JP3203972B2 - Wavefront sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavefront sensor for measuring a wavefront of a light wave, and more particularly to a wavefront sensor for measuring the wavefront with high accuracy even when the use environment or the condition of incident light changes.

[0002]

2. Description of the Related Art Conventionally, this type of device has been known as CSGardne.
r et al. "Design and Performance Analysis of Adapti
ve Optical Telescopes Using Laser Guide Stars "Pro
c.IEEEvol.78 NO.11 p1721-1743 (1990), and T. Noguc
hi et al. "Active Optics Experiments 1" Publ. Natl.
Astr. Obs. Japan vol.1 P49-55 (1989). FIG. 11 shows a combination of the above-mentioned documents. In the figure, 1 is a primary mirror of a telescope, 2 is a secondary mirror, 3 is a primary mirror controller, 4 is a lamp for a reference light source, 5
Is a lamp light focusing lens, 6 is a pinhole, 29 is a reference light source, 7 is a beam splitter, 8 is a collimator lens, 9
Is a lens array, 10 is a CCD, 11 is an optical system of a Shack-Hartmann type wavefront sensor, 25 is a field stop of the optical system 11 of the wavefront sensor, 12 is an optical collimator lens to be measured, 13 is a deformable mirror, and 14 is a beam splitter. , 15 is a reference wavefront generator, 16 is an objective lens, 17
Is an eyepiece, 28 is an afocal optical system comprising 16, 17, and 26, 18 is a lens array, 19 is a CCD,
0 is the optical system of the Shack-Hartmann wavefront sensor, 2
6 is a field stop of the optical system 20 of the wavefront sensor, 21 is a wavefront calculator, 22 is a deformable mirror controller, 23
Is the condenser lens for the observation device, 24 is the image plane of the observation device, 5
Numerals 0 and 51 are wavefront sensors.

[0003] First, the outline of the above-mentioned device will be described.
The light from the star is collected by the primary mirror 1 and the secondary mirror 2, passes through the field stop 25 and the beam splitter 7, and is converted into parallel light by the collimator lens 12. After that, the condenser lens 23 is passed through the deformable mirror 13 and the beam splitter 14.
Is focused on the image plane 24 of the observation device and observed. The above-mentioned primary mirror 1 is a large telescope having a length of several meters, and the primary mirror is easily deformed by its own weight. As a countermeasure against this, an active support mechanism is provided on the primary mirror 1 to correct the shape to an optimum shape. Since the light of the star is considered to be a plane wave when averaged over time, the light reflected by the beam splitter 7 is reflected by the optical system 1 of the wavefront sensor.
1, the shape of the primary mirror 1 can be known by calculating the wavefront shape by the wavefront calculator 21 based on the output. The primary mirror controller 3 drives the active support mechanism based on the output of the wavefront calculator 21 to correct the shape of the primary mirror 1.

[0004] When a short time interval is considered, the atmosphere has spatial and temporal fluctuations in the refractive index. as a result,
Light from a star is disturbed by a plane wave, and the image of the star moves or blurs even with a telescope that provides an ideal imaging state. The deformable mirror 13 is for correcting the movement and blurring of the star image which occurs in such a short time period as cannot be corrected by the primary mirror 1. The wavefront fluctuation of the light from the star is obtained by the optical system 20 of the wavefront sensor, and the deformable mirror controller 22 controls the deformable mirror 13 based on the measurement result to correct the wavefront.

Next, the configuration of the wavefront sensors 50 and 51 will be described. Optical systems 11 and 12 of wavefront sensors 50 and 51
The basic parts of 0 are lens arrays 9, 18 and CCD1
0,19. The wavefront sensor of this method measures the wavefront of the light to be measured at the positions of the lens arrays 9 and 18. Since the wavefront changes due to propagation, in the optical system 11 of the wavefront sensor, the wavefront of the primary mirror 1 is projected onto the lens array 9 by the collimator lens 8. The afocal optical system 28 of the wavefront sensor 51 matches the measurement range determined by the dimensions of the microlens array 18 with the diameter of the wavefront to be measured.

