensional coordinates of the pixel _{(x sens, y sens),} (x sensorg, y sensorg) x in _{sens, y sens, x sensorg,} y sensorg is the in the measuring apparatus 2-dimensional plane (x, y) It is an integer indicating how many pixels the pixel is deviated from the origin (0, 0) of the measurement device side two-dimensional plane (x, y) in the x and y directions.

In the present embodiment, the difference between the wavefront shape 630 of the readout light reflected by the beam sampler 50 and entering the lens array 610 and the ideal wavefront shape is expressed as 2 on the measurement device side two-dimensional plane (x, y). It is represented by a dimensional function W (x, y). Note that the xy coordinate value is expressed in polar coordinates as shown in Equation 1.

" Note that the partial slope of the function W (x, y) with x and y yields the local slope of the wavefront indicated by the function W (x, y). Here, the x and y partial differentiation of the function W (x, y) is defined by the following Equation 2.

"

In the present embodiment, it is assumed that the function W (x, y) is a two-dimensional Zernike polynomial W (ρ, θ) represented by Expression 3.

Here, ρ = r / r ₀ . r ₀ is the size of the unit circle of the Zernike polynomial and is a value depending on the predetermined beam diameter of the readout light incident on the lens array 610. K is the number of terms of a Zernike polynomial. The function Z _k (ρ, θ) of each term is a predetermined function. For example, the function Z _k (ρ, θ) of the first item (k = 1) to the tenth item (k = 10) is defined by the following Expression 4.

Further, among all the measurement points (x _sens , y _sens ) arranged on the light receiving surface 620 s, the control point corresponding measurement points (x _sens-cont , y _sens-cont ) are expressed by PAL-SLM 550 according to the following Expression 5. The control points are associated with the control points (X _cont , Y _cont ) above.

Here, Ps = Pl / (r ₀ × m). Note that Pl is the pixel size of the PAL-SLM 550, r ₀ is the size of a unit circle of the Zernike polynomial, and m is a relay lens (not shown) provided between the PAL-SLM 550 and the image sensor 620. Imaging magnification. The measurement point origin (x _sensor , y _sensor ) is associated with the control point origin (X _contour , Y _contour ).

  Next, returning to FIG. 1, the control device 80 will be described.

  The control device 80 is composed of, for example, a personal computer, and includes a CPU 81, a RAM 82, a hard disk 83, a ROM 84, a recording medium reading device 85 for reading data and parameters from a recording medium 90 such as a hard disk, a flexible disk, a CD-ROM, and a DVD. In addition to the input / output interface 86, a network connection device (not shown) and the like are provided. An electronic circuit (not shown) for electrically addressing the LCD 530 is connected to the control device 80 via the input / output interface 86.

In the hard disk, a control program, a wavefront code composed of data of function Z _k (ρ, θ) for 65 terms (k = 1 to 65) of the Zernike polynomial, a control point origin (X _contour , Y _contour ), The measurement point origin (x _sensor , y _sensor ) and the look-up table T are stored.

The look-up table T shows the relationship between the signal level of the control signal to be input to the LCD 530 and the phase modulation amount achieved by the PAL-SLM 550. An example of the lookup table T is shown in Table 1 below.

  The luminance value of the LCD 530 is 256 gradations from 0 to 255. The look-up table T represents each luminance value as an index (I) of 0 to 255. The look-up table T stores a 0 to 1 converted phase value (IN) and a signal level (OUT) for each index (I). The signal level (OUT) is a value of a control signal to be given to the LCD 530 in order to output writing light having a corresponding luminance (I). The 0 to 1 equivalent phase value (IN) is 0 or more and 1 or less in units of one wavelength (2π), which is the amount of phase modulation achieved by the PAL-SLM 550 when the LCD 530 outputs writing light with the corresponding luminance (I). It is shown as the value of. As is clear from Table 1, the 0-1 converted phase value (IN) and the signal level (OUT) are in a non-linear relationship.

  The control device 80 controls the wavefront modulation device 40 and the wavefront detection device 60 by the CPU 81 executing a control program and performing the processing shown in the flowcharts of FIGS. More specifically, the control device 80 performs a calculation using the multipoint spot image signal input from the wavefront detection device 60, creates feedback control data based on the calculation result, and the wavefront modulation device 40 based on the feedback control data. Closed loop feedback control.

  Here, the control program and the wavefront code are stored in advance in a recording medium 90 such as a flexible disk, a CD-ROM, or a DVD, and are read by the recording medium reading device 85 and stored in the hard disk 83.

On the other hand, the control point origin _{(X contorg, Y contorg)} and the measurement point origin _{(x sensorg, y sensorg)} and a look-up table T, created by set-up work, are stored in the hard disk 83. The setup operation is performed when the wavefront detection device 60 or the wavefront modulation device 40 is changed, such as in the manufacturing stage of the wavefront compensation apparatus 1 or the installation stage at the use site. The setup work includes setup of the wavefront modulation device 40, setup of the wavefront detection device 60, and setup of the lookup table T.

In setting up the wavefront detection device 60, the reference light is incident on the wavefront modulation device 40. The PAL-SLM 550 is set in a non-driven state or a uniform pattern is displayed on the LCD 530. A spot closest to the beam center (that is, the optical axis of the reference light) is set as a central spot in one multi-point spot image formed on the image sensor 620 through the beam splitter 50 and the lens array 610. . The center of gravity of the center spot is examined, and the pixel where the center of gravity is located (that is, the pixel at the intersection of the center of gravity and the light receiving surface 620s) is selected. The coordinates of the selected pixel are set as the measurement point origin (x _sensor , y _sensor ). The light beam passing through the measurement point origin (x _sensor , y _sensor ) is hereinafter referred to as a reference axis light beam.

In the setup of the wavefront modulation device 40, the pixel at the position where the reference axis ray passing through the measurement point origin (x _sensor , y _sense ) determined by the setup of the wavefront detection device 60 intersects the liquid crystal layer 550 f is used as the control point origin ( X _contour , Y _contour ). In this way, the control point origin (X _const , Y _cont ) is determined at a position that is substantially conjugate with the measurement point origin (x _sensor , y _sensor ).

  In the setup of the lookup table T, the input index to the LCD 530 is sequentially changed from 0 to 255, the phase change by the PAL-SLM 550 at that time is measured, and the correspondence table (Table 1) of the index and the phase change is created and looked up. Set as table T.

  Next, the operation of the control device 80 will be described in detail with reference to FIGS.

  FIG. 5 shows an operation block diagram of the control device 80.

  As shown in FIG. 5, in the control device 80, the input unit 100 inputs data and parameters necessary for processing. The wavefront calculation unit 200 uses the detection result of the wavefront detection device 60, the data and parameters input from the input unit 100, and the residual indicating the phase difference between the wavefront of the light output from the wavefront modulation device 40 and the ideal wavefront. Calculate the difference wavefront. The wavefront calculation unit 200 outputs the calculation result to the control data synthesis unit 300. The control data synthesis unit 300 creates feedback control data using the residual wavefront from the wavefront calculation unit 200, data from the input unit 100, and parameters. The converter 400 converts the feedback control data into a control signal and sends it to the controller 500. The controller 500 sends a control signal to the wavefront modulation device 40 to drive and control the wavefront modulation device 40.

  FIG. 6 shows an operation block diagram of the input unit 100.

  As shown in FIG. 6, in the input unit 100, the wavefront data input unit 110 inputs initial control data I (X, Y) indicating an ideal wavefront. The initial control data I (X, Y) indicates the phase value at all pixel points (X, Y) in the all pixel point region A. The parameter input unit 120 inputs various parameters necessary for driving the wavefront compensation device 1. The parameters include various parameters described below in addition to the feedback coefficient f. A memory unit 130 is prepared in the RAM 82. Data and parameters input by the wavefront data input unit 110 and the parameter input unit 120 are stored in the memory unit 130 and sent to the wavefront calculation unit 200 and the control data synthesis unit 300 as necessary.

  FIG. 7 shows an operation block diagram of the wavefront calculation unit 200.

In the wavefront calculation unit 200, the image input unit 210 receives a digital image signal from the wavefront detection device 60. An image memory 220 is prepared in the RAM 82. The digital image input from the image input unit 210 is stored in the image memory 220 and sent to the wavefront calculation unit 230 as necessary. The wavefront calculation unit 230 is based on the digital image from the image memory 220 and the data and parameters from the memory unit 130 (FIG. 6), and the wavefront 630 of the light actually output from the wavefront modulation device 40 and reaching the lens array 610. Data indicating the phase difference from the wavefront is calculated for each control point (X _cont , Y _cont ), and the data indicating the phase difference is determined as a residual wavefront R (X _cont , Y _cont ) for each control point. A calculation result memory 240 is prepared in the RAM 82. The data of the residual wavefront R (X _cont , Y _cont ), which is the calculation result of the wavefront calculation unit 230, is stored in the calculation result memory 240 and then sent to the control data synthesis unit 300.

