JP2001091223A - Spacing measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spacing measuring method and device, which can measure thickness and spacing of a lens with high accuracy in nondestructively and in noncontacting manner. SOLUTION: A luminous flux emitted from a low coherence light source 101 is divided by a luminous flux dividing means 102, and one is adjusted as reference light to be varied in optical path length by an optical path length varying means 103 to be reflected by a reflector 107. The reference light and measurement light are superposed by luminous flux composition means 105, and when the optical path length different between reflected light from a face (a) of a tested material 104 and reflected light from the reflector 107 is within a coherence length of the light source, interference occurs and an interference signal is detected by a photoelectric detector 106. The optical path length varying means 103 is moved to reflected light from the other face (b) of the tested material 104 to vary the optical path length, and when an interference signal is obtained by the photoelectric detector 105, spacing a-b is obtained by measuring the optical path length change of the optical path length varying means 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the thickness and the distance between lenses, that is, the distance between the surfaces.

[0002]

2. Description of the Related Art As a conventional surface distance measuring device, there is known a method of detecting a reflection image from the top of an optical element such as a lens and measuring the surface distance. There is also a method in which a cross section of an optical system is photographed using X-rays, and a distance between elements is obtained from an X-ray photograph.

[0003]

However, the above-mentioned conventional measuring instrument has a poor measurement accuracy of the surface spacing, and cannot meet the demand for higher precision of the optical system.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a non-destructive, non-contact, and highly accurate lens thickness and surface spacing, that is, a surface position that can be measured. An object of the present invention is to provide an interval measuring method and apparatus.

[0005]

A method and an apparatus for measuring a surface distance according to the present invention for achieving the above object are as follows, for example.

[1] A low coherence light source having a short spatial coherence length, a light beam splitting means for splitting a light beam emitted from the low coherence light source, and an optical path length of one of the light beams split by the light beam splitting device is variable. An optical path length changing means for causing the light beam splitting means to guide the other light beam split into the optical system as an object having a surface interval to be measured, the reflected or transmitted light from the object and the light beam splitting A light beam combining means for superimposing two light beams split by the means, and a surface distance measuring method and apparatus for measuring a surface distance of a test object from interference light superimposed by the light beam combining means.

[2] A low coherence light source having a short spatial coherence length, and a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam of an arbitrary shape;
A polarization state conversion unit that converts the light beam emitted from the light beam shaping unit into an arbitrary polarization state, a light beam division unit that divides the light beam emitted from the polarization state conversion unit according to the polarization state, and the light beam division unit. Second polarization state conversion means for converting the polarization state of one of the split light fluxes, reflection means for reflecting the light flux whose polarization state has been changed by the second polarization state conversion means, the reflection means and the light flux splitting An optical path length varying means for varying an optical path length in an optical path between the light beam splitting means and a third polarization state converting means for converting a polarization state of the other light beam split by the light beam splitting means; An optical element with an adjusting device that guides the light beam whose polarization state has been changed by the polarization state conversion device to an optical system as a test object having a surface interval to be measured, and the light beam is incident on the surface to be measured. , The luminous flux A plane distance measuring method comprising: a light beam combining means for superimposing two light beams split by a splitting means; and a photoelectric conversion means for converting the light intensity of the light beam superposed by the light beam combining means into an electric signal. And equipment.

[3] The method and apparatus according to the above item 1 or 2, wherein a prism is used as the optical path length varying means.

[4] A liquid crystal having a variable refractive index is used as the optical path length varying means.
The method and apparatus for measuring a surface distance according to the description.

[5] A low coherence light source having a short spatial coherence length, and a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam of an arbitrary shape;
A first polarization state conversion unit that converts a light beam emitted from the light beam shaping unit into an arbitrary polarization state, a light beam division unit that divides the light beam emitted from the polarization state conversion unit according to the polarization state, An optical path length changing unit disposed on an optical path of one of the light beams split by the first light beam splitting device, for changing an optical path length, a second polarization state converting unit for converting a polarization state of the light beam, and the light beam splitting device Third polarization state conversion means for converting the polarization state of the other light beam divided by the above, and an optical device as an object having a surface interval to measure a light beam whose polarization state has been changed by the third polarization state conversion means An optical element with an adjusting means that guides the light to the surface to be measured toward the surface to be measured, a reflecting means for reflecting the reflected light from the test object, and a reflected light from the reflecting means. Via the optical path length changing means A beam combining means for superimposing the light beam, the light beam combining means surface distance measuring method and apparatus characterized by comprising a photoelectric conversion means for converting into electrical signals the intensity of light beams superimposed by the.

[6] A low coherence light source having a short spatial coherence length, light beam splitting means for splitting a light beam emitted from the low coherence light source, and a first light beam for reflecting one of the light beams split by the light beam splitting means. Reflection means,
A second reflecting means for reflecting the light beam reflected by the first reflecting means, and an optical system as an object having a surface interval to measure the other light beam divided by the light beam dividing means. An optical element with an adjusting means for guiding the light beam toward the surface to be measured, a light beam combining means for superimposing the two light beams divided by the light beam dividing means,
A surface distance measuring method and apparatus, wherein a surface distance is obtained from interference information of light beams superimposed by the light beam combining means.

[7] A low coherence light source having a short spatial coherence length, and a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam of an arbitrary shape;
A reflecting means for reflecting a part of the light beam shaped by the light beam shaping means; and an optical system as an object having a surface interval to be measured and arranged on an optical path parallel to the light beam shaped by the light beam shaping means. And an optical element with an adjusting unit such that the light beam is incident on the surface to be measured, and a light beam combining unit that superimposes the light beam reflected by the reflecting unit and the light beam reflected by the test object. And an apparatus for measuring a surface interval from interference information of the light beams superimposed by the light beam combining means.

[8] The method and apparatus according to any one of the above items 1 to 7, wherein an optical fiber is used in an optical path.

[0014]

[9] The measuring method and apparatus according to the above item 8, wherein the refractive index of the liquid crystal is measured.

[10] In any one of the above items 1 to 7, the thickness of the optical element in the optical system as the test object is known from a design value or an actual measurement, and is obtained from a result of the distance measurement of the optical system. Calculate the group refractive index of the optical element from the optical path length, and agree with the measured group refractive index of the optical element from a table in which the group refractive index in a measurement wavelength range of a plurality of glass or plastic materials prepared in advance is calculated. A method and apparatus for determining an optical material, wherein a type of a glass or plastic material of an optical element to be inspected is specified by searching for a glass or plastic having a group index of refraction.

[11] The method according to any one of [1] to [10], wherein the low coherence light source emits a linearly polarized light beam, and is rotatable about an optical axis. apparatus.

[12] The low coherence light source emits a linearly polarized light beam, and a half-wave plate is disposed on the optical axis between the light source and the light beam splitting means.
The measurement method and apparatus according to any one of the above items 1 to 10, wherein the wave plate is rotatable about an optical axis.

[13] The measuring method and apparatus according to the above item 11 or 12, wherein the light source operates a single mode oscillation semiconductor laser at a threshold current or less.

[14] The measuring method and apparatus according to the above item 11 or 12, wherein the light source is a pulse laser.

[15] The measuring method and apparatus according to any one of [1] to [10], wherein the reflecting means is a variable reflectance mirror. .

[16] In the above item 15, the light intensity at the position where the reflected light reflected on the surface of the object to be measured is incident on the light beam combining means is I ₁ , and the reflected light reflected by the reflectivity variable mirror is The light intensity at the position where it enters the light beam combining means is I ₂
Wherein the reflectance of the variable reflectance mirror is adjusted such that 0.05 ≦ I ₁ / I ₂ ≦ 20.

[17] In the above 15, the light intensity at the position where the reflected light reflected on the surface of the test object to be measured is incident on the light beam combining means is I ₁ , and the reflected light reflected by the reflectivity variable mirror is The light intensity at the position where it enters the light beam combining means is I ₂
Wherein the reflectivity of the variable reflectivity mirror is adjusted such that 0.2 ≦ I ₁ / I ₂ ≦ 5.

[18] The reflecting means is a plurality of variable reflectivity mirrors arranged at intervals on a stage movable in the optical axis direction, and the reflectivity can be controlled independently. 18. The measuring method and apparatus according to any one of 1 to 17 above. .

[19] The measuring method and apparatus according to any one of [1] to [18], wherein a transparent medium is arranged on the optical axis between the light beam splitting means and the optical path length changing means. .

[20] The method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

0.5 <(n (λ _S ) −n (λ _L )) · d
/ (L _S -L _L ) <2, where: d: thickness of the transparent medium n (λ): group index of refraction of the transparent medium at an arbitrary wavelength λ λ _S : of the light emitted from the light source, the light intensity is the highest When the light intensity at the strong wavelength λ ₀ is I ₀ , the light intensity is 0.5 I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum.

[21] The method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

0.8 <(n (λ _S ) −n (λ _L )) · d
/ (L _S -L _L ) <1.25, where d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : light intensity of light emitted from the light source There when the light intensity of the strongest wavelength lambda ₀ and the I _0, the light intensity is 0.5I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum.

[22] The measurement method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

0.5 <(n (λ _S ) −n (λ _L )) · d
/ ((L _Sa −L _La ) / 2) <2, where d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : of light emitted from the light source When the light intensity at the wavelength λ ₀ where the light intensity is the strongest is I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths L _La at the wavelength λ _S above is the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object.

[23] The method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

0.8 <(n (λ _S ) −n (λ _L )) · d
/ ((L _Sa −L _La ) / 2) <1.25, where d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : light emitted from the light source When the light intensity at the wavelength λ ₀ where the light intensity is the strongest is defined as I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths L _La at the wavelength λ _S above is the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object.

[24] The measuring method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

| (N (λ _S ) −n (λ _L )) · d− (L
_{S− LL} ) | <100 [μm] where, d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : of the light emitted from the light source, the light intensity is When the light intensity at the strongest wavelength λ ₀ is I ₀ , the light intensity is 0.5 I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum.

[25] The method and apparatus according to the above item 19, wherein the transparent medium satisfies the following conditional expression.

| (N (λ _S ) −n (λ _L )) · d− (L
_S− L _L ) | <30 [μm] where d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : of the light emitted from the light source, the light intensity is When the light intensity at the strongest wavelength λ ₀ is I ₀ , the light intensity is 0.5 I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum.

[0037] [26] In any one of the above 20 to 25, the wavelength of the shorter wavelength side than the lambda ₀ of the wavelength where the light intensity lambda _S becomes 0.2i _0, lambda _L light intensity 0.2i A measurement method and apparatus, wherein a wavelength longer than λ ₀ among wavelengths that become ₀ is used.

[27] In any one of the above items 20 to 25, λ _S is a wavelength on the shorter wavelength side than λ ₀ and λ _L is a light intensity of 0.1 I ₀ among wavelengths where the light intensity is 0.1 I _0. A measurement method and apparatus, wherein a wavelength longer than λ ₀ among wavelengths that become ₀ is used.

[28] The measuring method and apparatus according to any one of the above items 19 to 25, wherein the transparent medium comprises a plurality of transparent media.

[29] A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is referred to as a reference light, and the other as a measuring light, which is guided to a test object whose interval is to be measured. An optical path and a measurement optical path are arranged in substantially the same direction, a method or an apparatus or a measured object in which the reference light and the measurement light are superimposed to determine a surface interval of an optical element, an optical system, or an optical device.

[30] An interferometer using a light source having a short coherence length, and a test object arranged in the optical path of the interferometer to cause interference, thereby reducing the surface distance between the optical element and the display device or the display element. The method or device to be determined or the measured object.

[31] An interferometer using a light source having a short coherence length, and a method or apparatus for measuring a surface shape by placing an object in the optical path of the interferometer to cause interference, or a measured object.

[32] A light source having a short coherence length,
A method or apparatus comprising a measurement optical path and a reference optical path, wherein light from the light source is incident on an object to be measured, and the emitted light and the light in the reference optical path interfere with each other to determine a surface shape or a measured object.

[33] The above-mentioned item 31 or 32, wherein a lens array is provided in the optical path incident on the object to be measured.
A method, apparatus, or measured object for obtaining the described surface shape.

[34] The method or apparatus for measuring the surface shape according to the above item 31 or 32, or a measured object, wherein a means for shaping a light beam into a plurality of light beams is provided in an optical path incident on the object to be measured.