Next, the measurement principle of the wavefront sensors 50 and 51 will be described. The wavefront calculator 21 measures the inclination of the wavefront incident on each lens (lenslet) of the lens arrays 9 and 18 from the movement of the condensed spot on the CCDs 10 and 19, and the inclination of the wavefront ΔW _i measured by each lenslet. To obtain the wavefront. The amount of movement Δr of the focused spot is determined by the inclination angle θ of the wavefront incident on the lenslet and the focal length f of the lens array.
It is obtained from _m by the following equation. _{Δr = f m · tanθ (1} ) Now, the wavefront slope to be measured by the i-th lenslets Δ
_Wi is obtained by the following equation, where _Dm is the lenslet aperture. The _{ΔW i = D m · tanθ i} = D m · Δr i / f m (2), measuring the wavefront W is expressed by the following equation. W = ΣΔW _i (3)

Since the wavefront measurement is performed based on the displacement of the spot from the reference position, a reference spot position is required. A light spot focused by the reference light source is used as a reference spot position. By measuring the output wavefront of the reference light source in advance, the reference wavefront indicated by the reference spot position can be determined. From the displacement of the spot position when the light to be measured enters, a change in the wavefront is determined, and the wavefront of the measurement light is determined by adding the change to the reference wavefront.

The reference light sources 15, 29 must have an outgoing light wavefront suitable for the wavefront sensor. Since the wavefront sensor 50 measures a mirror-shaped light wave, the incident light needs to be a spherical wave. The reference light source 29 is for obtaining a reference spot position of the wavefront sensor 11. The light emitted from the lamp 4 is focused on the pinhole 6 by the lens 5, and a spherical wave without distortion due to diffraction at the pinhole 6 is obtained. The wavefront sensor 51 having the afocal optical system 28 is provided with a reference wavefront generator 15 that emits collimated reference light.

[0009]

SUMMARY OF THE INVENTION Conventional wavefront sensors are:
With the above configuration, when the environmental temperature of the wavefront sensor changes, aberration occurs due to a change in the refractive index of the optical system, a change in the shape, and a change in the lens interval due to the thermal expansion of the lens barrel. there were.

[0010] Another problem is that aberrations in the optical system of the wavefront sensor are caused by changes in the refractive index of air due to changes in air pressure, resulting in a wavefront measurement error.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to obtain an apparatus for measuring a wavefront with high accuracy even when the use environment conditions change.

[0012]

According to a first aspect of the present invention, there is provided a wavefront sensor, comprising: a lens array; a lens for projecting light to be measured on the lens array; A photoelectric converter for detecting a position of a condensed spot of the lens array by the measured light, and a wavefront sensor for measuring a wavefront of the measured light, the temperature being provided in the optical system. based on the output of the sensor, to calculate the change in the focus position of the lens caused by temperature change from a predetermined equation, it converts the variation of the calculated focus position change amount of the wavefront, the wave
An error wavefront calculator for determining the variation of the surface, said determined based on an output of said photoelectric converter from the wavefront of the measuring light of the wavefront
And a wavefront calculator for subtracting the change .

Further, the wavefront sensor of the invention according to claim 2, change of the focus position of the lens is, the change of power caused by the refractive index change of the lens due to the temperature change,
And the expansion and contraction of the lens barrel.

According to a third aspect of the present invention, there is provided a wavefront sensor, comprising: a lens array; a lens for projecting light to be measured on the lens array; and a condensing spot position of the lens array by the projected light to be measured. the Le a photoelectric converter for detecting, in a wavefront sensor for measuring wavefront to the target measurement light includes an optical system having a, which based on the output of the pressure sensor provided in the optical system, caused by atmospheric pressure change
Calculate the change of the focus position of the lens from a predetermined formula,
Change the calculated focus position change to the wavefront change
In other words, an error wavefront calculator for calculating the change in the wavefront and a wavefront calculator for subtracting the change in the wavefront from the wavefront of the measured light obtained based on the output of the photoelectric converter are provided. Things.

[0015]

In the wavefront sensor according to the first aspect of the present invention, the error wavefront calculator projects the light to be measured on the lens array, which is generated by a temperature change, based on the output of the temperature sensor. The change amount of the wavefront is calculated from the change amount of the focus position of the lens, and the wavefront calculator subtracts the change amount of the wavefront from the measured wavefront obtained based on the output of the photoelectric converter to obtain the temperature. Highly accurate wavefront measurement that is not affected by changes can be performed.

[0016] In the wavefront sensor of the invention according to claim 2 constructed as above, the change in the focus position of the lens, change of power caused by the refractive index change of the lens due to temperature changes, and the This is calculated from the expansion and contraction of the lens barrel.

In the wavefront sensor according to the third aspect of the present invention, the error wavefront calculator operates according to a lens pressure generated by a pressure change based on the output of the pressure sensor.
Focus position of the lens that projects the measured light onto the ray
The change of the wavefront is calculated from the change of the wavefront, and the wavefront calculator calculates the change of the wavefront from the measured wavefront obtained based on the output of the photoelectric converter.
By subtracting the chemical component, highly accurate wavefront measurement that is not affected by changes in atmospheric pressure can be performed.

