JP2983673B2 - Method and apparatus for measuring radius of curvature - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a radius of curvature of a mirror surface having a spherical shape such as a lens surface.

[0002]

2. Description of the Related Art Such a measuring device is disclosed in
There is one described in JP-A-4-28534. The structure shown in FIG. 14 and FIGS. 15 to 16 is disclosed and proposed. That is, in FIG. 14, the light beam of the laser light source 21 is expanded by the expansion optical system 22 and then converged by the converging optical system 24. The DUT 29 is placed on a stage 26, and the stage 26 is supported on the optical bench 25 movably in the optical axis direction. The movement amount of the mounting table 26 is read by the length measuring device 30. Storage means 31 stores the distances L (back focal length) from the light beam irradiation side of the lens last surface 24a of the focusing optics 24 and the light beam converging point P _3. The calculating unit 32 calculates the radius of curvature r of the measured spherical surface 29a by using the moving distance S 'of the measured surface of the measured spherical surface 29a and the distance L according to Equation 1.

[0003]

(Equation 1)

Here, the moving distance S 'is, as shown in FIG. 15 or 16, the spherical surface 29a of the object 29 to be measured.
And position CP ₁ when but in the light beam converging point P _3, is folded back convergent light beam by the spherical surface to be measured 29a is close to the focusing optics 24 is reflected by the spherical surface to be measured 29a before converging light beam converging point P ₄ Is the lens surface 24a on the light beam exit side of the converging optical system 24
A moving distance between the position CP ₂ when in the. From the above description, it is described that the radius of curvature can be obtained by calculating the moving distance S ′ and the back focus distance L and substituting into the equation (Formula 1) for calculating the radius of curvature r. In FIG. 14, reference numeral 37 denotes a lens, 27 denotes a camera, and 28 denotes a monitor for observing the position of the light beam convergence point. 33 and 34 are lenses, 35
Is a half mirror, which constitutes the magnifying optical system 22, and 23 is a flat reflector that reflects a part of the light beam. Reference numeral 36 denotes a corner cube, which is attached to the stage 26 and guides light from the laser light source 38 to the processing unit 39 to calculate the moving distance of the stage 26, and is a well-known length measuring device. Is composed.

[0005]

The disadvantage of the equation (1) described as the prior art will be described with reference to FIG. In addition,
The explanation of the disadvantages of the prior art is that the difference between the radius of curvature obtained by the equation described in the prior art and the radius of curvature of the true value (that is, the true value) obtained by the present invention is determined by the measurement error ε.
And the measurement is performed when the measurement error ε exists. In FIG. 17, point O is a point on the half axis of the rear surface of the lens on the light beam exit side of the converging optical system, point A is a point on the optical axis of the spherical surface of the measured object, and point O 'is the converging optical system. The point C where the exit ray of the effective exit angle θ ₀ intersects with the optical axis, and the point C is the point where the normal and the optical axis intersect at the intersection P of the exit ray from the converging optical system and the spherical surface to be measured. . The effective injection angle θ ₀ is determined by θ and i, and θ = θ ₀
−i, θ ₀ and θ are in a unique relationship, and the angle of θ is determined by θ ₀ .

[0006] By applying the sine law to △ POC, Equation 2 is obtained.

[0007]

(Equation 2)

[0008] By applying the cosine law, Equation 3 is obtained.

[0009]

(Equation 3)

[0010] By applying the sine law to △ PO'C, Equation 4 is obtained.

[0011]

(Equation 4)

By applying the cosine law, Equation 5 is obtained.

[0013]

(Equation 5)

Further, the back focus distance L is obtained from the equation (6).

[0015]

(Equation 6)

From Equations 2 to 6, Equation 7 results. Equation 7 is a true value (true value) of the radius of curvature r.

[0017]

(Equation 7)

Now, since Expression 8, Expression 7 which is a true value becomes Expression 9 which is a true value.

[0019]

(Equation 8)

[0020]

(Equation 9)

If the value of the radius of curvature r of the surface to be inspected when θ = 0 in Expression 9 which is the true value is r ₀ , that is, the effective exit angle θ ₀ of the converging optical system is set to 0 degree on the optical axis. Radius of curvature r _{0 of}
Is obtained, this r ₀ is obtained from Expression 10.

