JP4814894B2 - Optical system for optical property evaluation equipment - Google Patents

Description

  The present invention relates to an optical system for an optical property evaluation apparatus, and more particularly to an optical system for a high performance optical property evaluation apparatus that can be evaluated at a plurality of wavelengths.

  Interferometers have been conventionally used to evaluate optical characteristics such as wavefront aberration and individual aberration. The wavelength used in these interferometers is mainly 633 nm of a He—Ne laser, and others include 405 nm. However, all of them are limited to use at a single wavelength, and the optical system used for them can also be used at a single wavelength.

  In recent years, light of various wavelengths has come to be used for inspection devices for semiconductor inspection, such as wavelengths in the ultraviolet region and wavelengths in the near infrared region in the communication field. Accordingly, there is a demand for an apparatus that can cover wavelengths other than the conventional wavelength of 633 nm, preferably from the ultraviolet region to the infrared region, and can evaluate the characteristics of the optical system at a desired wavelength. Furthermore, the performance of the optical system to be evaluated is required to be high performance, and the device for evaluating this is also required to have high performance.

  The technique disclosed in Patent Document 1 relates to an optical system used in the interferometer, and uses a relay lens system that allows a test wave to pass as an afocal system.

The technique disclosed in Patent Document 2 relates to an optical property evaluation apparatus using the Shack-Hartmann method. This is a method that does not use an interferometer, and has been attracting attention in recent years. This technique also has an optical system that relays a test wave, and is composed of an afocal system.
JP 7-198316 A Japanese Patent Laid-Open No. 10-216092

  The technique disclosed in Patent Document 1 is a technique premised on use at a single wavelength, and this technique alone cannot achieve the purpose of using at a plurality of wavelengths. In addition, this technology does not fully consider a high-performance optical system in which the wavefront aberration of the test wave is about 0.01λ (λ is a wavelength). Such an optical system cannot be fully evaluated.

  The technique disclosed in Patent Document 2 is not assumed to be used at a plurality of wavelengths. Therefore, the technique disclosed in Patent Document 2 alone cannot achieve the purpose of using a plurality of wavelengths.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide an optical system for an optical property evaluation apparatus that can be applied to a high-performance optical system and can be evaluated at a plurality of wavelengths. That is.

The optical system for an optical property evaluation apparatus of the present invention that achieves the above object collimates light from a light source with a collimating lens, makes the collimated light incident on a test surface or a test optical system, and reflects it on the test surface. Alternatively, the optical system for an optical characteristic evaluation apparatus that relays the light returned through the optical system to be tested directly with the afocal optical system or interferes with the reference light and then relays with the afocal optical system to measure the wavefront. Because
The afocal optical system is composed of two lens groups having a positive focal length, that is, a lens group Ga and a lens group Gb from the object side, and a rear focal position of the lens group Ga and the lens group Gb. It is arranged so that the front focal position is approximately the same,
₁ lambda the wavelength used from the shorter, lambda _2, ..., and lambda _n, the focal length at each wavelength of the lens group _{Ga f a1, f a2, ...} , f an, and, each wavelength of the lens group Gb _Where f _b1 , f _b2 ,..., F _bn are arbitrary wavelength λ _m (2 ≦ m ≦ n) at the used wavelength,
0.97 ≦ (f _bm / f _am ) / (f _b1 / f _a1 ) ≦ 1.03 (2)
Thus, the lens group Ga and the lens group Gb are configured.

  In this case, it is desirable that the lenses constituting the lens group Ga and the lens group Gb are made of the same material.

  Further, in the above, when the wavelength of the light from the light source is changed, the distance between the light source and the collimating lens and the distance between the lens group Ga and the lens group Gb can be changed. It is desirable to have a mechanism that can adjust the state of collimation and afocal after changing the wavelength of light.

In the above, the rear focal position of the lens group Ga and the front focal position of the lens group Gb are arranged so as to substantially coincide with each other.
It is desirable that a spatial filter is disposed near the rear focal position of the lens group Ga or near the front focal position of the lens group Gb.

ADVANTAGE OF THE INVENTION According to this invention, it can comprise with a comparatively simple optical system, can respond to a high performance optical system, and can provide the optical system for optical characteristic evaluation apparatuses which can be evaluated in several wavelengths.