[0018]

[Embodiment 1] FIG. 1 is a configuration diagram showing a first embodiment of the present invention. 1, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 1, 1 is the primary mirror of the telescope, 2 is the secondary mirror of the telescope, 8
Is a collimator lens, 9 is a lens array, 10 is CC
D and 11 are wavefront sensor optical systems, 100 is a wavefront sensor,
101 is a temperature sensor, 102 is an error wavefront calculator, 103
Is a wavefront calculator.

As described in the conventional example, a wavefront measurement error occurs due to an aberration caused by a change in refractive index and a shape of an optical material due to a change in temperature, a change in a lens interval due to thermal expansion of a lens barrel, and the like. In the present embodiment, a temperature sensor 101 and an error wavefront calculator 102 are provided, an aberration generated at a use temperature is obtained as an error wavefront, and the error wavefront is subtracted from the measurement wavefront obtained from the output of the CCD 10 by the wavefront calculator 103. Temperature compensation.

The details of the error wavefront calculator 102 will be described below. The error wavefront calculator 102 is connected to the temperature sensor 10
The change of the focus position generated in the collimator lens 8 due to the temperature change based on the output of 1 is calculated from a predetermined formula, and this is converted into a wavefront. Further, the error wavefront calculator 102 calculates a wavefront caused by a displacement of the spot position due to a difference in linear expansion rate between the lens array 9 and the CCD 10. The error wavefront calculator 102 outputs the sum of the two wavefronts to the wavefront calculator 103 as an error wavefront.

The calculation performed by the error wavefront calculator 102 is
A method for calculating a change in the focus position of the collimator lens 8 due to a change in temperature, a method for obtaining an error wavefront from the change in the focus position, a method for calculating the lens array 9 and the CCD 1
The method will be described below in order of the method of obtaining the error wavefront due to the difference in the linear expansion coefficient of 0.

A change in the focus position of the collimator lens 8 is caused by a change in power caused by a change in the refractive index of the collimator lens due to a change in temperature, and an expansion and contraction of the lens barrel. Assuming that the back focus of the collimator lens 8 is f _b and the linear expansion coefficient of the lens barrel is α, a change in the focus position with respect to a change in the temperature T can be expressed as in Expression (101). dx / dT = (df _b / dT) + αf _b = (− 1 / φ) · (β−α) (101) where β = (1 / φ) · dφ / dT: heat dispersion coefficient

Therefore, a change in focus position when a change in temperature is known can be obtained by the following equation. Δx = (− 1 / φ) · (β−α) · ΔT (102)

[0024] The focus position change Δx and error wavefront [Delta] W _T is related as follows. ΔW _T = Δx / 8λF ² (103) where λ is the wavelength and F is the F value of the lens.

Therefore, the error wavefront can be calculated by the following equation from the equation (103) and the equation (102) of the change of the focus position of the collimator lens due to the temperature change. ΔW _T = (1 / 8λF ² ) · (−1 / φ) · (β−α) · ΔT (104)

Next, a description will be given of an error wavefront caused by a difference in linear expansion coefficient between the lens array and the CCD. The linear expansion coefficient of the lens array substrate material is α _m , and the linear expansion coefficient of the CCD is α _c
Let r be the distance from the optical axis. The spot movement amount Δr generated by a shape change due to a temperature change is expressed by the following equation. Δr = (α _m −α _c ) ΔT · r (105)

The relationship between the spot movement amount Δr and the error wavefront is related as follows. Here, n is the number of lens arrays, f _m is the focal length of the lens array, and D _m is the aperture diameter of the lenslet.

From the above, the relationship between the change in the error wavefront and the change in temperature is expressed by the following equation. _{dW M / dT = Σ (D} m / f m) · (α m -α c) · r i (107)

Therefore, the error wavefront when the temperature change ΔT occurs can be calculated by equation (108). ΔW _M = (dW _M / dT) · ΔT (108)

The equations (104) and (1) described above
08), the error wavefront calculator 102 calculates the error wavefront ΔW
_T and ΔW _M are obtained, and the correct wavefront W _I can be obtained by subtracting the error wavefront from the measurement wavefront W affected by the temperature change by the wavefront calculator 103 as shown in Expression (109). W _I = W− (ΔW _T + ΔW _M ) (109)

Embodiment 2 FIG. FIG. 2 is a configuration diagram showing a second embodiment of the present invention. 2, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 2, 1 is the primary mirror of the telescope, 2 is the secondary mirror of the telescope, 8
Is a collimator lens, 9 is a lens array, 10 is CC
D and 11 are optical systems of a wavefront sensor, 200 is a wavefront sensor,
201 is an atmospheric pressure sensor, 202 is an error wavefront calculator, 203
Is a wavefront calculator.

