JP2015087198A5

JP2015087198A5 -

Info

Publication number: JP2015087198A5
Application number: JP2013224891A
Authority: JP
Filing date: 2013-10-30
Publication date: 2016-12-01

Description

本発明の計測装置は、光源と、光線分布センサと、光を被検物の被検面に照射して得られた反射光を、計測光として前記光線分布センサに投影するように構成された投影光学系と、基準光を発生させる基準光発生部と、前記計測光と前記基準光との少なくとも一方の光線角度を、前記投影光学系に入射される前に変更可能な光線分布可変素子と、前記光線分布センサで検出される前記計測光の光線分布と前記基準光の光線分布とを一致させるように、前記光線分布可変素子を制御して前記計測光と前記基準光との少なくとも一方の光線角度を変更し、前記光線分布可変素子の制御量に基づいて前記被検面の形状を演算する演算部と、を備えることを特徴とする。 Measurement apparatus of the present invention, a light source, a light ray distribution sensor, a reflected light obtained by irradiating the test surface of the test object light, configured to project the light distribution sensor as the measurement light a projection optical system that is, a reference light generator for generating a reference light, at least one of the ray angle of the measuring light and the reference light, changeable light rays distribution before being incident on the projection optical system The light distribution variable element is controlled to match the light distribution of the measurement light and the light distribution of the reference light detected by the light distribution sensor with the variable element, and the measurement light and the reference light are controlled. A calculation unit that changes at least one of the light beam angles and calculates the shape of the test surface based on a control amount of the light distribution variable element.

また、本発明は、光源と、光線分布センサと、光を被検物の被検面に照射して得られた反射光を、計測光として前記光線分布センサに投影するように構成された投影光学系と、基準光を発生させる基準光発生部と、前記計測光と前記基準光との少なくとも一方の光線角度を、前記投影光学系に入射される前に変更可能な光線分布可変素子と、演算部と、を備える計測装置の計測方法において、前記演算部は、前記光線分布センサで検出される前記計測光の光線分布と前記基準光の光線分布とを一致させるように、前記光線分布可変素子を制御して前記計測光と前記基準光との少なくとも一方の光線角度を変更する光線分布変更工程と、前記光線分布可変素子の制御量に基づいて前記被検面の形状を演算する形状演算工程と、を実行することを特徴とする。 Further, the present invention includes a light source, a light ray distribution sensor, a reflected light obtained by irradiating the test surface of the test object light, configured to project the light distribution sensor as the measurement light and a projection optical system, a reference light generator for generating a reference light, at least one of the ray angle of the measuring light and the reference light, changeable light rays distribution variable before being incident on the projection optical system In the measurement method of the measuring device including an element and a calculation unit, the calculation unit matches the light distribution of the measurement light detected by the light distribution sensor with the light distribution of the reference light. and the light distribution changing step of changing at least one of the ray angle of the beam distribution variable element and the measuring light by controlling the reference light, the shape of the test surface based on the control amount before Symbol light distribution variable element and shape calculation step of calculating, that the execution And butterflies.

本発明によれば、計測光の光線分布と基準光の光線分布とを検出して、これらの光線分布が一致するように計測光と基準光の少なくとも一方の光線角度を変更するようにしている。従って、基準計測時と被検面計測時とにおいて投影光学系での光線分布が異なることを抑制できるので、光線分布の違いにより発生し得る投影光学系の収差の違いを抑え、計測誤差を抑制できるようになる。 According to the present invention, by detecting the light distribution of the measuring light beam distribution and reference light, and at least one of the ray angle of the measuring light and the reference light, as these rays distribution matches to modify Yes. Therefore, it is possible to suppress the difference in the light distribution in the projection optical system between the reference measurement and the measurement of the surface to be measured. become able to.

ホルダ３１には、被検物２及び基準光を発生させる基準光学素子（基準光発生部）３が選択的に着脱可能になっている。基準光学素子３としては、例えば球面や非球面等の形状が既知であって光源光を反射する基準面３ａを有する基準レンズあるいは基準ミラー等を適用する。被検物２がホルダ３１により保持され被検位置に設置されると、光源光が被検物２の被検面２ａに照射され、該被検面２ａから計測光がビームスプリッタ２０に入射される。また、基準光学素子３がホルダ３１により保持された時は、光源光が基準光学素子３の基準面３ａに照射され、該基準面３ａから基準光がビームスプリッタ２０に入射される。即ち、本実施形態では、基準光学素子３は、基準面３ａの形状に応じた所定形状の基準波面を有する基準光を発生させ、計測光と選択的に基準光を投影光学系７０に入射可能になっている。 A specimen 31 and a reference optical element (reference light generator) 3 for generating reference light are selectively detachable from the holder 31. As the reference optical element 3, for example, a reference lens or a reference mirror having a reference surface 3a that has a known shape such as a spherical surface or an aspheric surface and reflects light source light is used. When the test object 2 is held by the holder 31 and placed at the test position, the light source light is irradiated onto the test surface 2a of the test object 2, and the measurement light is incident on the beam splitter 20 from the test surface 2a. The When the reference optical element 3 is held by the holder 31, the light source light is applied to the reference surface 3 a of the reference optical element 3, and the reference light is incident on the beam splitter 20 from the reference surface 3 a. In other words, in the present embodiment, the reference optical element 3 can generate reference light having a reference wavefront having a predetermined shape corresponding to the shape of the reference surface 3a, and can selectively enter the reference light into the projection optical system 70 as measurement light. It has become.