  Hereinafter, the reason and action of such an arrangement in the optical system for an optical property evaluation apparatus of the present invention will be described.

  An optical system for an optical property evaluation apparatus according to the present invention collimates light from a light source with a collimating lens, causes the collimated light to enter a test surface or a test optical system, and reflects the test surface or the test optical system. This is an optical system for an optical characteristic evaluation apparatus that relays light that has passed through and directly relayed by a relay optical system or caused to interfere with reference light and then relay by a relay optical system to measure the wavefront.

  Here, there is a Shack-Hartmann configuration as a configuration in which light reflected by the test surface or transmitted through the test optical system (test light) is directly relayed by the relay system to measure the wavefront. On the other hand, there is a Fizeau type interferometer as a configuration in which the test light is interfered with the reference light and then relayed by a relay optical system to measure the wavefront.

In the present invention, the collimating lens is a single lens or a cemented single lens,
Λ is the shortest wavelength in the operating wavelength range, D is the effective beam diameter of the collimated light, f is the focal length at the wavelength λ of the collimating lens, n is the refractive index at the wavelength λ when the collimating lens is a single lens, In the case of a cemented single lens, when the average value of the refractive index of each lens at the wavelength λ is n,
D / {(n−1) f ² } ≦ 0.0016 (mm ⁻¹ ) (1)
To meet.

  In the Fizeau interferometer, since the test light and the reference light pass through a common optical path, theoretically, even if there is residual aberration in the collimated light, it is not affected. This is correct only when there is no alignment error. If there is an error in the alignment of the interferometer optical system or the test optical system, even a Fizeau interferometer is affected by this error, resulting in a measurement error.

  Even if the test light and the reference light pass through the same optical system, the influence is not canceled unless they pass through the same optical path. Therefore, if there is an alignment error, it does not pass exactly the same optical path, so that it is affected by the residual aberration of the collimated light. In particular, when measuring a high-performance optical system, this measurement error affects. Therefore, it is desirable that the collimated light be as close to no aberration as possible within the effective light beam diameter range.

  In the present invention, a simple lens system such as a single lens or a cemented single lens is used to generate collimated light that can be regarded as almost no aberration within the range of the effective light beam diameter. The effect will be described in a little more detail.

  In general, the smaller the NA (numerical aperture), the smaller the aberration of the optical system. The NA in the collimating lens is related by the ratio of the beam diameter of collimated light and the focal length. However, even if the NA is the same, the amount of aberration that is generated is proportional to the focal length, so the longer the focal length, the greater the amount of aberration that is generated. Therefore, it is necessary to consider the NA standardized by the focal length. Furthermore, even when the focal length is the same, the amount of aberration that occurs when the refractive index of the lens medium is higher is smaller. Although it is easy to understand with a single lens, if the refractive index is high, a large power can be given even with a loose radius of curvature. Accordingly, even at the same focal length, the higher the refractive index, the smaller the radius of curvature and the smaller the resulting aberration. The effect of this refractive index n is proportional to n-1.

In view of the above, by using a lens having a focal length satisfying the expression (1) as a collimating lens with respect to a required light beam diameter, it is possible to generate a light beam that can be regarded as substantially no aberration in the effective light beam diameter. Here, “substantially non-aberration” means a state where the wavefront aberration is at least equal to or less than that in consideration of evaluation of a high-performance optical system having a wavefront aberration of about 0.01λ. If the upper limit of 0.0016 (mm ⁻¹ ) in the expression ( ¹ ) is exceeded, the collimated light cannot be said to have no aberration.

  Furthermore, in the present invention, a simple configuration such as a single lens or a cemented single lens is used. However, if a single lens or a cemented single lens is used, the configuration of the optical system becomes simple. Therefore, even if the adjustment of the optical system is required, the strict accuracy is not required. In addition, since the lens is used in a state where the NA is small, the aberration does not occur so much even with a simple configuration. In addition, when quartz or the like is used as the material, there is little light loss even when using light in the ultraviolet region. In the case of a simple configuration such as a single lens or a cemented single lens, it is difficult to make the focal lengths the same for a plurality of wavelengths. In the case of a single lens or a cemented single lens, since the focal length tends to be shorter as the wavelength is shorter, it is preferable to satisfy the above formula (1) for the shortest wavelength in the usable wavelength range.

