JP2002213926A - Instrument and method for measuring space, method of manufacturing optical system, and interferometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a space measuring instrument capable of measuring a space at high accuracy compared with the prior art. SOLUTION: In this space measuring instrument provided with an interferometer for light-guiding a light emitted from a light source to an optical system to be examined and an optical path-length-variable optical path, and for light-guiding measuring light reflected in an optional face in the optical system to be examined and reference light following the optical path onto a photoreceiving face of a photodetector, and provided with a displacement detector for detecting a displacement amount of an optical path length of the reference light, a beam diameter magnifying system for magnifying a beam diameter is inserted into either of the optical path of the measuring light incident into the photoreceiving face or the optical path of the reference light incident into the photoreceiving face. Since a difference is generated between a spot diameter by the beam of the measuring light and a spot diameter by the beam of the reference light, in the photoreceiving face, the spots are surely overlapped even when an optical axis of the measuring light is shifted by some extents. Significant information indicating an interference signal is surely obtained thereby based on an output from the photodetector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interval measuring apparatus, an interval measuring method, an optical system manufacturing method, and an interference measuring method for measuring a surface interval of an optical element in a test optical system using an interferometer. About the total.

[0002]

2. Description of the Related Art When measuring the distance between two surfaces, such as the distance between optical elements in an optical system such as a camera lens, the thickness of an optical element, and the level difference on the surface of an optical element, an interferometer is used. Applied (hereinafter the distance between these two surfaces is simply referred to as
That. ). In this interval measurement, the distance to be measured is longer than the wavelength of light (several mm), and therefore, in many cases, a white light source (wavelength of mountain shape) different from laser light and close to sunlight or fluorescent light is used as a light source. Which has a spectrum and is called a "low coherence light source").

[0003] The interference by the low coherence light source (low coherence interference) occurs only in a range where the coherence distance is short and the optical path difference between the two lights is sufficiently short, but an optical path difference-interference light intensity curve in that range. Generally has a peak when the optical path difference is zero. This property is used in the interval measurement. (By the way, Newton rings used for lens inspection and the like also use this property.)

FIG. 5 is a diagram showing an interval measuring apparatus using a low coherence interferometer. In the following, the distance measurement targets are the optical element 804 and the optical element 8 in the test optical system 80.
05 (the interval between the surface 8042 and the surface 8051). In addition, these two surfaces 804 to be measured for the distance are used.
The case where 2,8051 is a curved surface will be described.

In FIG. 5, light is emitted from a light source 101,
The measurement light that has entered the test optical system 80 via the measurement optical path 301 is applied to the respective surfaces 8041 and 804 in the test optical system 80.
After being reflected at 2, 8051 and 8052, the light enters the light receiving element 107 via the measurement optical path 301 and the beam splitter 103. In the present specification, of the light emitted from the light source 101, light that follows the path of the measurement optical path 301, the test optical system 80, the measurement optical path 301, and the light receiving element 107 is referred to as “measurement light”.

On the other hand, light emitted from the light source 101 and incident on the reference light deflecting optical element 108 via the reference light path 302 is reflected on a reference surface (mirror surface) 1081 of the reference light deflecting optical element 108. , Reference light path 302,
The light enters the light receiving element 107 via the beam splitter 103. In this specification, among the light emitted from the light source 101, the reference light path 302 and the reference light deflecting optical element 10
The light that follows the path from 8-reference optical path 302 to light receiving element 107 is referred to as “reference light”.

Here, the reference beam deflecting optical element 108 is
The optical path length of the reference optical path 302 is variable because it is fixed to the stage 206 movable in the optical axis direction. In addition, since the surfaces 8051 and 8042 for which the distance measurement is to be performed are curved surfaces, the measuring optical path 301 includes a condensing optical element for converging the light flux of the measuring light at the apex of the curved surface to generate a cat's eye reflection state. 901 are arranged. In the reference optical path 302, a condensing optical element 902 for condensing the light beam of the reference light on the reference surface 1081 is inserted (the condensing point of the condensing optical element 902 is on the reference surface 1081). It is fixed to the stage 206 together with the reference beam deflecting optical element 108 in a state where it is previously aligned so as to match.)