[35] The method or apparatus for determining the surface shape according to the above item 31 or 32, wherein the measurement is performed while moving the means for shaping the light beam disposed in the optical path incident on the object to be measured. Thing.

[36] The method or apparatus for determining a surface shape or the measured object according to the above item 31 or 32, wherein the object to be measured and the light receiving element are optically conjugate.

[37] An interferometer using a light source having a short coherence length, and a method of arranging a test object in an optical path of the interferometer to cause interference to obtain a surface position or a physical characteristic of the test object; Equipment or measured object.

[38] An interferometer using an optical fiber using a light source having a short coherence length, and a test object arranged in the optical path of the interferometer to cause interference, thereby causing the surface spacing or physical characteristics of the test object Method or device for measuring or measured object.

[39] In an interferometer using an optical fiber using a light source having a short coherence length, a member for changing the optical path length is provided in the optical path of the interferometer, and a test object is arranged in the optical path of the interferometer. A method or apparatus or a measured object that causes interference to determine the surface spacing or physical characteristics of a test object.

[40] In an interferometer using an optical fiber using a light source having a short coherence length, a test object is arranged in the optical path of the interferometer, and a member for changing the optical path length is provided in the optical path of the interferometer. A method or an apparatus or a measured object that causes interference between light that has passed through a member that changes the optical path length and light that has not passed, thereby causing interference, and determining the surface spacing or physical characteristics of a test object.

[41] In an interferometer using an optical fiber using a light source having a short coherence length, light is incident on a member for changing the optical path length provided in the optical path of the interferometer, and a member for changing the optical path length is used. A method or a device or a measured object that is incident on a test object together with light that does not pass therethrough, causes interference of emitted light to cause interference, and obtains a surface interval or physical characteristics of the test object.

[42] In an interferometer using an optical fiber using a light source having a short coherence length, a test object is arranged in the optical path of the interferometer, and light emitted from the test object is transmitted through the optical path of the interferometer. A method of determining the surface spacing or physical characteristics of a test object by causing interference with light emitted from a test object that is incident on a member that changes the optical path length and that does not pass through the member that changes the optical path length provided in Or a device or measured object.

[43] In an interferometer using a light source having a short coherence length, a test object is arranged in the optical path of the interferometer, a member for changing the optical path length is provided in the optical path of the interferometer, and the optical path length is reduced. A method or a device or a measured object that causes interference by causing light that has passed through a member to be changed and light that does not pass to cause interference, thereby obtaining the surface spacing or physical characteristics of a test object.

[44] A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is used as a reference light, and the other is used as a measuring light, which is guided to a test object whose distance is to be measured. A method or device for determining the distance by superimposing the measurement light with the measurement light.

[45] A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is used as a reference light, and the other is used as a measuring light by an endoscope or a rigid device. A method or an apparatus for guiding a light through a mirror optical system and superposing the reference light and the measurement light to obtain a distance.

First, the basic configuration of the method and apparatus for measuring a surface interval according to the present invention will be described with reference to FIG. The light beam emitted from the low coherence light source 101 is
2, one of which is divided as an optical path length
The optical path length is variably adjusted at 3 and reflected by the reflecting mirror 107. The reference beam and the measuring beam are separated by a beam splitting unit 1
02 overlaps with the light beam synthesizing means 105 also serving as the light source 02, but if the difference in the optical path length between the reflected light from the surface a of the test object 104 and the reflected light from the reflecting mirror 107 is within the coherence length of the light source, interference occurs, and photoelectric detection is performed. The interference signal is detected by the detector 106.
Next, for the reflected light from the other surface b of the test object 104, the optical path length changing means 103 is moved to change the optical path length, and when an interference signal is obtained by the photoelectric detector 105, the optical path length variable If the change in the optical path length by the means 103 is measured, the interval a-b can be obtained.

[0058]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method and apparatus for measuring a surface distance according to the present invention will be described below.

(Embodiment 1) FIG. 2 is a diagram showing the configuration of Embodiment 1 of the present invention. The light beam emitted from the low coherence light source 1 becomes parallel light by the collimator lens 2 and becomes linearly polarized light by the polarizer (polarizer) 3. A microscope objective lens may be used as the collimator lens 2. next,
When the linearly polarized light is split by the polarizing beam splitter (PBS) 4, the transmitted light and the reflected light have substantially the same light amount.
The azimuth of the transmission axis of the polarizer 3 is set in advance. Among the light beams split by the polarization beam splitter 4, the transmitted light becomes circularly polarized light by the first quarter-wave plate 5 as reference light, passes through the wedge-shaped prism 52 constituting the optical path length varying means 51, and passes through the reflecting mirror 6 After that, the light again passes through the wedge-shaped prism 52 and the quarter-wave plate 5 to become linearly polarized light again.
And is incident on a photoelectric detector (photodetector) 8. The wedge-shaped prism 52 can be moved in a direction perpendicular to the optical axis by a linear guide or the like, and the movement distance can be accurately measured by a length measuring device or the like.

On the other hand, the reflected light split by the polarization beam splitter 4 passes through the second quarter-wave plate 10 and becomes circularly polarized light as measurement light. A lens arranged on the incident side of the optical system 14 to be measured such that light is incident toward the vicinity of the spherical center or near the top of one surface a of the optical system 14 to be measured whose surface spacing or thickness is to be measured. The position of 30 is selected, and the circularly polarized light that has passed through the second quarter-wave plate 10 via this lens 30 enters the test optical system 14. The position of the lens 30 is obtained in advance by optical calculation such as ray tracing. By arranging in this way,
The light beam reflected by the surface a is converted by the lens 30 into, for example, substantially parallel light within ± 10 ° with respect to the optical axis. Then, the reflected light becomes linearly polarized light by the 波長 wavelength plate 10, passes through the polarization beam splitter 4, and enters the photoelectric detector 8.

As the photoelectric detector 8, one such as a CCD is used.
A two-dimensional or two-dimensional solid-state imaging device, imaging tube, photodiode, or the like can be used. If a two-dimensional photoelectric conversion element is used, reflected images from each surface of the test optical system 14 to be measured can be confirmed on the CRT, and thus there is an advantage that the test lens can be easily positioned.

Here, examples of the optical system 14 include a camera, a zoom lens of a digital camera, a single focus lens, a microscope, a lens of an endoscope, a spectacle lens, a contact lens, and the like.

In the photoelectric detector 8, for example, a photodiode, a CCD, a C-MOS sensor, an image pickup tube, a photomultiplier, a line sensor, a CdS, etc., the light reflected by the reflecting mirror 6 (reference light) and the test light The light reflected by the lens (measurement light) overlaps, and if the optical path length difference between them is within the range of the coherence length of the light source, interference occurs and an interference signal is observed. If a low coherence light source having a coherence length of about several tens of μm is used as the light source 1, an interference signal is observed when the optical path length difference between the reference light and the measurement light falls within the range of the coherence length.

As the low coherence light source 1, a light source having a coherence length of 0.1 μm to 200 μm in full width at half maximum or 1 nm to 500 nm in full width at half maximum of wavelength can be used. For example, a super luminescent diode (SL
Although D) is well known in recent years, a semiconductor laser may be operated at a threshold current or less, or a short pulse laser, a halogen lamp, an LED, or the like may be used.

In this state, the position of the wedge prism 52 is recorded or reset.

Next, the position of the lens 30 is selected such that light is incident toward the vicinity of the spherical center or the top of the other surface b of the optical system 14 to be measured, and the reflected light from the surface b is selected. Is incident on the photoelectric detector 8. Then, the position of the interference signal is obtained by changing the position of the wedge-shaped prism 52.

The position of the wedge prism 52 at this position is read. This value is subtracted from the value obtained on the surface a, and the difference is converted into the optical path length in the air to obtain the interval to be obtained.

Since the value obtained here is the air conversion length, if the medium between the intervals to be measured is air, the converted optical path length is the interval to be obtained as it is, but the interval is optically dense such as glass. In the case of a medium, the actual distance can be obtained by dividing the medium by the refractive index of the medium.

Here, since a low coherence light source such as an SLD is used, the wavelength of the light source has a wide range. Therefore, when the medium has chromatic dispersion, an accurate interval can be obtained by using the group refractive index in consideration of the dispersion.

The group refractive index _ng is represented by the following equation.

[0071] Here _{n g = n p -λ (dn} p / dλ) ··· Equation 1, represents the phase refractive index at n _p, lambda represents a wavelength.
This concept can be used throughout the present invention.

At this time, when the optical path length of the wedge-shaped prism 52 is converted to the position of the reflecting mirror (moving mirror) 6, the interference fringes are obtained when the refractive index and the surface interval of the optical system 14 to be measured are approximately known. It is advisable to calculate in advance the positions at which they occur.

The optical path length of the wedge-shaped prism 52 in which interference fringes occur
Is converted to the position of the reflecting mirror 6. _{j + 1}Is approximately
Can be calculated.

[0074] Here, z _{j + 1} is the above-mentioned converted position of the reflecting mirror 6 where the interference fringe generated by the j-th reflected light is generated. N _gi is the group refractive index of the known medium between the i-th and i + 1-th surfaces. It is. t _i is the known spacing between the i-th and (i + 1) -th surfaces. C varies depending on where the origin is taken in a constant term.

In this embodiment, the photoelectric detector is used to detect the interference fringes. However, the interference fringes may be projected on a screen such as a ground glass and observed directly with the naked eye. further,
The interference fringes may be observed with the naked eye on a CRT using a TV camera as a photoelectric detector, or the signals may be observed with a waveform monitor, an oscilloscope, or the like.

A polarizer is provided in front of the photoelectric detector 8 to make the polarization states of the reference light and the measurement light uniform so that the contrast of interference fringes is improved.

When it is desired to increase the contrast of the interference signal, the azimuth of the polarizer 3 is changed, and the ratio of the amount of reflected light to the amount of transmitted light in the polarizing beam splitter 4 is changed to reflect the reference light and the reflected light of the measurement light. By making the intensities uniform, the contrast of interference fringes is improved. In order to improve the accuracy, it is preferable that the light amount ratio between the reference light and the measurement light be approximately equal, that is, 1:20 to 20: 1. For this purpose, a filter or the like may be appropriately inserted into the optical path, or a reflecting mirror having a different reflectance may be used.

The lens 30 may be omitted, and the collimator lens 2 may be appropriately moved in the direction of the optical axis so that the measurement light is incident near the spherical center or near the top of the measurement surface. Even in this manner, the surface interval measurement is possible.

The lens 30 or the collimator lens 2 may be appropriately replaced depending on the test object.

The object to be measured is, in addition to the distance between the surfaces of the zoom lens, the distance between the zoom groups, etc., the distance between the lens surface and the film surface, the distance between the lens surface and the pressure plate, the distance between the lens surface and the CCD imaging surface, the distance between the prisms of the camera finder. Etc. may be measured.

When aligning the optical system, if the light source is invisible light, a visualization device having sensitivity to the wavelength of the light source is used. For example, a commercially available digital camera with a liquid crystal monitor or a television camera may be used instead. In general, an infrared cut filter is incorporated immediately before an image sensor of a digital camera.
Since the near-infrared light has some sensitivity, a beam is projected.
Therefore, if the digital camera has a function that can directly display the captured image of the camera on the LCD monitor in real time, it is easy to adjust the optical system without using an expensive visualization device by monitoring the beam using this function Can be done.

Hereinafter, what can be said in common to the present invention will be described.

When a solid-state image pickup device is used as the photoelectric detector 8, the output of the photoelectric detector 8 is observed with an oscilloscope, a waveform monitor, a television display, or the like, and the intensity of the interference signal reaches a peak or the contrast of the interference fringes. Alternatively, the position of the reflecting mirror at which the peak becomes may be obtained, and the lens surface interval may be obtained.

The allowable range when the measuring light is made to enter the vicinity of the spherical center or the top of the surface even if there is an error of about ± 15 ° with respect to the optical axis of the incident light or the outgoing light on the test surface. Good. In the case of precise measurement, the error may be within ± 10 °. This is because the interference fringes generated near the optical axis may be used for the measurement. At this time, in most cases, the interference fringes are concentric, but the contrast is relatively easy to see, which is convenient.

