JP2564452B2 - Adaptive optics controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive optics control device, and more particularly, it is a main element of an adaptive optics system in an adaptive optics system that corrects a phase difference of laser light on a target and improves laser irradiation density. One adaptive optics controller.

[0002]

2. Description of the Related Art A multi-dither type adaptive optics apparatus is
The laser is divided into a plurality of apertures by a plurality of divided mirrors called a deformable mirror, and the phase of the laser on the target is corrected by moving each mirror. Further, vibration (dither) having a small amplitude is applied to each mirror at a specific frequency. Then, by focusing the laser on the target and controlling the amplitude value of the dither signal included in the reflected signal to be zero, the phase of the laser disturbed during the propagation to the target is corrected. This is a device for improving the laser irradiation density.

As a conventional technique, the journal of
The Optical Society of America 6th
Volume 7, Issue 3 (March 1977) pp. 306-315 (JOURNAL OF THE OPTICAL SOCIETY OF AMERICA Vol. 6
7, No. 3 (March 1977) p.p. 306-315), and Applied Optics Vol. 15 No. 3 (March 1976), pages 611 to 621 (APPLIED OPTICS). Vol.15, No.3 (March 1
976) pp. 611-621).

[0004]

In the prior art described above, in a multi-dither type adaptive optics device, a laser is divided into a plurality of apertures and transmitted by a variable shape mirror. A small vibration (dither) is applied to each aperture at a specific frequency, which irradiates the target and occurs between each dither signal contained in the reflected signal and the reference signal oscillated at a specific frequency. The point of phase delay is not taken into consideration, and there is a problem that the laser irradiation density may not be improved even if the control is performed unless the sign of the dither signal is determined.

Further, there is a problem in determining whether the laser irradiation density on the target object can be improved by moving the mirror, which is obtained by dividing the laser into a plurality of apertures, in each of the positive direction and the negative direction.

The present invention utilizes the phase delay between the dither signal contained in the reflected signal and the oscillator, and is intended to determine the moving direction of the mirror divided into a large number. It is an object to provide an adaptive optics control device for detecting.

[0007]

In order to achieve the above object, the present invention utilizes a phase delay between a dither signal included in a reflected signal and an oscillator to detect a phase delay and a positive / negative judgment. The moving direction of the mirror divided into a large number by the container is determined.

Further, when the target moves, the distance measuring device measures the distance to the target, and corrects the delay change of the phase of the dither signal due to the change of the distance.

[0009]

In the adaptive diopter of the multi-dither system, the laser is divided into a plurality of apertures for transmission, and each aperture is subjected to microvibration (dither) at a specific frequency, which irradiates the target and its reflected signal. By detecting the amplitude value of the dither signal contained in the signal and controlling it so that it becomes zero, the phase of the laser disturbed during propagation to the target is corrected and the laser irradiation density is improved. .

However, when the amplitude value of the dither signal is obtained, the positive / negative of the amplitude value cannot be determined unless the phase delay is taken into consideration. Therefore, control is facilitated by measuring the phase delay in advance or by examining the relationship between cos θ and sin θ when the laser irradiation density and the phase delay are θ and using it as a material for determining whether the amplitude value is positive or negative. In addition, when the distance changes, the phase delay changes as shown in the following equation, so a control device is added to improve the control accuracy.

[0011]

[Equation 1]

Θ _l : amount of phase delay due to target distance _l : distance from target c: speed of light f: minute vibration frequency of each mirror

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an embodiment of the overall structure of a multi-dither type adaptive optics device, and FIG. 2 is a flowchart of the adaptive optics device. 3 and 4 are examples of the configuration of the synchronous detector shown in FIG.

In FIGS. 1 and 2, a laser beam is transmitted from the laser 1 (100). Next, the laser is divided into a plurality of apertures by the variable shape mirror 2 composed of a plurality of divided mirrors, and vibrations (dither) of minute amplitude at different frequencies are generated.
And give to the transmitted laser beam (101).
The laser is transmitted 10 to the target 4 by the condenser 3 and condensed (102). The phase of the laser is disturbed during the propagation from the transmission of the laser to the arrival of the target, and a phase difference occurs in the laser for each aperture (103). Then, the target 4 is irradiated with the laser (104). The reflected signal 11 is converted into an electric signal by the photodetector 5 (105). Then, the synchronous detector 6 detects the amplitude value of the signal of the frequency given to each mirror included in the reflected signal (106).
This amplitude value is a signal containing the phase difference on the target of another laser with respect to the laser given the frequency. The controller 7 determines each mirror movement amount of the variable shape mirror so that the signal becomes zero (107), and the variable shape mirror drive power source 9 is used to move the mirror (108). This eliminates the phase difference of the laser on the target and improves the laser irradiation density.

Upon completion, the laser transmission and the like are terminated (109). Here, the oscillator 8 is the variable shape mirror 2
Is used as a reference signal 13 for detecting the amplitude value of the dither signal included in the signal 12 for vibrating each mirror and the reflection signal 11. Here, in order to give different frequencies to a plurality of mirrors and to change the phase of each laser, the synchronous detector 6, the oscillator 8, the variable shape mirror drive power supply 9, and the controller 7 need the number of systems corresponding to the number of mirrors. Becomes

In FIG. 3, the reflected signal from the target (see FIG.
11) is converted into an electric signal by the photodetector (5 in FIG. 1), and the signal 24 is input. Then, the bandpass filter (BPF) 14 extracts only the target dither signal 26. In addition, the reference signal (sine wave) from the oscillator 25
The phase shifter 21 outputs two signals, a sine wave and a cosine wave, and the dither signal 26 is multiplied (15a, 15b).