Further, regarding the light-converging point of the light-collecting optical element 901, each surface (surfaces 8051, 804) of which the distance is to be measured
Since it is necessary to appropriately match 2), the condensing optical element 901 is fixed to the stage 201 that can move in the optical axis direction. Incidentally, when the converging point of the condensing optical element 901 is located on the surface 8042, the measurement light reflected on the surface 8042 becomes parallel light at the condensing optical element 901 and travels toward the light receiving element 107. . When the light-converging point of the light-collecting optical element 901 is located on the surface 8051, the measurement light reflected on the surface 8051 is
The condensing optical element 901 turns to parallel light and travels to the light receiving element 107.

In the distance measuring apparatus having the above-described configuration, the state where the light-collecting point of the light-collecting optical element 901 is aligned with one surface 8042 of the measurement object and the light-collecting optical element 9
The measurement is performed in each of the states where the light-collecting points 01 are aligned (hereinafter, the former measurement is referred to as “measurement of surface 8042”, and the latter measurement is referred to as “measurement of surface 8051”).

In each measurement, the optical path length of the reference optical path 302 is changed by moving the stage 206, and the position information signal 4 indicated by the output of the scale 206a at this time.
06 and the received light amount signal 40 indicated by the output of the light receiving element 107.
7 is sampled. FIG. 6 is a diagram (conceptual diagram) showing a relationship between the position information signal 406 and the received light amount signal 407. 6, the horizontal axis represents the position of the stage 206, and the vertical axis represents the light receiving intensity of the light receiving element 107.

The received light intensity shows only a flat (only DC component) signal at most of the stage positions, but shows an interference signal (including an AC component) partially having a contrast. Incidentally, the interference signal obtained by measuring the surface 8042 and the interference signal obtained by measuring the surface 8051 are the second interference signal from the left and the third interference signal from the left in FIG. 6, respectively.

Therefore, the distance between the surface 8042 and the surface 8051 is determined by the stage position at which the envelope of the second interference signal from the left has a peak and the stage position at which the envelope of the third interference signal from the left has a peak. Can be determined by the difference between

[0013]

However, due to a manufacturing error of the test optical system 80, even a slight displacement occurs between the optical element 804 and the optical element 805 disposed in the test optical system 80. In such a case, the above-described interval measurement may be difficult.

The same applies regardless of whether the type of the positional shift is a shift (lateral shift) of the optical axis, a tilt (tilt) of the optical axis, or both. This is because, before the distance measurement, the test optical system 80 and the distance measuring device are usually aligned, but if the optical element 804 and the optical element 805 are misaligned, at most the surfaces 8051 and 8042 Only one of the surfaces can be sufficiently aligned. This alignment problem becomes more remarkable as the number of optical elements provided in the test optical system 80 increases.

It is conceivable to perform the alignment on each of the measurement of the surface 8042 and the measurement of the surface 8051. However, when performing the interval measurement with high accuracy, the surface 804 is required.
In order to eliminate the difference in environment between the measurement of No. 2 and the measurement of the surface 8051, it is desirable to fix the optical system 80 to be measured.

By the way, if the alignment is insufficient, the following problem occurs (the measurement of the surface 8042 will be described as an example). At this time, since the surface 8042 does not directly face the optical axis of the distance measuring device, the condensing optical element 9
01 is a position shifted from the vertex of the surface 8042. Then, the cat's-eye reflection state does not occur, and the measurement light reflected on the surface 8042 changes its reflection direction and returns to parallel light in the light-collecting optical element 901, but as compared with the case where the measurement light is incident on the surface 8042. The optical axis shifts, and as a result, the optical axis shifts even with the optical axis of the reference light.

When this optical axis shift occurs, on the light receiving surface of the light receiving element 107, as shown in FIG. 7A, a spot 301a due to the light beam of the measuring light and a spot 302a due to the light beam of the reference light are formed. They no longer match, and the overlapping area between the two becomes smaller. At this time, the signal output from the light receiving element 107 contains little information indicating the interference signal.