  If the condition (1) is satisfied, adjustment for correcting chromatic aberration is required, but if only adjustment is performed, it can be made substantially non-aberration.

Another optical characteristic evaluation apparatus optical system according to the present invention collimates light from a light source with a collimator lens, causes the collimated light to enter a test surface or a test optical system, and reflects or reflects the test surface. This is an optical system for an optical characteristic evaluation apparatus that measures the wavefront by relaying the light that has passed through the detection optical system directly through the afocal optical system or interfering with the reference light and then relaying through the afocal optical system. And
The afocal optical system is composed of two lens groups having a positive focal length, that is, a lens group Ga and a lens group Gb from the object side, and a rear focal position of the lens group Ga and the lens group Gb. It is arranged so that the front focal position is approximately the same,
₁ lambda the wavelength used from the shorter, lambda _2, ..., and lambda _n, the focal length at each wavelength of the lens group _{Ga f a1, f a2, ...} , f an, and, each wavelength of the lens group Gb _Where f _b1 , f _b2 ,..., F _bn are arbitrary wavelength λ _m (2 ≦ m ≦ n) at the used wavelength,
0.97 ≦ (f _bm / f _am ) / (f _b1 / f _a1 ) ≦ 1.03 (2)
The lens group Ga and the lens group Gb are configured so that

  When performing wavefront measurement, it is common to relay the pupil plane of the optical system under test through a relay system, and image and measure with a CCD or the like. The merit of configuring this relay system with an afocal optical system is also known from Patent Document 1. When the afocal optical system is composed of the lens group Ga and the lens group Gb having a positive focal length, the projection magnification is determined by the focal length ratio. This magnification is usually determined by the size of the image sensor such as a CCD and the pupil diameter of the test optical system. In order to improve the measurement accuracy as much as possible, the pupil of the test optical system is usually not protruded from the image sensor. Project large. In particular, in the Shack-Hartmann method, which directly relays the test light and measures the wavefront, the pupil projected by the relay system (here, the afocal optical system) is sampled by a microlens, so the projection magnification increases the measurement accuracy. The impact is great.

  When the optical system for an optical characteristic evaluation apparatus is to be adapted to a plurality of wavelengths, it is not desirable that the magnification of the relay system greatly varies depending on the wavelength. In particular, the Shack-Hartmann method has a larger influence, but there is a situation in which the measurement accuracy changes depending on the measured wavelength.

  Therefore, in another optical system for an optical property evaluation apparatus of the present invention, the lens group Ga and the lens group Gb are configured so as to satisfy the expression (2). Ideally, the magnification does not change at an arbitrary wavelength. However, when an optical system for an interferometer is assumed, normally only a laser can be used as a light source. It should be satisfied. If the lower limit of 0.97 in equation (2) is not reached, the magnification becomes small, and the measurement accuracy is deteriorated particularly in the Shack-Hartmann method. When the upper limit of 1.03 is exceeded, the magnification increases, and in some cases, the pupil image protrudes from the image sensor when the wavelength is changed.

  As a specific means satisfying the expression (2), if the objective is to correspond to several wavelengths with a laser wavelength in the visible range, the lens group Ga and the lens group Gb are each composed of a cemented single lens, This can be achieved by selecting an appropriate radius of curvature.

  Further, in the other optical characteristic evaluation apparatus optical system described above, it is desirable that the lenses constituting the lens group Ga and the lens group Gb are made of the same material.

  This can make the wavelength dispersion the same by using the same material. Therefore, the rate of change in focal length when the wavelength is changed is the same in the lens group Ga and the lens group Gb, and is constant when the ratio is taken. That is, even if the wavelength is changed, the afocal state can be kept substantially the same. For example, if the lens group Ga and the lens group Gb are each composed of a single lens, and the same material and the lens shape is a plano-convex lens if the lens is a plano-convex lens, and a biconvex lens if the lens shape is unified, the magnification can be constant over the entire wavelength range .