As can be said in common with the surface distance measuring device of the present invention, when the light beam is incident on the surface to be measured, it is more likely that the light beam is incident near the spherical center than near the top of the surface. ,
It is more desirable because it is less susceptible to scratches and trash.

Further, the present invention can be used for measuring an optical element that is not a plane or an optical system including those optical elements, but in these cases, it is important to perform more accurate measurement. That is, the light beam incident on the test object is non-parallel. This is effective for causing the light beam to enter the vicinity of the spherical center or the top of the surface of the non-planar surface to be inspected.

The present invention can also be used for inspecting the thickness of an optical element during processing. When the optical element is a lens, the term "under processing" means that during the polishing and shaving (fine grinding) of the refracting surface of the lens, during the centering of one lens (during edge cutting), and during the assembly of a plurality of lenses. Surface spacing adjustment and eccentricity adjustment (centering of two or more lenses), lens thickness management after cemented lens (centering of cemented lens, lens thickness of cemented lens, adhesive thickness, in case of air space joining) Air spacing, alignment of both lenses).

Here, as the optical path length varying means 51 disposed in the reference optical path, various optical means can be used in addition to the wedge prism 52 whose thickness changes in a one-dimensional direction as shown in FIG. . The means shown in FIG. 3A is an arc-shaped prism 53 whose thickness changes in the circumferential direction, and the optical path length can be made variable by adjusting the rotation around a rotation axis parallel to the optical axis.

The means shown in FIG. 3B is a multi-stage prism 54 whose thickness changes stepwise in a one-dimensional direction. By using such a multi-stage prism 54, it is possible to use a multi-stage prism 54 in the direction orthogonal to the optical axis. By adjusting the position, the optical path length can be sampled and changed stepwise.

The means shown in FIG. 3C is a GRIN prism 55 in which the one-dimensional refractive index n changes continuously as shown in FIG. 3C '. The optical path length can be made continuously variable by adjusting the position in the direction orthogonal to the optical axis.

The means shown in FIG.
Between 57 'or one side is the transparent plate 57, the other is the reflection plate 5
The transparent liquid or fluid 5 is injected by the injection device 59 during 7 ′.
8 is a liquid prism 56 that continuously varies the optical path length by adjusting the thickness between the plates 57 and 57 ′ by injecting the same.

In addition to the above, an electro-optical material such as a liquid crystal, which can change the refractive index by changing the applied voltage or the like and change the optical path length, can also be used as the optical path length changing means 51.

(Embodiment 2) FIG. 4 is a diagram showing the configuration of Embodiment 2 of the present invention. The light beam emitted from the low coherence light source 1 becomes parallel light by the collimator lens 2 and becomes linearly polarized light by the polarizer 3. Next, this linearly polarized light is
When splitting by the BS 41, the azimuth of the transmission axis of the polarizer 3 is set so that the amount of transmitted light and the amount of reflected light are substantially equal. In the light beam split by the PBS 41, the reflected light is reflected by the reflecting means 21 as reference light, and is reflected by the optical path length changing means 51.
, The polarization plane is rotated 90 ° by the half-wave plate 19,
After passing through the second PBS 42, the polarizer (analyzer) 2
After that, the light enters the photoelectric detector 8. Optical path length varying means 51
Is any of those described in the first embodiment.

On the other hand, the transmitted light split by the first PBS 41 passes through the third PBS 43, passes through the quarter-wave plate 10, and becomes circularly polarized light. Circularly polarized light having passed through the quarter-wave plate 10 via the same lens 30 as in the first embodiment enters the test optical system 14. The light beam reflected on one surface of the test optical system 14 passes through the lens 30 and becomes linearly polarized light by the 波長 wavelength plate 10.
Reflected by the third PBS 43 and then the second PBS 42
And is incident on the photoelectric detector 8 via the polarizer 22.

The light (reference light) transmitted through the optical path length varying means 51 and the light (measurement light) reflected on one surface of the optical system to be measured 14 overlap, and the difference in optical path length between the two is the coherence length of the light source. If it is within the range, interference occurs and an interference signal is observed. If a low coherence light source having a coherence length of about several tens of μm is used as the light source 1, an interference signal is observed when the optical path length difference between the reference light and the measurement light falls within the range of the coherence length.

Next, the position of the lens 30 is selected such that light is incident toward the vicinity of the spherical center or the top of the other surface of the optical system 14 to be measured, and the reflected light from that surface is measured. It is made to enter the photoelectric detector 8. The position of the lens 30 is obtained in advance by optical calculation such as optical axis tracking. Then, the optical path length is changed by the optical path length varying means 51, and the position where the interference signal is obtained is obtained.

By subtracting the optical path length obtained at the first plane from the value of the optical path length at this position, and converting the difference into an optical path length in the air, an interval to be obtained can be obtained.

(Embodiment 3) FIG. 5 is a diagram showing the configuration of Embodiment 3 of the present invention. The light beam emitted from the low coherence light source 1 becomes parallel light by the collimator lens 2 and becomes linearly polarized light by the polarizer 3. Next, this linearly polarized light is
When the light is divided by, the azimuth of the transmission axis of the polarizer 3 is set so that the transmitted light and the reflected light have substantially the same light amount. PBS
Among the luminous fluxes divided by 4, the transmitted light enters the first reflecting mirror 61 composed of a roof mirror as reference light, is shifted and reflected in the opposite direction, and the reflected light is transmitted through the PBS 4 and is similarly reflected. The light is incident on a second reflecting mirror 62 composed of a roof mirror, is shifted in the opposite direction and is reflected, and the reflected light is P
After passing through the BS 4 and entering the first reflecting mirror 61 for the second time, the light is shifted and reflected in the opposite direction, and the reflected light is reflected by the PBS.
4 and is incident on the second reflecting mirror 62 for the second time, is reflected and shifted in the opposite direction, and the reflected light is transmitted through the PBS 4 and is incident on the first reflecting mirror 61 for the third time. Reflected in the opposite direction, and the reflected light is
At 9, the plane of polarization is rotated by 90 ° and is incident on the PBS 4, this time it is reflected by the PBS 4 and passes through the polarizer 22 to the photoelectric detector 8.
Incident on.

On the other hand, the reflected light split by the PBS 4 is 1
The light passes through the 波長 wavelength plate 10 and becomes circularly polarized light. Circularly polarized light having passed through the quarter-wave plate 10 via the same lens 30 as in the first embodiment enters the test optical system 14. The light beam reflected by one surface of the test optical system 14 becomes linearly polarized light by the quarter wavelength plate 10 through the lens 30, passes through the PBS 4, and enters the photoelectric detector 8 through the polarizer 22.

The position of the first reflecting mirror 61 can be adjusted as indicated by double arrows, and constitutes the optical path length varying means 51 of the present invention. The first reflecting mirror 61 and the second reflecting mirror 62 The reference light reflected a plurality of times between the reference light and the light (measurement light) reflected from one surface of the test optical system 14 overlaps, and if the optical path length difference between the two is within the range of the coherence length of the light source, interference occurs. The resulting interference signal is observed. Light source 1 has coherence length of tens of μm
If a light source with a low coherence level is used, an interference signal is observed when the optical path length difference between the reference light and the measurement light falls within the range of the coherence length.

Next, the position of the lens 30 is fixed so that light is incident near the spherical center or near the top of the other surface of the optical system 14 to be measured, and the reflected light from that surface is It is made to enter the photoelectric detector 8. The position of the lens 30 is obtained in advance by optical calculation. Then, the position of the first reflecting mirror 61 is moved to change the optical path length, and a position at which an interference signal is obtained is obtained.

The interval to be obtained is obtained by subtracting the optical path length obtained at the first plane from the value of the optical path length at this position and converting the difference into an optical path length in the air. That is, the difference between the positions of the two surfaces is obtained.

In this embodiment, the first reflecting mirror 61
Assuming that the number of reciprocations between the second mirror 62 and N is N,
The optical path length changes by 4N times the position change amount of the first reflecting mirror 61.

(Embodiment 4) FIG. 6A is a diagram showing the configuration of Embodiment 4 of the present invention. The light beam emitted from the low coherence light source 1 passes through a beam combiner 4 'and is converted into parallel light by a collimator lens 2, and a light beam in a peripheral portion of the light beam enters a reference mirror 6' as reference light. The position of the reference mirror 6 'can be adjusted as indicated by double arrows, and constitutes the optical path length varying means 51 of the present invention. The optical path length is variably adjusted and reflected.
Further, the central portion of the light beam collimated by the collimator lens 2 enters the test optical system 14 via the same lens 30 as in the first embodiment as measurement light. A light beam reflected by the reference mirror 6 'and a light beam reflected by one surface of the test optical system 14 enter the beam combiner 4' via the collimator lens 2, are reflected, and are prism members which act only on peripheral light beams. 63
Then, the light enters the photoelectric detector 8 via the lens 64 and overlaps.

If the optical path length difference between the reference light and the light reflected by one surface of the test optical system 14 is within the coherence length of the light source, interference occurs and an interference signal is observed. If a low coherence light source having a coherence length of about several tens of μm is used as the light source 1, an interference signal is observed when the optical path length difference between the reference light and the measurement light falls within the range of the coherence length.

Next, the position of the lens 30 is fixed so that light is incident near the spherical center or near the top of the other surface of the optical system 14 to be measured. It is made to enter the photoelectric detector 8. The position of the lens 30 is obtained in advance by optical calculation. And the reference mirror 6 '
And the position at which the interference signal is obtained is obtained.

By subtracting the optical path length obtained at the first plane from the value of the optical path length at this position, and converting the difference into an optical path length in the air, an interval to be obtained can be obtained.

In this embodiment, as shown in FIG. 6B, the arrangement is changed so that the upper part of the light beam collimated by the collimator lens 2 is used as reference light and the lower part is used as measurement light. You may. Since the left portion is the same as that in FIG. 6A due to the collimator lens 2 in FIG. 6B, it is not shown.

(Embodiment 5) FIG. 7 is a diagram showing the configuration of Embodiment 5 of the present invention. In this embodiment, the optical path length varying means 51 is used.
This is an embodiment in which an interferometer using a movable mirror 6 'is incorporated in the interferometer optical path at the same time as an interferometer for measuring the amount of movement of the movable mirror 6'.

First, a system for measuring the surface interval of the test optical system 14 will be described. The light beam emitted from the low coherence light source 1 is turned into parallel light by the collimator lens 2,
Becomes linearly polarized light. Next, when the linearly polarized light is split by the PBS 4, the transmitted light and the reflected light have substantially the same light amount.
The azimuth of the transmission axis of the polarizer 3 is set in advance. In the light beam split by the PBS 4, the transmitted light is the first 1
The light becomes circularly polarized light by the 板 wavelength plate 5, is reflected by the moving mirror 6 ′ constituting the optical path length changing means 51, becomes linearly polarized light again through the 波長 wavelength plate 5, is reflected by the PBS 4, and is reflected by the polarizer 22.
And enters the photoelectric detector 8.

On the other hand, the reflected light split by the PBS 4 passes through the second quarter-wave plate 10 and becomes circularly polarized light. Circularly polarized light having passed through the quarter-wave plate 10 via the same lens 30 as in the first embodiment enters the test optical system 14. The light beam reflected by one surface of the test optical system 14 passes through the lens 30, becomes linearly polarized light by the レ ン ズ wavelength plate 10, passes through the PBS 4, and passes through the polarizer 22.
And enters the photoelectric detector 8.

The position of the movable mirror 6 ′ can be adjusted as shown by double arrows, and the reference light reflected by the movable mirror 6 ′ and the optical system
Light (measurement light) reflected by one surface of the light source overlaps, and if the optical path length difference between the two is within the range of the coherence length of the light source, interference occurs and an interference signal is observed. If a low coherence light source having a coherence length of about several tens of μm is used for the light source 1,
An interference signal is observed when the optical path length difference between the reference light and the measurement light falls within the range of the coherence length.

Next, the position of the lens 30 is fixed so that light is incident near the spherical center or near the top of the other surface of the optical system 14 to be measured. It is made to enter the photoelectric detector 8. The position of the lens 30 is obtained in advance by optical calculation. And the moving mirror 6 '
Is moved to change the optical path length, and a position at which an interference signal is obtained is obtained.