As a result, it becomes difficult to distinguish the peak of the envelope from the interference signal, and the accuracy of the interval measurement decreases. Furthermore, if the deviation of the optical axis is large, FIG.
As shown in (b), the spot 30 due to the luminous flux of the measurement light
In some cases, the overlapping area of the spot 1a and the spot 302a due to the light beam of the reference light may disappear. At this time, the signal output from the light receiving element 107 does not include any information indicating the interference signal, so that the interval measurement cannot be performed.

As described above, this deviation of the optical axis is caused by a manufacturing error of the optical system 80 to be inspected.
The greater the number of optical elements in 0, the higher the possibility that the accuracy of the interval measurement is reduced or the interval measurement becomes impossible. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in consideration of the above problems, and has provided an interval measuring apparatus and an interval measuring method capable of measuring an interval with higher accuracy than before, and manufacturing of an optical system with higher performance than before. It is an object to provide a method, as well as an interferometer.

[0020]

According to a first aspect of the present invention, there is provided an interval measuring apparatus having a plurality of surfaces for emitting light emitted from a light source.
The test optical system in which the distance between the surfaces is measured, and light guided to an optical path having a variable optical path length, and measurement light reflected on an arbitrary surface in the test optical system and reference light following the optical path. An interferometer that guides the light on the light receiving surface of the light detector, and a displacement measuring device that includes a displacement detector that detects an amount of change in the optical path length of the reference light. A light beam diameter expanding optical system for expanding a light beam diameter is inserted into one of an optical path and an optical path of the reference light incident on the light receiving surface.

At this time, on the light receiving surface, either the diameter of the spot due to the luminous flux of the measurement light or the diameter of the spot due to the luminous flux of the reference light becomes wider. Spots will definitely overlap. Therefore, significant information indicating the interference signal can be reliably obtained from the output of the photodetector. The distance measuring device according to claim 2 guides the light emitted from the light source to a test optical system having a plurality of surfaces and measuring the distance between the surfaces, and an optical path having a variable optical path length. An interferometer that guides the measurement light reflected on an arbitrary surface in the test optical system and the reference light that has followed the optical path onto a light receiving surface of a photodetector; and a change in the optical path length of the reference light. In a distance measuring device provided with a displacement detector for detecting the amount, in the optical path of the reference light incident on the light receiving surface, a light beam diameter expanding optical system for expanding the light beam diameter of the reference light is inserted, characterized in that I do.

At this time, on the light receiving surface, the spot diameter of the reference light beam is larger than the spot diameter of the measurement light beam, so that even if the optical axis of the measurement light is slightly shifted, those spots are surely formed. Overlap. Therefore, significant information indicating the interference signal can be reliably obtained from the output of the photodetector. According to a third aspect of the present invention, in the distance measuring apparatus according to the second aspect, only the overlapping portion between the reference light having the increased light beam diameter and the measuring light is received. .

When measuring the surface interval of a transparent object such as a lens, the light from the light source is equally distributed to the measuring light and the reference light, and if a total reflection mirror is used in the reference light path, the measurement on the photodetector can be performed. The intensity difference between the light and the reference light increases. At this time, the contrast of the interference signal between the measurement light and the reference light decreases. Therefore, in this interval measuring device, in order to prevent a decrease in the contrast of the interference signal, by increasing the spot diameter of the reference light, the intensity difference between the measurement light and the reference light in the overlapping region of the reference light and the measurement light is reduced. Become. Therefore, if only the overlapping portion of the reference light and the measurement light is received by the photodetector, the contrast of the interference signal output from the photodetector increases. As a result, the interval is determined with high accuracy.

According to a fourth aspect of the present invention, there is provided a distance measuring method, comprising: a light emitted from a light source; a test optical system having a plurality of surfaces, the distance between the surfaces being measured; An interferometer that guides the measurement light reflected on an arbitrary surface in the test optical system and the reference light that has followed the optical path onto a light receiving surface of a photodetector, and A displacement detector for detecting an amount of change in the optical path length of the reference light, wherein one of the spot diameter of the measurement light or the spot diameter of the reference light formed on the light receiving surface Is enlarged, the optical path length of the reference light is changed, the output of the photodetector at that time, and the output of the displacement detector are referred to, based on the output referred to, the interval between the arbitrary surfaces Is obtained.

