JP2002250609A - Gap-measuring device, gap-measuring method, and manufacturing method of optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the gap of a curved surface with high accuracy. SOLUTION: This device is characterized by being equipped with a floodlighting means for emitting light to a measuring object, a converging means inserted in an optical path of light, for converging light onto the measuring object surface of the measuring object; an interferometer for separating reflected light on the measuring object surface into two beams having variable optical path difference, allowing the two beams to interfere with each other, and detecting interfering light; a moving means for moving the convergent point of the converging means; and a reference light generation means for generating reference light, having a fixed optical path length regardless of the movement and proceeding toward the interferometer together with reflected light, based on a part of light emitted from the floodlighting means. A generated pattern of interfering light, relative to the change of the optical path difference between the two beams, is observed both in a state with the convergent point of the converging means aligned to a first face in the measuring object, and in a state with the convergent point of the converging means aligned to a second face in the measurement object by utilizing the interferometer, to thereby measure the interval of the curved surface with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interval measuring device for measuring the interval, thickness, step, etc. of an optical element using interference, an interval measuring method using the interval measuring device, and an interval measuring method. The present invention relates to a method for manufacturing an optical system used.

[0002]

2. Description of the Related Art An interferometer is used for measuring distances such as the distance between optical elements in an optical system such as a camera lens, the thickness of the optical elements, and the steps of the surfaces of the optical elements with high accuracy. (In the present specification, these distances are simply referred to as “spaces”). In this interval measurement, a white light source (having a mountain-shaped wavelength spectrum and called a “low coherence light source”) which is different from laser light and is close to sunlight or fluorescent lamp light is sometimes used as a light source. .

[0003] Interference due to a low coherence light source (low coherence interference) occurs only in a range where the coherence distance is short and the optical path difference between two lights is sufficiently short, and the envelope of the optical path difference-interference light intensity curve in that range. The line has the property of peaking 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. 13 is a diagram showing an interval measuring apparatus using a low coherence interferometer. In the following, the distance measurement target is defined as the distance between optical element 804 and optical element 805 in measurement object 6000 (that is, surface 8042 and surface 805).
1 interval). In the following, a case will be described in which these two surfaces 8042 and 8051 to be measured are curved surfaces.

In this distance measuring apparatus, the state where the converging point of the converging optical element 901 is aligned with one surface 8042 of the object to be measured, and the converging point of the converging optical element 901 are aligned with the other surface 8051. Measurement is performed in each of the combined states (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.
6a and the position information signal 406 indicated by the output of the light receiving element 10
7 is sampled with the received light amount signal 407 indicated by the output of No. 7.

FIG. 14 is a diagram (conceptual diagram) showing the relationship between the position information signal 406 and the received light amount signal 407. FIG.
In the graph, 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 (DC component only) signal at most stage positions, but shows a signal (including an AC component) having a partial contrast (hereinafter, referred to as an “interference signal”). I have.

Because of the above-mentioned properties, interference is
Only when the optical path length of the measurement light reflected on the surface of the measurement object 6000 reflected by the converging optical element 901 and the reference light reflected by the reference light deflecting optical element 108 is substantially equal. Because it occurs. In addition,
In this specification, light reflected on a surface (measurement target surface) of the measurement object 6000 at which the light-converging optical element is focused is referred to as “measurement light”, and the reference light deflection optical element 108 The light reflected at is referred to as “reference light”.

[0008] Incidentally, in FIG.
The same graph shows the results of each measurement performed by adjusting the converging point of the converging optical element 901 to each surface inside. 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. 14, respectively.

Accordingly, 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. Is determined by the difference between

[0010]

By the way, in the distance measuring apparatus, in order to observe the above-mentioned interference signal, the two light beams contributing to the interference signal, that is, the optical path lengths of the measurement light and the reference light are made substantially the same length. I have to do it.

Therefore, when the measuring optical path 301 is long, for example, when the measuring object 6000 (in other words, the optical element 804 and the optical element 805) is located far from the beam splitter 103, the reference optical path 302 needs to be long. There is. However, at this time, the non-common optical path between the measurement light and the reference light naturally becomes long. Then, between these two lights, there is a high possibility that different changes occur in the optical path lengths due to disturbances (vibration, temperature, air disturbance).

If such a change occurs, the phase difference between the two lights changes regardless of the movement of the stage 206, and noise is superimposed on the interference signal. As a result, the envelope of the interference signal is disturbed, and it becomes difficult to detect the accurate peak, and the accuracy of the interval measurement is reduced. In addition, Japanese Patent Application No. 2000-1419
19 proposes a technique for solving this problem in distance measurement, but this technique can be applied only when the surface of the object to be measured is a flat surface, and when the surface of the object to be measured is a curved surface, It is difficult to apply.

The present invention has been made in view of the above problems, and has as its object to provide an interval measuring apparatus and an interval measuring method capable of measuring the interval between curved surfaces with high accuracy. It is another object of the present invention to provide a method of manufacturing an optical system capable of manufacturing a high-performance optical system.

[0014]

According to a first aspect of the present invention, there is provided an interval measuring apparatus for projecting light to a measuring object having a plurality of surfaces, and a light projecting from the projecting means. And a light condensing unit that condenses the light on the measurement target surface of the measurement target object, and light reflected on the measurement target surface (referred to as “measurement light” in this specification). Is separated into two light fluxes having variable optical path differences, interferes with the two light fluxes, detects an interference light obtained by the interference, a moving means for moving a converging point of the condensing means, and Based on a part of the light emitted from the light means, a reference light generating means for generating a reference light heading toward the interferometer together with the reflected light, wherein an optical path length is invariant regardless of the movement by the moving means; It is characterized by having.

According to the condensing means and the moving means, even if the surface of the object to be measured is a curved surface, light is appropriately condensed on each surface, and only in a minute area which can be regarded as a substantially flat surface. Light from the light projecting means can be irradiated. Also,
Measurement of the first measurement target surface and second measurement
The reference light common to the measurement of the measurement target surface is generated. The reference light is guided to the interferometer together with the reflected light on the surface to be measured, and thereafter separated into two light beams.

Further, the interferometer detects the interference light when the optical path difference between the lights separated into two light fluxes among the reflected light and the reference light becomes zero. If an interval measuring device having such a configuration is used, at least one of the surfaces for which the interval is measured is a curved surface, and an object in which an interference image cannot be obtained due to divergence due to a place where a light beam from the light projecting means is reflected. Also in the measurement of the distance between objects, the distance between the objects can be accurately measured by the interferometer. At this time, the first object to be measured is
In both the state where the light converging point of the light condensing means is aligned with the surface to be measured and the state where the light converging point is aligned with the light converging means on the second measurement surface, The occurrence pattern of the interference light can be observed by an interferometer.

Moreover, even if the object to be measured is far from the interferometer, the object before entering the interferometer is
The influence of the disturbance on the interference light can be suppressed by reducing the number of portions that receive different disturbances between the reflected light and the reference light. That is, according to the interval measuring device, the interval between the curved surfaces can be measured with high accuracy.