As shown in the conventional example, a change in the refractive index of the atmosphere due to a change in atmospheric pressure causes a wavefront measurement error. In this embodiment, the pressure sensor 201 is used as the compensation means.
And an error wavefront calculator 202 are provided to obtain an error wavefront at the used atmospheric pressure, and the wavefront calculator 203 performs pressure compensation by subtracting the error wavefront from the measurement wavefront affected by the pressure change obtained from the output of the CCD 10. Things.

The details of the error wavefront calculator 202 will be described below. The error wavefront calculator 202 is a
A change in the lens power generated in the collimator lens 8 due to a change in the atmospheric pressure is calculated based on the output of No. 1 and converted into a wavefront, which is output to the wavefront calculator 203 as an error wavefront.

A method for calculating a change in power of the collimator lens 8 due to a change in atmospheric pressure performed by the error wavefront calculator 202 will be described below.
Two points of a method of converting a power change into an error wavefront will be described.

First, the collimator lens 8 due to the change in air pressure
The calculation method of the power change will be described. The change in the power φ due to the change in the atmospheric pressure P is expressed by the following equation. (Dφ / dP) = (dφ / dn a) (dn a / dP) (201)

From this, the change dx of the focus position due to the change in atmospheric pressure is expressed by the following equation. dx / dP = (dx / dφ ) (dφ / dn a) (dn a / dP) = (- 1 / φ 2) (dφ / dn a) (dn a / dP) = (1 / φ) (1 / _{n-n a) (dn a} / dP) = (1 / φ) · γ · (dn a / dP) (202) where, γ = 1 / n-n a: pressure variance (203)

Therefore, the ratio of the defocus wavefront aberration due to the change in atmospheric pressure is expressed by the following equation through the change in the refractive index of the inter-lens medium. _{dW P / dP = (1 /} 8λF 2) (dx / dP) = (D / 8λF) · γ · (dn a / dP) (204)

[0038] Therefore, the error wavefront (variation of the wavefront) [Delta] W _P at the time when the change in air pressure ΔP caused can be calculated from equation (205). ΔW = (dW _P / dP) · ΔP (205)

[0039] As described above, determine the error wavefront [Delta] W _P in error wavefront calculator 202 according to equation (205), the wavefront calculator 2
In 03, the correct wavefront W _I can be obtained by subtracting the error wavefront from the measurement wavefront W affected by the atmospheric pressure change as in the equation (206). W _I = W−ΔW _P (206)

Embodiment 3 FIG. FIG. 3 is a configuration diagram showing a third embodiment of the present invention. 3, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 3, reference numeral 301 denotes a temperature-compensated afocal optical system;
02 is a lens array, 303 is an objective lens, 304 is an eyepiece, and 19 is a CCD. Here, CCD1
The wavefront calculator for obtaining the wavefront based on the output of the reference numeral 9 is not shown.

In this embodiment, the lens array 302 and the CC
An error wavefront generated due to a difference in linear expansion coefficient from D19 is compensated by residual aberration of the temperature compensation afocal optical system 301. Let the linear expansion coefficient of the substrate material of the lens array 302 be α _m and the linear expansion coefficient of the CCD 19 be α _c . The relationship between the spot movement amount and the error wavefront is expressed by the above equation (107). Here, n is the number of lens arrays, f _m is the focal length of the lens array, and D _m is the aperture diameter of the lenslet.

Next, the lens power of the afocal optical system 301 satisfying the temperature compensation condition will be described. First, a method of calculating a power change of the afocal optical system 301 due to a temperature change will be described. The power of the afocal optical system 301 is expressed by equation (302). φ = φ _o + φ _e −eφ _o φ _e = (m + 1) φ _o −meφ _o ² (302) where φ _o : power of the objective lens 303 φ _e : power of the eyepiece 304 m = φ _e / φ _o : Magnification of afocal optical system 301 e = (1 / φ _o ) + (1 / φ _e ) = {(m + 1) / m} · (1 / φ _o ) (303): Distance between objective lens 303 and eyepiece 304