The interval to be obtained is obtained by subtracting the optical path length obtained at the first plane from the value of the optical path length at this position, and converting the difference into the optical path length in the air.

By the way, another interference system for accurately measuring the position of the movable mirror 6 'is provided around the PBS 4, and the light beam emitted from the long coherence light source 70 such as a laser is reflected by the mirror 71. And is divided by the PBS 4 into transmitted light and reflected light. The transmitted light is the measurement light,
After being circularly polarized by the first quarter-wave plate 5 and reflected by the moving mirror 6 ', the light again passes through the quarter-wave plate 5 to become linearly polarized light.
The light is reflected by the PBS 4 and enters the photoelectric detector 76 for a length measuring device.

On the other hand, the reflected light split by the PBS 4 passes through the second quarter-wave plate 10 to become circularly polarized light as reference light, is reflected by the mirror 72, and becomes linearly polarized light by the quarter-wave plate 10. The reflected light is transmitted through the PBS 4 and reflected in the opposite direction by the reflection member 73 composed of a roof mirror. The reflected light is transmitted through the PBS 4 and passes through the second quarter-wave plate 10 to become circularly polarized light. Reflected by the mirror 74, the ４ wavelength plate 10
Then, the light becomes linearly polarized light, is reflected by the PBS 4, is reflected by the mirror 75, is incident on the photoelectric detector 76 for the length measuring device, interferes with the measuring light, and forms an interference fringe. By counting the interference fringes, the position of the movable mirror 6 'is measured.

In the first to fifth embodiments, an optical fiber may be used in the optical path, and the optical path may be formed in the optical fiber.

Further, it is of course possible to measure the refractive index of the liquid crystal between the planes with the plane distance being known.

(Embodiment 6) The material of the lens in the test optical system 14 can be determined by using the above embodiments.
This will be described as a sixth embodiment. However, a description will be given assuming that a movable mirror (reference mirror) is used as the optical path length varying unit 51.

FIG. 8 is a flowchart showing this determination procedure.

First, in step ST1, a group refractive index of a plurality of glasses or plastics in a measurement wavelength range is calculated and summarized in a table. Next, in step ST2, thickness data (d) of the optical element to be measured of the test optical system 14 is input. In this input, as the thickness data, a design value or an actual measurement value (for example, a measurement value by a mechanical means) is input.

Next, in step ST3, the reference mirror 6 'is moved to search for a position where an interference fringe appears. Then, in step ST4, the optical path length difference ( _ng d) between both surfaces is obtained from the movement amount of the reference mirror 6 '.

Next, in step ST5, the thickness (d) of the optical element is known (step ST2), and the group refractive index ( _ng ) is determined ( _ng d / d).

Lastly, in step ST6, a search is made for a glass or plastic having the group refractive index obtained by the measurement from the table compiled in step ST1 to find a match, thereby obtaining the optical element of the optical system 14 to be measured. The type of glass or plastic material can be specified.

Embodiments 7 to 11 shown below are common to any of the above embodiments, but the case of a Michelson interferometer using a movable mirror 6 'as an optical path length varying means will be described as an example. Will be explained. The procedure for measuring the distance between the two surfaces a and b in the test optical system 14 is clear from the description of each of the above-described embodiments, and a description thereof will be omitted.

(Embodiment 7) FIG. 9 is a diagram showing the configuration of Embodiment 7 of the present invention. In this embodiment, the low-coherence light source 1 emits a linearly polarized light beam. In order to increase the contrast of an interference signal, the light source 1 itself is rotated around the optical axis and the polarization direction of the light beam incident on the PBS 4 is increased. change. When the polarization direction of the light beam incident on the PBS 4 changes, the intensity ratio between the p-polarized light and the s-polarized light changes, and the test optical system 14
The intensity ratio between the measurement light branched toward the movable mirror 6 ′ and the reference light branched toward the movable mirror 6 ′ changes. When the reflectance of the test optical system 14 is low and the reflectance of the movable mirror 6 ′ is high, the light source 1 is rotated so that the light intensity of the measurement light is high and the light intensity of the reference light is low, and the direction of the polarized light is changed. Once determined, the intensities of the light reflected by the test optical system 14 and the movable mirror 6 'become substantially equal. In the opposite case, the direction of the light source 1 may be changed.

In FIG. 9, reference numeral 9 denotes a length measuring device for accurately measuring the moving distance of the movable mirror 6 '.

In this embodiment, since the light intensities reflected by the test optical system 14 and the movable mirror 6 'can be made substantially equal,
The contrast of the interference signal obtained by superimposing both light beams is improved, and the surface spacing can be measured with higher accuracy. In addition, since it is not necessary to use a polarizing plate, the amount of light used for interference increases, and a measurement surface with lower reflectance can be measured.

(Eighth Embodiment) FIG. 10 is a diagram showing a configuration of an eighth embodiment of the present invention. In this embodiment, the low coherence light source 1 emits a linearly polarized light beam,
The half-wave plate 19 disposed between the light source 1 and the PBS 4 is rotated around the optical axis. The half-wave plate 19 changes the polarization direction of incident light without reducing the light amount. 1 /
When the two-wavelength plate 19 is rotated by θ, the polarization direction of the emitted light rotates by 2θ. As described in Example 7, PBS4
By changing the polarization direction of the light beam incident on the light source, the intensity ratio between the measurement light and the reference light can be changed. Therefore, by rotating the half-wave plate 19, the intensity ratio of the measuring light and the reference light is changed, and the intensity of the light reflected by the test optical system 14 and the moving mirror 6 'can be made substantially equal.

In this embodiment, since the light intensities reflected by the optical system under test 14 and the movable mirror 6 'can be made substantially equal,
The contrast of the interference signal obtained by superimposing both light beams is improved, and the surface spacing can be measured with higher accuracy. In addition, since it is not necessary to use a polarizing plate, the amount of light used for interference increases, and a measurement surface with lower reflectance can be measured.

In the above seventh and eighth embodiments, as the low coherence light source 1 for emitting a linearly polarized light beam, a single mode oscillation semiconductor laser operated at a threshold current or less, or a pulse laser is used. Can be used. A single mode oscillation semiconductor laser generally emits a linearly polarized light beam. If the semiconductor laser is operated at a threshold current or less, the coherence length is short, and
A linearly polarized light beam is obtained. In addition, even if a linearly polarized pulse laser is used, a coherence length is short and a linearly polarized light beam can be obtained. In addition, some of these lasers emit light in the visible region, and if they are used, scattered light and the like can be visually observed, and alignment becomes easy. In addition, many semiconductor lasers are inexpensive, and the apparatus can be inexpensive.

(Embodiment 9) FIG. 11 is a diagram showing the configuration of Embodiment 9 of the present invention. In this embodiment, since the reflecting means such as the movable mirror is constituted by the variable reflectivity mirror 6 ", the light intensity of the light reflected by the variable reflectivity mirror 6" and returned to the PBS 4 as the light beam combining means is reduced. Can be adjusted freely. When the reflectance of the measurement target surface in the test optical system 14 is low, if the reflectivity of the variable reflectivity mirror 6 ″ is also low, the intensity of light reflected by the test optical system 14 and the reflection mirror 6 ″ can be made substantially equal. . As the reflectivity variable mirror 6 ", for example," NATURE "Vol.
79 (1998) using liquid crystal is available.

In this embodiment, since the light intensities reflected by the test optical system 14 and the movable mirror 6 "can be made substantially equal,
The contrast of the interference signal obtained by superimposing both light beams is improved, and the surface spacing can be measured with higher accuracy. When measuring a deeper lens in the test optical system 14, that is, a surface where light must pass through more reflecting surfaces, the intensity of the reflected light becomes weaker. On the other hand,
In the case of measuring a lens on the nearer side, that is, a surface where light does not transmit much through the reflecting surface, the intensity of the reflected light increases. As described above, the intensity of the reflected light from the surface to be measured changes depending on the position of the surface to be measured. However, if the reflectivity of the reflectivity variable mirror 6 ″ is changed in each case, a more optimal intensity ratio can be obtained on any surface. And the contrast of the interference signal can be further improved.

In this case, the light intensity at the position where the reflected light reflected on the surface to be measured in the optical system 14 to be measured returns to the PBS 4 and is combined is I ₁ , and the reflected light reflected by the reflectance variable mirror 6 ″ is Assuming that the light intensity at the position where the light returns to the PBS 4 and is combined is I ₂ , the reflectivity of the reflectivity variable mirror 6 ″ is matched within the range of 0.05 ≦ I ₁ / I ₂ ≦ 20.

Since the light intensities of the measuring light and the reference light are more matched, the contrast of the obtained interference signal becomes higher,
The surface spacing can be measured with higher accuracy.

More preferably, they are set to be in the range of 0.2 ≦ I ₁ / I ₂ ≦ 5.

In this case, since the light intensities of the measuring light and the reference light are further matched, the contrast of the obtained interference signal is further increased, and the surface interval can be measured with higher accuracy.

(Embodiment 10) FIG. 12 shows Embodiment 1 of the present invention.
FIG. 3 is a diagram showing a configuration of a zero. In this embodiment, a plurality of variable reflectivity mirrors 6 ″ are mounted on a stage 1 that is movable in the optical axis direction.
6, and can independently control the reflectance. In the plurality of variable reflectance mirrors 6 ″, the distance from the PBS 4, which is the light beam splitting unit, is set to the distance from the PBS 4 to the test optical system 14.
The reflectivity of only the variable reflectivity mirror 6 ″ a closest to the optical path length to the surface a to be measured is increased, and the reflectivity of the other variable reflectivity mirrors 6 ″ is reduced. And
The stage 16 is moved in the optical axis direction and adjusted so that the reflected light reflected by the reflectivity variable mirror 6 ″ a and the surface to be measured in the optical system 14 to be measured, for example, the reflected light reflected by the surface a interfere with each other. I do.

Next, the reflectance variable mirror 6 ″ b is located at a position that is closest to the surface a from the PBS 4 or a surface separated by several surfaces, for example, the surface b from the PBS 4 to the optical path length. Only the reflectance is increased, and the reflectance of the other variable reflectance mirrors 6 ″ is reduced. Then, as in the case of the surface a, the stage 16 is moved in the direction of the optical axis to adjust the reflected light reflected by the reflectivity variable mirror 6 ″ b and the reflected light reflected by the surface b to interfere with each other.

As described above, since the reflectivity variable mirror 6 ″ that reflects the reference light by increasing the reflectivity is changed and the stage 16 is further moved, the range in which the mirror can be moved is smaller than when only one mirror is used. It becomes narrower and the device can be downsized.
In addition, the moving time can be shortened, and the measuring time is shortened.

(Embodiment 11) FIG. 13 shows Embodiment 1 of the present invention.
1 is a diagram showing a configuration of FIG. In this embodiment, a glass plate 17 as a transparent medium is arranged on the optical axis between the PBS 4 as the light beam splitting means and the movable mirror 6 'as the optical path length changing means. The transparent medium may be a liquid or solid other than a glass plate. When the low coherence light source 1 has a wavelength width, when the light passes through a lens or the like, the refractive index differs depending on the wavelength, so that the optical path length differs for each wavelength. on the other hand,
The reference light reflected by the movable mirror 6 'does not pass through the lens. Therefore, particularly when measuring the inner surface of the test optical system 14,
Since the measurement light passes through more lenses, the optical path length difference due to the wavelength increases, whereas the reference light hardly causes the optical path length difference due to the wavelength. At this time, the range in which an interference signal is generated when the movable mirror 6 'is moved is widened, and it is difficult to find a position where the contrast is highest. Also, the contrast is reduced.

Here, if the glass plate 17 is arranged between the PBS 4 and the movable mirror 6 ', the optical path length difference due to the wavelength also occurs in the reference light. By arranging a glass plate such that an optical path length difference substantially equal to the optical path length difference generated in the measurement light is obtained, the optical path lengths at the respective wavelengths of the measurement light and the reference light are simultaneously equal, and the range in which an interference signal is generated is narrowed. And the contrast is also improved.

As described above, when the glass plate 17 as the chromatic dispersion compensating means is arranged in the reference optical path, the moving range of the movable mirror 6 'in which an interference signal is generated is narrowed, and the contrast is improved. Even when measuring the innermost surface of the device, the accuracy can be prevented from lowering, and the measurement can be performed with high accuracy.