[0022]

(Equation 10)

The equation (10) is the same as the equation obtained by applying the equation (8) to the equation (1). From Equation 9 for finding the true value r of the radius of curvature and Equation 10 for finding the radius of curvature r ₀ on the optical axis, the true value r of the radius of curvature and the radius of curvature r found on the optical axis
_Equation 11 indicating the relationship with ₀ is calculated.

[0024]

[Equation 11]

Now, assuming that the measured value of the radius of curvature r ₀ on the optical axis is given by equation (10), the true value is given by equation (9). From 10 to Equation 12 is obtained.

[0026]

(Equation 12)

With respect to r ₀ obtained by Expression 10 and ε / r obtained by Expression 12, L (back focus distance) is changed to 50, 150, and 300 mm, and θ is set to 5 °, 15
FIG. 18 shows an example in which the angles are changed to 30 ° and 30 °. The following can be seen from FIG. That is, the smaller the L, the smaller the range of measurable r ₀ (for example, L = 5
In the case of ₀ mm, even if the value of K changes, r ₀ is almost 0, so that the range of measurable r ₀ becomes narrower), and θ
Is larger (for example, when the value of K is specified, the measurement error ε / r becomes larger when θ is 30 ° than 5 °). Therefore, in order to increase the range of measurable r, L must be increased, and in order to reduce the error, the effective exit angle θ ₀ of the collimator lens forming the converging optical system must be reduced to reduce the angle θ. Must. The effective emission angle is an angle between an effective light beam emitted from the collimator lens and used for measuring the radius of curvature of the surface to be measured and the optical axis.

In general, when θ is reduced, the detection accuracy of S ′ is deteriorated, and when θ is increased, the error is increased as described above. Considering these two contradictory phenomena, high-accuracy measurement cannot be expected as shown in FIG.

An object of the present invention is to provide a small and lightweight curvature radius measuring method and a measuring apparatus capable of measuring with high accuracy.

[0030]

That is, in the method of measuring the radius of curvature of the present invention, Equation 13 is obtained from Equations 2 to 6. That is, the position where the measured spherical surface of the measured object is at the point of the back focus distance L, and the light flux reflected by the measured spherical surface moved from this position and turned back are collected on the lens surface on the light emitting side of the collimator lens. It is determined based on the movement distance S ′ between the position when the light is emitted.

[0031]

(Equation 13)

In the case of Expression 14, Expression 13 becomes Expression 15.

[0033]

[Equation 14]

[0034]

(Equation 15)

Here, the position on the optical axis at the intersection of the optical axis of each light beam obtained when x is varied from 0 to tan θ per light beam forming a light beam is synthesized. S '
Is defined as Sw '(that is, the value of S' changes along with the position of the intersection of each ray with the optical axis on the optical axis depending on the value of X). Assuming that the center of gravity of the moving distance of S 'on the optical axis is Sw', Sw 'can be obtained from Expression 16.

[0036]

(Equation 16)

Expression 17 is obtained from Expression 15 and Expression 16, and
Equation 18 is obtained by transforming Equation 17.

[0038]

[Equation 17]

[0039]

(Equation 18)

By squaring and rearranging both sides in Equation 18, Equation 19 is given.

[0041]

[Equation 19]

By calculating the higher-order equation given by Expression 19, r can be obtained. In addition, Equation 19
Sw ′ and r at θ = 0 are represented by S ′
And r ₀ , both sides of Equation 19 can be divided by (r ² + L ² ) ³ to obtain Equation 20.

[0043]

(Equation 20)

It goes without saying that equation (20) coincides with equation (10).

The above is a method for obtaining an accurate r when all the luminous fluxes smaller than θ (that is, angles from 0 to θ) are used. The exact r when used can be obtained by Equation 21 where S ′ = Sw ′ in Equation 7.

[0046]

(Equation 21)

FIG. 1 is a conceptual diagram showing the configuration of the present invention, and FIGS. 2 and 3 are enlarged views showing the main parts. In FIG. 1, 101 is a point light source, 102 is a beam splitter, 103 is a collimator lens forming a converging optical system, and 104 is a test object, which are arranged on the same optical axis as shown in the figure. Reference numeral 105 denotes an object holding unit for holding the object 104, and the object holding unit 105 is movable on a moving stage 106 in a direction parallel to the optical axis. Reference numeral 107 denotes a point image position at which a light beam reflected by the object 104 is reflected by the beam splitter 102 and is formed by the point light source 10.
It is a focus detection unit for matching the conjugate position of No. 1. 1
08 denotes the test object 10 held by the test object holding unit 105.
A length measuring unit for measuring the moving distance S ′ of No. 4 as the moving distance Sw ′ based on the center of gravity value of the convergence point of the test object 104;
Reference numeral 109 denotes a moving distance S measured based on the value of the center of gravity.
w ', the back focus distance L and the effective exit angle theta ₀ by determined angle theta of (L and theta ₀ is a constant determined by the optical arrangement), the number 19 or number and these values the function 2
The arithmetic unit for calculating the radius of curvature r of the test lens 104 as the test object by substituting into 1
Is a display unit for displaying. Here, the stage 105 serving as the object holding unit is movable, but instead, the point light source 101 and the beam splitter 10 are used.
2. The collimator lens 103 and the focus detection unit 107 may be configured to be movable as one body in the optical axis direction. In this case, these movement amounts are measured. Reference numeral 103a denotes a surface of the collimator lens 103 on the surface to be inspected, and reference numeral 104a denotes a surface to be inspected of the object 104.

The operation is performed in the same manner as in the prior art, and the moving distance S, which becomes the value of the center of gravity of the test object holder 105, is obtained.
w ′ (see FIGS. 2 and 3) is detected by the length measuring unit 108, and the point light source 101 and the collimator lens 10 are detected by the calculating unit 109.
The back focus distance L determined by 3 and the angle θ determined by the effective emission angle θ ₀ and the moving distance Sw ′ are substituted into Equations 19 and 21 having these values as functions, and the surface 104a of the object 104 to be measured 104a. Is calculated, and this is displayed on the display unit 110. Here, in the case of a uniform emitted light beam of an effective emission angle θ ₀ or less of the collimator lens 103, that is, a uniform emitted light beam in the angle range of the effective emission angle θ ₀ , Equation 1 is given.
9, and in the case of a very narrow annular luminous flux having an effective emission angle θ ₀ , Equation 21 is used.

The point light source is generally given as a light emitting point of a semiconductor laser, but can also be obtained by adding a lens to a He-Ne laser. When a normal white lamp is used, it can be obtained even when a small field stop is added. Point light source 1
Since 01 and the reference focus of the focus detection unit 107 are in a conjugate relationship, there is no problem if they are interchanged.

[0050]

Embodiment 1 FIG. 4 is a view showing Embodiment 1 according to the present invention. In FIG. 4, reference numeral 113 denotes a main body, which includes a laser diode 111, a half prism 112, and a relay lens 11.
4, a pupil quadrant prism 11 as shown in FIG. 5 or FIG.
5. The television camera 116 is arranged and configured as shown in FIG. The prism 115 is configured by combining prism elements 115a to 115f and 115e to 115h having the same shape. The main body 113 can move on the moving stage 106 so as to be able to advance and retreat in the optical axis direction of the test object 104. An image measuring unit 117 for processing the output of the television camera 116 has a built-in arithmetic unit. Reference numeral 118 denotes a monitor, and reference numeral 119 denotes a mounting table which can be moved in a height direction and a horizontal direction perpendicular to the optical axis (not shown). Other parts are the same as those in FIG. 1 and are indicated by the same numbers.

It is desirable that all surfaces of the lens included in the main body 113 be coated with an antireflection film except for the surface 103a of the collimator lens 103 on the object side. Next, this operation will be described. The divergent light beam emitted from the laser diode 111 passes through the half prism 112 and
The light is condensed at a position on the optical axis that is separated from the collimator lens 103 by a certain distance. Then, by the above-described movement, the focal point is changed to the surface 104a of the object
It can be located nearby. At this time, the test surface 104
The reflected light beam from a is transmitted through the collimator lens 103 again, part of the light beam is reflected by the half prism 112, and is condensed again near a point conjugate with the light emitting point of the laser diode 111. Here, since the inclination of the light beam is dispersed in four directions by the pupil four-splitting prism 115 in the optical path, the condensing points in the case of the pupil four-splitting prism 115 shown in FIG. 5 are four points as shown in FIG. An image is formed near the imaging surface of the television camera 116. This image formation state can be observed on the monitor 118. The area of each point image after binarizing the four point images is calculated, and the stage 1 is set so that all of the areas become equal.
19 is moved and adjusted. Also, the barycentric coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ) of the four point images at this time
And (x ₄ , y ₄ ) are measured by the image measurement unit 117, and (x ₂ −x ₄ ) − (y ₁ −y ₃ ) is calculated by the built-in calculation unit, and an amount proportional to this value is calculated. The image is displayed on the monitor 118 together with the four point images. And the previous equation (x ₂ −
Since x ₄ ) − (y ₁ −y ₃ ) is proportional to the amount of defocus, the above-described movement is performed so that this display value becomes 0, so that the conjugate point of the laser diode 111 can be accurately determined. An image can be formed. In this state, it can be guaranteed that an image is accurately formed on the surface of the test surface 104a.

Next, the main body 113 is again moved to the moving stage 10.
6 and move in a direction approaching the lens 104 to be inspected,
The aforementioned point image disappears and a new point image is observed. In this state, the main body 113 is slightly moved so that the display value of (x ₂ −x ₄ ) − (y ₁ −y ₃ ) becomes 0. In this state, it can be guaranteed that an image is accurately formed on the exit-side lens surface of the collimator lens 103. Then, the movement amount Sw 'of the main body 113 from the former state to the latter state.
(The difference between the positions at which the center of gravity value of the main body 113 in the moving direction is obtained, that is, the moving distance) is detected by the length measuring unit 108, and the calculation unit 10
From this amount of movement Sw 'and the angle determined by the effective exit angle theta ₀ of the collimator lens defined by a back focus distance L between the collimator lens or the sample lens determined by the collimator lens theta at 9, and these values functions The curvature radius r is obtained by calculation using Equation 19, and the value of this r is displayed on the display unit 110.

An advantage unique to the present embodiment is that measurement can be performed with particularly high accuracy in order to improve sensitivity by using a pupil four-segment prism.

[0054]

Second Embodiment FIG. 8 is a diagram showing a second embodiment. In FIG. 8, reference numeral 120 denotes a lamp, and 121 denotes a lens. These constitute an illumination optical system 122. 123 is a chart, 12
Reference numeral 4 denotes a half mirror, and reference numeral 125 denotes a test object chuck. Reference numeral 126 denotes a focusing screen which is arranged at a position conjugate with the chart 123 with respect to the half mirror 124. 1
Reference numeral 27 denotes an eyepiece for observing a point image formed on the focusing screen 126. The other components are the same as those shown in FIGS. 1 and 2 and are denoted by the same reference numerals and description thereof is omitted. The test object chuck 125 is preferably a centripetal chuck such as a three-jaw chuck. The specimen chuck 125 is movable in the optical axis direction determined by the collimator lens 103 and the pinhole 123a. The chart 123 may be of any type, but generally a pinhole chart or a cross chart is preferably used.

Next, the operation of these configurations will be described. The chart 123 is illuminated by the illumination optical system 122. The light beam emitted from the chart 123 is the half mirror 12
4. The light passes through the collimator lens 103 and forms an image at a predetermined position. When the surface to be measured 104a is made coincident with the image forming position, the reflected light flux is again reflected by the collimator lens 103a.
Through the half mirror 124 and partially reflected by the half mirror 124.
26. And this imaging state is the eyepiece 1
Since it can be visually checked through 27,
While observing this, the test object is moved together with the test object chuck 125 so as to be in focus, and the position at this time is output by the length measuring unit 108. Next, the test object chuck 125 is provided on the main body 113 side.
Then, the chart image appears again, so that the subject is moved so as to be in focus while watching the chart image, and the position at this time is output by the length measuring unit 108 in the same manner. These two
The calculation unit 109 calculates the difference Sw 'between the output values at the two positions (that is, the moving distance at which the barycenter value is obtained), and
09, this Sw ′, the back focus distance L determined by the collimator lens, and the angle θ determined by the effective exit angle θ ₀ of the collimator lens or the test lens determined by the collimator lens or the lens to be inspected, are expressed by the following equation (19). Is used to calculate the radius of curvature r, and the value of this r is displayed on the display unit 110.

An advantage unique to the present embodiment is that it can be constructed at low cost.

[0057]

Third Embodiment FIGS. 9 and 10 show a third embodiment. In FIG. 9, reference numeral 128 denotes an annular stop, which is formed by depositing an impermeable film 128a on a transparent plate 128b as shown in FIG. The other parts are the same as those in FIGS. 1 to 8, and thus the same reference numerals are given and the description is omitted.

Next, the operation will be described. Laser diode 1
The light beam emitted 11 passes through the half prism 112, after passing through the collimator lens 103, will be focused on a certain position the light beam is annular beam by annular diaphragm 128 (i.e., very fine effective exit angle theta ₀ Annular light flux). When the test surface 104a of the test lens 104 is made coincident with the focus point, the reflected light passes through the collimator lens 103 again, and
The light is partially reflected by the half prism 112 and condensed at a position conjugate with the laser diode 111. Since the light receiving surface of the television camera 116 is arranged at this light condensing position, the state of light condensing can be observed on the monitor 118. The main body 113 is moved on the moving stage 106 while watching the monitor 118,
It stops at the position where focus is achieved, and the position of the main body 113 at this time is output by the length measuring unit 108. Next, when the main body 113 is moved to the test object 104 side, a point image is observed again on the monitor 118, so that the moving stage 1 is focused on the point image.
06 and stop in focus, and the position of the main body 113 at this time is output by the length measuring unit 108. The difference Sw ′ between these two output values (that is, the moving distance at which the center of gravity value is obtained) is calculated by the calculation unit 109, and the calculation unit 109 also calculates this Sw ′, the back focus distance L determined by the collimator lens, and the collimator. Effective exit angle θ _{0 of the} collimator lens determined by the lens or the lens to be inspected
From the angle θ determined by
Is used to calculate the radius of curvature r, and the value of this r is displayed on the display unit 110. Note that a plurality of annular diaphragms 128 having different sizes may be prepared and exchanged.

An advantage unique to the present embodiment is that particularly high-precision measurement can be performed in order to improve sensitivity by the annular zone.

[0060]

Fourth Embodiment FIG. 11 is a diagram showing a fourth embodiment. FIG.
, 129 is a second collimator lens, 130 is a polarizing prism, 131 is a 1 / 4λ plate, 132 is a moving frame having a test object holding ring 132a, and the other is the same as in FIGS. 1 to 9. The same reference numerals are given and the description is omitted.

Next, the operation will be described. Laser diode 1
The light beam emitted from 11 becomes a parallel light beam by the second collimator lens, becomes circularly polarized light after passing through the polarizing prism 130 and the ４λ plate 131, and is condensed by the collimator lens 103. When the test surface 104a is made to coincide with the converging point, the reflected light flux becomes a counterclockwise circularly polarized light, passes through the collimator lens 103, and further passes through the ４λ plate 131. This transmitted light becomes S-polarized light by the function of the １ ／ λ plate,
It becomes a parallel light flux that is all reflected on the reflection surface of the polarizing prism 130. This parallel light beam is focused on the television camera 116 by the relay lens 114. Here, the inclination of the luminous flux is dispersed in four directions by the pupil four-splitting prism 115 in the optical path, and four point images are formed on the television camera 116. Hereinafter, the radius of curvature can be measured by exactly the same operation as in the first embodiment.

An advantage unique to the present embodiment is that the positioning of the test object can be performed only by placing the test surface on the lower side, so that measurement with higher accuracy and operability can be performed.

[0063]

Fifth Embodiment FIGS. 12 and 13 show a fifth embodiment. 12, reference numeral 133 denotes an iris diaphragm; 134, a moving frame; 135, an object holding adapter;
Of the optical axis. 136 is moving frame 1
A pulse motor 137 for moving up and down 34 has a nominal radius of curvature (that is, a design value of the radius of curvature of the surface 104a to be measured).
And an input unit for inputting a start signal for measurement, an operation unit 138 for determining a moving condition of the moving frame 134, an iris diaphragm control unit 139 for controlling an iris diaphragm diameter, and a reference numeral 140. The pulse motor control unit operates the pulse motor 136 in accordance with the input moving condition of the moving frame 134, controls a built-in pulse counter based on a focus signal from the image measuring unit 117, and outputs the output of the pulse counter to an image. It has a function of outputting to the measuring unit 117. Other parts are the same as those in FIGS. 1 to 11, and thus the same reference numerals are given and the description is omitted.

Next, the operation will be described with reference to the flow chart of FIG. First, the nominal radius of curvature r of the surface to be measured is input to the input unit 137.
Is input, the position of the moving frame 134 is calculated so that the focal point of the collimator lens 103 coincides with the surface 104a to be measured. However, since the exact radius of curvature of the surface 104a to be measured is unknown, The position of about 1 mm above and below this position is set as the stop position in consideration of the margin. Next, in detecting two states of reflection point images by the surface 104a to be inspected, the maximum diameter of the diaphragm having the same effective aperture value is calculated, and based on the result, the iris diaphragm control unit 139 sets the iris diaphragm 133 to a desired value. Set to the size of. With this set, the effective emission angle θ ₀ of the collimator lens 103 is determined, and the angle θ at the test object is determined. On the other hand, the test object 10
4 with the test surface 104a facing down
Place on top of 35. This test object holding adapter 135 is
It is preferable to prepare a plurality of types according to the size of the test object, and use the largest one among them. When the setting of the test object is completed, the start signal is input to the input unit 137.
Enter by. Regarding the operation after the input, first, the position of the moving frame 134 is adjusted at high speed by the pulse motor control unit 140 based on the above-described calculation result.

Next, the moving frame 134 is lowered at a low speed by the pulse motor control unit 140. Image measurement unit 1 during descent
Although the in-focus amount is always detected by 17, it changes as it goes down. As soon as the sign of the output value of the focus shift amount is inverted, the pulse counter built in the pulse motor control unit 140 is reset. Immediately after resetting, the moving frame 13 is
4 descends at high speed. Next, the speed is lowered at a low speed slightly before the set stop position (preferably about 1 mm). Then, the value of the pulse counter is output immediately after the sign of the detected value of the focus shift amount is inverted. Then, a calculation unit built in the image measurement unit 117 is obtained from the moving distance Sw ′ of the center of gravity value obtained from the output value, the aforementioned L as a measurement constant, and the aforementioned θ corresponding to the opening based on the set iris diaphragm 133, The radius of curvature r is calculated by using the equation (19) having these values as functions, and this is displayed on the monitor 118.

An advantage unique to the present embodiment is that the radius of curvature can be automatically measured with high accuracy simply by placing a test object on a holder and inputting a start signal.

[0067]

According to the present invention, the radius of curvature of a mirror surface having a spherical shape, such as a lens surface, can be measured with high accuracy with a small size.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is an enlarged view of the main part.

FIG. 3 is an enlarged view of the main part.

FIG. 4 is a diagram showing a first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a pupil-divided prism shown in FIG. 4;

FIG. 6 is an explanatory diagram of a pupil four-segment prism in FIG. 4;

FIG. 7 is an explanatory diagram of a pupil four-segment prism in FIG. 4;

FIG. 8 is a diagram showing a second embodiment.

FIG. 9 illustrates a third embodiment.

FIG. 10 is an explanatory diagram of the annular stop in FIG. 9;

FIG. 11 shows a fourth embodiment.

FIG. 12 is a diagram showing a fifth embodiment;

FIG. 13 shows a fifth embodiment.

FIG. 14 is a view showing a conventional measuring method and apparatus.

FIG. 15 is a diagram showing a conventional measuring method and apparatus.

FIG. 16 is a diagram showing a conventional measuring method and apparatus.

FIG. 17 is a view for explaining the concept of a conventional measuring method and the measuring method of the present invention.

FIG. 18 is a view for explaining a measurement error of the conventional technique from the difference between the conventional measurement method and the measurement method of the present invention.

[Explanation of symbols]

 103 collimator lens 104 test object 106 moving stage 108 length measuring unit 109 calculating unit 110 display unit 111 laser diode 112 half prism 114 relay lens 115 pupil quadrant prism 116 television camera 117 image measuring unit 118 monitor 119 stage 120 lamp 121 Lens 123 Chart 124 Half mirror 125 Object chuck 126 Focusing plate 127 Eyepiece 128 Ring iris diaphragm 129 Second collimator lens 130 Polarizing prism 131 1 / 4λ plate 132 Moving frame 133 Iris diaphragm 134 Moving frame 135 Object holding Adapter 136 Pulse motor 138 Operation unit 140 Pulse motor control unit

Claims (6)

(57) [Claims] 1. A light beam from a light source is condensed by a converging optical system and guided to a test surface of a test object, and the test surface is moved along an optical axis, or the light source and the converging optical system are connected to each other. The object is moved along the optical axis so that the surface to be detected comes to a converging point where the light beam is condensed, and the light beam is detected by changing the distance between the surface to be measured and the converging optical system. Reflected on the surface and turned back so that the converging point of the reflected light beam comes to the lens surface on the light beam exit side of the converging optical system, and the above-described surface to be measured is defined by the intersection of the optical axis of each light beam forming the light beam. The moving distance Sw 'of the converging optical system or the test object from the position of the center of gravity until the position of the center of gravity of the intersection of each light beam forming the reflected light beam with the optical axis becomes the lens surface on the light beam exit side.
The moving distance Sw ′, the distance from the lens surface on the light beam exit side of the converging optical system to the focal point, and the effective exit angle on the surface to be inspected of the converging optical system, A method for measuring a radius of curvature, comprising calculating a radius of curvature of a surface to be measured. 2. The barycentric position when calculating the moving distance Sw ′ is obtained by dispersing a reflected light beam reflected on the surface to be measured into a plurality of point images, and then calculating the area and barycentric coordinates of the point image of the reflected light beam. 2. The curvature radius measuring method according to claim 1, wherein the calculation is performed such that there is no difference between the calculated values. 3. The radius of curvature measurement according to claim 1, wherein when the light beam from the light source is condensed by a converging optical system and guided to the surface of the test object, the light beam is guided through an annular stop. Method. 4. A light source, a converging optical system that converges a light beam from the light source, and a test object such that a test surface of the test object is located at a condensing position of the light beam condensed by the converging optical system. And a holding structure for relatively moving the converging optical system and a focusing optical system; a focus detecting unit for detecting a focus state of the reflected light flux via a beam splitter for guiding a reflected light flux reflected on the surface to be inspected; Due to the relative movement between the object and the converging optical system, the luminous flux is detected at the barycentric position of the intersection with the optical axis of each light beam forming the luminous flux condensed by the converging optical system, and at a position shifted from the barycentric position. A length measuring unit for measuring a moving distance Sw ′ at a double center position until the light beam is reflected by a surface and turned back to a barycentric position of an intersection with an optical axis of each light beam forming the reflected light flux; The moving distance Sw 'obtained by the long part, and the moving distance Sw' obtained by the light source and the focusing optical system. Back focus distance,
A calculating unit for calculating a radius of curvature of the surface to be measured based on the effective exit angle of the converging optical system on the surface to be measured. 5. The focus detecting section has a pupil splitting prism for dispersing the reflected light flux guided by the beam splitter into a plurality of light beams. The curvature radius measuring device according to claim 4, further comprising an image measuring unit that calculates an area and a barycentric coordinate of the formed point image of the light flux. 6. The curvature radius measuring apparatus according to claim 4, wherein an annular stop is provided between the light source and the surface of the test object.