次に、本実施形態の特徴部である光線分布可変素子６０について説明する。光線分布可変素子６０は、屈折率が可変な透明物質を備え、屈折率の空間的な分布を制御することで、透過する光の位相の空間分布を変調する位相変調素子である。例えば、液晶層の配向状態を電気的に制御することで屈折率を制御するものが周知であるが、これに限られないのは勿論である。この光線分布可変素子６０は、対物レンズ２４と被検物２または基準光学素子３との間に設置され、透過する光の空間位相を変調可能になっている。即ち、光線分布可変素子６０は、計測光と基準光との少なくとも一方の光線角度を、投影光学系７０に入射される前に変更可能になっている。 Next, the light distribution variable element 60 that is a characteristic part of the present embodiment will be described. The light distribution variable element 60 is a phase modulation element that includes a transparent material having a variable refractive index and modulates the spatial distribution of the phase of transmitted light by controlling the spatial distribution of the refractive index. For example, it is well known that the refractive index is controlled by electrically controlling the alignment state of the liquid crystal layer. However, the present invention is not limited to this. This light distribution variable element 60 is installed between the objective lens 24 and the test object 2 or the reference optical element 3, and can modulate the spatial phase of the transmitted light. That is, light distribution variable element 60, at least one of the ray angle of the measurement light and the reference light, and is changeable before being incident on the projection optical system 70.

この光線分布可変素子６０による位相変調量は、演算部５０の光線分布変更部５６から入力される制御信号によって制御される。光線分布可変素子６０を用いることにより、光線角度を例えば部分ごとに変化させることができ、その後の光線分布を変化させることができる。 The amount of phase modulation by the light distribution variable element 60 is controlled by a control signal input from the light distribution changing unit 56 of the calculation unit 50. By using the light distribution variable element 60, the light angle can be changed, for example , for each part, and the subsequent light distribution can be changed.

光線分布変更部５６は、光線分布可変素子６０を制御して計測光と基準光との少なくとも一方の光線角度を変更することにより、計測光線分布と基準光線分布とを一致させるようになっている。また、形状演算部５７は、光線分布可変素子６０の制御量に基づき、被検面２ａと基準面３ａとの形状差を演算し、基準面３ａの形状及び形状差に基づいて被検面２ａの形状を演算するようになっている。本実施形態では、形状演算部５７は、光線分布可変素子６０で変調した位相の分布に基づいて演算する。 Light distribution changing unit 56, by modifying the at least one of the ray angle of the measurement light and the reference light by controlling the light distribution variable element 60, so as to match the measured light distribution and reference light distribution Yes. The shape calculating unit 57 calculates the shape difference between the test surface 2a and the reference surface 3a based on the control amount of the light distribution variable element 60, and the test surface 2a based on the shape and the shape difference of the reference surface 3a. The shape is calculated. In the present embodiment, the shape calculation unit 57 calculates based on the phase distribution modulated by the light distribution variable element 60.

そこで、本実施形態では、光線分布変更部５６が、被検面２ａの反射光の位相分布を光線分布可変素子６０で変調し、光線分布を変化させる。これにより、被検面２ａの反射光が投影光学系７０を透過する際の光線分布を、基準面３ａの反射光の光線分布と一致させるようにできる（ステップＳ６、光線分布変更工程）。光線分布が一致したか否かは、シャックハルトマンセンサ４０の出力、即ちＣＣＤカメラ４２上でのスポット分布が一致したか否かによって、光線分布変更部５６により判断される。 Therefore, in the present embodiment, the light distribution changing unit 56 modulates the phase distribution of the reflected light of the test surface 2a by the light distribution variable element 60 to change the light distribution. This allows to match the light distribution, light distribution of the reflected light of the reference plane 3a when the reflected light of the test surface 2a passes through the projection optical system 70 (step S6, light distribution changing step). Whether or not the light distributions match is determined by the light distribution changing unit 56 based on whether or not the output of the Shack-Hartmann sensor 40, that is, the spot distribution on the CCD camera 42 matches.