At this time, on the light receiving surface, either the diameter of the spot due to the luminous flux of the measurement light or the diameter of the spot due to the luminous flux of the reference light is widened. The spots will definitely overlap. Therefore, significant information indicating the interference signal can be reliably obtained from the output of the photodetector, and as a result, the interval can be obtained with high accuracy.

In the distance measuring method according to the fifth aspect, the spot diameter of the measurement light and the spot diameter of the reference light formed on the light receiving surface are set to be larger in the latter. According to a sixth aspect of the present invention, in the method of manufacturing an optical system, an interval between arbitrary surfaces of the optical element disposed in the optical system is measured by the interval measuring method according to the fourth or fifth aspect, and the measurement is performed. The optical system is adjusted according to a surface distance. As long as the measurement of the interval is performed with high accuracy,
High performance can be imparted to the optical system.

According to a seventh aspect of the present invention, in the interferometer for receiving an interference image of a plurality of lights emitted from the same light source and passing through different optical paths, the light beam diameter is enlarged to at least one of the optical paths. A beam diameter expanding optical system was inserted.
Regardless of the distance measuring device described above, even when a plurality of light spots are shifted at the light receiving position for some reason, by expanding the diameter of at least one light beam, the plurality of light spots overlap at the light receiving position. . Therefore,
Significant information indicating the interference signal can be obtained.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an interval measuring device according to the present embodiment.

In the following, the distance measurement target is the distance between the optical element 804 and the optical element 805 in the test optical system 80 (the distance between the surfaces 8042 and 8051). Further, in the present embodiment, these two surfaces 804 to be subjected to the interval measurement are used.
The case where 2,8051 is a curved surface will be described (when the surface is a flat surface, the stage 201 and the condensing optical element 901 become unnecessary).

The distance measuring apparatus of this embodiment is different from the distance measuring apparatus shown in FIG. 5 in that a light beam diameter expanding optical system 903 such as a beam expander for expanding the light beam of the reference light is provided. With the optical system 903 for expanding the light beam diameter,
The reference light is incident on the light receiving element 107 as parallel light whose light beam diameter is enlarged. In addition, in order to secure an optical path into which the light beam diameter expanding optical system 903 is inserted, in the present embodiment, the optical path of the reference light is separated into a reference optical path 303 (outgoing path) and a reference optical path 304 (return path). I have.

In this configuration, instead of the reference light deflecting optical element 108 shown in FIG. 5, a reference light deflecting optical element 106 such as a retroreflector or corner cube prism for reflecting reference light in a direction different from the incident light path is used. It is realized by preparing. Further, the reference light deflecting optical element 10
A beam splitter 109 is provided to guide the reference light emitted from 6 to the same optical path as the measurement light.

Here, in FIG. 1, an optical system 9 for expanding the light beam diameter is used.
03 is inserted into the reference optical path 304, the insertion location may be either the reference optical path 303 or the reference optical path 304. However, the reference light path 304 is more preferable in that the size of the reflection surface of the reference light deflection optical element 106 can be suppressed. Also, to save space, the reference light path 30
It is preferable to design and arrange the reference beam deflecting optical element 106 so that the reference beam path 3 and the reference optical path 304 are parallel to each other.

In this embodiment, the condensing optical element 9 is used.
Since reference numeral 02 (see FIG. 5) is omitted, the reflecting surface of the reference light deflecting optical element 106 is assumed to be large enough to reflect a parallel light beam. Further, the stage 206 in the present embodiment has such a size that such a reference light deflecting optical element 106 can be securely fixed.

As described above, the main components of the distance measuring apparatus of the present embodiment are a light source 101, a light beam diameter conversion optical system 102 for adjusting the light emitted from the light source 101 into a parallel light beam, and the parallel light beam as a measurement light. A beam splitter 103 for splitting into two light beams with the reference light, a reference light deflecting optical element 106 for reflecting the reference light incident along the reference light path 303 in the direction of the reference light path 304, and a reference light deflecting optical element 106 are fixed. A stage 206 which is provided and is movable in a direction in which the reference light paths 303 and 304 expand and contract, a measurement light and a reference light path 303 which follow a path of the measurement light path 301, the test optical system 80, and the measurement light path 301; 106—Beam splitter 109 that guides the reference light tracing the light beam diameter enlarging optical system 903 to the same optical path, and arranges interference light generated by the measurement light and the reference light in the optical path. Receiving element 107 to the light, and the like.