  FIG. 8 shows a block diagram of the control data synthesis unit 300.

In the control data synthesis unit 300, the multiplication operation unit 310 multiplies the feedback coefficient f from the memory unit 130 and the residual wavefront R (X _cont , Y _cont ) for each control point from the calculation result memory 240. An aberration wavefront memory 340 is prepared in the RAM 82. Data indicating the aberration wavefront A (X _cont , Y _cont ) for each control point is stored in the aberration wavefront memory 340. The first addition operation unit 320 adds the multiplication result fxR (X _cont , Y _cont ) and the aberration wavefront A (X _cont , Y _cont ) currently stored in the aberration wavefront memory 340 for each control point, The result is overwritten and saved in the aberration wavefront memory 340 as a new aberration wavefront A (X _cont , Y _cont ). The second addition operation unit 330 adds the addition result of the first addition operation unit 320 and the initial control data I (X, Y) from the memory unit 130 for each control point, and feedback control for each control point. Data B (X _cont , Y _cont ) is created. A control data memory 350 is prepared in the RAM 82. The feedback control data B (X _cont , Y _cont ) is temporarily stored in the control data memory 350 and then sent to the conversion unit 400.

The initial control data I (X, Y) that is input to the wavefront data input unit 110 and stored in the memory unit 130 is a converted phase obtained by converting the phase value into a value of a ratio to one wavelength (2π). The value is shown. For example, when the phase value is π, the converted phase value is 0.5, and when the phase value is −2π, the converted phase value is −1. Thus, an input unit 100 and the wavefront calculation unit 200 and the control data combining unit 300, initial control data I (X, Y), the residual wavefront _{R (X cont, Y cont)} , aberration wavefront _{A (X cont, Y} cont ) And feedback control data B (X _cont , Y _cont ) are handled in the form of converted phase values in units of one wavelength (2π).

  FIG. 9 shows an operation block diagram of the conversion unit 400.

As shown in FIG. 9, a look-up table memory 420 is prepared in the RAM 82. The lookup table T is read from the hard disk 83 and stored in the lookup table memory 420. The converter 410 refers to the look-up table T and converts the feedback control data B (X _cont , Y _cont ) from the control data memory 350 into a control signal S (X _cont , Y _cont ). A control signal memory 430 is prepared in the RAM 82. The data of the signal level of the control signal S (X _cont , Y _cont ) is temporarily stored in the control signal memory 430 and then sent to the control unit 500. The control unit 500 outputs a control signal S (X _cont , Y _cont ) to the transparent pixel electrode on the LCD 530 corresponding to all the control points (X _cont , Y _cont ) in the control point region C of the PAL-SLM 550, and the LCD 530 The electric address is driven.

  Next, the operation of the wavefront compensation apparatus 1 will be described in more detail with reference to FIGS.

  As shown in FIG. 10, the CPU 81 first executes an initial process (step S1).

  The initial process is performed according to the procedure shown in FIG.

  First, the CPU 81 prepares a memory (step S11). Specifically, various memory areas necessary for processing such as the memory 130, the image memory 220, the calculation result memory 240, the aberration wavefront memory 340, the control data memory 350, and the feedback control data memory 430 are secured in the RAM 82. . Further, necessary resets are performed on the calculation result memory 240, the aberration wavefront memory 340, the control data memory 350, and the like. Specifically, memory values such as the calculation result memory 240, the aberration wavefront memory 340, and the control data memory 350 are initialized to “0”. The control signal memory 430 is also reset. Specifically, a control signal S (X, Y) to be first applied to all the pixels in the LCD 530 is stored in the control signal memory 430. In this example, since the ideal wavefront is a plane wave, the control signal S (X, Y) is zero (0) for all pixels (X, Y).

  Next, the CPU 81 reads parameters (step S12).

Specifically, the CPU 81 first reads the data of the measurement point origin (x _sensor , y _sensor ) and the control point origin (X _const , Y _cont ) from the hard disk 83 and stores them in the memory 130. Further, the data of the lookup table T is read from the hard disk 83 and stored in the lookup table memory 420.

If the wavefront detection device 60 or the wavefront modulation device 40 is changed at the manufacturing stage or the installation stage of the wavefront compensation device 1, the measurement point origin (x _sensor , y _sensor ), the control point origin in S 12. Instead of reading the data of (X _{cont rg} , Y _{cont g} ) and the look-up table T from the hard disk 83, the wave-front detection device 60, the wave-front modulation device 40, and the look-up table T are set up to create these data To do.

  In S 12, the CPU 81 further reads the initial control data I (X, Y) from the recording medium 90 and stores it in the memory 130. The CPU 81 may download the initial control data I (X, Y) from the network by controlling a network connection device (not shown).

  In this example, since the ideal wavefront is a plane wave, the initial control data I (X, Y) has 0 for all pixel points (X, Y).

  Next, the CPU 81 reads parameters from the parameter file stored in the recording medium 90 and stores them in the memory 130. The CPU 81 may download parameters from the network by controlling a network connection device (not shown).

The parameters include the wavelength λ of the readout light and a predetermined beam diameter, the pitch Pr of the lens array 610, the focal length Fr of the small lens 612, the pixel size Pc and the pixel pitch Ps of the image sensor 620, and the pixel size P1 and the pixel pitch of the LCD 530. And the number of pixels, the spatial positional relationship between the wavefront modulation device 40 and the wavefront detection device 60, the imaging magnification m of a relay lens system (not shown) disposed between the wavefront modulation device 40 and the wavefront detection device 60, and the bias shift threshold value , Evaluation threshold, centroid calculation range size, centroid validity evaluation parameter VMAX, VPV, VAREA, VEFF, polynomial data (specifically, the number K of terms of the Zernike polynomial to be used and Zernike units) Circle size r ₀ ) and feedback factor f included Yes.

  The center-of-gravity calculation range size is the size of the center-of-gravity calculation range CA used in the center-of-gravity calculation described later. The center-of-gravity calculation range CA is a rectangular area having a side smaller than the diameter of the small lens 612 or a circular area having a diameter smaller than the diameter of the small lens 612. Therefore, the center-of-gravity calculation range size is the length of the side when the center-of-gravity calculation range CA is a square region, and the length of the diameter when the center-of-gravity calculation range CA is a circular region. The center-of-gravity calculation range size is represented by the number of pixels equal to or larger than the integer obtained by rounding (1.22 · Fr · λ) / (Pr · Ps) and less than or equal to the integer obtained by rounding Pr / Ps. .

  The number K of terms of the Zernike polynomial is set as a value depending on the order of the aberration to be controlled. The term number K is a natural number of 65 or less in this example. Specifically, when it is desired to control the aberration up to the I-th order (where I is a natural number), the term number K is set so as to satisfy the equation K = I (I + 3) / 2.

  Next, the CPU 81 performs setup data processing (step S13).

The setup data process is a process for calculating various necessary data based on the parameters stored in the memory 130 in S12. Here, various necessary data are arranged on the light receiving surface 620s of all the pixels (X, Y) of the PAL-SLM 550, all the control points (X _cont , Y _cont ) located in the control point region C, and so on. All measurement points (x _sen , y _sens ), measurement points corresponding to all control points (x _sens-cont , y _sens-cont ), lens area data LA, reference centroid data RC (x, y), and partial differential data Q _k (ρ, θ), R _k (ρ, θ) and the like are included.

All pixels (X, Y) of the PAL-SLM 550 are set with reference to the control point origin (X _contour , Y _contour ). The control point region C is set as a region centered on the control point origin ( _Xcontour , _Ycontour ), including the reference light incident region B0, and larger than the reference light incident region B0 by the annular portion E. Then, all the control points _{(X cont, Y} cont) located at the control point area C is set the control point origin _{(X contorg, Y contorg)} as reference. The reference light incident area B0 is set as a circular area having a diameter equal to a predetermined beam diameter with the control point origin ( _Xcontour , _Ycontour ) as the center.

The coordinates (x _sens , y _sens ) of all measurement points arranged on the light receiving surface 620 s are set with reference to the measurement point origin (x _sensor , y _sensor ). A measurement point that satisfies Equation 5 among all measurement points (x _sens , y _sens ) is set as a control point corresponding measurement point (x _sens-cont , y _sens-cont ).