The temperature change rate of the power of the afocal optical system 301 is expressed by equation (304). _{(Dφ / dT) = φ o} {d (m + 1) / dT} + (m + 1) (dφ O / dT) -mφ o 2 (de / dT) -2meφ o (dφ O / dT) -eφ o 2 (dm / DT) (304) By making the thermal dispersions β _o and β _e of the power of the objective lens 303 and that of the eyepiece 304 equal, the afocal optical system 3 is obtained.
Assuming that the magnification m of 01 does not change with temperature,
It is expressed by the following equation. dm / dT = 0 (305) Using the above equations (303), (304), and (305), the temperature change rate of the power of the afocal optical system 301 is expressed by equation (306). dφ / dT = − (m + 1) φ _o (α _B + β _o ) (306) where α _B = (1 / e) · (de / dT): linear expansion coefficient of the lens barrel β _o = (1 / φ _o) ) ・ (Dφ _o / dT)

Therefore, as a temperature compensation condition, a wavefront that cancels the error wavefront θ generated by the spot movement is generated.
The following equation must be satisfied. (DW _T / dT) = (８λF ² ) · (dΔx / dφ) · (dφ / dT) = (１ ／ λF ² ) · (−1 / φ ² ) · (dφ / dT) = − θ ( 307)

On the other hand, in a synthetic lens in which thin lenses composed of a plurality of types of materials are brought close to each other, when the dispersion of the i-th material is μ _i and the lens power is φ _i , Must be satisfied. The power of each lens is determined from this equation and three equations obtained by adding the equation (307) relating to the power satisfying the above temperature compensation condition.

As described above, by constructing the objective lens 303 and the eyepiece 304 using at least three kinds of materials, the wavefront which satisfies the combined power condition, achromatizes, and always satisfies the two conditions of temperature compensation. A sensor can be configured.

Embodiment 4 FIG. FIG. 4 is a configuration diagram showing a fourth embodiment of the present invention. 4, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 4, 1 is the primary mirror of the telescope, 2 is the secondary mirror of the telescope, 4
00 is a wavefront sensor, and 401 is a barometric compensation collimator lens. Here, a wavefront calculator for obtaining a wavefront based on the output of the CCD 10 is not shown.

The atmospheric pressure dispersion γ represented by the equation (401) can be handled in the same manner as the dispersion μ in a so-called achromatic lens. γ = 1 / (n-n a) (401)

When the collimator lens 401 is composed of a plurality of lenses combining different materials, it is possible to equivalently synthesize and create material characteristics such as atmospheric pressure dispersion γ. In a synthetic lens in which thin lenses made of a plurality of types of materials are brought close to each other, when the ith material has a dispersion of μ _i , a pressure dispersion of γ _i , and a lens power of φ _i , the following conditions are satisfied for the collimator lens 401. Needs to be satisfied.

As described above, if a collimator lens is formed by using at least three kinds of materials, an afocal optical system that satisfies the combined power condition, achromatizes, and always satisfies the two conditions of the atmospheric pressure compensation is required. Can be.

Embodiment 5 FIG. FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention. 5, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 5, reference numeral 501 denotes a calibration value calculator, 502 denotes a wavefront sensor angle controller, and 29 denotes a reference light source.

In the present embodiment, the distance between the CCD 10 and the lens array 9 required for accurately calculating the inclination of the wavefront is not directly measured, but is measured and calibrated in the mounted state.

As shown in the conventional example, the relationship between the deviation amount Δr of the spot position on the CCD 10 and tan θ is expressed by the following equation. _{tanθ = Δr / l m (501} ) , where, l _m is the distance between the microlens array 9 and CCD 10. Now, light having an incident angle θ is incident on the wavefront sensor, the deviation Δr from the reference spot position is measured, and the distance l _m is obtained from the above θ and Δr by the equation (501).

Hereinafter, a method of calibrating the wavefront sensor will be described. (1) The wavefront calculator 21 measures the reference spot position by the reference light source 29. (2) The wavefront sensor angle controller 502 tilts the optical system 11 of the wavefront sensor by θ, and calculates the tilt angle θ as a calibration value calculator 501. To send to. (3) The wavefront calculator 21 measures the calibration data spot position, and (4) the wavefront calculator 21 subtracts the reference spot position from the calibration data spot position to obtain a displacement Δr of the spot position.
Is sent to the calibration value calculator 501. (5) The calibration value calculator 501 calculates a distance l _m between the lens array 9 and the CCD 10 in pixel units from Δr and θ, and the wavefront calculator 21 stores data in an internal memory. Thus, the calibration is completed.

When the wavefront measurement is performed, the actual calibration of the lens array 9 and the CCD 10
The distance between them is accurately determined, and the accuracy of wavefront measurement can be improved.