In this case, it is desirable that the glass plate 17 satisfies the following conditional expression.

0.5 <(n (λ _S ) −n (λ _L )) · d
/ (L _S -L _L ) <2, where: d: thickness of the transparent medium n (λ): group index of refraction of the transparent medium at an arbitrary wavelength λ λ _S : of the light emitted from the light source, the light intensity is the highest When the light intensity at the strong wavelength λ ₀ is I ₀ , the light intensity is 0.5 I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum.

[0146] At this time, the optical path length difference L _S -L _L due to the wavelength that occurs the measurement light, the optical path length difference that causes the glass plate 17 to the reference light _{(n (λ S) -n (} λ L)) · d and But,
The agreement is within a range of half to twice. Therefore, the optical path lengths of the measurement light and the reference light at the respective wavelengths can be effectively matched.

The glass plate 17 is, for example, SB
With the use of SL7 (manufactured by OHARA), when light reciprocates in a glass plate having a thickness of 20 mm, the wavelength is 833 nm and 858 nm.
In nm, an optical path length difference of about 32 μm occurs. When the thickness of the glass plate is 50 mm, an optical path length difference of about 80 μm occurs. In other glasses, for example, S-TIM2 (made by OHARA), when the thickness of the glass plate is 20 mm, the optical path length difference is about 74 μm, and when the thickness of the glass plate is 50 mm, the optical path length difference is about 188 μm.

As described above, by changing the thickness of the glass and the type of the glass, the difference in the optical path length caused by the glass plate 17 can be changed, and the above conditional expression can be satisfied.

As described above, when the glass plate 17 satisfying the above conditional expression is arranged in the reference optical path, the moving range of the movable mirror 6 'in which an interference signal is generated is narrowed, and the contrast is improved. Even when measuring the innermost surface of the device, the accuracy can be prevented from lowering, and the measurement can be performed with high accuracy.

It is desirable that the glass plate 17 satisfies the following conditional expressions.

0.8 <(n (λ _S ) −n (λ _L )) · d
/ (L _S -L _L ) <1.25 At this time, the optical path length difference L _S -L due to the wavelength generated in the measurement light
_L and the optical path length difference (n (λ _S ) −n (λ _L )) · d caused by the glass plate 17 in the reference light are even better matched than in the above case. Therefore, the optical path lengths at the respective wavelengths of the measurement light and the reference light can be more effectively matched.

As described above, when the glass plate 17 satisfying the above conditional expression is arranged in the reference optical path, the moving range of the movable mirror 6 'in which an interference signal is generated is further narrowed, and the contrast is further improved. Even when measuring the inner surface of the system 14, the accuracy can be further prevented from lowering, and the measurement can be performed with high accuracy.

It is desirable that the glass plate 17 satisfies the following conditional expression.

0.8 <(n (λ _S ) −n (λ _L )) · d
/ ((L _Sa −L _La ) / 2) <1.25, where d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : light emitted from the light source When the light intensity at the wavelength λ ₀ where the light intensity is the strongest is defined as I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths at the wavelength λ _S above L _La : the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object At this time, the optical path length difference caused by the wavelength generated by the glass plate 17 is When the glass plate 17 is not provided, the optical path length difference due to the wavelength of the measurement light reflected on the innermost surface in the test optical system 14 is about half. Therefore, the test optical system 1
In the case of measuring the surface near the middle of the optical path 4, the optical path length difference due to the wavelengths of the measurement light and the reference light substantially coincides. Further, when measuring the front surface or the back surface in the test optical system 14, the difference in the optical path length difference between the measurement light and the reference light due to the wavelength generated between the test light and the reference light is the same as when the glass plate 17 is not disposed. Optical system 1
4, the optical path length difference caused by the wavelength of the measurement light reflected on the innermost surface becomes about half, and the difference in the optical path length difference caused by the wavelengths of the measurement light and the reference light becomes smaller on the intermediate surface. .

With this arrangement, even when any surface in the optical system 14 to be measured is measured, the difference between the optical path lengths caused by the wavelengths of the measurement light and the reference light can be measured by using the test system without the glass plate 17. The optical path length difference due to the wavelength of the measurement light reflected on the innermost surface in the optical system 14 can be set to about half or less,
It is possible to obtain an interference signal having a high contrast on any surface and a narrow range generated with respect to the movement of the movable mirror 6 ′, and it is possible to always effectively prevent a decrease in measurement accuracy and perform accurate measurement.

It is desirable that the glass plate 17 satisfies the following conditional expression.

0.5 <(n (λ _S ) −n (λ _L )) · d
/ ((L _Sa −L _La ) / 2) <2.0 At this time, the difference in the optical path length due to the wavelength generated by the glass plate 17 is the deepest in the optical system 14 to be measured when the glass plate 17 is not disposed. Is about half of the optical path length difference due to the wavelength of the measurement light reflected by the surface, and is more exactly half as compared with the above case. Therefore, when measuring the front surface or the back surface in the test optical system 14, the difference in the optical path length difference due to the wavelength generated by the measurement light and the reference light is more accurate when the glass plate 17 is not disposed. Is about half the optical path length difference caused by the wavelength of the measurement light reflected on the innermost surface of the test optical system 14, and the difference between the optical path length differences caused by the wavelengths of the measurement light and the reference light on the intermediate surface. Is less than that.

With this arrangement, even when any surface in the optical system 14 to be measured is measured, the difference between the optical path lengths caused by the wavelengths of the measurement light and the reference light is not accurately arranged on the glass plate 17. In this case, the optical path length difference due to the wavelength of the measurement light reflected on the innermost surface in the test optical system 14 can be set to about half or less. It is possible to obtain an interference signal having a high contrast and a narrow range generated in response to the movement of the movable mirror 6 ′, and it is possible to effectively prevent a decrease in measurement accuracy and to perform accurate measurement.

It is desirable that the glass plate 17 satisfies the following conditional expression.

| (N (λ _S ) −n (λ _L )) · d− (L
_S− L _L ) | <100 [μm] At this time, the optical path length difference L _S −L due to the wavelength generated in the measurement light
_L and the optical path length difference (n (λ _S ) −n (λ _L )) · d caused by the glass plate 17 in the reference light are identical within 100 μm. Therefore, the optical path lengths of the measurement light and the reference light at the respective wavelengths can be effectively matched.

With this arrangement, the range of movement of the movable mirror 6 ′ in which an interference signal is generated is narrowed, and the contrast is improved. Therefore, even when measuring a deep surface in the optical system 14 to be measured, the measurement accuracy is further reduced. Can be prevented and measurement can be performed with high accuracy.

It is desirable that the glass plate 17 satisfies the following conditional expression.

| (N (λ _S ) −n (λ _L )) · d− (L
_S− L _L ) | <30 [μm] At this time, the optical path length difference L _S −L due to the wavelength generated in the measurement light
_L and the optical path length difference (n (λ _S ) −n (λ _L )) · d caused by the glass plate 17 in the reference light are even better matched than in the above case. Therefore, the optical path lengths at the respective wavelengths of the measurement light and the reference light can be more effectively matched.

With this arrangement, the range of movement of the movable mirror 6 'in which an interference signal is generated is further narrowed, and the contrast is further improved. Therefore, even when measuring a deep surface in the optical system 14 to be measured, the measurement accuracy is further improved. Can be prevented and the measurement can be performed with high accuracy.

In the above description, the light intensity of λ _S is equal to 0.
Λ _L , the wavelength on the shorter wavelength side than λ ₀ among the wavelengths that become 2I ₀
Is more preferably set to a wavelength longer than λ ₀ among wavelengths at which the light intensity becomes 0.2I ₀ .

Λ _S and λ _L are wavelengths at which the light intensity becomes 0.2I _0, and the wavelength range for estimating the optical path length difference depending on the wavelength is wider. Therefore, the difference in optical path length on the short wavelength side and the long wavelength side away from the center wavelength λ ₀ can be considered, and the optical path length difference can be made uniform over a wider wavelength range included in the light emitted from the light source. Can be measured more accurately with a good interference signal.

Further, λ _S is a wavelength shorter than λ ₀ among wavelengths at which the light intensity is 0.1 I _0, and λ _L is a light intensity of 0.1 I 0.
It is more desirable that the wavelength be longer than λ ₀ among the wavelengths of 1I ₀ .

Λ _S and λ _L are the wavelengths at which the light intensity is 0.1 I _0, and the wavelength range for estimating the optical path length difference depending on the wavelength is wider than the above case. Therefore, the center wavelength λ
The optical path length difference on the short wavelength side and the long wavelength side farther from ₀ can also be considered, and the optical path length difference can be made uniform over a wider wavelength range included in the light emitted from the light source, and an interference signal with better contrast Can be measured with high accuracy.

Further, in the above description, the transparent medium may be composed of a plurality of transparent media.

In this case, the glass plate 17 is composed of a plurality of glass plates. Therefore, if the number of glass plates to be combined is changed, the total thickness d can be changed, and the optical path length difference depending on the wavelength given to the reference light can be changed. Also, by combining various types of glass with different Abbe numbers,
Even with the same thickness, the difference in optical path length depending on the wavelength given to the reference light can be changed. Therefore, when measuring the front surface of the test optical system 14 in which the optical path length difference due to the wavelength does not significantly occur in the measurement light, the glass plate 17 is not inserted, or only one glass plate is inserted, or the Abbe number is large. By using a glass plate in which the optical path length difference due to the wavelength does not significantly occur, the optical path length difference due to the wavelengths of the measurement light and the reference light can be made uniform. On the other hand, when measuring the inner surface of the test optical system 14 where the optical path length difference due to the wavelength of the measurement light is large, the number of glass plates may be increased to increase the overall thickness, or the Abbe number may be reduced. For example, by partially using a glass plate in which a large optical path length difference due to the above occurs, the optical path length difference between the wavelengths of the measurement light and the reference light can be made uniform.

As described above, a plurality of glass plates can be used in combination by changing the number and type of glass.
The optical path length difference depending on the wavelength given to the reference light can be variously changed. For this reason, when measuring various surfaces in the optical system 14 to be measured, the measurement light has an optical path length difference due to different amounts of wavelengths, and the glass plate 17 is used as an optimal combination in each case. In this measurement, the optical path length difference caused by the wavelengths of the reference light and the measurement light can be optimally adjusted. Therefore, even when measuring any surface, an interference signal with good contrast can be obtained and measurement can be performed with high accuracy.

Embodiment 12 FIG. 14 shows Embodiment 1 of the present invention.
FIG. 2 is a diagram illustrating a configuration of a second embodiment. This embodiment is an example of an interferometer that measures the thickness of the resin thin film 89 during the manufacture of the resin thin film aspheric lens 88. In the figure, reference numeral 90 denotes a mold of the resin thin film 89, and reference numeral 88 denotes an aspheric lens serving as a substrate of the resin thin film 89. Low coherence light source (SLD in this case)
The light exiting from 1 is reflected downward by the half prism 84,
The light is divided by a half mirror 91 into reflected light 1 (dotted line) and transmitted light m (solid line). The transmitted light m passes through the lens 30,
The light is reflected by the test surface b. Then, in order, the half mirror 9
1, transmitted through the half prism 84 and the half prism 92, reflected by the half mirror 93,
At the right side, and is incident on the photoelectric detector 8 through the light amount adjustment filter 94.

On the other hand, the reflected light 1 (dotted line) is reflected by the half mirror 91, then passes through the half prism 84, the half prism 92, and the half mirror 93 in order, is reflected by the moving mirror 6 ', and is reflected by the half mirror 93. And is reflected by the half prism 92 and enters the photoelectric detector 8 together with the light m.

At this time, when the movable mirror 6 ′ is moved in the z direction and the optical path length of the light m and the light 1 is substantially within the coherence distance of the low coherence light source 1, the light m and the light 1 interfere with each other, and the photoelectric detection is performed. The interference light enters the device 8. The position of the moving mirror 6 'the contrast of the interference light intensity or the interference fringes is maximized and Z _b.

[0175] Further, the position Z _c of the interference fringe intensity or interference light intensity Similarly, the light m reflected by the test surface c is movable mirror 6 that maximizes'.

| Z _b −Z _c | / _ng = t The thickness t of the resin thin film 89 can be obtained from Expression 3.