  Even if they are made of the same material, if the lens shape is different, such as a plano-convex lens and a biconvex lens, the method of changing the focal length with respect to the wavelength will change slightly, so the magnification will not be constant, but only to satisfy equation (2) You can do it.

  Next, in the optical system for another optical property evaluation apparatus, when the wavelength of light from the light source is changed, the distance between the light source and the collimating lens, and the distance between the lens group Ga and the lens group Gb are respectively It is desirable to have a mechanism that can change the collimation and afocal states after changing the wavelength of light from the light source.

  If a cemented single lens is used for the collimator lens or relay lens and the wavelength used is two wavelengths, it is possible to correct the chromatic aberration of the optical system with these two wavelengths and use it without adjustment even if the wavelength is changed. is there. However, when trying to cope with three or more wavelengths, it is difficult to sufficiently correct chromatic aberration in a state where the position of the cemented single lens is fixed. Therefore, it is desirable to have a mechanism that can adjust the collimated state and the afocal state.

  It is desirable that a spatial filter is disposed in the vicinity of the rear focal position of the lens group Ga or in the vicinity of the front focal position of the lens group Gb. When performing wavefront measurement, it is very important to conjugate the test surface and the imaging surface such as a CCD. The adjustment to make this conjugate is usually performed by moving the CCD or the like in the optical axis direction so that the imaging surface such as the CCD is in focus. If this adjustment is inadequate, the wavefront will not be relayed correctly, so the correct wavefront cannot be measured. Since the degree of adjustment affects measurement accuracy, it is an important factor for evaluating high-performance optical systems. This is the same even in the case of the Shack-Hartmann method. However, in the case of the Shack-Hartmann method, a spot train passing through the microlens is observed, so it is often difficult to determine whether or not the focus is in focus than in the case of an interferometer. Actually, the focus position is obtained while looking at the state before and after focusing. However, if there is no spatial filter, it is difficult to focus while looking at the state before and after focusing because of the influence of scattering and diffraction at the edge of the frame etc. that determines the effective range of the test surface. is there.

  Therefore, a spatial filter is arranged in the vicinity of the rear focal position of the lens group Ga or the front focal position of the lens group Gb, and the influence of scattering and diffraction at the edge portion such as a frame that determines the effective range of the test surface is detected. By removing the focus position adjustment can be facilitated. Even if the focus position adjustment is slightly sweet, the influence of scattering and diffraction is eliminated, so that the measurement accuracy can be prevented from being affected so much.

  If a spatial filter is arranged near the rear focal position of the lens group Ga or near the front focal position of the lens group Gb, evaluation other than evaluation of a high-performance optical system or evaluation using a plurality of wavelengths is performed. Also useful.

  Next, first to third embodiments of the optical system for an optical property evaluation apparatus of the present invention will be described below with reference to the drawings.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a diagram showing the configuration of the first embodiment of the present invention. The light from the laser 1 is condensed by the condensing lens 2 and is incident on one end of the single mode fiber 3, and the light emitted from the other end of the fiber 3 is collimated by the collimating lens 4. The collimated light is split into two light beams by the half mirror 7, one light beam is guided to the reference concave mirror 5 through the lens 6 to be tested, and the other light beam is guided to the reference mirror 12. These two light beams are coupled again by the half mirror 7, and interference fringes of these two light beams are relayed through the relay lenses 8 and 10, imaged by the CCD 11, and wavefront measurement can be performed. As shown in FIG. 3, the collimating lens 4 is composed of one plano-convex lens. Since the glass material is quartz, it can be used even in the ultraviolet region. In this embodiment, since the measurement in the wavelength range from 266 nm to 1064 nm is assumed, the shortest wavelength is 266 nm. The effective beam diameter of the light collimated by the lens 4 is φ10 mm, and the refractive index and focal length at 266 nm are 1.49968 and 184.117 mm. The expression (1) is satisfied. Further, since the wavefront aberration when used at a wavelength of 266 nm and an effective light beam diameter of φ10 mm is 0.0083λ, it can sufficiently cope with measurement and evaluation of a high-performance optical system.