According to a second aspect of the present invention, in the distance measuring apparatus according to the first aspect, the reference light generating means is inserted between the light projecting means and the light condensing means; It is a transmission / reflection member that transmits the part of the light emitted from the light projecting unit to the side of the light condensing unit and generates the reference light by reflecting the other part of the light. And

According to a third aspect of the present invention, in the distance measuring apparatus according to the first aspect of the present invention, the reference light generating means measures the distance in the vicinity of the measuring object irrespective of the movement by the moving means. A reflecting member that is arranged with the relative position to the object unchanged and reflects incident light,
The light emitted from the light projecting unit is separated into a first light beam going to the light collecting unit and a second light beam going to the reflecting member, and light reflected by the reflecting member is used as the reference light. And a separating / integrating means for integrating the reflected light on the measurement target surface into the same light beam as the reflected light.

According to a fourth aspect of the present invention, in the distance measuring apparatus according to the third aspect, a wave plate and a polarizing beam splitter are used as the separation and integration means. The distance measuring device according to claim 5 is the distance measuring device according to claim 3 or 4, wherein the reference light generating unit is configured to detect when the reflected light on the surface to be measured enters the interferometer. The polarization direction of the, the wave plate that gives a difference between the polarization direction when the reference light is incident on the interferometer is used, the interferometer, as the separating means, the reflected light and the reference light A polarization beam splitter is used to separate the reflected light and the reference light into one and the other of the two light beams.

According to a sixth aspect of the present invention, there is provided an interval measuring method using the interval measuring device according to any one of the first to fifth aspects. A first measurement procedure of observing, by the interferometer, an occurrence pattern of the interference light with respect to a change in an optical path difference between the two light beams while the light-collecting point of the light-collecting unit is aligned with a measurement target surface;
By driving the moving means, the converging point of the condensing means is adjusted to the second measuring object surface of the measuring object, and in that state, the pattern of occurrence of the interference light with respect to the change in the optical path difference between the two light fluxes A second measurement procedure observed by the interferometer, and a pattern observed in the first measurement procedure as information indicating an interval between the first measurement target surface and the second measurement target surface, And a calculation procedure for obtaining a difference from the pattern observed in the second measurement procedure.

According to a seventh aspect of the present invention, there is provided a method of manufacturing an optical system, comprising measuring an interval between predetermined positions in the optical system by the interval measuring method according to the sixth aspect, and according to the interval obtained by the measurement. And adjusting the optical system.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIGS. 1, 2, 3, and 4
A first embodiment of the present invention will be described with reference to FIG. (Configuration) First, the configuration of the interval measuring system of the present embodiment will be described. FIG. 1 is a configuration diagram of an interval measurement system according to the present embodiment (and a second embodiment described later).
FIG. 5 is a configuration diagram of a light collecting unit 5000 (and a measurement target 6000) in the interval measurement system of the present embodiment.

As shown in FIG. 1, the distance measuring system according to the present embodiment includes a distance measuring device 2000 and a light collecting unit 50.
00. The light collecting unit 5000 is arranged between the interval measuring device 2000 and the measurement object 6000.
Incidentally, this interval measuring system is disclosed in Japanese Patent Application No. 2000-14.
The light collecting unit 50 is added to the distance measuring device described in 1919.
Equivalent to adding 00.

The interval measuring device 2000 is used for measuring the object 60 to be measured.
A light projecting unit 3000 for irradiating light to
And a measuring unit 4000 for receiving the reflected light from the light source 00. The light projecting unit 3000 includes a low coherence light source 101, a light beam diameter conversion optical system 102, and a beam splitter 103.

In the light projecting section 3000, the light emitted from the low coherence light source 101 is converted into a light beam diameter converting optical system 1.
02, becomes parallel light and enters the beam splitter 103.
The reflected light from the beam splitter 103 is incident on the light collecting unit 5000 and the measuring object 6000 in this order. As illustrated in FIG. 2, a part of the light that has entered the measurement target 6000 via the light collection unit 5000 is transmitted to the surfaces 8041, 8042, 8051, and 8 in the measurement target 6000.
After each reflection at 052, the light collection unit 5000,
And the beam splitter 1 in the light projecting unit 3000 shown in FIG.
03 in this order, and then enter the measuring unit 4000.

As shown in FIG. 1, the measuring section 4000 includes:
Beam splitter 111, optical element for changing optical path difference (retro reflector, corner cube prism, etc.) 11
2a, optical element for deflection (retro reflector, corner cube prism, etc.) 112b, beam splitter 1
21, light receiving elements 107a and 107b, deflection optical elements (mirrors) 113a and 113b, and the like.

Incidentally, the measuring section 4000 of the present embodiment is:
It forms a Mach-Zehnder interferometer. Measuring unit 400
At 0, the light incident from the light collection unit 5000 is
The light enters the beam splitter 111 and is split into reflected light and transmitted light. The reflected light split by the beam splitter 111 passes through an optical path (M optical path) indicated by “M” in FIG.
The light is reflected by the optical path difference changing optical element 112a, enters the beam splitter 121 via the deflecting optical element 113a, is split into reflected light and transmitted light, and the reflected light and transmitted light enter the light receiving elements 107a and 107b, respectively.

The transmitted light split by the beam splitter 111 passes through an optical path (R optical path) indicated by "R" in FIG. 1 and is reflected by the deflecting optical element 112b, and passes through the deflecting optical element 113b. The reflected light and the transmitted light are incident on the light receiving element 121 and are divided into reflected light and transmitted light.

Here, the optical path difference changing optical element 112a
Is a stage 20 movable in a direction to expand and contract the M optical path.
1 and the optical path length of the M optical path is variable. The position of the stage 201 can be read by a scale (not shown). Further, the position information signal of the stage 201 output by the scale and the light amount signal of the light receiving elements 107a and 107b are:
It is input to a processing system (not shown) such as a computer.

On the other hand, as shown in FIG.
000 includes a light-collecting optical element 903 and a reflection-transmission optical element 221. First, the condensing optical element 903
Is a condensing lens or the like that condenses a light beam at one point. The reflection-transmission optical element 221 is a Fizeau member or the like having a reference surface (Fizeau surface) 2211 that reflects part of the incident light in the same direction as the incident optical path and transmits the remaining part of the incident light. is there.

In the light collecting unit 5000, the light incident from the distance measuring device 2000 is reflected by the reflection / transmission optical element 22.
1 and a part of the light is reflected by the reference plane 2211 and another part is transmitted through the reference plane 2211. Reference surface 2
The light reflected at 211 (reference light, details of which will be described later) returns to the interval measuring device 2000 and is reflected on the reference surface 221.
The light transmitted through 1 is incident on the condensing optical element 903.
The light incident on the light-collecting optical element 903 travels in the direction of the measurement object 6000 while being collected.

Here, the condensing optical element 903 is fixedly mounted on the stage 203 movable in the optical axis direction in the condensing unit 5000. By moving the stage 203, the converging point of the condensing optical element 903 moves in the optical axis direction. Therefore, by adjusting the position of the stage 203, the converging point is appropriately adjusted to each surface in the measurement object 6000. .