[0177] Here, n _g is the group refractive index of the resin film 89, the formula 1: is defined as _{n g = n p -λ (dn} p / dλ) ··· Equation 1. Here, n _p is the refractive index (phase refractive index) of the resin thin film 89.

Similarly, the thickness of the aspherical lens 88 can be known by using the light m reflected on the surface a to be measured of the aspherical lens 88.

The above measurement may be automated as follows.

After adjusting the center of the optical axis of the interferometer while observing the aspheric lens 88 on the monitor 86, the moving mirror 6 'is moved in one direction by a motor, and at that time, the photoelectric detector 8 is moved.
Are sequentially taken into the memory 95. Then, when the movable mirror 6 ′ scans the range including Z _b and Z _c , the image processing device 96 analyzes the interference fringes, obtains the peak of the intensity or interference fringe contrast, and obtains Z _b and Z _c
Is obtained, and the thickness t is obtained from Expression 3. The result is displayed on the television monitor 97.

If the thickness t of the resin thin film 89 is known, conversely, the group refractive index _ng of the resin thin film 89 may be obtained from Expression 3. This concept can be applied to other embodiments of the present invention.

Here, it is desirable that the light amount adjusting filter 94 be disposed obliquely with respect to the optical path in order to avoid a ghost. The angle is preferably 1 ° or more, and more preferably 5 ° or more with respect to a plane perpendicular to the optical axis.

One of the features of FIG. 14 is that the reference light path and the measurement light path are arranged in substantially one direction, so that no space is required for the entire apparatus. The same direction means that the bending of the optical axis is within 20 °.

Further, the light path of m and the light path of 1 are made of glass,
If the amount of chromatic aberration generated by the resin or the like is different, the coherence of the two light beams is reduced. Therefore, in order to equalize the amount of chromatic aberration generated in the two optical paths, the half mirror 93 and the half mirror 9 are used.
It is good to choose a thickness such as 1. Alternatively, in order to make the chromatic aberration uniform, a parallel flat plate such as glass or resin, a prism, a lens, or the like may be inserted into one optical path (see Embodiment 11).
This concept can be applied to other embodiments of the present invention.

In the example shown in FIG. 14, the test object is a resin thin film 89.
Measurement of surface distance, zoom group distance, lens thickness, distance between lens surface and film pressure plate, distance between image sensor, distance between liquid crystal display and optical elements such as prism, etc. It goes without saying that it can be used to

Further, it can be used for measuring the distance between the LCD and the free-form surface prism of the image display device comprising the LCD and the free-form surface prism disclosed in JP-A-9-281430.

[0187] The distance between the boundaries of the medium of the living body such as the human body, animal eyes or skin, plants, etc. can also be measured. When targeting a human body, a low-output light source for living body observation is used as a light source.

The present invention can also be used for inspecting the thickness of an optical element during processing. When the optical element is a lens, the term "under processing" means that during the polishing and shaving (fine grinding) of the refracting surface of the lens, during the centering of one lens (during edge cutting), and during the assembly of a plurality of lenses. Surface spacing adjustment and eccentricity adjustment (centering of two or more lenses), lens thickness management after cemented lens (centering of cemented lens, lens thickness of cemented lens, adhesive thickness, in case of air space joining) Air spacing, alignment of both lenses).

In addition, as can be said in common to the present invention, in addition to the objects already described, the measuring objects include various machines, that is, optical device manufacturing devices, optical device manufacturing devices, and other optical-related manufacturing devices. Or the surface spacing of machines other than optics. The present invention is effective for optical elements, optical systems, optical devices, and various machines, particularly when the surface shape is non-planar. In the case where the surface shape is an aspherical surface, the above description may be applied to a tangent spherical surface or an approximate spherical surface near the light beam incident point. For example, as the “sphere center”, a sphere center of a tangent spherical surface or an approximate spherical surface may be applied.

Embodiment 13 FIG. 15 shows Embodiment 1 of the present invention.
3 is a diagram illustrating a configuration of FIG. This embodiment is an example of an apparatus for sampling and measuring an aspheric surface 500 using a low coherence light source 1 having a short coherence length.

The light beam emitted from the low-coherence light source 1 passes through the lens 509 and the collimator lens 2 to become a parallel light beam.
The measurement light split into two by the beam splitter 510 and reflected passes through the lens array 502 and enters the aspheric surface 500.

On the other hand, the reference light transmitted through the beam splitter 510 enters the reflecting mirror 6 and is reflected. The two luminous fluxes are combined again by the beam splitter 510 to form another lens array 5.
07, an interference fringe is formed on the two-dimensional photoelectric detector 8 '.

First, the aspherical surface 5 is adjusted so that one point of the aspherical surface 500 coincides with the light converging surface (dotted line in the figure) of the lens array 502.
Move 00 up and down to adjust.

Next, the position of the reflecting mirror 6 is adjusted so that interference fringes occur at one point. In FIG. 15, it occurs at point A.

Next, while the reflecting mirror 6 is fixed and the aspheric surface 500 is moved upward, the position where the interference fringe occurs is detected by the two-dimensional photoelectric detector 8 '. When the optical path length of the light beam reflected by the aspheric surface 500 and the light beam reflected by the reflecting mirror 6 are substantially equal, interference fringes occur in the two-dimensional photoelectric detector 8 '. Therefore, if the position of the aspheric surface 500 is read while moving the aspheric surface 500 and the position where the interference fringe occurs is detected by the two-dimensional photoelectric detector 8 ′, the shape of the aspheric surface 500 becomes smaller than the pitch of the lens array 502. It will be obtained at the sampling interval.

In FIG. 15, reference numeral 503 denotes a device for driving the aspherical surface 500 of the aspherical lens 501 and a device for detecting the position of the aspherical surface 500, and is mounted on the vibration isolation table 505.

The intensity, phase, and position of the aspherical surface 500 of the interference fringe of the two-dimensional photoelectric detector 8 'are input to the calculator 504, and the monitor 86 displays the aspherical shape.

In this embodiment, the lens array 50
Reference numeral 2507 may be made of a DOE (diffractive optical element), a glass or plastic mold, or a number of heterogeneous lenses.

Also, by driving and moving the aspheric surface 500 by the driving device 503, instead of obtaining the aspheric surface shape, the aspheric surface 500 is fixed, and the two-dimensional photoelectric detection is performed while the reflecting mirror 6 is moved by the driving mechanism 508. The interference fringes may be detected by the detector 8 'to determine the aspherical shape. At this time, the lens array 502
The position may be appropriately adjusted by the driving device 506 so that the light-converging surface comes to the portion of the aspheric surface 500 where the interference fringes appear. The driving device 506 is controlled by the computer 504.

When the position of the interference fringes on the two-dimensional photoelectric detector 8 'and the position where the interference fringes occur are detected while moving the position of the aspherical surface 500 or the reflecting mirror 6,
Is moved while vibrating in the direction in which the optical path length changes, and only the output signal of the two-dimensional photoelectric detector 8 ′ that changes at the frequency of the vibration is extracted and amplified, so that the detection sensitivity of the interference fringes is improved, which is more preferable.

A lens 509 is a cylindrical lens.
This is to correct astigmatism generated when a semiconductor laser or the like is used as the low coherence light source 1. The cylindrical lens 509 may be used when necessary, and may not be used depending on the low coherence light source 1.

As the low coherence light source 1, an LED,
A combination of a white light source such as an SLD and a halogen lamp with a filter is used.

In the apparatus shown in FIG. 15, first, a plane may be measured instead of the aspherical surface 500, and the error may be corrected so that the output of the computer 504 at that time becomes a plane. The error correction value may be stored in the form of a table in the computer 504 program.

The apparatus of this embodiment can measure at a higher speed than a conventional aspherical shape measuring instrument using a contact needle, and has the advantage of not damaging the object to be measured because it is non-contact.

This measuring apparatus includes an aspherical lens, an aspherical mirror, a mold, and other optical elements using a free-form surface,
And it can be used for measurement of various curved surfaces such as a mold thereof, a curved surface of an automobile, and the like.

(Embodiment 14) FIG. 16 shows Embodiment 1 of the present invention.
4 is a diagram showing a configuration of FIG. In this embodiment, an area light source 513 including a halogen lamp 511 and a diffusion plate 512 is used as the low coherence light source 1 of the thirteenth embodiment. For this reason, the lens arrays 502 and 507 become unnecessary, and there is a merit that it is easy to manufacture.

The other operations are the same as those of the thirteenth embodiment. However, when measuring the shape of the aspheric surface 500 while moving the reflecting mirror 6 or the aspheric surface 500, the lenses 514 and 515 and the two-dimensional photoelectric detector 8 are used. 'In conjunction with the driving devices 516, 517,
518 moves in the direction of the arrow,
The difference is that the two and the two-dimensional photoelectric detector 8 'are moved so that they are optically conjugate, and the imaging magnification of the aspheric surface 500 on the two-dimensional photoelectric detector 8' does not change. However, since the change in the imaging magnification of the aspheric surface 500 on the two-dimensional photoelectric detector 8 'can be corrected by the computer 504, only the lens 514 may be moved.

(Embodiment 15) FIG. 17 shows Embodiment 1 of the present invention.
5 is a diagram showing a configuration of FIG. This embodiment is an example of an apparatus for measuring the thickness of a lens 530 that is being processed and attached to a polishing plate 550 by an interferometer using an optical fiber.

The light emitted from the low coherence light source 1 is condensed by the condensing lens 540 and
It is incident on 41. The light introduced into the optical fiber 541 is separated by an optical fiber splitter 542 into an optical path m and an optical path l.
Divided into Lenses 543 and 544 are arranged in the optical path 1 so that the optical path is longer by Δ than the optical path m. By changing the interval P between the lenses 543 and 544, the value of Δ can be changed. The lights on the optical paths l and m are combined into one by the optical fiber splitter 545, and enter the lens 530 being processed via the single mode optical fiber 546 and the lens 30.

By moving the lens 30 in the direction of the optical axis, a
Light can be condensed in the vicinity of the spherical center of the surface or the surface b or in the vicinity of the surface. The lens 30 may be omitted, but when used, its position is determined in advance by optical calculation.

The light reflected by the lens 530 is
Through the optical fiber splitter 547,
The light passes through the lens 548 and enters the photoelectric detector 8.

The thickness of the lens 530 is d, and the group refractive index is _ng.
And Considering the interference between the light reflected on the b-plane through the optical path m and the light reflected on the a-plane through the optical path l, the two lights are expressed only when Δ−L ≦ d · _ng ≦ Δ + L. Interference, d · _ng gΔ ... In the case of Expression 5, the intensity of the interference light of the photoelectric detector 8 takes the maximum value.
Here, L is the coherence length of the low coherence light source 1. L is preferably the light source 1 having a full width at half maximum of 100 μm or less. Desirably, it is 50 μm or less.

Therefore, the signal intensity of the photoelectric detector 8 is detected while changing P, and when the signal intensity reaches the maximum, d = Δ / _ng ... You can know.

In FIG. 17, reference numeral 549 denotes a signal processing circuit which performs data processing by a computer 504 and outputs the result to a monitor 8;
6 is displayed.

[0215] in the reverse, if the thickness d is known, it is also possible to obtain the n _g by n _g = delta / d · · · Equation 7. In the above, the phase refractive index _np may be used instead of _ng if not very high accuracy is desired.

The example shown in FIG. 17 is not limited to the lens thickness, and can be used for measuring physical characteristics such as various surface intervals and refractive indexes as in the other embodiments of the present invention.

In the example of FIG. 17, an interferometer is formed by using an optical fiber. However, instead of an optical fiber, an equivalent interferometer is formed by using a half prism, a beam splitter, or the like as in other embodiments. May be.

In the example shown in FIG. 17, the low coherence light source 1 and the photoelectric detector 8 may be replaced with each other. FIG. 18 shows such an example, in which a member for changing the optical path length composed of lenses 543 and 544 is arranged on the exit optical path of the test lens 530. Even in that case, Equations 4 to 7 described in the example of FIG. 17 can be similarly applied.

Also in this case, instead of an optical fiber, an equivalent interferometer may be formed by using a half prism, a beam splitter, or the like as in other embodiments.

A member for changing the optical path length may be arranged on both the entrance side and the exit side of the test lens 530.