  When changing the wavelength, it is necessary to change the distance between the single mode fiber 3 and the collimating lens 4. In this embodiment, although not shown, a single mode fiber 3 is attached to each laser 1 to be used, and the wavelength is changed by replacing the fiber 3. Therefore, the configuration is such that the exit side portion of the fiber 3 is adjusted in the optical axis direction. Of course, it is needless to say that the position of the fiber 3 may be fixed and the collimating lens 4 may move in the optical axis direction.

  Table 1 shows lens data for each wavelength of the collimating lens 4 portion. In Table 1, r represents the radius of curvature of the surface, d represents the surface interval, and the numbers in the left column correspond to the surface number and surface interval number in FIG. same as below.

次に、リレー光学系部分について説明する。その構成は図４に示した通りである。レンズ群Ｇａ（８）及びレンズ群Ｇｂ（１０）共に平凸の単レンズにて構成されていて、平面側で相互に向かい合っている。硝材は何れも石英で構成されている。

Next, the relay optical system part will be described. The configuration is as shown in FIG. Both the lens group Ga (8) and the lens group Gb (10) are composed of plano-convex single lenses, and face each other on the plane side. All the glass materials are made of quartz.

  When the wavelength is changed and used, the relay lenses 8 and 10 move independently in the optical axis direction. In order to adjust the conjugate relationship between the test surface and the CCD surface, as another mechanism, the relay lenses 8 and 10 and the spatial filter 9 are integrally moved in the optical axis direction. The CCD 11 can also be moved in the optical axis direction.

Table 2 shows lens data for each wavelength of the relay optical system, and Table 3 shows the relay magnification after performing the afocal adjustment when changing the focal lengths f _a and f _b and the wavelength at each wavelength.

使用波長域の中で最も短い波長が２６６ｎｍなので、これがλ₁ となる。また、リレーレンズ８及び１０が石英製の平凸単レンズで構成されているために、波長が変化した際の焦点距離の変化率は、リレーレンズ８と１０とで同じになる。すなわち、（２）式の計算式部分の値は１で一定となる。したがって、（２）式を満たしている。

Since the shortest wavelength in the used wavelength range is 266 nm, this is λ ₁ . Further, since the relay lenses 8 and 10 are made of quartz plano-convex single lenses, the rate of change of the focal length when the wavelength is changed is the same between the relay lenses 8 and 10. That is, the value of the formula part of the formula (2) is 1 and constant. Therefore, the formula (2) is satisfied.

(Second embodiment)
A second embodiment of the present invention will be described. FIG. 2 is a diagram showing the configuration of the second embodiment of the present invention. The light emitted from the lamp 13 passes through the mirror 14 and the collector lens 15 in this order, and is condensed on the pinhole 16. The pinhole diameter of the pinhole 16 is set to be less than or equal to the diffraction diameter of the light collected by the collector lens 15. The light transmitted through the pinhole 16 is collimated by the collimating lens 4, reflected by the half mirror 7, and guided to the reference concave mirror 5 through the test optical system 6. The light returned from the test optical system 6 passes through the half mirror 7 and enters the microlens array 17 through the relay lenses 8 and 10. The spot train collected by the microlens array 17 is imaged by the CCD 11 and analyzed, whereby the wavefront aberration of the test optical system 6 is obtained.

  In this embodiment, the collimating lens 4 is constituted by a cemented single lens as shown in FIG. This cemented single lens is composed of a quartz negative meniscus lens and a fluorite biconvex positive lens. In this embodiment, the operating wavelength range is 248 nm to 900 nm. At a wavelength of 248 nm, quartz has a refractive index of 1.50855 and fluorite has a refractive index of 1.46803. The effective beam diameter of the light collimated by the collimating lens 4 is φ10 mm, and the average refractive index and focal length at a wavelength of 248 nm are 1.48829 and 194.363 mm. Therefore, the expression (1) is satisfied. Further, since the wavefront aberration when used at a wavelength of 248 nm and an effective light beam diameter of φ10 mm is 0.0038λ, it can sufficiently cope with a high-performance optical system.

  When the wavelength is changed, the collimator lens 4 is adjusted by moving in the optical axis direction.

Table 4 shows lens data for each wavelength of the collimating lens 4 portion. N _d and ν _d in the table indicate the refractive index and Abbe number at the d-line, respectively. same as below.