The interval measuring device has a measuring optical path 301.
And a condensing optical element 901 for converging the measurement light on each surface in the test optical system 80.
201 and stage 20 for moving the lens in the optical axis direction
6, scale 206a for detecting the position of light receiving element 107
Received light amount signal 407 output from the device and scale 206a
And a processing system 500 (computer or the like) that takes in the position information signal 406 output from the CPU and performs arithmetic processing.

The correspondence between FIG. 1 and the claims is as follows: the light source 101, the light beam diameter conversion optical system 102, the beam splitter 103, the condensing optical element 901, the reference light deflecting optical element 106, the stage 206, Beam splitter 10
Reference numeral 9 and the light receiving element 107 correspond to an interferometer, the scale 206a corresponds to a displacement detector, and the
03 corresponds to a light beam diameter expanding optical system.

FIG. 2 is a diagram for explaining each light incident on the light receiving surface of the light receiving element 107. In the present embodiment, the diameter of the spot 303a due to the reference light beam and the spot 3a due to the measurement light beam are changed by inserting the light beam diameter expanding optical system 903.
The diameter of 01a is different.

The light beam diameter expanding optical system 903 is inserted particularly in the reference light path 304 (or the reference light path 303).
Therefore, the spot 303a due to the luminous flux of the reference light is larger. In the interval measuring apparatus having the above configuration, FIG.
The measurement of the surface 8042 and the measurement of the surface 8051 are performed in the same manner as the interval measurement by the interval measuring device having the configuration shown in FIG.

In the measurement of the surface 8042, the position of the stage 201 is adjusted so that the converging point of the condensing optical element 901 is aligned with the surface 8042.
6, the optical path lengths of the reference optical paths 303 and 304 are changed. At this time, the processing system 500 samples the positional information signal 406 obtained from the scale 206a and the received light amount signal 407 obtained from the light receiving element 107 in association with each other.

In the measurement of the surface 8051, the stage 2
By adjusting the position of the light condensing optical element 90,
1 is focused on the surface 8051, and in this state, the stage 206 is moved to thereby obtain the reference optical paths 303 and 30.
4 is changed. At this time, the processing system 500 samples the positional information signal 406 obtained from the scale 206a and the received light amount signal 407 obtained from the light receiving element 107 in association with each other.

Here, it is assumed that the optical axis of the measuring light incident on the light receiving surface of the light receiving element 107 is shifted due to a manufacturing error of the optical system to be tested 80 or the like. However, in the present embodiment, as shown in FIG. 2, since there is a difference between the spot 303a and the spot 301a, even if the optical axis is slightly shifted, the spot 301a is
a.

Therefore, measurement of surface 8042, surface 805
In any one of the measurements, the sampled data reliably contains significant information indicative of the interference signal. Therefore, the processing system 500 can reliably determine the distance between the surface 8051 and the surface 8042 in the arithmetic processing described later.

FIG. 3 is a diagram (conceptual diagram) showing the relationship between the position information signal 406 and the received light amount signal 407 obtained by the interval measuring device of the present embodiment. 3, the horizontal axis represents the position of the stage 206, and the vertical axis represents the received light intensity of the light receiving element 107 (obtained from the stage position information 406 and the received light amount signal 407, respectively).

The interference signal obtained by measuring the surface 8042 and the interference signal obtained by measuring the surface 8051 are a second interference signal from the left and a third interference signal from the left in FIG. 3, respectively. In FIG. 3, four interference signals are shown, and these are obtained by setting the converging point of the converging optical element 901 to each of the surfaces 8041, 8042, 8051,
It is obtained by each measurement performed in accordance with the data of the data 8052.

The relationship between the four stage positions corresponding to the four interference signals is as follows: surfaces 8041, 8042, 805
1,8052. The processing system 500 analyzes data sampled by the measurement of the surface 8042 and the measurement of the surface 8051 by the method described in Japanese Patent Application No. 2000-264247, for example, and the envelope of the second interference signal from the left in FIG. Stage position X2 to take and 3 from the left
Stage position X at which the envelope of the second interference signal has a peak
Ask for 3. Further, the processing system 500 calculates the difference | X
3-X2 |, and the value of the difference | X3-X2 |
The distance is output as the distance between 051 and the surface 8042.