The lens area LA is set on the light receiving surface 620s corresponding to each small lens 612. Specifically, the lens area LA corresponds to each small lens 612, the intersection of the optical axis of the small lens 612 and the light receiving surface 620s is the center, and the width is the diameter of the small lens 612 or the small lens 612. It is a region that is substantially equal to the pitch. The shape of the lens area LA is set corresponding to the arrangement shape of the lens array 610. In this example, since the small lenses 612 are arranged in a matrix, the shape of the lens area LA is a quadrangle. The lens area LA corresponding to each small lens 612 is set by a plurality of measurement point coordinates (x _sens , y _sens ) included in the lens area LA.

Reference centroid data RC (x, y) is also defined for each small lens 612. The reference centroid RC (x, y) for each small lens 612 is the position of the centroid of the light spot formed by the small lens 612 condensing readout light having an ideal wavefront on the light receiving surface 620s. The reference centroid RC (x, y) is also set as a coordinate based on the measurement point origin (x _sensor , y _sensor ). In this example, since the ideal wavefront is a plane wave, the reference center-of-gravity data RC (x, y) corresponding to each small lens 612 is the coordinates of the intersection of the optical axis of the small lens 612 and the light receiving surface 620s.

The partial differential data Q _k (ρ, θ) and R _k (ρ, θ) are the polynomial terms k (k = 1 to 1) obtained by partial differentiation of the function W (ρ, θ) of Equation 3 with x and y. K) and is defined by Equation 6 below. Note that x and y are set with reference to the measurement point origin (x _sensor , y _sensor ), and ρ and θ satisfy Equation 1 and ρ = r / r ₀ for x and y. Is defined as a value to

The partial differential data Q _k (ρ, θ) and R _k (ρ, θ) are obtained by calculating the following Expression 7 based on the data of the function Z _k (ρ, θ) of the wavefront code.

  Next, the CPU 81 performs a driving process for making the PAL-SLM 550 operable (step S14).

  Next, the CPU 81 sets the image sensor 620 in a state in which an image can be taken and image data can be sent to the control device 80 (step S15).

  When the initial process of S1 is completed by the above procedure, the CPU 81 starts a feedback process.

  First, the CPU 81 performs wavefront measurement in step S2 (FIG. 10).

  The wavefront measurement is performed according to the procedure shown in FIG.

  First, the CPU 81 performs processing for capturing and saving an image (step S21).

  Specifically, the CPU 81 outputs the control signal S (X, Y) of the control signal memory 430 to all the pixels of the LCD 530. The LCD 530 emits the write light with the intensity modulated in accordance with the control signal S (X, Y), and enters the PAL-SLM 550. Read light having a phase distortion 30 (FIG. 1) and a predetermined beam diameter is incident on the PAL-SLM 550. The PAL-SLM 550 performs phase modulation on the read light according to the intensity pattern of the write light. The phase-modulated light emitted from the PAL-SLM 550 is divided by the beam sampler 50, a part of the light is transmitted, and the rest is reflected and enters the wavefront detection device 60. Here, the phase-modulated light incident on the wavefront detection device 60 has a wavefront 630. The wavefront 630 includes an ideal wavefront (initial control data I (X, Y) = 0), a phase distortion 30 caused by the disturbance factor 20 and the like, and other disturbance factors (for example, temporal variations in the phase modulation characteristics of the PAL-SLM 550). ) Is a wavefront formed by adding together the phase distortion.

  The light guided to the wavefront detection device 60 enters the lens array 610. The lens array 610 converges the incident light for each small region 601 and forms a multipoint spot image on the light receiving surface 620 s of the image sensor 620. The image sensor 620 captures an incident image, creates image data, and sends the image data to the control device 80. The CPU 81 stores image data in the image memory 220.

  Next, the CPU 81 performs a bias shift process on the image captured in the image memory 210 as an initial process for wavefront measurement (step S22).

  Specifically, the CPU 81 compares the pixel value (luminance) obtained at each pixel on the light receiving surface 620s with a bias shift threshold value. If the pixel value is smaller than the threshold value, the pixel value is changed to “0”. If the pixel value is larger than the threshold value, the difference between the pixel value and the threshold value is reset to the pixel value at that position. The CPU may further perform a smoothing process on the bias-shifted pixel value.

  Next, the CPU 81 calculates the center of gravity for each small lens 612 using the pixel value calculated in S22 (step S23).

  Specifically, the CPU 81 first obtains the maximum position of the pixel value in the lens area LA corresponding to each small lens 612. Next, based on the local maximum position and the centroid calculation range size data obtained for each small lens 612, the CPU 81 has a quadrangle or circular centroid having a centroid calculation range size centered on each local maximum position on the light receiving surface 620s. A calculation range (hereinafter referred to as “centroid calculation range CA”) is set. Further, the CPU 81 calculates the barycentric positions of the pixel values of a plurality of pixels located within the barycentric calculation range CA obtained for each small lens 612.

  Specifically, the center of gravity of the focused spot formed by each small lens 612 (jth (j is a natural number of 1 or more) th small lens 612 (j)) is obtained as follows.

  First, a pixel having a maximum pixel value is selected from the pixels located in the lens area LA (j) corresponding to the small lens 612 (j). The lens area LA (j) is a quadrangular area centered on the point where the optical axis of the corresponding small lens 612 (j) intersects the light receiving surface 620s. Next, a pixel located within the center-of-gravity calculation range CA (j) centered on the position of the maximum value is selected. The center-of-gravity calculation range CA (j) is a circular or quadrangular region having a center-of-gravity calculation range size centered on the position of the maximum value. Next, the barycentric position of the pixel value of the pixel located in the barycentric calculation range CA (j) is calculated. In this way, the center of gravity C (j) (x, y) with respect to the j-th small lens 612 (j) is obtained.

  If there are two or more maximum values in the lens area LA (j), a pixel corresponding to the geometric center of two or more pixels having the maximum value is calculated by proportional distribution, and this pixel is determined as the maximum value. Determine as position. Specifically, for example, the maximum value is obtained at five pixels (240, 250), (241, 250), (239, 250), (240, 251), and (240, 252) in the lens area LA (j). Is obtained. In this case, these five geometric centers can be calculated as (240, 250.6). For this reason, the pixel (240, 251) is determined as the maximum value position based on the value 251 obtained by rounding off 250.6. A circular or quadrangular area centered on the pixel (240, 251) and having the centroid calculation range size is set as the centroid calculation range CA (j), and the centroid is calculated for the pixel values in the centroid calculation range CA (j). .

  Next, the CPU 81 evaluates the center of gravity effectiveness (step S24).

  That is, the CPU 81 evaluates the effectiveness of the center-of-gravity calculation range CA set for each small lens 612 in S23. Here, for each small lens 612, the CPU 81 determines the maximum pixel value of the pixels in the centroid calculation range CA, the difference between the maximum value and the minimum value (hereinafter referred to as the maximum and minimum difference), and the centroid calculation range CA. The total number of pixels whose pixel values exceed the evaluation threshold (hereinafter referred to as threshold area) and the pixel value distribution near the center in the centroid calculation range CA (hereinafter referred to as center pixel value distribution) are calculated. . Here, the center pixel value distribution is an average value of nine pixel values located in a 3 × 3 square area centered on a pixel (that is, a maximum value pixel) located at the center of the center of gravity calculation range CA. This is a value divided by the center pixel value (that is, local maximum value) in the center of gravity calculation range CA. The CPU 81 also reads out the centroid validity evaluation parameters VMAX, VPV, VAREA, and VEFF from the memory 130. Here, VMAX is a threshold value for the maximum value, VPV is a threshold value for the maximum / minimum difference, VAREA is a threshold value for the threshold area, and VEFF is a threshold value for the central pixel value distribution. The CPU 81 compares the calculated maximum value, maximum / minimum difference, threshold area, and central pixel value distribution with VMAX, VPV, VAREA, and VEFF, respectively. Based on the comparison result, the CPU 81 determines whether or not the center-of-gravity calculation range CA set for the small lens 612 is valid.

Specifically, for the centroid calculation range CA (j) for each small lens 612 (jth small lens 612 (j)), the CPU 81 determines the maximum pixel value Vmax (j in the centroid calculation range CA (j). ), The difference Vmax (j) −Vmin (j) between the maximum value Vmax (j) and the minimum value Vmin (j), the threshold area Varea (j), and the central pixel value distribution Veff (j). The CPU 81 compares Vmax (j) and VMAX, Vmax (j) −Vmin (j) and VPV, Varea (j) and VAREA, Veff (j) and VEFF, and compares the following four conditions (1) to ( Determine whether at least one condition of 4) is fulfilled:
(1) Vmax (j) <VMAX;
(2) Vmax (j) −Vmin <VPV;
(3) Varea (j) <VAREA; and (4) Veff (j) <VEFF.