By the way, if the focal point is coincident with the surface 8041, the light reflected from the surface 8041 is
03, it returns to the interval measuring device 2000 as parallel light, and if the focal point matches the surface 8051, the surface 80
The reflected light from the light 51 is converted into parallel light in the condensing optical element 903 and returns to the distance measuring device 2000. In the light collecting unit 5000, the image formed on the light receiving elements 107a and 107b by the light flux from the surface inside the measurement target 6000 and the light flux from the reference surface 2211 are formed on the light receiving elements 107a and 107b. A relay system (light-collecting optical element 904 and light-collecting optical element 905) as shown by a dotted line in FIG. That is, the condensing optical element 904 is arranged so that the converging point comes on the reference surface 2211, and the condensing optical element 905 is arranged so that the light incident on the condensing optical element 903 becomes parallel light. . The purpose of aligning the directions of the images is to generate interference efficiently and detect interference signals more accurately.

The correspondence between the elements shown in FIGS. 1 and 2 and the claims is as follows. The light projecting section 3000 corresponds to the light projecting means, the measuring section 4000 corresponds to the interferometer, and the light collecting optics. The element 903 corresponds to a condensing unit, the stage 203 corresponds to a moving unit, and the reflection / transmission optical element 221 corresponds to a reference light generating unit.

(Operation) Next, a procedure of the interval measurement by the interval measuring system having the above-described configuration will be described. In the present embodiment, the distance between the optical element 804 and the optical element 805 in the measurement object 6000, that is, the surfaces 8042 and 8051
The description will be made assuming that the distance D (see FIG. 2) between the two is measured.

At this time, the state where the converging point of the condensing optical element 903 is aligned with one surface 8042 and the other surface 8051
The measurement is performed in each of the states where the converging point of the condensing optical element 903 is adjusted (hereinafter, the former measurement is referred to as “measurement of the surface 8042”, and the latter measurement is referred to as “measurement of the surface 805”).
1 measurement ". ). However, between the two measurements, at least the positional relationship between the measurement object 6000 and the light collecting unit 5000 is not changed.

This defines the optical path of the reference light between the two measurements,
This is to fix the optical path of each measurement light in each measurement. In this specification, light reflected on a reference surface is referred to as “reference light” in order to be compared with “measurement light” and to be distinguished from “reference light” in a conventional distance measuring device.

However, “measurement light” and “reference light” do not include stray light (light that is reflected a plurality of times on the same surface). That is, the “measuring light” is emitted from the low coherence light source 101, and then travels through the beam splitter 103, the condensing optical element 903, the surface 8042, the condensing optical element 903, the beam splitter 103, and the beam splitter 111 in this order. The “reference light” is emitted from the low-coherence light source 101, and then emitted from the beam splitter 103-
The light passes through the reference plane 2211-the beam splitter 103-the beam splitter 111- in this order.

Hereinafter, the measurement of the surface 8042 will be described.
Except that the object to be focused on No. 3 is the surface 8051, the description is omitted because it is the same. In the measurement of the surface 8042, the position of the stage 203 is adjusted so that the converging point of the condensing optical element 903 is aligned with the surface 8042, and in this state, the stage 201 is moved to change the optical path length of the M optical path. Let it.

The processing system (not shown) reads a position information signal of the stage 201 read by a scale (not shown) at this time,
Sampling is performed in association with the received light amount signals obtained from the light receiving elements 107a and 107b. Here, in the configuration of the measuring section 4000 shown in FIG.
7b are inverted in phase (18).
0 °), the processing system obtains the difference between the output signals of the light receiving elements 107a and 107b as the received light amount signal.

As described above, the two light receiving elements 107
By using the difference between the output signals a and 107b, the same type of noise superimposed on the two light receiving elements 107a and 107b in the same phase is eliminated, and the measurement result can be obtained with higher accuracy. The light to be considered in the measurement of the surface 8042 is the measurement light reflected on the surface 8042 and the reference surface 2
Reference light reflected at 211.

However, in this embodiment, the R light path and the M light of the measurement light and the reference light contribute to the interference signal.
These are lights that individually traced the optical path. Therefore, hereinafter, of the measurement light, the light passing through the R optical path is converted to the measurement light (R
8042_R), the light passing through the M optical path among the measuring lights is referred to as the measuring light via the M (L8042_M), and the light passing through the R optical path among the reference lights is the reference light via the R (L2211_R).
And the light that reaches the light receiving element 107a through the M optical path in the reference light is referred to as reference light via M (L2211_M).

The “R optical path” is the beam splitter 1
11-deflection optical element 112b-beam splitter 12
1 and the “M optical path” is an optical path that passes through the beam splitter 111, the optical path difference changing optical element 112 a, and the beam splitter 121. FIG. 3 is a diagram comparing the optical path length of each light.

In FIG. 3, the line segment shown in the first row is light passing through R, that is, reference light passing through R (L2211_L).
R) and the optical path length of the measurement light (L8042_R) via R. On the other hand, the line segments shown in the second to fourth rows indicate the optical path lengths of the light passing through M, that is, the reference light passing through M (L2211_M) and the measuring light passing through M (L8042_M). Here, as described above, when measuring the surface 8042, the optical path length of the M optical path changes due to the movement of the stage 201.

Therefore, in the second to fourth stages in FIG. 3, when the M optical path is equal to the R optical path (M = R), when the M optical path is shorter than the R optical path by 2D1 (M = R−2D1). , And when the M optical path is longer than the R optical path by 2D1 (M = R + 2D
Each state of 1) is shown. However, "2D1"
When measuring the surface 8042, between the measurement light and the reference light,
This is an optical path difference generated before the light enters the measurement unit 4000. Hereinafter, such an optical path difference is simply referred to as “an optical path difference before division between the measurement light and the reference light”.

In the interval measuring system having the above-described configuration (see FIGS. 1 and 2), when light passing through R and light passing through M are compared, they interfere with each other when their optical path lengths are equal. As shown in the second stage of FIG. 3, when the M optical path is equal to the R optical path (M = R), the optical path lengths of the reference light via L (L2211_R) and the reference light via L (L2211_M) are equal. At the same time, the measurement light passing through R (L8042_R) and the measurement light passing through M (L8042_M) have the same optical path length, so that the reference light passing through R (L2211_R) and the reference light passing through M (L2211_M) interfere with each other. At the same time, the measurement light via R (L8042_R) and the measurement light via M (L804)
2_M).

As shown in the third row of FIG. 3, when the M optical path is shorter than the R optical path by 2D1 (M = R-2D1)
, The reference light (R2211_R) passing through R and the measurement light (L8042_M) passing through M interfere with each other because they have the same optical path length. As shown in the fourth row of FIG.
When the optical path is longer than the R optical path by 2D1 (M = R + 2D
In 1), the measurement light (R8042_R) passing through R and the reference light (L2211_M) passing through M interfere with each other because they have the same optical path length.

FIG. 4 is a diagram (conceptual diagram) showing the relationship between the position information signal and the received light amount signal obtained by measuring the surface 8042. In FIG. 4, the horizontal axis represents the position of the stage 201, and the vertical axis represents the received light intensity of the light receiving elements 107a and 107b (obtained from the stage position information and the received light amount signal, respectively).