Assuming that the amplitude value of the dither signal is A and the phase difference between the dither signal and the reference signal is θ, if only the DC component is passed by the low pass filter 16a, Acos θ
Signal (28a) of the low pass filter 16b is output.
When only the DC component is passed by, the signal of Asinθ (2
8b) is output. The signal is multiplied by the multipliers (17a, 17a
b) squared, and the two signals are added by the adder 18,
When the square root 19 is taken, the amplitude value A is output. Since this amplitude value is squared and expressed as an absolute value, a mechanism for attaching positive and negative signals to it is required.

Therefore, the signals of Acos θ and Asin θ described above are taken out, the signs of cos θ and sin θ are measured in advance, and
The phase lag detector 22 takes out a signal having a larger value of Acos θ and Asin θ. This is to reduce signal error. Then, the sign of the amplitude value is judged by the positive / negative judging device 23, and the amplitude value A (29) is multiplied (20) to obtain a signal having a positive / negative sign.

According to this embodiment, since the value extracted as the amplitude value is positive or negative, it can be determined whether each mirror of the deformable mirror should move in the positive direction or the negative direction. Therefore, the control system becomes more stable and the control time can be shortened. FIG. 4 shows the simplest example of this synchronous detector. The sine wave is synchronized with the dither signal 26 by the synchronous amplifier 31, and the phase delay amount is θ = 2n
If π (n is an integer), the amplitude value can be detected by the LPF 16. Further, in the phase delay detector 22, it suffices to measure the sign of cos θ, and the number of parts can be reduced.

Further, FIG. 5 shows an example of the structure of the synchronous detector when the target moves.

As described above, when the distance to the target changes, the phase difference θ also changes. Therefore, by providing a device for measuring the distance to the target by using the distance measuring device 32 and correcting the phase delay due to the distance to the target by the distance phase corrector 33, the phase delay detector is always unique within the device. Can be recorded as the value of.

[0023]

Since the present invention is constructed as described above, it has the following effects.

That is, it is possible to determine whether each mirror of the deformable mirror should move in the positive direction or the negative direction by giving a positive or negative signal to the amplitude value using the phase delay. Further, the number of parts can be reduced by causing the phase shifter to output a signal synchronized with the dither signal. Further, by providing a mechanism for measuring the distance to the target and correcting the phase delay due to the distance to the target, it is possible to deal with a moving object.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an adaptive optics device by a multi-dither method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a system of an adaptive optics apparatus using a multi-dither method.

FIG. 3 is a configuration diagram showing an example of a synchronous detector for extracting a control signal in an adaptive optical device using a multi-dither method.

FIG. 4 is a configuration diagram showing another example of a synchronous detector for taking out a control signal in an adaptive optical device using a multi-dither method.

FIG. 5 is a configuration diagram showing still another example of a synchronous detector for extracting a control signal in an adaptive optical device using a multi-dither method.

[Explanation of symbols]

1 ... Laser, 2 ... Deformable mirror, 3 ... Focusing device, 4 ... Target, 5 ... Photodetector, 6 ... Synchronous detector, 7 ... Control device, 8
... Oscillator, 9 ... Variable shape mirror drive power supply, 14 ... Bandpass filter, 16 ... Lowpass filter, 21 ... Phase shifter, 2
2 ... Phase lag detector, 23 ... Positive / negative judgment device, 31 ... Synchronous amplifier, 32 ... Distance measuring device, 33 ... Distance phase corrector.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Toshiaki Ueno 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi, Ltd. (72) Inventor Shunichi Kishi 3-1-1, Saiwaicho, Hitachi, Ibaraki Stock Company Hitachi, Ltd., Hitachi Plant (72) Inventor, Haruo Tsunoi, 1-1, Sachimachi, Hitachi, Ibaraki Prefecture Hitachi, Ltd., Hitachi, Ltd. (72) Inventor, Yuji Ichinose, 1168, Moriyama Town, Hitachi City, Ibaraki Hitachi, Ltd. Energy Research Institute (72) Inventor Kuniaki Takahara 3-2, Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Nuclear Engineering Co., Ltd. (72) Inventor Kazuhiro Onuma 3-18-1 Omikacho, Hitachi City, Ibaraki Prefecture Ibaraki Hitachi Information Service Co., Ltd. (56) Reference JP-A-4-84477 (JP, A) JP-A 2-259615 (JP, A)

Claims (2)

(57) [Claims] 1. In a multi-dither type adaptive optics device, minute vibrations (dither) are respectively applied to a plurality of apertures for transmitting laser at specific frequencies, and the vibrations are applied to a target, and the reflected signals are reflected in the reflected signal. By utilizing the phase delay between the included dither signal and the reference signal from the oscillator, each mirror of the deformable mirror used to divide into a plurality of apertures can be moved to either the positive or negative side. For example, the adaptive optics control device is provided with a mechanism for determining whether the laser irradiation density can be improved on the target. 2. A compensating optical system comprising a distance measuring device and a compensating optical control device according to claim 1 for compensating for a delay change in the phase of a dither signal due to a change in distance when a target moves. Control device.