  When at least one of the conditions (1) to (4) is satisfied, the CPU 81 determines that the centroid calculation range CA (j) for the j-th small lens 612j is invalid, and thus the centroid C (j ) (X, y) is determined to be invalid. On the other hand, when none of the conditions (1) to (4) is satisfied, the center-of-gravity calculation range CA (j) of the j-th small lens 612j is valid, and therefore the center of gravity C (j ) (X, y) is determined to be valid.

  Next, the CPU 81 reads the reference centroid data RC (x, y) for each small lens 612 from the memory unit 130, and calculates the centroid shift (δx, δy) for each small lens 612 (step S25). Here, the center-of-gravity shift (δx, δy) for each small lens 612 is the center-of-gravity position C (x, y) calculated in S23 for the small lens 612 and the reference center-of-gravity position RC ( x, y) in the x-axis direction and the y-axis direction. For the small lens 612 in which the center of gravity is determined to be invalid in S24, the center of gravity shift (δx, δy) = (0, 0) is forcibly set.

Next, the CPU 81 performs a wavefront equation calculation process (step S26). In the present embodiment, the wavefront equation indicating the wavefront shape of the phase difference between the wavefront 630 incident on the lens array 610 and the ideal wavefront has the form of a Zernike polynomial W (ρ, θ) of Equation 3. Assume that However, the weighting coefficient A _k (where k = 1 to K) is unknown among the Zernike polynomials W (ρ, θ) of Equation 3. Therefore, in this step, the center of gravity shifts the weight coefficient _{A k (δx, δy)} determined based on to determine the Zernike of formula 3 (Zernike) polynomial W (ρ, θ).

  Hereinafter, a method for determining the Zernike polynomial W (ρ, θ) will be described in detail.

Here, the local inclination at the position on the optical axis of each small lens 612 in the wavefront equation W (ρ, θ) is proportional to the centroid shift (δx, δy) with respect to the small lens 612. Therefore, for each small lens 612, the x and y partial differentiation of the wavefront equation W (ρ, θ) and the centroid shift (δx, δy) should be in the relationship of Equation 8.

The proportionality constant c is a parameter determined by the system configuration, and is represented by c = r ₀ · Pc / (λ · Fr). Note that r ₀ is the size of a unit circle in which a Zernike polynomial is defined, Pc is the pixel size of the image sensor 620, Fr is the focal length of the small lens 612, and λ is the wavelength of the readout light.

Therefore, CPU 81, as follows, performs fitting by applying the least squares method to the equation 8 to calculate the weighting coefficients _{A k} of the respective terms of the Zernike (Zernike) polynomial W (ρ, θ).

Specifically, the evaluation formula is defined as shown in Formula 9.

Here, N is the total number of small lenses 612, and n (n = 1 to N) indicates each small lens 612. Equation 9 is rewritten as Equation 10 below according to Equation 6.

In order for the evaluation formula of Formula 10 to be the minimum value, the partial differential formula of Formula 10 needs to be 0 with respect to all A _k (where k = 1, 2,..., K). In other words, the condition that the evaluation formula 10 becomes the minimum value is expressed by the following simultaneous equations 11.

Each expression δΔ / δA _k = 0 (where k = 1, 2,..., Or K) of Expression 11 is expressed by Expression 12 below.

Here, k = 1, 2,..., Or K. In other words, the simultaneous equations 11 include a total of K expressions 12 having different values of k (i.e., expression 12 with k = 1, expression 12 with k = 2, expression 12 with k = 3,..., And the following equation 12) where k = K. Thus, K following simultaneous equations to unknown all the K weighting coefficients A ₁ to A _K is obtained.

Next, the CPU 81 finds solutions A _{1 to} A _K of the simultaneous equations 11. Specifically, the CPU 81 performs two operations by numerical calculation by a computer. The first calculation is a K × K matrix composed of Q _k1 (ρ, θ) Q _k (ρ, θ) and R _k1 (ρ, θ) R _k (ρ, θ) on the left side of Equation 12. This is an operation for calculating an inverse matrix. The second operation is an operation for calculating the multiplication of the inverse matrix obtained by the first operation and the vector composed of Q _k (ρ, θ) and R _k (ρ, θ) on the right side of Expression 12. is there. Thus, to determine the total of K weighting coefficients _A 1 to A _K.

The weighting factor A ₁ to A _K thus obtained substituted into Equation 3, the function W (ρ, θ) representing the wavefront shape of the phase difference between the wavefront 630 and the ideal wavefront incident on the lens array 610 to determine the . In this example, since the ideal wavefront is a plane wave, the function W (ρ, θ) indicates the phase of the wavefront 630 incident on the lens array 610. Here, since the function W (ρ, θ) is defined with respect to ρ, θ, the function W (ρ, θ) is changed to x, y based on Equation 1 and ρ = r / r _0. The function W (x, y) is defined.

Next, the CPU 81 performs a calculation for _obtaining a residual wavefront R (X _cont , Y _cont ) at all control points (X _cont , Y _cont ) in the control point region C using the wavefront equation W (x, y). (Step S27).

Specifically, the CPU 81 assigns each control point corresponding measurement point (x _sens-cont , y _sens-cont ) to the wavefront equation W (x, y), and then each control point corresponding measurement point (x _sens-cont). , Y _{sens- cont} ) to calculate a phase value W (x _sens-cont , y _sens-cont ). The calculated phase value W (x _sens-cont , y _sens-cont ) is modulated by the corresponding control point (X _cont , Y _cont ) on the PAL-SLM 550 and the phase pattern of the readout light reaching the lens array 610 The phase difference from the ideal wavefront is shown. In this example, since the ideal wavefront is a plane wave, the phase value W (x _sens-cont , y _sens-cont ) is modulated by the corresponding control point (X _cont , Y _cont ) on the PAL-SLM 550 and the lens. The phase pattern of the readout light that has reached the array 610 is shown. The CPU 81 sets the phase value W (x _sens-cont , y _sens-cont ) as residual wavefront data R (X _cont , Y _cont ) for the corresponding PAL-SLM control point (X _cont , Y _cont ). And stored in the calculation result memory 240. Thus, the wavefront measurement procedure in step S2 is completed.

Thus, the residual wavefront R (X _cont , Y _cont ) at all control points (X _cont , Y _cont ) in the control point region C can be calculated using the wavefront equation W (ρ, θ). Here, for the control point (X _cont , Y _cont ) in the reading light incident region where the reading light is actually incident in the control point region C, the obtained residual wavefront R (X _cont , Y _cont ) represents the phase difference between the wavefront of the readout light actually incident on the PAL-SLM 550 and modulated and the ideal wavefront. On the other hand, the residual wavefront R (X _cont , Y _cont ) obtained for the control point (X _cont , Y _cont ) in the area surrounding the readout light incident area in the control point area C is controlled by the readout light. The phase difference between the wavefront estimated to be included in the readout light and the ideal wavefront when it is assumed that the light is incident and modulated over the entire point region C is shown.

  Next, the CPU 81 synthesizes control data as shown in FIG. 10 (step S3).

  The control data combining process in S3 is performed according to the procedure shown in FIG.

As shown in FIG. 13, the CPU 81 multiplies the residual wavefront R (X _cont , Y _cont ) for each control point stored in the calculation result memory 240 by the feedback coefficient f (step S31).

Here, the feedback coefficient f is a numerical value of 1 or less and a kind of gain. The feedback coefficient is obtained by adding a percentage of the residual wavefront R (X _cont , Y _cont ) to the initial control data I (X _cont , Y _cont ) of the corresponding control point (X _cont , Y _cont ). Indicates whether feedback should be provided. By adjusting the feedback coefficient f, it is possible to adjust the degree of convergence until the phase pattern close to the ideal wavefront is corrected, the number of closed-loop feedbacks, and the like. Note that the value of the feedback coefficient f may vary depending on the number of feedback loops, and may be constant regardless of the number of feedback loops.

  In this example, the feedback coefficient in the first measurement is 1. Therefore, 100% of the residual wavefront obtained by measurement is used for feedback. Since the second feedback coefficient is 0.2, 20% of the residual wavefront obtained by measurement is used for feedback. The first feedback coefficient may not be 1. Also, the second feedback coefficient may be another numerical value, for example, 0.1, 0.05, 0.32, or the like.