Embodiment 6 FIG. FIG. 6 is a configuration diagram showing a sixth embodiment of the present invention. 6, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 6, 600 is a wavefront sensor, 601 is a half mirror, 602 is a calibration light introducing half mirror, 603 is an array-shaped light source NA adjustment mask, 604 is an array-shaped light source,
5 is a shutter. Here, a wavefront calculator for obtaining a wavefront based on the output of the CCD 19 is not shown.

In the present embodiment, the reference light is obtained by a simple configuration instead of the reference wavefront generator 15 for emitting the collimated reference light required for the wavefront sensor having the afocal system 28 described in the section of the prior art. Like that.

First, the configuration of the wavefront sensor will be described. The light emitted from the array-shaped light source 604 is converted into the optical system 2 of the wavefront sensor
0, the half mirror 602 for introducing the calibration light
Are arranged in front of the CCD 19. An array light source 604 is installed at a mirror image position of the CCD 19 generated by the half mirrors 601 and 602. Array light source 6
The NA adjustment mask 603 provided on the front surface of the light source 04 has a number of openings corresponding to the number of the array light sources 604 in a flat plate, and limits the emission angle of each light source constituting the array light source 604. The light emitted from the light source and the lenses constituting the lens array 18 are made to correspond one-to-one. F of lens array 18
When the value is F and the distance from the array light source 604 to the mask 603 is x, the aperture diameter D of the mask 603 is obtained by the following equation. D = x / F (601)

The light emitted from the array light source 604 is introduced into the wavefront sensor via the calibration light introducing half mirror 602,
After being reflected by the half mirror 601, the light is focused on the CCD 19 by the lens array 18. When the reference light source is used, the measured light is blocked by the shutter 605.

Next, a method of correcting a measurement wavefront using a reference light source will be described. The output light of the array light source 604 is
Since the light passes through the optical system of the wavefront sensor twice, the effect of twice the optical system aberration is measured. Array light source 60
In No. 4, an accurate arrangement can be obtained by using, for example, a laser diode array, and the disturbance of the arrangement of the spots is caused by the influence of the optical system aberration. The wavefront is determined based on the measured disorder of the arrangement of the spots, and the half is obtained.
Is the error wavefront caused by the aberration of the optical system,
By subtracting the previously obtained error wavefront from the measured wavefront at the time of wavefront measurement, the correct wavefront can be measured.

In the conventional method, when the position of the reference light source 29 moves in the optical axis direction due to a change in ambient temperature or the like, a distorted spherical wave enters the wavefront sensor, and the position of the spot changes. However, in this embodiment, when the installation position of the array-like light source 604 moves in the optical axis direction, spot blurring occurs due to collapse of the conjugate relationship with the CCD. But,
If the wavefront calculator 21 defines spot position measurement using the center of gravity of a commonly used spot, the position of the center of gravity does not change even when blur occurs.

As described above, it is possible to realize a reference light source that is strong against a change in use environment conditions. This also reduces the manufacturing tolerance when the arrangement position of the array-like light source is conjugate with the CCD. Can be taken.

Embodiment 7 FIG. FIG. 7 is a configuration diagram showing a seventh embodiment of the present invention. 7, the same reference numerals as those in FIGS. 11 and 6 indicate the same or corresponding parts. 7, reference numeral 700 denotes a wavefront sensor, 701 denotes a polarizing plate, and 704 denotes an array-shaped polarized light source. Here, a wavefront calculator for obtaining a wavefront based on the output of the CCD 19 is not shown.

In this embodiment, the light to be measured is polarized.
A polarizing plate 701 is used instead of the half mirror 601 of the sixth embodiment, and an array-like polarized light source 704 is used as the array-like light source 604.
Is used.

The array-shaped polarized light source 704 is installed at a mirror image position of the CCD 19 generated by the half mirror 602 and the polarizing plate 701, and is orthogonal to the polarization direction of the light to be measured. When the polarization direction of the polarizing plate 701 and the polarization direction of the measured light are set to coincide with each other, the measured light transmits through the polarizing plate 704,
A focused spot is formed on the CCD 19. The reference light is reflected by the polarizing plate 701 and forms a spot on the CCD 19. When the array-shaped polarized light source 704 is used, the measured light is blocked by the shutter 605. Other operations are the same as in the sixth embodiment.

As described above, the polarizing plate 701 reflects the calibration light almost 100%, and the measured light almost 100%.
Since the light is transmitted, it is possible to realize an optical system in which the amount of light loss of the reference light and the light to be measured by the polarizing plate 701 inserted for calibration is extremely small.