By the way, in the conventional distance measuring apparatus, when the intensity of the measuring light contributing to the interference signal and the intensity of the reference light are compared, unless the reference and the reflectance of the beam splitter 103 have a special bias, the reference The light intensity was higher. This is because the measurement light has a loss of light amount due to reflection or absorption in each optical element in the test optical system 80, whereas the reference light has almost no such loss.

On the other hand, in the present embodiment, the spot 303a due to the luminous flux of the reference light is enlarged, and a portion where the spots of the measurement light and the reference light overlap each other is:
Their strength is almost equal. Therefore, when the measurement light and the reference light are received only in the overlapping range, the contrast of the interference signal is in a better state than when the light flux of the reference light is not enlarged.

However, when the light receiving element 107 receives a portion of the spot of the reference light that does not overlap with the measurement light, the intensity of this portion is also reflected in the output signal. The contrast is not good.
Therefore, in the present embodiment, only the portion where the measurement light and the reference light overlap with each other is incident on the light receiving surface of the light receiving element 107, and the portion where only the reference light only reaches is covered with a mask or the like to partially block the reference light. Is preferred.

Here, since the spot position of the measurement light changes depending on the surface shape of the object to be measured, when the reference light is blocked in this way, the masked area of the mask can be changed according to the spot position of the measurement light. Is preferably applied. For example, a mechanism for moving the support mechanism for determining the position of the mask to change the masked area of the mask is applied.

As described above, according to the present embodiment, since one of the reference light and the measurement light is enlarged, the accuracy of the interval measurement is increased. Further, since the object to be enlarged is the reference light, the accuracy of the interval measurement is also improved. If the group refractive index of the optical element 804 and the optical element 805 is known, the thickness of the optical element 804 is obtained by dividing the difference | X2−X1 | by the group refractive index. The processing system 500 calculates and outputs this thickness as needed.

The difference | X4− between the stage position X3 where the envelope of the third interference signal from the left in FIG. 3 has a peak and the stage position X4 where the envelope of the fourth interference signal from the left has a peak. The thickness of the optical element 805 is obtained by dividing X3 | by the group refractive index. The processing system 500 calculates and outputs this thickness as needed. In this embodiment,
Some or all processes of the interval measurement may be automated.
In the case of automation, necessary elements (for example, stage 201, stage 206,
The light receiving element 107 and the like may be electrically driven by a motor or the like, and a control circuit for driving and controlling the elements so that the processing is executed may be provided.

When automating the process of moving the stage 201 (the process of aligning the focal point on the surface), the control circuit determines the two surfaces (surface 805) at which the focal point should be adjusted.
(1,8042) (this is determined by the design data of the test optical system 80 and the arrangement of the test optical system 80, etc.) in advance. Further, instead of the control circuit, a computer on which a control board dedicated to the interval measuring device is mounted may be used.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a diagram illustrating the interval measuring device according to the present embodiment. In this embodiment,
Only differences from the first embodiment will be described. The difference between the present embodiment and the first embodiment is that the insertion point of the optical system 903 for expanding the light beam diameter is an optical path of the measurement light. That is, the luminous flux of the measurement light is expanded.

In this case, the spot 303a by the reference light
Since the spot 301a due to the measuring light is larger than the spot light, the effect of increasing the accuracy of the interval measurement can be obtained as in the first embodiment. [Others] In the above embodiments, the two surfaces to be measured are curved surfaces. However, the present invention is applicable to a case where one or both of the surfaces to be measured are flat surfaces. .

Each of the above embodiments can be applied to the manufacture of an optical system. That is, in the manufacturing process of the optical system composed of a plurality of optical elements, after the step of assembling the optical elements, the surface spacing of the optical elements is measured by any of the above-described embodiments, and the measured surface spacing is calculated. Accordingly, the optical system is adjusted, such as adjusting the position of the optical element and polishing the surface of the optical element.

Even if any of the well-known techniques are applied to the adjustment method performed in accordance with the measured surface spacing, high performance is achieved by the high accuracy of the spacing measurement as described above. It can be applied to an optical system.