Next, the CPU 81 uses the multiplication result “fxR (X _cont , Y _cont )” obtained in step S31 and the aberration wavefront A (X _cont , Y _cont ) currently stored in the aberration wavefront memory 340 as control points. Add together for each (X _cont , Y _cont ) (step S32). Note that the value “0” is initially set as the aberration wavefront A (X _cont , Y _cont ) of all control points (X _cont , Y _cont ).

The CPU 81 overwrites and saves the addition result “A (X _cont , Y _cont ) + fxR (X _cont , Y _cont )” in the aberration wavefront memory 340 as a new aberration wavefront A (X _cont , Y _cont ) (step S33). .

Next, in S <b> 34, the CPU 81 reads a new aberration wavefront A (X _cont , Y _cont ) for each control point (X _cont , Y _cont ) from the aberration wavefront memory 340. The CPU 81 also reads the ideal wavefront I (X _cont , Y _cont ) (in this example, I (X _cont , Y _cont ) = 0) from the memory 130 for each control point. The CPU 81 adds the ideal wavefront I (X _cont , Y _cont ) and the new aberration wavefront A (X _cont , Y _cont ) for each control point. The CPU 81 stores the addition result in the control data memory 350 as new control data for each control point (X _cont , Y _cont ), that is, feedback control data B (X _cont , Y _cont ) (step S35).

  This is the end of the control data composition procedure in step S3.

  Next, the CPU 81 performs a look-up table process as shown in FIG. 10 (step S4).

  The lookup table processing in S4 is performed according to the procedure shown in FIG.

As shown in FIG. 14, CPU 81 is feedback control data _{B (X cont, Y} cont) of the respective control points from the control data memory 350 reads out the feedback control data _{B (X cont, Y} cont) the integer part of the zero By converting, the feedback control data B (X _cont , Y _cont ) is converted into a value consisting only of the decimal part (step S41). For example, when the feedback control data B (X _cont , Y _cont ) read from the control data memory 350 is 0.51, 1.2, −0.4, or −2.34, 0 is set respectively. Convert to .51, 0.2, -0.4, -0.34.

Next, the CPU 81 determines whether or not the feedback control data B (X _cont , Y _cont ) converted in step S41 is a negative number, and if it is a negative number, the following processing is performed. This is performed (step S42). That is, the CPU 81 adds 1 to the feedback control data B (X _cont , Y _cont ) to convert it to a positive number, and resets the converted value as the feedback control data B (X _cont , Y _cont ). On the other hand, if the feedback control data B (X _cont , Y _cont ) converted in step S41 is positive, the value is set as the feedback control data B (X _cont , Y _cont ). In this way, the folding process is performed by executing steps S41 and S42.

For example, when the feedback control data B (X _cont , Y _cont ) converted in step S41 is −0.4 or −0.34, 1 + (− 0.4) = 0.6, Reset to 1 + (− 0.34) = 0.66. On the other hand, when the feedback control data B (X _cont , Y _cont ) converted in step S41 is 0.51 or 0.2, the values 0.51 and 0.2 are set as they are. Thus, the feedback control data B (X _cont , Y _cont ) is converted into a phase value of 0 or more and less than 1.

Next, the CPU 81 refers to the look-up table T in the look-up table memory 420 based on the value of the feedback control data B (X _cont , Y _cont ) converted to a phase value of 0 or more and less than 1 in step S42. The feedback control data B (X _cont , Y _cont ) is converted into a control signal S (X _cont , Y _cont ) (step S43). Here, assuming that IN (I) and OUT (I) are 0 to 1 converted phase values and signal levels in the index I (= 0 to 255) in the lookup table T, IN (I) ≦ The index I (0 to 255) satisfying B (X _cont , Y _cont ) <IN (I + 1) is selected, and the value of OUT (I) corresponding to the index I is the signal of S (X _cont , Y _cont ) Set as level.

Next, the CPU 81 overwrites and saves the control signal S (X _cont , Y _cont ) in the control signal memory 430 as a new control signal for each control point (X _cont , Y _cont ) (step S44).

  Thus, the procedure of step S4 is completed.

Subsequently, the CPU 81 updates the control signal as shown in FIG. 10 (step S5). In other words, the CPU 81 controls an electronic circuit (not shown) via the input / output interface 86, so that the control signal S (X _cont , Y _cont ) for each control point newly stored in the control signal memory 430 is controlled. Input to the transparent pixel electrode in the LCD 530 corresponding to the point (X _cont , Y _cont ). When the updated control signal S (X _cont , Y _cont ) is input to the LCD 530, the PAL-SLM 550 outputs read light with a phase modulation amount corresponding to the updated feedback control data B (X _cont , Y _cont ). Modulate. Note that the control signal S (X, Y) = 0 is continuously input to the pixels on the LCD 530 corresponding to the pixels (X, Y) in the non-control point region D as usual. Accordingly, the pixel (X, Y) in the non-control point region D of the PAL-SLM 550 does not perform phase modulation of the readout light.

  The wavefront compensation apparatus 1 is closed-loop feedback controlled by the above procedure.

  Thereafter, the CPU 81 determines whether or not to end a series of phase modulation procedures (step S6).

For example, if the residual wavefront R (X _cont , Y _cont ) calculated in step S2 becomes less than a predetermined value at all control points, the CPU 81 determines that the phase modulation procedure should be terminated (step Yes in S6) Proceed to step S7. On the other hand, while the residual wavefront R (X _cont , Y _cont ) at any one of the control points (X _cont , Y _cont ) is greater than or equal to a predetermined value, the CPU 81 determines that the phase modulation procedure should not be terminated ( You may make it return to step S2 and repeat closed loop feedback control by No in step S6.

Here, the aberration wavefront A _i (X _cont , Y _cont ) and feedback control data B _i (X _cont ) obtained in the feedback routines S2 to S6 executed at an arbitrary i-th time (where i is a positive number of 1 or more). , Y _cont ) can be _summarized as follows.

i-th aberration wavefront A _i (X _cont , Y _cont ) = f _i × R _i (X _cont , Y _cont ) + (i−1) -th aberration wavefront A _i-1 (X _cont , Y _cont ),

i-th feedback control data B _i (X _cont , Y _cont ) = A _i (X _cont , Y _cont ) + I (X _cont , Y _cont )

Here, f _i is the feedback coefficient used in step S31 in the i-th feedback routine, and R _i (X _cont , Y _cont ) is the residual wavefront R (X) obtained in step S27 in the i-th feedback routine. _cont , Y _cont ). The aberration wavefront A ₀ (X _cont , Y _cont ) = 0.

If it is determined that the phase modulation procedure should be terminated (Yes in step S6), the CPU 81 performs a termination process (step S7). Specifically, the memory 130 is opened, the application of the control signal to the LCD 530 is stopped, the driving of the PAL-SLM 550 is ended, and the driving of the wavefront detection device 60 is ended. When the setup operation is performed in step S12, the data (control point origin ( _Xcontour , _Ycontour ), measurement point origin ( _xsensor , _ysensor )) and the lookup table T created in the setup operation are _compared . Data) is stored in the hard disk 83.

In S7, for example, the CPU 81 controls the control signal S (based on the feedback control data B (X _cont , Y _cont ) obtained in the last feedback routine until the generation of the readout light is stopped by the external switch. X _cont , Y _cont ) may continue to be input to the LCD 530. When the generation of the reading light is stopped, the memory 130 is opened and the driving of the LCD 530, the PAL-SLM 550, and the wavefront detection device 60 is ended.

  The result of wavefront compensation by the wavefront compensation device 1 operating as described above will be described with reference to FIGS. 15 to 16 (e).

  FIG. 15 is a diagram illustrating an average value of the residual wavefronts obtained when the closed-loop feedback control is repeated up to 40 times in the wavefront compensation apparatus 1. The horizontal axis represents the number of feedbacks in the closed-loop feedback control, and the vertical axis represents the average of the residual wavefront as a ratio to the wavelength (2π).

  As shown in FIG. 15, it can be seen that the residual wavefront gradually converges to a constant value as the number of feedback increases. That is, by repeatedly performing the closed-loop feedback control, it is possible to reduce wavefront distortion and obtain desired phase-modulated light close to the ideal wavefront.

  The inventors of the present invention conducted the following experiment and confirmed that an ideal plane wave can be obtained by wavefront compensation.

  First, control data of 0 or any identical value was given as initial control data to all the pixels of the LCD 530. In this case, the LCD 530 emitted intensity-modulated light having a uniform intensity pattern as shown in FIG. A condensing lens for condensing the light transmitted through the beam sampler 50 is disposed at the subsequent stage of the beam sampler 50. A CCD camera was placed on the focal plane of the condenser lens. FIG. 16B is obtained by photographing an image emitted from the PAL-SLM 550 and transmitted through the beam sampler 50 and collected by the condenser lens when the intensity pattern of FIG. 16A is input to the PAL-SLM 550. It is the obtained spot image. Here, when the light emitted from the PAL-SLM 550 is a plane wave having a phase close to the ideal wavefront, this light should be converged into a circular spot image by the condenser lens. However, as is apparent from FIG. 16B, the spot image taken by the CCD camera is blurred due to distortion.

  On the other hand, FIG. 16C shows an intensity-modulated light pattern obtained by inputting feedback control data obtained after 40 times of closed-loop feedback control to the LCD 530. The pattern shown in FIG. 16C was input to the PAL-SLM550. An image formed by the light emitted from the PAL-SLM 550 passing through the beam sampler 50 and condensed by the condenser lens was taken by a CCD camera. In this case, since the light emitted from the PAL-SLM 550 is a plane wave having the same phase, the spot image photographed by the CCD camera is a clean circular spot having a diffraction limit as shown in FIG. It was. For comparison, FIG. 16E shows a spot image at the diffraction limit. It was confirmed that the phase distortion was corrected to a level comparable to that in FIG. 16E by the closed loop feedback control.

For evaluation of the results of wavefront compensation, the spot images in FIGS. 16B, 16D, and 16E are digitized and shown in Table 2 below.

  In Table 2, the maximum luminance represents the maximum luminance value of the photographed spot image.

Further, the condensing size (pixel) is the condensing spot size indicated by the number of pixels (pixels) of the CCD camera. That is, it is the number of pixels detected in the spot image when the luminance value is larger than a predetermined threshold value (in this example, 1 / e ² of the maximum value (35 when the maximum luminance value is 255)).

In addition, “M ² ” in the lower part of the second row of Table 2 is a ratio of (condensed spot size) to (spot size at the diffraction limit). Here, the spot size at the diffraction limit is the spot size of the condensing spot in FIG.

  The average luminance is a value obtained by dividing (the sum of pixel values within the focused spot size) by (the focused spot size).

  The energy (upper stage) is the sum of the pixel values within the focused spot size.

  The energy (lower stage) is the sum of the pixel values within the radius R pixel centered on the maximum value. Here, the radius R is the radius of the diffraction-limited Airy disk with an aperture having the same size as the beam diameter or an approximate value thereof.

  The improvement magnification is the ratio of the value after compensation in each parameter to the value before compensation.

  As is clear from Table 2, according to the wavefront compensation apparatus 1 according to the present embodiment, the light modulated by the wavefront modulation device 40 is condensed and formed by performing closed-loop feedback control using the ideal wavefront as a plane wave. The spot can be made almost equal to the diffraction limit. That is, it is possible to obtain a substantially ideal plane wave that is incident substantially perpendicularly to a condenser lens (not shown).

  Although the wavefront compensation operation of the wavefront compensation device 1 has been described above in the case where the ideal wavefront is a plane wave, the ideal wavefront may not be a plane wave.

  When the ideal wavefront is not a plane wave, the reference centroid RC (x, y) for each small lens 612 is obtained in advance by simulation calculation. Specifically, by performing ray tracing calculation using the optical parameters of the wavefront compensation device 1, the position of the center of gravity of the spot image formed by the ideal wavefront being imaged by each small lens 612 is obtained.

  Alternatively, the reference center of gravity RC (x, y) for each small lens 612 may be obtained by performing an optical experiment in advance. Specifically, the reference light is incident on the wavefront modulation device 40 and a control signal corresponding to the ideal wavefront is input to the LCD 530. The center of gravity of the spot image formed by forming the ideal wavefront phase pattern output from the PAL-SLM 550 by each small lens 612 is obtained and set as reference centroid data.

  The reference centroid data thus obtained may be stored in advance in the recording medium 90 together with, for example, the initial control data I (X, Y) indicating the ideal wavefront. These data are read from the recording medium 90 and stored in the memory 130 in the parameter reading process of S12.

In this case, when the control signal memory 430 is reset in S13, the data I (X _cont , Y _cont ) for each control point in the control point region C among the initial control data I (X, Y). The control signal S (X _cont , Y _cont ) may be obtained by performing the same processing as S41 to S43 and stored in the control signal memory 430. However, the control signal S (X, Y) = 0 is stored for the pixels of the LCD 530 corresponding to the pixels in the non-control point region D of the PAL-SLM 550.

  As described above, the wavefront compensation device 1 and the wavefront compensation method according to the embodiment of the present invention are based on the spot centroid and the ideal wavefront of the multipoint spot image photographed by the image sensor 620 as the procedure for performing the closed loop feedback control. The difference between the spot centroid and the reference centroid set in advance is calculated as the centroid shift, and the polynomial weighting coefficient is calculated by the fitting process in which the least square method is applied to the relational expression between the centroid shift and the first order differential expression of the polynomial Find the wavefront equation. The residual wavefront for each control point is obtained by substituting the coordinates of the measurement points corresponding to each control point into the wavefront equation, and feedback control data is obtained for each control point. The feedback control data is converted into a control signal by the look-up table T. Thus, since the residual wavefront can be obtained for each control point, the wavefront modulation device 40 can be obtained even if there is no constant consistency between the pitch of the control point of the PAL-SLM 550 and the lens pitch of the lens array 610. It is possible to accurately calculate the residual wavefront in a state where the spatial resolution is fully utilized.

  Further, parameters necessary for the processing are preliminarily collected and saved in one parameter file, and are read out and stored in the memory 130 in S12. Other necessary parameters are automatically calculated in S13. Therefore, the user does not have to input parameters one by one. If the user does not need to change any parameters, the parameters may be set as fixed values and stored in the hard disk 83 in advance together with the control software.

  Since the bias shift process is executed in S2, the influence of noise and background can be suppressed, and the influence of the phase discontinuity line generated by the folding process executed in S42 can be suppressed to some extent.

  In the center-of-gravity calculation algorithm of the present embodiment, the center-of-gravity calculation includes a procedure for calculating the position of the maximum value and a procedure for calculating the center of gravity of the pixel value around the maximum value position. Here, the region for searching for the maximum value position is fixed to a lens region LA centered on the intersection of the optical axis of the small lens 612 and the image sensor 620. On the other hand, the center of the center-of-gravity calculation range CA, which is an area for calculating the center of gravity, is not fixed because it is a maximum position. Since the center-of-gravity calculation range CA is thus variable, correction with high accuracy and a large dynamic range is possible. In addition, since the maximum value position is not searched in the entire area of the image sensor 620 but is searched for each lens area LA of each small lens 612, the speed can be improved and the correspondence between the maximum value and the small lens 612 can be easily performed. It has become. For this reason, the correspondence between the finally obtained barycentric value and the small lens 612 is also easy.

  Further, the effectiveness of the obtained center of gravity of the spot is evaluated, and the center-of-gravity shift amount is calculated for the center of gravity evaluated as effective other than the specific center of gravity to obtain the wavefront equation. Here, as a case of occurrence of a singular point, for example, when a part of a beam such as reading light or writing light is blocked, it becomes impossible to form a condensed spot by diffraction at the peripheral portion of the optical element. In this case, there may be a case where there is an influence of noise, a case where there is an influence of a quantization error due to the aliasing process, and the like. In the present embodiment, since the singular point is excluded when calculating the centroid shift, even if a singular point occurs because the wavefront compensation device 1 is used in a complicated environment, it is stable and precise. The wavefront correction operation can be continued.

  The PAL-SLM 550 performs phase modulation on the pixels in the control point area C, which is an area necessary and sufficient for modulating the readout light. Control data is not calculated for pixels in the non-control point region D that are not necessary for the wavefront compensation process. Therefore, the calculation speed is improved.

  Since the size of the control point region C is sufficiently larger than the size of the reference light incident region B0, the readout light incident region B continues to be within the control point region C even when the readout light fluctuates due to distortion. Is possible.

  Further, since the calculated feedback control data is converted into a control signal using the look-up table T in Table 1, the wavefront is accurately corrected even though the PAL-SLM 550 has a nonlinear modulation characteristic. be able to. By using the look-up table T, the wavefront can be accurately corrected even when a relatively inexpensive SLM having an arbitrary modulation characteristic is used instead of the PAL-SLM 550.

  Since the initial processing of S1 is executed outside the closed loop feedback S2 to S6 for controlling the wavefront modulation device 40, the processing speed is improved.

  The control device 80 is a personal computer, is controlled by a control program provided in the personal computer, and operates as described above. For this reason, it is possible to implement | achieve the control apparatus 80 by arbitrary computers by using the recording medium which recorded the program.

  In the above embodiment, the control device 80 is constituted by a general-purpose personal computer, and the wavefront compensation operation is performed by executing the stored software. Instead, the control device 80 may be configured by a dedicated electronic circuit that achieves the function shown in FIG.

  The preferred embodiments of the wavefront compensation device, the wavefront compensation method, the program, and the recording medium according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments. Those skilled in the art can make various modifications and improvements within the scope of the technical idea described in the claims.

For example, the lookup table T is not limited to that described with reference to the example shown in Table 1. Another example of the lookup table T is shown in Table 3 below.

  In the look-up table T in the example of Table 3, instead of showing the converted phase value as a phase value of 0 or more and 1 or less in units of one wavelength as in the example of Table 1, −1 or more in units of 1 wavelength. It is shown as a value less than +1. When the lookup table T in the example of Table 3 is used, step S42 is not executed, and in step S43, the signal level (OUT) is determined based on the phase value of only the fractional part obtained in step S41.

Further, another example of the lookup table T is shown in Table 4 below.

  In Table 4, N and k are non-negative integers, and K is a positive or negative integer.

  Unlike the examples in Table 1 and Table 3, the lookup table T in the example of Table 4 does not convert the converted phase value to 0 or more and 1 or less, or −1 or more and +1 or less, but simply uses one wavelength as a unit. Shown as an arbitrary value. In this example, when the index I is shifted by 1, the converted phase value is shifted by 1/255. When the look-up table T in the example of Table 4 is used, both steps S41 and S42 are not executed. In step S43, the signal level is based on the phase value in units of one wavelength of the calculation result of step S3. (OUT) is determined.

  In the above-described embodiment, the wavefront modulation device 40 is composed of an electrical address type liquid crystal phase modulation module including an LCD and a PAL-SLM 550. However, the wavefront compensation device of the present invention can employ any electrical address type spatial light phase modulation device. That is, the electrical address type spatial light phase modulation device employed by the wavefront compensation device of the present invention is not limited to the liquid crystal, and any configuration can be adopted as long as the phase can be modulated by electrical address driving. Can do.

  Further, in the lens array 610, the small lenses 612 may be arranged in a two-dimensional manner and may not be a matrix arrangement.

Further, due to reflection by the imaging and the mirror by a lens, the measurement point origin coordinates _{(x sens, y} sens) of the image sensor 620 and the PAL-SLM550 control point origin coordinates _{(x cont, y} cont) is correspondence between the If the image cannot be taken, a process of flipping the image horizontally / vertically may be performed.

  Instead of the control device 80 executing the initial process (step S22), the centroid calculation (step S23), and the centroid validity evaluation (step S24), the built-in circuit of the wavefront detection device 60 may execute. In this case, the wavefront detection device 60 outputs the centroid value of the focused spot and the centroid data determined to be invalid. The center-of-gravity shift calculation (step S25) and the wavefront equation calculation (step S26) may also be executed by the built-in circuit of the wavefront detection device 60, instead of being executed by the control device 80. In this case, the wavefront detection device 60 outputs a polynomial weighting factor representing the phase difference between the incident wavefront and the ideal wavefront.

  In the centroid validity evaluation (step S24), the centroid shift at the invalid centroid is set to “0”. However, the invalid centroid is marked, and the information on the invalid centroid is completely removed to eliminate the wavefront equation. Calculation may be performed. In this case, N in Equation 9 is not the total number of small lenses 612 but the total number of small lenses 612 determined to have obtained an effective center of gravity (that is, small lenses determined to be invalid from the total number of small lenses 612). 612 minus the number of 612). Further, n (n = 1 to N) indicates each small lens 612 from which an effective center of gravity is obtained.

  When converting the feedback control data into the control signal, a lookup table is used. Instead of using the lookup table, for example, the control data is transferred to the control signal using a mathematical expression indicating the relationship between the feedback control data and the control signal. May be converted to

  In the above-described embodiment, the beam transmitted through the beam sampler 50 is output as the wavefront 70 and the beam reflected by the beam sampler 50 is disposed so as to enter the wavefront detection device 60. The beam may be output as the wavefront 70, and the beam transmitted through the beam sampler 50 may be arranged to enter the wavefront detection device 60.

  The present invention relates to a configuration and a control method of a wavefront compensation device using an electrical address type spatial light phase modulation device. The present invention relates to a laser processing with high energy utilization efficiency, an imaging / measurement optical device with high spatial resolution (for example, a microscope, a fundus camera). ) And the like.

It is a schematic block diagram of the wavefront compensation apparatus concerning embodiment of this invention. FIG. 2 is a schematic cross-sectional view of a wavefront modulation device included in the wavefront compensation device of FIG. 1. It is a figure which shows the relationship between the control point area | region in the cross section along the III (a) -III (a) line | wire of FIG. It is an enlarged view of the part F in Fig.3 (a). It is a figure which shows a mode that the position and magnitude | size of a reading light incident area are fluctuate | varied within a control point area | region. FIG. 2 is a schematic partial cross-sectional view of a wavefront detection device provided in the wavefront compensation device of FIG. It is a functional block diagram of the control apparatus with which the wavefront compensation apparatus of FIG. 1 is provided. It is a functional block diagram of the input part in the control apparatus of FIG. FIG. 6 is a functional block diagram of a wavefront calculation unit in the control device of FIG. 5. FIG. 6 is a functional block diagram of a control data synthesis unit in the control device of FIG. 5. It is a functional block diagram of the conversion part in the control apparatus of FIG. It is a flowchart which shows operation | movement of the wavefront compensation apparatus of FIG. It is a flowchart explaining operation | movement of step S1 of FIG. It is a flowchart explaining operation | movement of step S2 of FIG. It is a flowchart explaining operation | movement of step S3 of FIG. It is a flowchart explaining operation | movement of step S4 of FIG. It is a figure which shows the return frequency dependence of the residual wavefront by the wavefront compensation apparatus of FIG. It is a figure which shows the intensity | strength modulation light with uniform intensity | strength radiate | emitted from LCD in the experiment of the wavefront compensation by the wavefront compensation apparatus of FIG. 16A is a spot image obtained by photographing an image emitted from the PAL-SLM and collected by the condenser lens when the intensity pattern of FIG. 16A is input to the PAL-SLM. It is an intensity-modulated light pattern obtained by inputting feedback control data obtained after 40 times of closed-loop feedback control to the LCD. FIG. 16C is a spot image obtained by photographing an image emitted from the PAL-SLM and collected by the condenser lens when the intensity pattern of FIG. 16C is input to the PAL-SLM. It is an image of a diffraction limited spot when a plane wave is condensed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wavefront compensation apparatus 10, 30, 70 Wavefront 40 Wavefront modulation device 50 Beam sampler 60 Wavefront detection device 80 Control apparatus

Claims (14)