(Embodiment 16) When autofocus is realized by an endoscope, a TV camera for a rigid endoscope, or the like, a problem is how to measure the distance to an object. A method of estimating a distance with a necessary illumination light intensity has been proposed, but the accuracy is poor.

Therefore, a distance measuring system using a low coherence light source and an interferometer according to the present invention will be applied.

FIG. 19 is a diagram showing the configuration of the sixteenth embodiment of the present invention. This embodiment is an example in which the present invention is applied to an autofocus of a rigid endoscope observed by a TV camera.

The rigid endoscope observation system includes a rigid endoscope 600, a television camera 603 mounted on the eyepiece thereof, and a TV monitor 60.
The TV camera 603 includes a photographing lens 601 and a CCD 602 serving as an image sensor.
The focusing of 03 is performed by the motor 605 and the taking lens 60
1 is moved in the optical axis direction.

The distance measuring system includes an SLD for emitting infrared light as the low coherence light source 1, a power supply 610 for driving the low coherence light source 1, a half prism 84, an eyepiece of the hard mirror 600, and the photographing lens 601. The light beam emitted from the low coherence light source 1 is divided by the half prism 84, and the reflected light moves as reference light. After being reflected by the mirror 6 ', the half prism 84
, And in the future, will pass through and enter the photoelectric detector 8.

On the other hand, the measurement light transmitted through the half prism 84 is reflected by the prism 85 having an infrared light reflection coat,
The object O is irradiated through the rigid mirror 600, and the reflected light from the object O is reflected by the prism 85 with the infrared light reflection coat through the rigid mirror 600, reflected by the half prism 84, and reflected by the photoelectric detector 8. Incident.

Assuming that the distance to the object O is S, when the distance S2, S3, S4 shown in the figure is such that the movable mirror 6 'is located at a position satisfying the relationship of S + S2 + S3 = S4, the interference light of the photoelectric detector 8 Since the intensity has the maximum value, the distance detection circuit 611 detects the distance S to the object O at that time,
Focusing can be performed by moving the photographing lens 601 by the motor 605 via the drive circuit 612 so as to correspond to the distance S.

By the way, as can be generally said of the present invention, when an SLD, LED or the like is used as the light source 1,
The use of a device that emits infrared light is preferable because the reflectance is high even on a lens surface coated with anti-reflection and measurement can be performed with less noise.

In order to know the position or the amount of movement of the reflecting mirror 6 or the moving mirror 6 ', a laser length measuring device is used.
The position or the amount of movement of the reflecting mirror 6 or the moving mirror 6 'can be known with high accuracy.

If a Sony Magnescale (trade name) or a glass scale (trade name) is used instead of the laser measuring device for the same purpose, the cost may be reduced. Alternatively, a ruler, caliper, micrometer, or the like may be used.

[0231]

As is apparent from the above description, the method and the apparatus for measuring the distance between surfaces according to the present invention provide a lens, a mirror,
Non-destructive, non-contact, high-precision measurement of the surface spacing and surface position of optical elements such as prisms becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a surface distance measuring method of the present invention.

FIG. 2 is a diagram illustrating a configuration of a first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a modification of the optical path length varying means.

FIG. 4 is a diagram illustrating a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a fifth embodiment of the present invention.

FIG. 8 is a flowchart illustrating a determination procedure according to a sixth embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a seventh embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of an eighth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a ninth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a tenth embodiment of the present invention.

FIG. 13 is a diagram illustrating a configuration of an eleventh embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a twelfth embodiment of the present invention.

FIG. 15 is a diagram illustrating a configuration of a thirteenth embodiment of the present invention.

FIG. 16 is a diagram showing a configuration of a fourteenth embodiment of the present invention.

FIG. 17 is a diagram illustrating a configuration of a fifteenth embodiment of the present invention.

FIG. 18 is a diagram showing a configuration of a modification of the fifteenth embodiment of the present invention.

FIG. 19 is a diagram showing a configuration of Embodiment 16 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Low coherence light source 2 ... Collimator lens 3 ... Polarizer (polarizer) 4 ... Polarization beam splitter (PBS) 4 '... Beam combiner 5 ... 1/4 wavelength plate 6 ... Reflecting mirror 6' ... Moving mirror 6 "... Reflection Variable ratio mirror 6 "a, 6" b Variable reflectance mirror 8 Photoelectric detector 8 'Two-dimensional photoelectric detector 9 Length measuring device 10 1/4 wavelength plate 14 Optical system under test 16 Stage 19 ... Half-wave plate 21 Reflecting means 22 Polarizer (analyzer) 30 Lens 41, 42, 43 PBS 51 Optical path length varying means 52 Wedge prism 53 Arc-shaped prism 54 Multi-stage prism 55 GRIN prism 56: liquid prism 57, 57 ': transparent plate (reflecting plate) 58: transparent liquid or fluid 59: injection device 61: roof mirror (first reflecting mirror) 62: roof mirror (second mirror) Projection mirror) 63 Prism member 64 Lens 70 Long coherence light source 71, 72, 74, 75 Mirror 76 Photoelectric detector for length measuring device 73 Roof mirror (reflective member) 17 Glass plate 84 Half prism 85 Prism with infrared light reflection coating 86 ... Monitor 88 ... Aspherical lens 89 ... Resin thin film 90 ... Resin thin film type 91 ... Half mirror 92 ... Half prism 93 ... Half mirror 94 ... Light amount adjustment filter 95 ... Memory 96 ... Image processing Device 97 TV monitor 101 Low coherence light source 102 Light beam splitting means 103 Light path length changing means 104 Subject 105 Light beam combining means 106 Photoelectric detector 107 Reflecting mirror 500 Aspheric surface 502 Lens array 503 Driving / position detecting device 504 ... Computer 505 ... Vibration isolation table 506 ... Drive Arrangement 507 Lens array 508 Drive mechanism 509 Cylindrical lens 510 Beam splitter 511 Halogen lamp 512 Diffusion plate 513 Area light source 514, 515 Lens 516, 517, 518 Driving device 530 Lens (under processing) 540: Condensing lens 541: Single mode optical fiber 542: Optical fiber splitter 543, 544: Lens 545: Optical fiber splitter 546: Single mode optical fiber 547: Optical fiber splitter 548: Lens 549: Signal processing circuit 550: Polishing plate 600: Hard mirror 601 Shooting lens 602 CCD 603 TV camera 604 TV monitor 605 Motor 610 Power supply 611 Distance detection circuit 612 Drive circuit O Object

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[Procedure amendment]

[Submission date] November 18, 1999 (1999.11.
18)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 26

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 27

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

[0037] [26] In any one of the above 20 to 25, the wavelength of the shorter wavelength side than the lambda ₀ of the wavelength where the light intensity lambda _S becomes 0.2i _0, lambda _L light intensity 0.2i A measurement method and apparatus, wherein a wavelength longer than λ ₀ among wavelengths that become ₀ is used.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

[27] In any one of the above items 20 to 25, λ _S is a wavelength on the shorter wavelength side than λ ₀ and λ _L is a light intensity of 0.1 I ₀ among wavelengths where the light intensity is 0.1 I _0. A measurement method and apparatus, wherein a wavelength longer than λ ₀ among wavelengths that become ₀ is used.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0154

[Correction method] Change

[Correction contents]

0.5 <(n (λ _S ) −n (λ _L )) · d
_{/ ((L Sa -L La)} / 2) <2.0 , however, d: thickness of the transparent medium n (lambda): the group index of the transparent medium at an arbitrary wavelength lambda lambda _S: the light emitted from the light source When the light intensity at the wavelength λ ₀ where the light intensity is the strongest is defined as I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths at the wavelength λ _S above L _La : the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object At this time, the optical path length difference caused by the wavelength generated by the glass plate 17 is When the glass plate 17 is not provided, the optical path length difference due to the wavelength of the measurement light reflected on the innermost surface in the test optical system 14 is about half. Therefore, the test optical system 1
In the case of measuring the surface near the middle of the optical path 4, the optical path length difference due to the wavelengths of the measurement light and the reference light substantially coincides. Further, when measuring the front surface or the back surface in the test optical system 14, the difference in the optical path length difference between the measurement light and the reference light due to the wavelength generated between the test light and the reference light is the same as when the glass plate 17 is not disposed. Optical system 1
4 is about half the optical path length difference due to the wavelength generated in the measurement light reflected on the innermost surface, and in the intermediate plane, the difference in the optical path length difference due to the wavelength generated between the measurement light and the reference light is smaller. .

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

0.8 <(n (λ _S ) −n (λ _L )) · d
/ ((L _Sa −L _La ) / 2) <1.25 At this time, the difference in the optical path length due to the wavelength generated by the glass plate 17 is the deepest in the optical system 14 to be measured when the glass plate 17 is not disposed. Is about half of the optical path length difference due to the wavelength of the measurement light reflected by the surface, and is more exactly half as compared with the above case. Therefore, when measuring the front surface or the back surface in the test optical system 14, the difference in the optical path length difference due to the wavelength generated by the measurement light and the reference light is more accurate when the glass plate 17 is not disposed. Is about half the optical path length difference caused by the wavelength of the measurement light reflected on the innermost surface of the test optical system 14, and the difference between the optical path length differences caused by the wavelengths of the measurement light and the reference light on the intermediate surface. Is less than that.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kimihiko Nishioka 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Co., Ltd. (reference) 2F065 AA01 AA22 AA30 AA61 BB05 CC16 CC21 CC25 FF51 FF02 GG06 GG07 JJ01 JJ02 JJ03 JJ18 JJ19 JJ25 JJ26 LL00 LL02 LL08 LL21 LL31 LL35 LL36 LL37 LL46 LL53 NN03 QQ23 QQ29 QQ31 SS02 SS13 2G086 FF01

Claims (45)