As can be seen in FIG. 4, the interference signals appear at three stage positions. These three interference signals indicate that when the position of the stage 201 is such that the M optical path is equal to the R optical path (M = R), the M optical path is shorter than the R optical path by 2D1 (M = R−2D1), Is longer than the R optical path by 2D1 (M = R + 2D1).

As described above, when M = R, two sets of light interfere with each other, whereas when M = R−2D1 and R + 2D1, only one set of light interferes. Since it is light, the amplitude of the interference signal generated when M = R is the largest. Here, assuming that the stage position corresponding to the interference signal having the largest amplitude is the zero position, the stage position corresponding to the interference signal on both sides around the zero position is +
It should be the position of D1 and the position of -D1.

Therefore, based on these interference signals indicated by the sampled data, D1 (however, 2D
1: Pre-division optical path difference between measurement light and reference light). That is, the processing system is, for example, disclosed in Japanese Patent Application No. 2000-2.
By the method described in 64247, the stage position S ₊ when the envelope of the right of the interfering signal takes a peak, stage position S when taking the peak envelope of the left-stage interference signal _- determined and these The value of D1 is obtained by dividing the difference | S ₊ −S ₋ |

[0054] Alternatively, the processing system, the values of D1, the left (or right) stage position S at which the envelope of the interference signal taking the peak of the _- (or S _+), the envelope of the center of the interference signal Difference from stage position S ₀ when peak is taken | S ₋ −S ₀
(Or | S ₊ -S ₀ |) (the former calculation method can reduce the measurement error).

As described above, the value of D1 (2D1: the optical path difference before division between the measurement light and the reference light) was determined by measuring the surface 8042. Further, in the present embodiment, the measurement of the surface 8051 is performed in the same manner as the above procedure. At this time, the processing system obtains the value of D2 in the same manner as the value of D1. However, 2D2 is used when measuring the surface 8051.
This is the optical path difference before division between the measurement light and the reference light.

The optical element 80 to be finally obtained is
4 and the optical element 805 (the distance between the surface 8042 and the surface 805).
1) is the difference between D1 and D2 obtained by measuring the surface 8042 and the surface 8051. Note that, from the above definitions of “2D1” and “2D2”, the surface 8
It is clear that the distance D between the surface 042 and the surface 8051 is represented by the difference between D1 and D2 (see FIG. 2).

The processing system calculates the difference | D between D1 and D2.
1−D2 | is calculated, and the optical element 804 and the optical element 805 are determined.
Output as interval D. It should be output as the interval D
The value is the stage position S when obtaining the value of D1. ₊Or
Tage position S_-And the stage position S for obtaining D2₊
Or stage position S_-From the stage position difference from
Can be

(Effect) As described above, in this embodiment, the surface 804
In order to generate reference light common to the measurement of No. 2 and the measurement of the surface 8051, an optical element 221 for reflection and transmission is prepared. Moreover, the reflection / transmission optical element 221 is disposed between the measurement object 6000 and the interval measurement device 2000 together with the light collection optical element 903 for collecting light on a curved surface.

Then, the reference light is guided together with the measuring light into the inside of the measuring section 4000, and thereafter separated into an M optical path and an R optical path. Here, in the present embodiment, of the measurement light and the reference light, the light that individually traces the R optical path and the M optical path contributes to the interference signal. The non-common optical paths of these lights are a difference corresponding to an optical path difference before division between the measurement light and the reference light (2D1 in the measurement of the surface 8042, 2D2 in the measurement of the surface 8051), and a difference between the M optical path and the R optical path. However, since the M optical path and the R optical path are arranged relatively close to each other, they are hardly affected by disturbance. Therefore, it is mainly the former that should be considered as a non-common optical path that is subject to disturbance.

However, in the present embodiment, even if the surface 804
Even if the second surface (or the surface 8051) is apart from the distance measuring device 2000, the non-common optical path which is subject to disturbance can be reduced by setting the arrangement position of the reference surface 2211 as close as possible to the measurement object 6000. Can be kept.
As a result, in the present embodiment, the interval between the curved surfaces can be measured with high accuracy.

In this embodiment, the reflection / transmission optical element 221 for generating the reference light is provided with the distance measuring device 20.
It is configured as a common unit with the light-collecting optical element 903 that collects light from 00 on the surface inside the measurement object 6000. Therefore, when the surface of the measurement target 6000 is a plane, if the light-collecting unit 5000 is separated, the distance between such surfaces can be measured by the method described in Japanese Patent Application No. 2000-141919.

(Others) In this embodiment, the surface 80
Although the distance D between 51 and the surface 8042 is measured, the distance between other surfaces in the measurement object 6000 can be measured in the same manner. For example, the measurement of the surface 8051 and the surface 804
In addition to the measurement 2, by performing measurement (measurement of the surface 8052) with the light-converging point of the light-collecting optical element 903 aligned with the surface 8052, the measurement light and the reference light reflected from the surface 8052 can be obtained. Is obtained.

Further, the measurement (measurement of the surface 8041) is performed by adjusting the converging point of the condensing optical element 903 to the surface 8041, so that the measurement light which is the reflected light from the surface 8041 and the reference light are not divided. The optical path difference 2D0 is obtained. At this time, if the group refractive indices of the optical elements 804 and 805 are known, the difference between D3 and D2 divided by the group refractive index is the thickness of the optical element 805, and the difference between D1 and D0 is obtained. Is divided by the group refractive index to be the thickness of the optical element 804. The processing system is
The thicknesses are obtained and output as needed.

In the light projecting section 3000 shown in FIG. 1, if the beam splitter 103 is a polarization beam splitter and a quarter-wave plate 109 indicated by a broken line is inserted, the beam is split by the beam splitter 103 and is wasted. Since no light is generated, the interval measurement can be performed with higher accuracy. [Second Embodiment] A second embodiment of the present invention will be described with reference to FIGS.

The second embodiment is the same as the distance measuring system of the first embodiment except that the light collecting unit 5002 is provided instead of the light collecting unit 5000. FIG. 5 shows a light collecting unit 5 in the distance measuring system according to the second embodiment.
002 (and the measurement object 6000).

As shown in FIG. 5, the light collecting unit 5002 of the present embodiment is different from the light
An arm type interference optical system (generally called a Michelson type, Twyman Green type, etc.) is used. That is, the light-collecting optical element 90 is
3. In addition to the stage 203, the beam splitter 131,
An optical element for deflection (mirror) 1201 and an optical element for reflection (mirror) 122 are provided.

In the condenser unit 5002, the light incident from the interval measuring device 2000 is transmitted to the beam splitter 13
1 and is split into transmitted light (first light flux) and reflected light (second light flux). The first light beam split by the beam splitter 131 passes through the first optical path 305 and enters the measurement object 6000 via the condensing optical element 903. Some of the light is on the surfaces 8041, 8042, 80
The first optical path 305
Through the converging optical element 903, the light passes through the beam splitter 131, and returns to the distance measuring device 2000.