An electrical address type spatial light phase modulation device that includes a modulation unit in which a plurality of control points are arranged two-dimensionally, and modulates the phase of the readout light incident on the modulation unit for each control point;
A lens array in which a plurality of lenses are arranged in a two-dimensional manner, and the readout light whose phase is modulated by the electrical address type spatial light phase modulator is converted into a multi-point spot image composed of a plurality of spots,
Image detection means for detecting the light intensity distribution of the multipoint spot image;
A plurality of spot centroids indicating the positions of the centroids of the plurality of spots are calculated based on the detected light intensity distribution, and a plurality of spots indicating differences between the calculated plurality of spot centroids and a plurality of preset reference centroids are calculated. Centroid difference calculating means for calculating the centroid difference;
Weight coefficient calculation means for obtaining a weight coefficient of a predetermined polynomial by fitting the calculated plurality of centroid differences to a first-order differential expression of the predetermined polynomial using a least square method;
A residual distortion calculating means for calculating a residual distortion for each control point by substituting a value corresponding to the coordinates of each control point into the predetermined polynomial using the calculated weighting factor;
Control data calculating means for obtaining closed loop control data for the control point based on the residual distortion of each calculated control point;
And a control means for controlling each control point of the electrical address type spatial light phase modulator based on the closed loop control data. Each control point of the electrical address type spatial light phase modulation device modulates the incident readout light with a phase modulation amount corresponding to the input control signal,
The control means further includes a signal conversion means, which determines a phase modulation amount to be modulated by each control point based on a residual distortion of each control point, and uses a preset lookup table. 2. The wavefront compensation device according to claim 1, wherein the determined phase modulation amount is converted into a control signal, and each control point of the electric address type spatial light phase modulation device is controlled based on the control signal. . The center-of-gravity difference calculating unit evaluates the calculated plurality of spot centroids, and the weighting factor calculating unit calculates a spot centroid other than the spot centroid evaluated as an invalid spot centroid among the plurality of spot centroids. The wavefront compensator according to claim 1, wherein the weighting factor is calculated based on a centroid difference calculated with respect to the center of gravity. 2. The size of a control point area in which the control points are arranged in the modulation unit of the electrical address type spatial light phase modulation device is larger than the size of readout light incident on the modulation unit. 2. The wavefront compensation device according to 1. A wavefront compensation method for compensating a wavefront of readout light by performing closed-loop feedback control of an electrically addressed spatial light phase modulator having a plurality of control points arranged two-dimensionally,
A multi-point spot comprising a plurality of spots formed by reading light whose phase is modulated at each control point by the electrical address type spatial light phase modulator through a lens array in which a plurality of lenses are arranged two-dimensionally An image detection step for detecting the light intensity distribution of the image;
Based on the detected light intensity distribution, a plurality of spot centroids indicating the centroid positions of the plurality of spots are calculated, and a plurality of spots indicating differences between the calculated plurality of spot centroids and a plurality of preset reference centroids are calculated. A centroid difference calculating step for calculating a centroid difference;
A weighting coefficient calculation step for obtaining a weighting coefficient of the predetermined polynomial by fitting the calculated plurality of centroid differences to a first-order differential expression of the predetermined polynomial using a least square method;
A residual distortion calculation step of obtaining a residual distortion for each control point by substituting a value corresponding to the coordinates of each control point into the predetermined polynomial using the calculated weighting factor;
A control data calculation step for obtaining closed loop control data for the control point based on the residual distortion of each calculated control point;
A control step of controlling each control point of the electrical address type spatial light phase modulation device based on the closed loop control data,
A wavefront compensation method, wherein the steps are repeated. A program for causing a computer to perform closed-loop feedback control of an electrical address type spatial light phase modulation device having a plurality of control points arranged in a two-dimensional manner to compensate the wavefront of readout light,
A multi-point spot comprising a plurality of spots formed by reading light whose phase is modulated at each control point by the electrical address type spatial light phase modulator through a lens array in which a plurality of lenses are arranged two-dimensionally Calculate a plurality of spot centroids indicating the positions of the centroids of a plurality of spots based on the light intensity distribution of the image, and calculate a plurality of centroid differences indicating differences between the calculated plurality of spot centroids and a plurality of preset reference centroids. The center of gravity difference calculation procedure to calculate,
A weighting coefficient calculation procedure for obtaining a weighting coefficient of the predetermined polynomial by fitting the calculated plurality of centroid differences to a first-order differential expression of the predetermined polynomial using a least square method;
A residual distortion calculation procedure for obtaining a residual distortion for each control point by substituting a value corresponding to the coordinates of each control point into a predetermined polynomial using the calculated weighting factor;
A control data calculation procedure for obtaining closed loop control data for the control point based on the residual distortion of each calculated control point;
A control procedure for controlling each control point of the electrical address type spatial light phase modulator based on the closed-loop control data;
A program for repeating each of the above procedures. A computer-readable recording medium on which the program according to claim 6 is recorded. A plurality of control points are arranged in a two-dimensional manner, and an electrical address type spatial light phase modulation device that generates a phase pattern by phase-modulating readout light based on control data for each control point;
A lens array in which a plurality of lenses are arranged two-dimensionally, the phase pattern output from the electrical address type spatial light phase modulator is converted into a multi-point spot image composed of a plurality of spots, and the multi-point spot image Wavefront detection means for detecting the light intensity distribution of
Based on the detected light intensity distribution, a plurality of spot centroids representing the centroid positions of the plurality of spots are calculated, and a difference between the plurality of spot centroids and a plurality of reference centroids corresponding to preset ideal wavefronts is indicated. A wavefront equation representing a phase difference between the phase pattern output from the electrical address type spatial light phase modulator and the ideal wavefront is calculated based on a plurality of barycentric differences, and the wavefront equation corresponds to the coordinates of the control point. Calculating means for substituting a value and calculating a phase difference for each control point as a residual wavefront;
An aberration wavefront calculation storage means for adding the residual wavefront and the aberration wavefront for each control point, and storing the result as a new aberration wavefront for each control point;
Wavefront synthesis means for adding the new aberration wavefront and the ideal wavefront for each control point, and creating feedback control data based on the result,
Control means for outputting the feedback control data as the control data to the electrical address type spatial light phase modulator,
The wavefront compensation device, wherein the electrical address type spatial light phase modulation device repeats phase modulation of readout light based on the feedback control data input from the control means. The wavefront equation is a polynomial, and the calculation means calculates a weighting factor of the polynomial by applying a least square method to a relational expression between the centroid difference and the first-order differential expression of the polynomial, and The wavefront compensation device according to claim 8, wherein the wavefront compensation device is obtained. An electric address type spatial light phase modulator having a plurality of control points arranged in two dimensions is subjected to closed-loop feedback control, and the electric address type spatial light phase modulator is phase-modulated based on control data for each control point. A wavefront compensation method for compensating the wavefront of read light,
A light intensity distribution of a multi-point spot image formed by a plurality of spots formed by transmitting readout light output from the electrical address type spatial light phase modulation device through a lens array in which a plurality of lenses are arranged two-dimensionally. A wavefront detection process to detect;
Based on the detected light intensity distribution, a plurality of spot centroids representing the centroid positions of the plurality of spots are calculated, and a difference between the plurality of spot centroids and a plurality of reference centroids corresponding to preset ideal wavefronts is indicated. Calculates a wavefront equation representing a phase difference between the wavefront of the readout light output from the electrical address type spatial light phase modulator and the ideal wavefront based on a plurality of center-of-gravity differences, and corresponds to the coordinates of the control point in the wavefront equation Calculating a phase difference for each control point as a residual wavefront by substituting a value to be
An aberration wavefront calculating and storing step of adding the residual wavefront and the aberration wavefront for each control point, and storing the result as a new aberration wavefront for each control point;
A wavefront synthesis step of adding the new aberration wavefront and the ideal wavefront for each control point, and creating feedback control data based on the result,
A control step of outputting the feedback control data as the control data to the electrical addressing spatial light phase modulator;
And a step of repeating each of the above steps. The wavefront equation is a polynomial, and the calculating step calculates a weighting factor of the polynomial by applying a least square method to a relational expression between the centroid difference and the first-order differential expression of the polynomial, The wavefront compensation method according to claim 10, wherein the wavefront compensation method is obtained. An electric address type spatial light phase modulation device having a plurality of control points arranged two-dimensionally is closed-loop feedback controlled by the computer, and the electric address type spatial light phase modulation device uses the control data for each control point based on the control data. A program for compensating the wavefront of phase-modulated readout light,
The readout light output from the electrical address type spatial light phase modulation device has a light intensity distribution of a multi-point spot image formed of a plurality of spots formed by passing through a lens array in which a plurality of lenses are two-dimensionally arranged. A plurality of spot centroids indicating the centroid positions of the plurality of spots based on the plurality of spot centroids, and a plurality of centroid differences indicating a difference between the plurality of spot centroids and a plurality of reference centroids corresponding to preset ideal wavefronts; Calculate a wavefront equation representing a phase difference between the wavefront of the readout light output from the address type spatial light phase modulator and the ideal wavefront, and substitute the value corresponding to the coordinates of the control point into the wavefront equation to perform the control A calculation procedure for calculating a phase difference for each point as a residual wavefront;
An aberration wavefront calculation storage procedure for adding the residual wavefront and the aberration wavefront for each control point, and storing the result as a new aberration wavefront for each control point;
A wavefront synthesis procedure for adding the new aberration wavefront and the ideal wavefront for each control point, and creating feedback control data based on the result,
A control procedure for outputting the feedback control data as the control data to the electrical addressing spatial light phase modulator;
A program for repeating each of the above procedures. The wavefront equation is a polynomial, and the calculation procedure calculates a weighting factor of the polynomial by applying a least square method to a relational expression between the centroid difference and the first-order differential expression of the polynomial, and 13. The program according to claim 12, wherein the program is obtained. A computer-readable recording medium on which the program according to claim 12 is recorded.

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