[Claims] 1. A low coherence light source having a short spatial coherence length, a light beam splitting means for splitting a light beam emitted from the low coherence light source, and an optical path length of one of the light beams split by the light beam splitting device is varied. An optical path length variable unit, and the other light beam split by the light beam splitting device is guided to an optical system as a test object having a surface interval to be measured, and reflected or transmitted light from the test object and the light beam splitting device. A light beam combining means for superimposing two light beams split by the method, and a surface distance measuring method and apparatus for measuring a surface distance of a test object from interference light superimposed by the light beam combining means. 2. A low-coherence light source having a short spatial coherence length, a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam having an arbitrary shape, and a light beam emitted from the light beam shaping device having an arbitrary shape. A polarization state conversion unit that changes the polarization state of the light beam, a light beam division unit that divides the light beam emitted from the polarization state conversion unit according to the polarization state, and converts the polarization state of one of the light beams divided by the light beam division unit. A second polarization state converting means, a reflecting means for reflecting a light beam whose polarization state has been changed by the second polarization state converting means, and an optical path length in an optical path between the reflecting means and the light beam splitting means. A variable optical path length varying means, a third polarization state converting means for converting the polarization state of the other light beam split by the light beam splitting means, and a polarization state being changed by the third polarization state converting means. The changed light beam is guided to an optical system as a test object having a surface interval to be measured, and an optical element with an adjusting device such that the light beam is incident on the surface to be measured, and is split by the light beam splitting device. A light beam combining means for superposing the two light beams, and a photoelectric conversion means for converting the light intensity of the light beam superposed by the light beam combining means into an electric signal. 3. The method and apparatus according to claim 1, wherein a prism is used as the optical path length varying means. 4. The method and apparatus according to claim 1, wherein a liquid crystal having a variable refractive index is used as the optical path length varying means. 5. A low-coherence light source having a short spatial coherence length, a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam having an arbitrary shape, and a light beam emitted from the light beam shaping device having an arbitrary shape. A first polarization state conversion unit that changes the polarization state of the light beam, a light beam division unit that divides the light beam emitted from the polarization state conversion unit according to the polarization state, and one of the light beam division units that is divided by the first light beam division unit. An optical path length changing unit disposed on the optical path of the light beam for changing the optical path length, a second polarization state converting unit for converting the polarization state of the light beam, and a polarization state of the other light beam split by the light beam splitting unit. A third polarization state conversion means for converting,
An optical element with an adjusting means for guiding a light beam whose polarization state has been changed by the polarization state converting means to an optical system as a test object having a surface interval to be measured, and allowing the light beam to enter the surface to be measured. And a reflecting means for reflecting the reflected light from the test object, and a light beam combining means for superimposing the reflected light from the reflecting means and the light beam passing through the light path length changing means,
A photoelectric conversion means for converting the light intensity of the light beam superimposed by the light beam combining means into an electric signal; 6. A low-coherence light source having a short spatial coherence length, a light beam splitting device for splitting a light beam emitted from the low coherence light source, and a first light beam for reflecting one of the light beams split by the light beam splitting device. Reflecting means, the first
And a second reflecting means for reflecting the light beam reflected by the reflecting means, and the other light beam split by the light beam splitting means is guided to an optical system as an object having a surface interval to be measured. An optical element with an adjusting unit such that a light beam is incident on a surface to be irradiated; a light beam combining device for superimposing two light beams split by the light beam dividing device; and a light beam combining device for superimposing the light beams by the light beam combining device. A method and apparatus for measuring a surface distance, wherein the surface distance is obtained from interference information. 7. A low coherence light source having a short spatial coherence length, a light beam shaping means for shaping a light beam emitted from the low coherence light source into a light beam having an arbitrary shape, and one of the light beams shaped by the light beam shaping device. A reflecting means for reflecting the portion, and guided to an optical system as a test object having a surface interval to be measured, which is disposed on an optical path parallel to the light beam shaped by the light beam shaping means, toward the surface to be measured. An optical element with an adjusting unit such that a light beam is incident thereon, a light beam combining unit that superimposes the light beam reflected by the reflecting unit and the light beam reflected by the test object, and a light beam combining unit that superimposes the light beam by the light beam combining unit. A method and apparatus for measuring a surface distance, wherein the surface distance is obtained from interference information. 8. The method and apparatus according to claim 1, wherein an optical fiber is used in an optical path. 9. The measuring method and apparatus according to claim 8, wherein the refractive index of the liquid crystal is measured. 10. The optical element according to claim 1, wherein the thickness of the optical element in the optical system as the test object is known from a design value or an actual measurement, and is obtained from a result of the distance measurement of the optical system. Calculate the group refractive index of the optical element from the optical path length, and agree with the measured group refractive index of the optical element from a table in which the group refractive index in a measurement wavelength range of a plurality of glass or plastic materials prepared in advance is calculated. A method and apparatus for determining an optical material, wherein a type of a glass or plastic material of an optical element to be inspected is specified by searching for a glass or plastic having a group index of refraction. 11. The light source according to claim 1, wherein the low coherence light source emits a linearly polarized light beam, and is rotatable about an optical axis.
The measuring method and apparatus according to the item. 12. The half-wave plate, wherein the low-coherence light source emits a linearly polarized light beam, and a half-wave plate is arranged on an optical axis between the light source and the light beam splitting means. The measuring method and apparatus according to any one of claims 1 to 10, wherein the device is rotatable about an optical axis. 13. The measuring method and apparatus according to claim 11, wherein the light source is a single mode oscillation semiconductor laser operated at a threshold current or less. 14. The measuring method and apparatus according to claim 11, wherein the light source is a pulse laser. 15. The measuring method and apparatus according to claim 1, wherein the reflecting means is a variable reflectance mirror. . 16. The method according to claim 15, wherein the light intensity at the position where the reflected light reflected by the surface of the test object to be measured enters the light beam combining means is I ₁ , and the reflected light reflected by the variable reflectance mirror is The reflectance of the variable-reflectance mirror is adjusted so that 0.05 ≦ I ₁ / I ₂ ≦ 20, where the light intensity at the position where the light enters the light beam combining means is I _2. Measurement method and device. 17. The method according to claim 15, wherein the light intensity at a position where the reflected light reflected by the surface of the test object to be measured is incident on the light beam combining means is I ₁ , and the reflected light reflected by the variable reflectance mirror is The reflectance of the variable-reflectance mirror is adjusted so that 0.2 ≦ I ₁ / I ₂ ≦ 5, where I ₂ is the light intensity at a position incident on the light beam combining means. Measurement method and device. 18. The reflection means is a plurality of variable reflectance mirrors arranged at intervals on a stage movable in the optical axis direction, wherein the reflectance can be controlled independently. Item 18. The measurement method and apparatus according to any one of Items 1 to 17. . 19. The measuring method and apparatus according to claim 1, wherein a transparent medium is arranged on an optical axis between the light beam splitting means and the optical path length changing means. . 20. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. 0.5 <(n (λ _S ) −n (λ _L )) · d / (L _S −L
_L) <2 However, d: thickness of the transparent medium n (lambda): the group index of the transparent medium at an arbitrary wavelength lambda lambda _S: Of the light emitted from the light source, the light intensity of the strongest wavelength lambda ₀ When the light intensity is I ₀ , the light intensity is 0.5I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum. 21. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. 0.8 <(n (λ _S ) −n (λ _L )) · d / (L _S −L
_L) <1.25 However, d: thickness of the transparent medium n (lambda): the group index of the transparent medium at an arbitrary wavelength lambda lambda _S: Of the light emitted from the light source, the strongest wavelength light intensity lambda ₀ when the light intensity was I ₀ in the light intensity 0.5I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum. 22. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. 0.5 <(n (λ _S ) −n (λ _L )) · d / ((L _Sa −
L _La) / 2) <2 However, d: thickness of the transparent medium n (lambda): the group index of the transparent medium at an arbitrary wavelength lambda lambda _S: Of the light emitted from the light source, the light intensity is strongest wavelength When the light intensity at λ ₀ is I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths L _La at the wavelength λ _S above is the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object. 23. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. 0.8 <(n (λ _S ) −n (λ _L )) · d / ((L _Sa −
L _La ) / 2) <1.25, where: d: thickness of the transparent medium n (λ): group index of refraction of the transparent medium at an arbitrary wavelength λ λ _S : of the light emitted from the light source, the light intensity is the highest When the light intensity at the strong wavelength λ ₀ is I ₀ , the light intensity is 0.5 I
Of the wavelengths that become ₀ , wavelengths on the shorter wavelength side than λ ₀ λ _L : Wavelengths on the longer wavelength side than λ ₀ among wavelengths where the light intensity becomes 0.5I ₀ L _Sa : Optical axes of all lenses in the test object The sum of the optical path lengths L _La at the wavelength λ _S above is the sum of the optical path lengths at the wavelength λ _L on the optical axes of all the lenses in the test object. 24. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. _{| (N (λ S) -n} (λ L)) · d- (L S -L L) |
<100 [μm] However, d: thickness of the transparent medium n (lambda): the group index of the transparent medium at an arbitrary wavelength lambda lambda _S: Of the light emitted from the light source, the strongest wavelength light intensity lambda ₀ when the light intensity and I _0, the light intensity is 0.5I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum. 25. The measuring method and apparatus according to claim 19, wherein the transparent medium satisfies the following conditional expression. _{| (N (λ S) -n} (λ L)) · d- (L S -L L) |
<30 [μm] where, d: thickness of the transparent medium n (λ): group refractive index of the transparent medium at an arbitrary wavelength λ λ _S : wavelength λ ₀ at which the light intensity is the highest among the lights emitted from the light source. when the light intensity and I _0, the light intensity is 0.5I
Among the wavelengths that become ₀ , the wavelengths on the shorter wavelength side than λ ₀ λ _L : The wavelengths on the longer wavelength side than λ ₀ among the wavelengths where the light intensity becomes 0.5I ₀ L _S : The wavelengths on the incident side of the surface to be measured the sum of the optical path length at the wavelength lambda _S on the optical axis of the lens in Kenbutsu L _L: optical path length at the wavelength lambda _L on the optical axis of the lens of the object in at the incident side of the surface to be measured It is sum. 26. A any one of claims 20 25, among the wavelengths of light intensity lambda _S becomes 0.2i ₀ lambda ₀
A measuring method and apparatus, wherein a shorter wavelength, λ _L , is a wavelength longer than λ ₀ among wavelengths at which light intensity becomes 0.2I ₀ . 27. The any one of claims 20 25, among the wavelengths of light intensity lambda _S becomes 0.1I ₀ λ ₀
A measurement method and apparatus, wherein a shorter wavelength, λ _L , is a wavelength longer than λ ₀ among wavelengths at which the light intensity is 0.1I ₀ . 28. The measuring method and apparatus according to claim 19, wherein the transparent medium comprises a plurality of transparent media. 29. A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is guided as a reference light and the other is guided as a measurement light to an object to be measured, and a reference light path is provided. And a measurement optical path, wherein the reference light and the measurement light are superimposed on each other, and a method or apparatus for measuring the surface distance of an optical element, an optical system, or an optical device, or a measured object. 30. An interferometer using a light source having a short coherence length, and a test object arranged in an optical path of the interferometer to cause interference, thereby obtaining a surface distance between the optical element and the display device or the display device. Method or device or measured object. 31. An interferometer using a light source with a short coherence length, and a method or apparatus for measuring a surface shape by placing an object in an optical path of the interferometer to cause interference, or a measured object. 32. A light source having a short coherence length, a measurement light path, and a reference light path, wherein light from the light source is incident on an object to be measured, and the emitted light and light on the reference light path interfere with each other to form a surface. Method or device for measuring or measured object. 33. The method or apparatus for determining a surface shape or a measured object according to claim 31, wherein a lens array is provided in an optical path incident on the object to be measured. 34. A device according to claim 31, further comprising means for shaping a light beam into a plurality of light beams in an optical path incident on the object to be measured.
Or a method or apparatus for determining the surface shape according to 32 or a measured object. 35. The method or apparatus for determining a surface shape or a device for measuring a surface shape according to claim 31, wherein the measurement is performed while moving a means for shaping a light beam arranged in an optical path incident on the object to be measured. Thing. 36. The method or apparatus for determining a surface shape or a measured object according to claim 31, wherein the object to be measured and the light receiving element are optically conjugate. 37. An interferometer using a light source having a short coherence length, and a method or apparatus for arranging a test object in an optical path of the interferometer to cause interference and obtaining a surface position or a physical characteristic of the test object Or the measured object. 38. An interferometer using an optical fiber using a light source having a short coherence length, and a test object arranged in an optical path of the interferometer to cause interference, thereby reducing a surface interval or a physical characteristic of the test object. The method or device to be determined or the measured object. 39. An interferometer using an optical fiber using a light source having a short coherence length, wherein a member for changing an optical path length is provided in an optical path of the interferometer, and an object is arranged in an optical path of the interferometer. A method or an apparatus or a measured object which causes interference to determine the surface spacing or physical characteristics of a test object. 40. An interferometer using an optical fiber using a light source having a short coherence length, a test object is arranged in an optical path of the interferometer, and a member for changing an optical path length is provided in the optical path of the interferometer, A method or an apparatus or a measured object that obtains interference by causing light that has passed through a member that changes the optical path length and light that does not pass to cause interference, thereby obtaining the surface spacing or physical characteristics of a test object. 41. In an interferometer using an optical fiber using a light source having a short coherence length, light is incident on a member for changing the optical path length provided in the optical path of the interferometer and passes through the member for changing the optical path length. A method or a device or a measured object that is incident on a test object together with non-existing light, causes interference of emitted light to cause interference, and obtains a surface interval or a physical characteristic of the test object. 42. In an interferometer using an optical fiber using a light source having a short coherence length, a test object is arranged in an optical path of the interferometer, and emitted light from the test object is transmitted in an optical path of the interferometer. A method of determining the surface spacing or physical properties of the test object by causing interference with light emitted from the test object that is incident on the provided member that changes the optical path length and that does not pass through the member that changes the optical path length, or Equipment or measured object. 43. In an interferometer using a light source having a short coherence length, a test object is arranged in the optical path of the interferometer, and a member for changing the optical path length is provided in the optical path of the interferometer, and the optical path length is changed. A method or a device or a measured object that causes interference between light that has passed through a member to be caused and light that does not pass to cause interference, and determines the surface spacing or physical characteristics of a test object. 44. A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is used as reference light and the other is used as measurement light, which is guided to a test object whose distance is to be measured. A method or device for determining a distance by superimposing a measuring light. 45. A light beam emitted from a light source having a short coherence length is split by a light beam splitting means, one of which is used as a reference light and the other is used as a measuring light for an object to be measured for an endoscope or a rigid endoscope. A method or apparatus for guiding a distance through an optical system and superimposing the reference light and the measurement light to obtain a distance.