The second light beam split by the beam splitter 131 passes through the second optical path 306, passes through the deflecting optical element 1201, and is reflected by the reflecting surface (reference surface) 1221 of the reflecting optical element 122. Then, the light passes through the second optical path 306 in the opposite direction and returns to the distance measuring device 2000 via the deflecting optical element 1201 and the beam splitter 131 (this is the reference light of the present embodiment).

Here, the condensing optical element 903 is fixed to the stage 203 which can be moved in the optical axis direction, and its function is the same as that of the condensing optical element 903 in the first embodiment. The second optical path 306 has a reference surface 1221
The light-collecting optical element 906 may be arranged such that the light-collecting point is located at a position. 5 shows the correspondence between the elements shown in FIG. 5 and the claims. The light-collecting optical element 903 corresponds to the light-collecting means, the stage 203 corresponds to the moving means, and the reference surface 122.
1. Deflection optical element 1201, beam splitter 131
Corresponds to the reference light generating means.

The procedure of the interval measurement of the present embodiment using the above-described light collecting unit 5002 is the same as the procedure of the interval measurement of the first embodiment. However, in the interval measurement system of the present embodiment, a part of the measurement light is guided to a second optical path 306 different from the first optical path 305 in order to generate the reference light. With this configuration, the optical path differences before division (2D1, 2D2, 2D3, 2D0) between the measurement light and the reference light can all be reduced.

Therefore, the stroke of the stage 201 is further reduced, and the apparatus can be further downsized. Further, if the second optical path 306 serving as the optical path of the reference light is arranged as close as possible to the first optical path 305 serving as the optical path of the measuring light, the influence of disturbance on the non-common optical path of both lights can be suppressed to a small level. .

Third Embodiment A third embodiment of the present invention will be described with reference to FIGS. 6, 7, and 8. (Configuration) First, the configuration of the interval measuring system of the present embodiment will be described. FIG. 6 is a configuration diagram of an interval measurement system according to the present embodiment (and fourth, fifth, sixth, and seventh embodiments described below).

As shown in FIG. 6, the distance measuring system of this embodiment is different from the second embodiment shown in FIG. 1 in that a light collecting unit 5003 is provided instead of the light collecting unit 5002, and Instead, it is equivalent to the one provided with a light emitting unit 3002 and the measurement unit 4002 instead of the measurement unit 4000. As shown in FIG. 6, the light projecting unit 3002 of the present embodiment is provided with a function of adjusting the polarization direction of emitted light.

That is, in the light projecting unit 3002, the light emitted from the low coherence light source 101 is converted into parallel light by the light beam diameter conversion optical system 102, and the deflection optical element (mirror) 1
The light enters the half-wave plate 110 via 42, and travels to the light collecting unit 5003 with the polarization direction adjusted. Also, the optical path of the return light from the light collection unit 5003 of the present embodiment has its optical axis shifted from the outward path, and
The light directly enters the measurement unit 4002 without passing through the optical system 002. In the present embodiment, a 波長 wavelength plate may be used instead of the 波長 wavelength plate 110.

As shown in FIG. 7, the light-collecting unit 5003 of this embodiment is different from the light-collecting unit 5 of the second embodiment.
Unlike 002 (see FIG. 5), each light is guided according to its polarization direction by using a polarization beam splitter and a wave plate. Thus, useless light loss is suppressed. That is, the light incident on the light collecting unit 5003 from the light projecting unit 3002 is reflected by the polarization beam splitter 15.
1 and is split into transmitted light (P-polarized light) and reflected light (S-polarized light).

The transmitted light (P-polarized light) split by the polarizing beam splitter 151 passes through the first optical path 307 and
The light is converted into circularly polarized light by the 波長 wavelength plate 161, and the condensing optical element 90
After that, the light is incident on the object 6000 to be measured. Some of the light is reflected by the surfaces 8041, 8042, 8051, and 8052, respectively, and passes through the first optical path 307 in the opposite direction, and
The light becomes s-polarized light by the 波長 wavelength plate 161, is reflected by the polarization beam splitter 151, and is incident on the measuring unit 4002 via the deflecting optical element (mirror) 143.

Therefore, the measuring light of this embodiment enters the measuring section 4002 in the state of S-polarized light. The reflected light (S-polarized light) split by the polarization beam splitter 151 is
The light passes through the second optical path 308, becomes circularly polarized by the quarter-wave plate 162, passes through the deflecting optical element (mirror) 1201, is reflected by the reference surface 1221 of the reflecting optical element 122, and turns the second optical path 308 in the opposite direction. As described above, the light becomes P-polarized light by the 波長 wavelength plate 162, passes through the polarization beam splitter 151, and enters the measurement unit 4002 via the deflection optical element 143.

Therefore, the reference light of the present embodiment enters the measuring section 4002 in the state of P-polarized light. Here, the condensing optical element 903 is mounted on the stage 20 movable in the optical axis direction.
3 and its function is the same as that of the condensing optical element 903 in the second embodiment. Note that, in the second optical path 308, a light-collecting optical element 906 shown by a dotted line may be arranged so that the light-converging point is located on the reference surface 1221.

As shown in FIG. 8, the measuring section 4002 of the present embodiment is different from the measuring section 4000 (FIG. 1) of the second embodiment.
), By using a deflection beam splitter and a wave plate, the measurement light and the reference light (in this embodiment,
(The polarization directions are different from each other) according to the polarization direction, and the measurement light and the reference light are separated into one and the other of the two light fluxes.

That is, in the measuring section 4002, the light from the light collecting unit 5003 is
And is split into reflected light and transmitted light. Here, the reflected light is S-polarized measurement light, and the transmitted light is P-polarized reference light. The transmitted light (P-polarized light), that is, the reference light, split by the polarization beam splitter 152, passes through the M optical path, is reflected by the optical path difference changing optical element 112a, and enters the beam splitter 132 via the deflecting optical element 113a. Then, the light is divided into reflected light and transmitted light, and the reflected light and transmitted light enter the light receiving elements 107a and 107b, respectively.

The reflected light (S-polarized light), that is, the measurement light, split by the polarization beam splitter 152, passes through the R optical path, is reflected by the deflecting optical element 112b, passes through the deflecting optical element 113b, and receives a 波長 wavelength light. The light becomes P-polarized light by the plate 163, enters the beam splitter 132, is divided into reflected light and transmitted light, and the reflected light and transmitted light enter the light receiving elements 107b and 107a, respectively.

Here, the optical path difference changing optical element 112a
Is fixed to the stage 201 that expands and contracts the M optical path, and the optical path length of the M optical path is variable. The position of the stage 201 can be read by a scale (not shown). Further, the position information signal of the stage 201 output from the scale and the light receiving element 10
The received light quantity signals 7a and 107b are input to a processing system (not shown) (such as a computer).

The half-wave plate 163 may be disposed in the M optical path, or may be disposed in both the M optical path and the R optical path. It suffices if the polarization directions can be matched between them. 6 and 7, the light projecting unit 3002 corresponds to a light projecting unit, and the measuring units 4002, 4003, 4004, 4
005 and 4006 correspond to the interferometer, and
Numeral 03 corresponds to the condensing means, stage 203 corresponds to the moving means, and the reference plane 1221 and the polarization beam splitter 15
1, deflection optical element 1201, deflection optical element 143,
And the 波長 wavelength plate 161 corresponds to a reference light generation unit.

(Operation) Next, the procedure of the interval measurement by the interval measuring system having the above configuration will be described. Also in the present embodiment, the optical element 804 in the measurement object 6000 is used.
Between the optical element 805, that is, the surface 8042 and the surface 8
The description will be made assuming that the distance D from the image 051 is measured.

At this time, the state where the converging point of the condensing optical element 903 is aligned with one surface 8042 and the other surface 8051
The measurement is performed in each of the states where the converging point of the condensing optical element 903 is adjusted (hereinafter, the former measurement is referred to as “measurement of the surface 8042”, and the latter measurement is referred to as “measurement of the surface 805”).
1 measurement ". ).

However, between the two measurements, at least the positional relationship between the measuring object 6000 and the light collecting unit 5003 is not changed. Hereinafter, the measurement of the surface 8042 will be described. However, the measurement of the surface 8051 is the same except that the focus point of the light-collecting optical element 903 is the surface 8051, and thus the description is omitted.

In the measurement of the surface 8042, the position of the stage 203 is adjusted so that the converging point of the condensing optical element 903 is aligned with the surface 8042.
By moving 1, the optical path length of the M optical path is changed. The processing system (not shown) samples the position information signal of the stage 201 read by the scale (not shown) at this time in association with the received light amount signals obtained from the light receiving elements 107a and 107b.

Here, in the configuration of the measuring section 4002 shown in the figure, the light incident on each of the light receiving elements 107a and 107b is in a relationship of inverting the phase (shifting by 180 °). As a signal, the light receiving element 107
The difference between the output signals a and 107b is obtained. As described above, if the difference between the output signals of the two light receiving elements 107a and 107b is used, the same type of noise superimposed on the two light receiving elements 107a and 107b in the same phase is eliminated, and the measurement result can be obtained with higher accuracy. Can be obtained.

As described above, in the present embodiment, the measurement light (light reflected on the surface 8042) is guided to the R optical path, and the reference light (light reflected on the reference surface 1221) is guided to the M optical path. Therefore, in the present embodiment, the measurement light and the reference light contribute to the interference signal.

That is, the interference signal is observed when the position of the stage 201 causes the optical path length of the reference light to be equal to the optical path length of the measurement light. This is because the sum of the optical path length of the second optical path 308 (from the polarizing beam splitter 151 to the reference plane 1221) and the optical path length of the M optical path is equal to the first optical path 307 (the plane from the polarizing beam splitter 151 to the surface 804).
2) and the optical path of the R optical path.

Therefore, the processing system obtains the stage position S1 when the envelope of the interference signal takes a peak based on the sampled data, for example, by the method described in Japanese Patent Application No. 2000-264247. Further, in the present embodiment, the measurement of the surface 8051 is performed in the same manner as the above procedure. At this time, the processing system obtains the stage position S2 when the envelope of the interference signal has a peak in the same manner as the position S1.

The optical element 80 to be finally obtained is
4 and the optical element 805 (surfaces 8042 and 8051
D) is the difference between the stage position S1 and the stage position S2 obtained by the measurement of the surface 8042 and the measurement of the surface 8051. The processing system obtains the difference | S1−S2 | between these stage positions S1 and S2, and
It is output as a distance D between the optical element 04 and the optical element 805.

(Effect) As described above, in the present embodiment, since the loss of light amount in the light collecting unit 5003 is suppressed by using polarized light, an interference signal is detected with high accuracy. As a result,
The measurement accuracy of the interval measurement is improved. Moreover, in the present embodiment, the measurement unit 4002 also distinguishes the measurement light and the reference light according to the polarization direction, and separates the measurement light and the reference light into one and the other of the two light fluxes. And the reference light can be reflected on the interference signal without waste.

(Others) In this embodiment, the surface 80
Although the distance D between 51 and the surface 8042 is measured, the distance between other surfaces in the measurement object 6000 can be measured in the same manner. For example, it is assumed that each measurement is performed in such a manner that the converging point of the condensing optical element 903 is adjusted to the surfaces 8041, 8042, 8051, and 8052, and the stage positions obtained in each measurement are S0, S1, S2, and S3. , Optical element 80
If the group indices of 4 and 805 are known, S0 and S1
Is the thickness of the optical element 804 divided by the group refractive index, and the thickness of the optical element 805 is obtained by dividing the difference between S2 and S3 by the group refractive index.

[Fourth Embodiment] A fourth embodiment of the present invention will be described with reference to FIG. 6, FIG. 7, and FIG. FIG.
It is a lineblock diagram of an interval measuring system of this embodiment (and 3rd embodiment, 5th embodiment mentioned later, 6th embodiment, and 7th embodiment). The distance measuring system according to the present embodiment is different from the distance measuring system according to the third embodiment in that the measuring unit 400
2 is the same as that in which a measuring unit 4003 shown in FIG.

As shown in FIG. 9, the measuring section 4003 has the same function as the measuring section 4002 of the third embodiment, although the arrangement of the optical elements is different. Measuring unit 400
In 3, the light from the light collecting unit 5003 enters the polarizing beam splitter 152 and is split into reflected light and transmitted light. Here, the reflected light is S-polarized measurement light, and the transmitted light is P-polarized reference light.

The reference light transmitted through the polarization beam splitter 152 passes through the M optical path and passes through the optical path difference changing optical element 112a.
And enters the polarization beam splitter 153 via the deflecting optical element 113a. The reference light that is P-polarized light is then reflected by the polarization beam splitter 153, and then the polarization direction is rotated by approximately 45 degrees in the half-wave plate 164. Such reference light enters the polarizing beam splitter 154 and is split into reflected light and transmitted light. The reflected light and the transmitted light are respectively transmitted to the light receiving element 107.
b, 107a.

The measurement light reflected by the polarization beam splitter 152 passes through the R optical path, is reflected by the deflection optical element 112b, and enters the polarization beam splitter 153 via the deflection optical element 113b. The measurement light, which is the S-polarized light, then passes through the polarization beam splitter 153, and its polarization direction is rotated by approximately 45 degrees in the half-wave plate 164. Such measurement light is supplied to the polarization beam splitter 154.
And is split into reflected light and transmitted light. The reflected light and the transmitted light enter the light receiving elements 107b and 107a, respectively.

The procedure of the interval measurement by the interval measuring system having the above configuration is the same as that of the third embodiment. Also in the present embodiment, the light collecting unit 5003 and the measuring unit 400
Since the loss of the light amount in 3 is suppressed, the measurement accuracy of the interval measurement is improved as in the third embodiment.

[Fifth Embodiment] A fifth embodiment of the present invention will be described with reference to FIG. 6, FIG. 7, and FIG. FIG.
Is a configuration diagram of an interval measurement system according to the present embodiment (and a third embodiment, a fourth embodiment, and a sixth embodiment and a seventh embodiment described later). The interval measurement system according to the present embodiment includes:
In the interval measuring system according to the second embodiment shown in FIG.
A light collecting unit 5003 is provided instead of the light collecting unit 5002, and a light emitting unit 3002 is provided instead of the light emitting unit 3000.
, And is equivalent to that provided with a measuring unit 4004 shown in FIG.