次に、リレー光学系部分について説明する。その構成は図６に示した通りである。レンズ群Ｇａ（８）及びレンズ群Ｇｂ（１０）共に接合単レンズにて構成されており、レンズ群Ｇａは両凸正レンズと負メニスカスレンズの接合単レンズ、レンズ群Ｇｂは負メニスカスレンズと両凸正レンズの接合単レンズからなる。硝材は何れも凸レンズは蛍石、凹レンズは石英で構成されている。さらに、レンズ群Ｇｂはレンズ群Ｇａの曲率半径及び肉厚を係数倍することで構成されている。

Next, the relay optical system part will be described. The configuration is as shown in FIG. The lens group Ga (8) and the lens group Gb (10) are both constituted by a cemented single lens. The lens group Ga is a cemented single lens of a biconvex positive lens and a negative meniscus lens, and the lens group Gb is a negative meniscus lens and both. It consists of a cemented single lens with a convex positive lens. Each glass material is made of fluorite for the convex lens and quartz for the concave lens. Further, the lens group Gb is configured by multiplying the radius of curvature and thickness of the lens group Ga by a coefficient.

  When the wavelength is changed, the relay lenses 8 and 10 are independently moved in the optical axis direction as in the first embodiment. In order to adjust the conjugate relationship between the test surface and the CCD surface, the relay lenses 8 and 10 and the spatial filter 9 are moved together in the optical axis direction as a separate mechanism. Further, the CCD 11 and the microlens array 17 can be moved integrally in the optical axis direction.

Table 5 shows lens data for each wavelength of the relay optical system, and Table 6 shows the relay magnification after performing the afocal adjustment when changing the focal lengths f _a and f _b and the wavelength at each wavelength.

使用波長域の中で最も短い波長が２４８ｎｍなので、これがλ₁ となる。また、リレーレンズ１０がリレーレンズ８を係数倍して構成されているために、波長が変化した際の焦点距離の変化率がリレーレンズ８と１０が同じとなる。すなわち、（２）式の計算式部分の値は１で一定となる。したがって、（２）式を満たしている。

Since the shortest wavelength in the used wavelength range is 248 nm, this is λ ₁ . Further, since the relay lens 10 is configured by multiplying the relay lens 8 by a factor, the rate of change of the focal length when the wavelength changes is the same for the relay lenses 8 and 10. That is, the value of the formula part of the formula (2) is 1 and constant. Therefore, the formula (2) is satisfied.

(Third embodiment)
A third embodiment of the present invention will be described. The basic configuration is the same as that shown in FIG. Further, in this embodiment, the collimating lens 4 is the same as that used in the first embodiment. The difference from the first embodiment is that the relay optical system portion is designed so as to be substantially free of aberrations only at five wavelengths of 405 nm, 488 nm, 514.5 nm, 532 nm, and 633 nm in the visible range. .

  Table 7 shows lens data for each wavelength of the collimating lens portion.

本実施例では、４０５ｎｍから６３３ｎｍまでの波長に対応することを想定しているので、最も短い波長は４０５ｎｍである。このレンズ４でコリメートされた光の有効光束径はφ１０ｍｍであり、４０５ｎｍでの屈折率及び焦点距離は、1.46958 、195.919 ｍｍであるから、（１）式の左辺を計算すると、0.00055 となるので、（１）式を満たしている。また、波長４０５ｎｍ、有効光束径φ１０ｍｍで使用した際の波面収差は0.0051λであるので、高性能な光学系にも十分に対応できる。

In the present embodiment, it is assumed that the wavelengths from 405 nm to 633 nm are supported, so the shortest wavelength is 405 nm. The effective beam diameter of the light collimated by the lens 4 is φ10 mm, and the refractive index and focal length at 405 nm are 1.46958 and 195.919 mm. Therefore, when the left side of the equation (1) is calculated, it becomes 0.00055. The expression (1) is satisfied. Further, since the wavefront aberration when used at a wavelength of 405 nm and an effective light beam diameter of 10 mm is 0.0051λ, it can sufficiently cope with a high-performance optical system.

  Next, the relay optical system part will be described. The configuration is as shown in FIG. The lens group Ga (8) is composed of a biconvex single lens, and the lens group Gb (10) is composed of a cemented single lens of a convex plano-positive lens and a plano-concave negative lens.

  When the wavelength is changed and used, the relay lenses 8 and 10 move independently in the optical axis direction. In order to adjust the conjugate relationship between the test surface and the CCD surface, the relay lenses 8 and 10 and the spatial filter 9 are moved together in the optical axis direction as a separate mechanism. The CCD 11 can also be moved in the optical axis direction.

Table 8 shows lens data for each wavelength of the relay optical system, and Table 9 shows the relay magnification after performing the afocal adjustment when changing the focal lengths f _a and f _b and the wavelength at each wavelength.

使用波長域の中で最も短い波長が４０５ｎｍなので、これがλ₁ となる。表９から明らかなように、（２）式を満たしている。

Since the shortest wavelength in the used wavelength range is 405 nm, this is λ ₁ . As apparent from Table 9, the expression (2) is satisfied.

  The optical systems used in the three examples shown above are not limited to the interferometer or Shack-Hartmann method shown above, but can be used for other ones if the desired purpose is achieved. Needless to say, it doesn't matter. For example, the collimating lens and the relay optical system shown in the first embodiment may be used for the Shack-Hartmann method.

  As described above, according to the present invention, an optical system for an optical property evaluation apparatus that can be configured with a relatively simple optical system, is compatible with a high-performance optical system, and can be evaluated at a plurality of wavelengths is provided. can do.

It is a figure which shows the structure of 1st Example of the optical system for optical property evaluation apparatuses of this invention. It is a figure which shows the structure of 2nd Example of the optical system for optical property evaluation apparatuses of this invention. It is sectional drawing which shows the structure of the collimating lens of 1st Example. It is sectional drawing which shows the structure of the relay optical system of 1st Example. It is sectional drawing which shows the structure of the collimating lens of 2nd Example. It is sectional drawing which shows the structure of the relay optical system of 2nd Example. It is sectional drawing which shows the structure of the relay optical system of 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Condensing lens 3 ... Single mode fiber 4 ... Collimate lens 5 ... Reference concave mirror 6 ... Test optical system 7 ... Half mirror 8 ... Relay lens Ga
9 ... Spatial filter 10 ... Relay lens Gb
11 ... CCD
12 ... Reference mirror 13 ... Lamp 14 ... Mirror 15 ... Collector lens 16 ... Pinhole 17 ... Micro lens array

Claims (4)

The light from the light source is collimated by a collimating lens, the collimated light is incident on the test surface or optical system, and the light reflected by the test surface or transmitted through the optical system is directly afocal. An optical system for an optical property evaluation apparatus that relays with an optical system or interferes with a reference light, then relays with an afocal optical system, and measures a wavefront,
The afocal optical system is composed of two lens groups having a positive focal length, that is, a lens group Ga and a lens group Gb from the object side, and a rear focal position of the lens group Ga and the lens group Gb. It is arranged so that the front focal position is approximately the same,
₁ lambda the wavelength used from the shorter, lambda _2, ..., and lambda _n, the focal length at each wavelength of the lens group _{Ga f a1, f a2, ...} , f an, and, each wavelength of the lens group Gb _Where f _b1 , f _b2 ,..., F _bn are arbitrary wavelength λ _m (2 ≦ m ≦ n) at the used wavelength,
0.97 ≦ (f _bm / f _am ) / (f _b1 / f _a1 ) ≦ 1.03 (2)
An optical system for an optical characteristic evaluation apparatus, wherein the lens group Ga and the lens group Gb are configured so as to satisfy 2. The optical system for an optical property evaluation apparatus according to claim 1, wherein the lenses constituting the lens group Ga and the lens group Gb are made of the same material. When the wavelength of light from the light source is changed, the distance between the light source and the collimating lens or the distance between the lens group Ga and the lens group Gb can be changed. The optical system for an optical property evaluation apparatus according to claim 1, further comprising a mechanism capable of adjusting a collimated or afocal state after changing. 4. The optical characteristic evaluation apparatus according to claim 1, wherein a spatial filter is disposed near a rear focal position of the lens group Ga or near a front focal position of the lens group Gb. 5. Optical system.

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