Embodiment 8 FIG. FIG. 8 is a configuration diagram showing Embodiment 8 of the present invention. 8, the same reference numerals as those in FIGS. 11 and 6 denote the same or corresponding parts. In FIG. 8, 800 is a wavefront sensor, 801 is a dichroic mirror, and 804 is an array-like light source having a wavelength different from that of the light to be measured. Here, a wavefront calculator for obtaining a wavefront based on the output of the CCD 19 is not shown.

In this embodiment, the wavelengths of the light to be measured and the reference light are different. The dichroic mirror 801 is configured to transmit light in the wavelength range of the light to be measured and reflect the light in the wavelength range of the reference light.

The array-like light source 804 is
CCD 19 generated between the light source 2 and the dichroic mirror 801
It is installed at the mirror image position of. The measured light passes through the dichroic mirror 801 to form a spot on the CCD 19. On the other hand, the light emitted from the array light source 804 is introduced by the half mirror 602 and reflected by the dichroic mirror 801 to form a spot on the CCD 19. When the reference light source is used, the measured light is blocked by the shutter 605. Other operations are the same as in the sixth embodiment.

As described above, the dichroic mirror 80
1 reflects almost 100% of the reference light and transmits almost 100% of the light to be measured, so that it is possible to realize an optical system in which the dichroic mirror 801 has a very small loss of light amount of the reference light and the light to be measured.

Embodiment 9 FIG. FIG. 9 is a configuration diagram showing a ninth embodiment of the present invention. 9, the same reference numerals as those in FIG. 11 denote the same or corresponding parts. 9, reference numeral 900 denotes a wavefront sensor, 901 denotes a diaphragm having a variable diameter, 902 denotes a diaphragm diameter controller, 903 denotes a diaphragm diameter calculator as aperture diameter calculator, and 904 denotes an FFT calculator as FFT calculator.

In this embodiment, in order to suppress stray light, the aperture diameter is changed in accordance with the state of light condensing by the objective lens 16 of the afocal optical system.

In order to suppress stray light, it is necessary to reduce the diameter of the stop so as not to cut off the light to be measured. When the front focal plane of the objective lens 16 is set as the wavefront measurement position, the point image intensity distribution by the objective lens 16 follows the Fourier transform result of the measurement wavefront. The FFT calculator 904 performs a Fourier transform of the measured wavefront obtained by the wavefront calculator 21 to obtain a point image intensity distribution. An aperture diameter calculator 903 gives a threshold value to the point image intensity distribution, and sets a range exceeding the threshold value as an aperture diameter. The aperture diameter controller 902 adjusts the aperture diameter based on this information.

As described above, stray light which has been a problem in the case of a fixed aperture can be reduced, and malfunction can be suppressed.

Embodiment 10 FIG. FIG. 10 is a configuration diagram showing a tenth embodiment of the present invention. FIG.
At 0, the same reference numerals as those in FIG. 11 indicate the same or corresponding parts. In FIG. 10, reference numeral 8 denotes a first collimator lens, 1
11 and 113 are first and second dichroic mirrors, 114 and 115 are band-pass filters, 116 and 115, respectively.
118 is a mirror, 117 is a second collimator lens, 1
10 is a wavefront sensor. Here, a wavefront calculator for obtaining a wavefront based on the output of the CCD 19 is not shown.

The telescope has a configuration in which the sub-mirror 2 is exchanged, and the F-number changes as the sub-mirror 2 is changed, as shown by the broken line in FIG. As shown in the conventional example, it is necessary to replace the collimator lens 8 according to a change in the F value or to prepare another wavefront sensor corresponding to each F value.

To make the diameters of the wavefronts incident on the lens array 18 with different F-numbers the same, the first collimator lens 8
May be changed according to the F value. In the present embodiment, the optical path is separated by the first dichroic mirror 111, and a second collimator lens 117 suitable for the F value is installed in the separated optical path to cope with a change in the F value.

Since the second collimator lens 117 and the optical path length can be freely set by changing the optical path, the second collimator lens 117 suitable for the F-number can be used, and the lens array 18 and subsequent ones can be shared. it can. Since light of two wavelengths enters the lens array, the wavelength selection is performed by exchanging the bandpass filters 114 and 115.

As described above, it is not necessary to replace the entire optical system depending on the F value, and since there are no movable parts other than the bandpass filters 114 and 115, the tolerance of the optical system can be suppressed to a small value and high accuracy can be achieved. Wavefront measurement can be realized.

[0080]

According to the present invention configured as described above, it is possible to obtain a wavefront sensor capable of measuring the wavefront of the light to be measured with high accuracy even when the use environment conditions change.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a wavefront sensor according to a first embodiment.

FIG. 2 is a configuration diagram of a wavefront sensor according to a second embodiment.

FIG. 3 is a configuration diagram of a wavefront sensor according to a third embodiment.

FIG. 4 is a configuration diagram of a wavefront sensor according to a fourth embodiment.

FIG. 5 is a configuration diagram of a wavefront sensor according to a fifth embodiment.

FIG. 6 is a configuration diagram of a wavefront sensor according to a sixth embodiment.

FIG. 7 is a configuration diagram of a wavefront sensor according to a seventh embodiment.

FIG. 8 is a configuration diagram of a wavefront sensor according to an eighth embodiment.

FIG. 9 is a configuration diagram of a wavefront sensor according to a ninth embodiment.

FIG. 10 is a configuration diagram of a wavefront sensor according to a tenth embodiment.

FIG. 11 is a configuration diagram of an apparatus (telescope) including a conventional wavefront sensor.

[Explanation of symbols]

 1: Primary mirror of telescope 2: Secondary mirror of telescope 4: Lamp for reference light source 5: Lamp light focusing lens 6: Pinhole 7: Beam splitter 8: Collimator lens (first collimator lens) 9: Lens array 10: CCD 11: Optical system of wavefront sensor 13: Deformable mirror 14: Beam splitter 16: Objective lens 17: Eyepiece 18: Lens array 19: CCD 20: Optical system of wavefront sensor 21: Wavefront calculator 22: Deformable mirror 28: Afocal optical system 29: Reference light source 50: Wavefront sensor 51: Wavefront sensor 100: Wavefront sensor 101: Temperature sensor 102: Error wavefront calculator 103: Wavefront calculator 110: Wavefront sensor 111, 113: Dichroic mirror 114, 115: Band Pass filter 117: second collimator lens 11 6, 118: mirror 200: wavefront sensor 201: barometric pressure sensor 202: error wavefront calculator 203: wavefront calculator 301: temperature compensation afocal optical system 302: lens array 303: objective lens 304: eyepiece 400: wavefront sensor 401: Barometric pressure compensation collimator lens 501: Calibration value calculator 502: Wavefront sensor angle controller 600: Wavefront sensor 601: Half mirror 602: Half mirror for introducing calibration light 603: Array-shaped light source NA adjustment mask 604: Array-shaped light source 605: Shutter 700: Wavefront sensor 701: Polarizing plate 704: Array-like polarized light source 800: Wavefront sensor 801: Dichroic mirror 804: Array-like light source having a different wavelength from the light to be measured 900: Wavefront sensor 901: Variable-diameter aperture 902: Aperture diameter controller 903: Aperture Diameter calculator 904: FFT calculator

Continuation of the front page (56) References JP-A-5-18719 (JP, A) JP-A-5-323213 (JP, A) JP-A-4-372811 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G01M 11/00 G02B 23/02

Claims (3)

(57) [Claims] 1. An optical system comprising: a lens array; a lens for projecting light to be measured on the lens array; and a photoelectric converter for detecting a position of a condensed spot of the lens array by the projected light to be measured. A wavefront sensor for measuring a wavefront of the measured light, comprising a system, based on an output of a temperature sensor provided in the optical system, a change amount of a focus position of the lens caused by a temperature change is calculated from a predetermined formula. Calculate, convert the calculated change in the focus position into a change in the wavefront, and an error wavefront calculator for obtaining the change in the wavefront, and the measured light obtained based on the output of the photoelectric converter. A wavefront calculator for subtracting the change in the wavefront from the wavefront. 2. The method according to claim 1, wherein the change in the focus position of the lens is calculated from a change in power caused by a change in the refractive index of the lens due to a change in temperature, and expansion and contraction of a lens barrel of the lens. A wavefront sensor as described. 3. An optical system comprising: a lens array; a lens for projecting light to be measured on the lens array; and a photoelectric converter for detecting a position of a condensed spot of the lens array by the projected light to be measured. A wavefront sensor for measuring the wavefront of the light to be measured, comprising a system, based on an output of a pressure sensor provided in the optical system, a change in focus position of the lens caused by a change in pressure.
Is calculated from a predetermined formula, and the change of the calculated focus position is calculated.
An error wavefront calculator that converts the chemical component into a change in the wavefront, and obtains the change in the wavefront, and subtracts the change in the wavefront from the wavefront of the measured light obtained based on the output of the photoelectric converter. A wavefront sensor, comprising: a wavefront calculator.