Claims

And a light source,
And a light-ray distribution sensor,
The reflected light obtained by irradiating the test surface of the test object light, and configured projection optical system to project the light distribution sensor as the measurement light,
A reference light generator for generating reference light;
At least one of the ray angle of the measuring light and the reference light, and changeable rays distribution variable element before being incident on the projection optical system,
The light distribution variable element is controlled to match at least one of the measurement light and the reference light so that the light distribution of the measurement light detected by the light distribution sensor matches the light distribution of the reference light. A calculation unit that changes an angle and calculates the shape of the test surface based on a control amount of the light distribution variable element,
A measuring device characterized by that.

The reference light generator is a reference optical element that can be installed at a predetermined position and has a reference surface that is irradiated with light from the light source when installed at the predetermined position;
The reference light is light obtained by reflecting light from the light source on the reference surface,
When the test object is installed at a test position, the light from the light source is irradiated onto the test surface, the measurement light is incident on the projection optical system from the test surface, and the light distribution The light distribution of the measurement light is detected by a sensor,
When the reference optical element is installed at the predetermined position, the light from the light source is irradiated onto the reference surface, the reference light is incident on the projection optical system from the reference surface, and the light distribution sensor A light distribution of the reference light is detected;
The measuring apparatus according to claim 1.

The predetermined position is the test position,
The reference optical element can be selectively installed with the test object at the test position.
The measuring device according to claim 2.

The reference light generation unit is a reflection type light distribution variable element that can be installed at a predetermined position and has a reflection surface that is irradiated with light from the light source when installed at the predetermined position.
The reference light is light obtained by reflecting light from the light source on the reflection surface,
When the test object is installed at a test position, the light from the light source is irradiated onto the test surface, the measurement light is incident on the projection optical system from the test surface, and the light distribution The light distribution of the measurement light is detected by a sensor,
When the light distribution variable element is installed at the predetermined position, the light from the light source is irradiated onto the reflection surface, the reference light is incident on the projection optical system from the reflection surface, and the light distribution sensor. The light distribution of the reference light is detected by
The measuring apparatus according to claim 1.

The predetermined position is a position where light from the light source has passed through the test position,
The test object can be installed and removed from the test position.
The measuring apparatus according to claim 4.

The projection optical system includes a condensing element that condenses light from the light source,
The reference light generation unit is an optical element that can be installed at a focal position of the condensing element, and has a condensing point that collects and reflects light from the light source when installed at the focal position. Yes,
The reference light is light obtained by reflecting light from the light source at the condensing point,
When the test object is installed at a test position, the light from the light source is irradiated onto the test surface, the measurement light is incident on the projection optical system from the test surface, and the light distribution The light distribution of the measurement light is detected by a sensor,
When the optical element is installed at the focal position, the light from the light source is irradiated onto the condensing point, the reference light is incident on the projection optical system from the condensing point, and the light distribution sensor. The light distribution of the reference light is detected by
The measuring apparatus according to claim 1.

The test object is displaceable between the test position and the focus position,
The optical element is the test object,
The condensing point is provided on the test surface,
The measuring apparatus according to claim 6.

The light distribution variable element is a transmissive type.
The measuring apparatus according to claim 2, wherein the measuring apparatus is one of the following.

The light distribution variable element is a reflective type.
The measuring apparatus according to claim 2, wherein the measuring apparatus is one of the following.

The projection optical system receives light from the light source, emits the light toward the test surface, and enters the measurement light reflected by the test surface to separate it from the light from the light source. A separation optical system that emits
The measuring apparatus according to claim 1, wherein

The light distribution sensor is a Shack-Hartmann sensor,
The measuring apparatus according to claim 1, wherein

And a light source,
And a light-ray distribution sensor,
The reflected light obtained by irradiating the test surface of the test object light, and configured projection optical system to project the light distribution sensor as the measurement light,
A reference light generator for generating reference light;
At least one of the ray angle of the measuring light and the reference light, and changeable rays distribution variable element before being incident on the projection optical system,
In a measurement method of a measurement device comprising a calculation unit,
The computing unit is
The light distribution variable element is controlled to match at least one of the measurement light and the reference light so that the light distribution of the measurement light detected by the light distribution sensor matches the light distribution of the reference light. A ray distribution changing process for changing the angle;
The run shape calculation step of calculating the shape of the surface, a based on the control amount before Symbol light distribution variable element,
A measuring method characterized by this.