Light emitting unit 3002 and light condensing unit 5003
Are the same as those described in the third embodiment (see FIGS. 6 and 7). That is, the light projecting unit 3002 and the light condensing unit 5003 use a polarizing beam splitter and a wave plate to guide each light according to its polarization direction, thereby suppressing unnecessary light loss.

The measuring section 4004 has the following configuration. That is, as shown in FIG.
At 004, the light from the light collection unit 5003 is 1
The polarization direction is rotated by approximately 45 degrees by the half-wave plate 165,
Thereafter, the light enters the polarization beam splitter 152 and is split into reflected light and transmitted light. Here, the reflected light includes the S-polarized measurement light and the S-polarized reference light, and the transmitted light includes the P-polarized measurement light and the P-polarized reference light.

The transmitted light (P-polarized light) in the polarizing beam splitter 152 passes through the M optical path, is reflected by the optical path difference changing optical element 112a, enters the beam splitter 132 via the deflecting optical element 113a, and transmits the reflected light and the reflected light. Split into light. The reflected light and the transmitted light are respectively transmitted to the light receiving element 10
7a and 107b. Polarizing beam splitter 15
2, the reflected light (S-polarized light) passes through the R optical path and is reflected by the deflecting optical element 112b.
, And becomes P-polarized light by the half-wave plate 163, enters the beam splitter 132, and is split into reflected light and transmitted light.
The reflected light and the transmitted light are respectively transmitted to the light receiving elements 107b and 107b.
07a.

In the interval measuring system having the above configuration, the interference signal occurs at the same stage position as that of the second embodiment (ie, the same stage position as that of the first embodiment). The interval measurement can be performed (that is, the same procedure as in the first embodiment). However, in the distance measuring system of the present embodiment, the light quantity loss in the light collecting unit 5003 is suppressed by using the polarized light, so that the interference signal is accurately detected.

As a result, the measurement accuracy of the interval measurement is more reliably improved than in the second embodiment. [Sixth Embodiment] A sixth embodiment of the present invention will be described with reference to FIGS.

FIG. 6 shows this embodiment (and the third embodiment,
Fourth embodiment, fifth embodiment, seventh embodiment described later)
1 is a configuration diagram of an interval measurement system of FIG. The distance measuring system according to the present embodiment is different from the distance measuring system according to the second embodiment in that the light collecting unit 50
03, and the light emitting unit 3 is provided instead of the light emitting unit 3000.
002 is provided, and the measuring unit 4000 is replaced with the one shown in FIG.
The measurement unit 4005 shown in FIG.

Light projecting unit 3002 and light condensing unit 5003
Are the same as those described in the third embodiment (see FIGS. 6 and 7). That is, the light projecting unit 3002 and the light condensing unit 5003 use a polarizing beam splitter and a wave plate to guide each light according to its polarization direction, thereby suppressing unnecessary light loss.

The measuring section 4005 has the following configuration. That is, as shown in FIG.
In 005, the light from the light collecting unit 5003 is 1
The polarization azimuth is rotated by approximately 45 degrees by the half-wave plate 165, and thereafter enters the polarization beam splitter 152 and is split into reflected light and transmitted light. Here, the reflected light includes the S-polarized measurement light and the S-polarized reference light, and the transmitted light includes the P-polarized measurement light and the P-polarized reference light.

The transmitted light (P-polarized light) in the polarizing beam splitter 152 passes through the M optical path, is reflected by the optical path difference changing optical element 112a, and is reflected by the polarizing beam splitter 153 through the deflecting optical element 113a. The light reflected by the polarization beam splitter 153 is transmitted to a half-wave plate 164.
With the polarization azimuth rotated by approximately 45 degrees, the light enters the polarization beam splitter 154 and is split into reflected light and transmitted light. The reflected light and the transmitted light are respectively transmitted to the light receiving element 107.
b, 107a.

The reflected light (S-polarized light) from the polarizing beam splitter 152 passes through the R optical path and passes through the deflecting optical element 112.
b, and passes through the polarizing beam splitter 153 via the deflecting optical element 113b. The light transmitted by the polarization beam splitter 153 enters the polarization beam splitter 154 with the polarization direction rotated by approximately 45 degrees in the half-wave plate 164, and is split into reflected light and transmitted light. The reflected light and the transmitted light are respectively transmitted to the light receiving elements 107b and 107b.
7a.

In the interval measuring system having the above configuration, the interference signal occurs at the same stage position as that of the second embodiment (ie, the same stage position as that of the first embodiment). The interval measurement can be performed (that is, the same procedure as in the first embodiment). However, in the distance measuring system of the present embodiment, the light quantity loss in the light collecting unit 5003 is suppressed by using the polarized light, so that the interference signal is accurately detected.

As a result, the measurement accuracy of the interval measurement is more reliably improved than in the second embodiment. Seventh Embodiment A seventh embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a configuration diagram of the interval measurement system according to the present embodiment (and the third, fourth, fifth, and sixth embodiments).

The distance measuring system of the present embodiment is different from the distance measuring system of the second embodiment in that
It is the same as that in which a light collecting unit 5003 is provided in place of 02, a light projecting unit 3002 is provided in place of the light projecting unit 3000, and a measuring unit 4006 shown in FIG. The light emitting unit 3002 and the light collecting unit 5003 are the same as those described in the third embodiment (see FIGS. 6 and 7).

That is, the light projecting unit 3002 and the light condensing unit 5003 use a polarizing beam splitter and a wave plate to guide each light according to its polarization direction, thereby suppressing unnecessary light loss. .

The measuring section 4006 has the following configuration. That is, as shown in FIG.
At 006, the light from the light collecting unit 5003 enters the beam splitter 133 and is split into reflected light and transmitted light. Here, both the reflected light and the transmitted light include the S-polarized measurement light and the P-polarized reference light.

The transmitted light in the beam splitter 133 passes through the M optical path, is reflected by the optical path difference changing optical element 112a, enters the beam splitter 134 via the deflecting optical element 113a, and is split into reflected light and transmitted light. . The reflected light and the transmitted light are received by light receiving elements 107a and 107, respectively.
b. The reflected light from the beam splitter 133 passes through the R optical path, is reflected by the deflecting optical element 112b, and passes through the deflecting optical element 113b.
5 and serve as P-polarized measurement light and S-polarized reference light.
These measurement light and reference light are transmitted to the beam splitter 134.
And is divided into reflected light and transmitted light, and the reflected light and transmitted light are incident on the light receiving elements 107b and 107a, respectively.

The half-wave plate 165 may be arranged in the M optical path or in both optical paths. The measuring light in the M optical path and the reference light in the R optical path, the reference light in the M optical path and the R It suffices if the polarization directions of the measurement lights in the optical path can be matched. In the interval measurement system having the above-described configuration, the interference signal occurs at the same stage position as the second embodiment (that is, the same stage position as the first embodiment). The interval measurement can be performed by the same procedure as in the first embodiment).

However, in the distance measuring system of the present embodiment, since the loss of light amount in the light collecting unit 5003 is suppressed by using polarized light, an interference signal is detected with high accuracy. As a result, the measurement accuracy of the interval measurement is more reliably improved than in the second embodiment. [Others] In each of the above embodiments, the measuring unit is a Mach-Zehnder interferometer, but is a two-arm interference optical system (generally referred to as a Michelson type, Twyman Green type, or the like). You may.

In each of the above embodiments, a part or all of the interval measurement may be automated. In the case of automation, a necessary element (a stage or the like) in the interval measuring device may be motorized by a motor or the like, and a control circuit for driving and controlling the element to execute the process may be provided. Further, when automating the process of moving the stage in the light-collecting unit (the process of aligning the light-condensing point on the surface), the control circuit determines the approximate positions of the two surfaces (the surfaces 8051 and 8042) to which the light-condensing points are to be aligned. Position (this is the design data of the measurement object 6000 and the measurement object 6000
It is determined by the arrangement position and the like. ) Is stored 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. Further, 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 according to the measured surface spacing, the higher performance is achieved by the higher accuracy of the spacing measurement as described above. It can be applied to an optical system.

[0122]

As described above, according to the present invention,
An interval measuring device and an interval measuring method capable of measuring the interval between curved surfaces with high accuracy can be provided. Also,
It is also possible to manufacture a high-performance optical system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an interval measurement system according to a first embodiment (and a second embodiment).

FIG. 2 is a configuration diagram of a light collecting unit 5000 (and a measurement target 6000) in the distance measuring system according to the first embodiment.

FIG. 3 is a diagram comparing the optical path length of each light.

FIG. 4 is a diagram (conceptual diagram) showing a relationship between a position information signal and a received light amount signal.

FIG. 5 is a configuration diagram of a light collecting unit 5002 (and a measurement object 6000) in the distance measuring system according to the second embodiment.

FIG. 6 is a configuration diagram of an interval measurement system according to a third embodiment (and fourth, fifth, sixth, and seventh embodiments).

FIG. 7 is a light collecting unit 50 according to a third embodiment (and fourth, fifth, sixth, and seventh embodiments).
FIG. 3 is a configuration diagram of an object 03 (and a measurement object 6000).

FIG. 8 is a configuration diagram of a measurement unit 4002 according to the third embodiment.

FIG. 9 is a configuration diagram of a measurement unit 4003 according to the fourth embodiment.

FIG. 10 is a configuration diagram of a measuring unit 4004 according to a fifth embodiment.

FIG. 11 is a configuration diagram of a measurement unit 4005 according to a sixth embodiment.

FIG. 12 is a configuration diagram of a measurement unit 4006 according to a seventh embodiment.

FIG. 13 is a diagram showing an interval measuring device using a low coherence interferometer.

FIG. 14 is a diagram (conceptual diagram) showing a relationship between a position information signal 406 and a received light amount signal 407.

[Explanation of symbols]

6000 Object to be measured 8041, 8042, 8051, 8052 Surface 804, 805 Optical element 5000, 5002, 5003 Condenser unit 2000 Interval measuring device 3000, 3002 Light emitting unit 4000, 4002, 4003, 4004, 4005
4006 Measurement unit 101 Low coherence light source 102 Beam diameter conversion optical system 103 Beam splitter 112a Optical path difference changing optical element 112b, 113a, 113b, 1201, 142, 1
43 Deflection optical element 201, 203 Stage 107a, 107b Light receiving element 121, 131, 132 Beam splitter 221 Reflection / transmission optical element 2211, 1221 Reference plane 122 Reflection optical element 903, 904, 905, 906 Condensing optical element 305 , 307 First optical path 306, 308 Second optical path 151, 152, 153, 154 Polarizing beam splitter 110, 163, 164, 165 1/2 wavelength plate 162, 161 1/4 wavelength plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F064 AA01 BB03 CC04 EE04 GG12 GG16 GG22 GG23 GG38 GG39 HH00 JJ01 2F065 AA22 AA25 AA30 BB25 CC21 DD03 FF51 GG01 JJ00 LL04 LL12 LL17 LL36 LL37 LL37 LL37 LL37 LL37 LL36 LL37

Claims (7)

[Claims] 1. A light projecting means for emitting light to a measuring object having a plurality of surfaces, and inserted into an optical path of light emitted from the light projecting means, and transmitting the light to the measuring object. A condensing means for converging light on the surface to be measured, and an interferometer for separating the reflected light from the surface to be measured into two light beams with variable optical path differences, causing the two light beams to interfere with each other, and detecting interference light obtained by the interference Moving means for moving the light-converging point of the light-condensing means, based on a part of the light emitted from the light projecting means, the optical path length is invariable regardless of the movement by the moving means, and And a reference light generating means for generating reference light directed toward the interferometer together with the reflected light. 2. The distance measuring device according to claim 1, wherein the reference light generating unit is inserted between the light projecting unit and the light collecting unit, and the light emitted from the light projecting unit. A distance measuring device, which transmits a part of the light to the light condensing means and reflects the other part of the light to generate the reference light. 3. The distance measuring apparatus according to claim 1, wherein the reference light generation unit is configured to change a relative position with respect to the measurement object in the vicinity of the measurement object regardless of the movement by the movement unit. And a reflecting member that reflects the incident light, and converts the light emitted from the light projecting means into a first light flux toward the light collecting means and a second light flux toward the reflecting member. A two-arm interference optical system having separation and integration means for separating the light reflected by the reflecting member and integrating the reflected light on the measurement target surface into the same light beam as the reference light as the reference light. And an interval measuring device. 4. The distance measuring apparatus according to claim 3, wherein a wavelength plate and a polarizing beam splitter are used as the separation and integration means. 5. The distance measuring device according to claim 3, wherein the reference light generating means includes: a polarization direction when the reflected light on the surface to be measured enters the interferometer; A wave plate that gives a difference to the polarization direction when the reference light is incident on the interferometer is used. In the interferometer, as the separating unit, the reflected light and the reference light are polarized in their polarization directions. And a polarization beam splitter for separating the reflected light and the reference light into one and the other of the two light beams. 6. A distance measuring method using the distance measuring device according to claim 1, wherein the light condensing means is arranged on a first measurement object surface of the measurement object. A first measurement procedure of observing, using the interferometer, an occurrence pattern of the interference light with respect to a change in an optical path difference between the two light beams, with the focusing points adjusted; A second point in which the converging point of the condensing means is aligned with the second measurement target surface of the object, and in that state, the interferometer is used to observe the occurrence pattern of the interference light with respect to the change in the optical path difference between the two light beams. A measurement procedure, as information indicating an interval between the first measurement target surface and the second measurement target surface, a pattern observed in the first measurement procedure, and a pattern observed in the second measurement procedure. Calculation procedure for finding the difference between Interval measurement method. 7. The method according to claim 6, further comprising: measuring an interval between predetermined positions in the optical system, and adjusting the optical system according to the interval obtained by the measurement. Manufacturing method of optical system.