[0057]

As described above, according to the present invention,
An interval measuring apparatus, an interval measuring method, a method of manufacturing an optical system with higher performance than before, and an interferometer capable of measuring an interval with higher accuracy than before are realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an interval measuring device according to a first embodiment.

FIG. 2 is a diagram illustrating each light incident on a light receiving surface of a light receiving element 107 in the distance measuring device according to the first embodiment.

FIG. 3 is obtained by the distance measuring device of the first embodiment;
FIG. 4 is a diagram showing a relationship between a position information signal 406 and a received light amount signal 407.

FIG. 4 is a diagram illustrating an interval measuring device according to a second embodiment.

FIG. 5 is a diagram showing an interval measuring device using a low coherence interferometer.

FIG. 6 is a diagram showing a relationship between a position information signal 406 and a received light amount signal 407 obtained by a conventional interval measuring device.

FIG. 7 shows a light receiving element 10 in a low coherence interferometer.
FIG. 7 is a diagram illustrating each light incident on a light receiving surface of No. 7;

[Explanation of symbols]

 Reference Signs List 101 light source 102 beam diameter conversion optical system 103, 109 beam splitter 106, 108 reference light deflection optical element 107 light receiving element 407 received light amount signal 500 processing system 201, 206 stage 206a scale 301 measurement optical path 302, 303 reference optical path 301a, 303a spot Reference Signs List 80 optical system to be inspected 406 position information signal 805, 804 optical element 8041, 8042, 8051, 8052 surface 901 902 light-collecting optical element

Claims (7)

[Claims] 1. An optical system according to claim 1, wherein the light emitted from the light source is guided to a test optical system having a plurality of surfaces, the distance between the surfaces being measured, and an optical path having a variable optical path length. An interferometer that guides measurement light reflected on an arbitrary surface in the system and reference light that has followed the optical path onto a light receiving surface of a photodetector, and displacement detection that detects an amount of change in the optical path length of the reference light. A distance measuring apparatus comprising: a light beam path for enlarging a light beam diameter on one of an optical path of the measurement light incident on the light receiving surface and an optical path of the reference light incident on the light receiving surface. An interval measuring device having an enlarged optical system inserted therein. 2. The optical system according to claim 1, wherein the light emitted from the light source is guided to a test optical system having a plurality of surfaces, the distance between the surfaces being measured, and an optical path having a variable optical path length. An interferometer that guides measurement light reflected on an arbitrary surface in the system and reference light that has followed the optical path onto a light receiving surface of a photodetector, and displacement detection that detects an amount of change in the optical path length of the reference light. A distance measuring apparatus comprising: a light beam diameter expanding optical system that expands a light beam diameter of the reference light in an optical path of the reference light incident on the light receiving surface. . 3. The distance measuring apparatus according to claim 2, wherein the photodetector receives only an overlapping portion between the reference light having the enlarged light beam diameter and the measurement light. 4. The optical system according to claim 1, wherein the light emitted from the light source is guided to a test optical system having a plurality of surfaces, the distance between the surfaces being measured, and an optical path having a variable optical path length. An interferometer that guides measurement light reflected on an arbitrary surface in the system and reference light that has followed the optical path onto a light receiving surface of a photodetector, and displacement detection that detects an amount of change in the optical path length of the reference light A distance measuring method comprising: enlarging one of a spot diameter of the measurement light or a spot diameter of the reference light formed on the light receiving surface, and changing an optical path length of the reference light. And an output of the photodetector and an output of the displacement detector at that time, and obtaining an interval between the arbitrary surfaces based on the output referred to. 5. The distance measuring method according to claim 4, wherein: a spot diameter of the measurement light formed on the light receiving surface;
An interval measuring method, wherein the spot diameter of the reference light is set larger in the latter. 6. An interval between arbitrary surfaces of an optical element arranged in an optical system is measured by the interval measuring method according to claim 4 or 5, and the optical system is provided according to the measured surface interval. A method for manufacturing an optical system, comprising adjusting a system. 7. An interferometer for receiving interference images of a plurality of lights emitted from the same light source and passing through different light paths, wherein a light beam diameter expanding optical system for expanding a light beam diameter is inserted into at least one of the light paths. An interferometer characterized in that: