CN108139205B - Optical element characteristic measuring device - Google Patents

Abstract

Provided is a device for measuring the characteristic value of a lens to be inspected by simultaneously irradiating a convergent light beam having a light intensity distribution in a ring shape when viewed from the optical axis of a reflective light sensor unit and a parallel light beam irradiated to the vicinity of the center of the lens to be inspected. Provided is a lens surface shift amount measuring device which measures the surface shift amount of a lens to be inspected without rotating the lens to be inspected by measuring the position of a converging point of a ring-shaped converging light beam transmitted through the lens to be inspected or a parallel light beam irradiated to the vicinity of the center of the lens to be inspected. The optical element characteristic measuring apparatus includes an annular condensed light irradiating portion for irradiating an optical element to be detected with a condensed light having an annular light intensity distribution and a parallel light beam, wherein a surface of the optical element to be detected on a side of the annular condensed light irradiating portion is a front surface, and an opposite side of the front surface is a back surface, and the shape characteristic of the optical element to be detected is measured by analyzing the intensity of the light reflected by or transmitted through the optical element to be detected on the front surface or the back surface of the optical element to be detected, or a light path of the light.

Description

Optical element characteristic measuring device

Technical Field

The present invention relates to an apparatus for measuring a characteristic value of a lens to be inspected by simultaneously irradiating a convergent light beam having a light intensity distribution in a ring shape when viewed from an optical axis of a reflective light sensor section and a parallel light beam irradiated to a vicinity of a center of the lens to be inspected. More particularly, the present invention relates to a device for measuring the thickness of a thin test lens of 200 μm or less, or a device for measuring the amount of surface displacement of a lens, which is adjusted so that the central axis of the test lens (the normal line of the first surface of the test lens) is aligned with the optical axis of a reflective optical sensor unit, and then measures the position of the converging point of a ring-shaped converging beam transmitted through the test lens or a parallel light beam irradiated to the vicinity of the center of the test lens, thereby measuring the amount of surface displacement of the test lens without rotating the test lens.

Background

Conventionally, as shown in fig. 1, in order to measure the thickness of an optical element such as a lens, the following techniques are known: the thickness of the optical element 11 to be inspected is measured by arranging the optical element 11 to be inspected on a straight line connecting two displacement meters 10a and 10b, irradiating the optical element 11 to be inspected with light beams 12a and 12b by the two displacement meters 10a and 10b, respectively, measuring a distance a1 to the surface of the optical element 11 to be inspected measured by one displacement meter 10a and a distance a2 to the back surface of the optical element 11 to be inspected by the other displacement meter 10b, and subtracting the distance a1 and the distance a2 from a0 which is the distance between the two displacement meters 10a and 10b, and techniques for measuring the thickness of the optical element using two optical displacement meters are described in, for example, japanese patent laid-open publication No. 1-235806 (patent document 1) and japanese patent laid-open publication No. 10-239046 (patent document 2).

As a conventional technique for measuring the thickness of an optical element using one sensor unit 12, there is known the following technique for measuring the thickness of an optical element in a non-contact manner: as shown in fig. 2a, the converging light 13 is irradiated to the optical element 15 to be inspected which is already set on the holding frame 14, while the optical element 15 to be inspected is moved in the z-axis direction shown in fig. 2B on the reference plane of the rotation stage 16, the light intensity of an image generated on the front and back surfaces of the optical element 15 to be inspected which is imaged by an imaging optical system (not shown) which is already set on the sensor unit 20 is measured, the light intensity with respect to the z-axis is sampled as digitized data by a processing unit (not shown), the maximum value of the two light intensities is extracted, and the thickness of the optical element 21 to be inspected is calculated based on the z-axis interval (measurement value d) between the two light intensities.

Further, as an apparatus for measuring the eccentricity amount of a lens, japanese patent laid-open No. 2007-206031 (patent document 3) describes a transmission-type eccentricity measuring apparatus capable of measuring the eccentricity amount of a lens to be inspected by rotating the lens to be inspected with reference to the outer circumference thereof.

Further, for example, japanese patent laid-open No. 2008-298739 (patent document 4) or japanese patent laid-open No. 2007-327771 (patent document 5) describes an eccentricity amount measuring device that obtains an eccentricity amount of a test surface by imaging an image of an index of a predetermined shape on a focal plane of the test surface while rotating the test surface of a test optical element (test lens) around a predetermined rotation axis, and measuring a radius of a circle that moves so as to trace a circular trajectory along with the rotation of the test surface while the image of the index that is relayed and imaged on the imaging surface through the test surface.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. Hei 1-235806

Patent document 2: japanese patent laid-open publication No. Hei 10-239046

Patent document 3: japanese patent laid-open No. 2007-206031

Patent document 4: japanese patent laid-open No. 2008-298739

Patent document 5: japanese patent laid-open publication No. 2007-327771

Disclosure of Invention

Technical problem to be solved

In the thickness measuring devices for optical elements described in patent documents 1 and 2, two optical displacement meters are required, which results in a large scale of the device and an increase in cost.

In the conventional thickness measuring device for an optical element using a single proximity sensor, as shown in fig. 3, when the converging point 202 is present on the front surface 203a of the optical element 203 to be detected, an image 204a is generated on the front surface 203a of the optical element 203 to be detected where the light beam 201 is converged, and an image 204b is generated on the rear surface 203b of the optical element to be detected, but the image 204a generated on the front surface 203a and the image 204b generated on the rear surface 203b are both superimposed on the converging light optical axis 210, that is, Z, and are difficult to separately measure. Fig. 4 shows the results of plotting values of the light intensity of the image measured while moving the rotation stage in the z-axis direction and the light intensity measured as digitized data on the horizontal axis and the vertical axis for the thin optical element (t to 200 μm) to be tested. As shown in fig. 4, the difference between the maximum value and the minimum value of the light intensity of the image is small, and the peak and the valley of the graph change slowly, and as described later, it is difficult to measure the z-axis interval (measured value d) corresponding to the two maximum values accurately and reliably.

Next, in the apparatus for measuring the decentering amount of the lens, the upper surface (hereinafter, also referred to as "first surface") and the lower surface (hereinafter, also referred to as "second surface") of the optical lens having a convex shape (hereinafter, also referred to as "subject lens") are spherical surfaces. Further, the centers of the upper surface and the lower surface are not located on the optical axis in the design of the lens to be inspected, and a surface shift may occur in the manufacturing process. Due to such a surface shift, decentering (decentering) occurs in the lens to be inspected. For example, a process of measuring the decentering amount and checking the quality of each batch of optical lenses is advantageous. Conventionally, as described above, a measuring device based on a method of measuring a core shift amount, a plane shift angle, and the like by rotating a test lens is used for measuring a plane shift amount (decentering amount) of the test lens.

Now, since the diameter of the lens to be inspected is further reduced, it is more difficult to rotate the lens to be inspected with higher accuracy than before.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an apparatus for measuring a characteristic value of a lens to be inspected by simultaneously irradiating a convergent light beam having a light intensity distribution in a ring shape when viewed from an optical axis of a reflective light sensor section and a parallel light beam irradiated to a vicinity of a center of the lens to be inspected. In particular, the present invention provides a device for measuring the thickness of a thin test lens of 200 μm or less, or a device for measuring the amount of surface displacement of a lens, which is capable of measuring the amount of surface displacement of the test lens without rotating the test lens by adjusting the center axis of the test lens (the normal line of the first surface of the test lens) to be aligned with the optical axis of a reflective optical sensor unit and then measuring the position of a converging point of an annular converging beam transmitted through the test lens or a parallel beam irradiated to the vicinity of the center of the test lens.

(II) technical scheme

The above object of the present invention can be achieved by: an optical element characteristic measurement device comprising an annular condensed light irradiation light unit for irradiating an optical element to be tested with condensed light having an annular light intensity distribution on a plane perpendicular to an optical axis and parallel light having a center of the light intensity distribution on the optical axis, wherein a surface of the optical element to be tested on the side of the annular condensed light irradiation light unit is a front surface, and an opposite side of the front surface is a back surface, and wherein the shape characteristic of the optical element to be tested is measured by analyzing the intensity of light reflected from or transmitted through the optical element to be tested on the front surface or the back surface of the optical element to be tested, or the optical path of the light.

The above object of the present invention can be more effectively achieved by: the annular condensed light irradiation light portion includes a light source, a first optical element, and a first lens, and the light source, the first optical element, and the first lens are arranged in this order along the optical axis, and the first optical element is formed with an annular gap perpendicular to the optical axis and is arranged with the first lens having a diameter smaller than a diameter of an inner side of the annular gap; alternatively, the apparatus comprises: a reflected light detection unit that irradiates the optical element to be inspected with the annular convergent light, forms an image of a first annular image generated on a front surface of the optical element to be inspected and an image of a second annular image generated on a rear surface of the optical element to be inspected on a light-receiving surface, and generates data for calculating light intensities of the first annular image and the second annular image; and a processing unit that calculates a thickness of the optical element to be inspected based on a change in a distance that the optical intensity moves in the optical axis direction with respect to the optical element to be inspected; alternatively, the optical element to be inspected is a lens, two local maximum values of the change in light intensity of the first annular image and the second annular image based on the data are detected, and a difference between the moving distances of the optical element to be inspected, that is, a measured value d, a refractive index n of a material of the optical element to be inspected, and the measured value d are used, the difference corresponding to the two local maximum valuesA radius of curvature r of the optical element to be inspected, and a converging angle theta of the converging beam light, which is an angle formed by a center point of the radius of curvature r and the optical axis and the converging beam light₁Calculating the thickness t of the lens of the detected optical element; alternatively, the slope a and the intercept B of a line segment BC connecting a point C at which the annular convergent light beam on the front surface of the optical element to be inspected refracts and an annular convergent point B on the rear surface of the optical element to be inspected are respectively set as:

b＝r-d，

and use

A distance e between the point C and the optical axis of the annular convergent light is calculated, and when the radius of curvature r is positive (the optical element to be inspected is a convex surface), a positive value is adopted for a sign of the distance e in a twosign-sym-sequential (japanese-kojic) manner, and when the radius of curvature r is negative (the optical element to be inspected is a concave surface), a negative value is adopted for a sign of the distance e in a twosign-sym-sequential manner

Calculating the thickness t of the lens of the optical element to be detected; alternatively, the apparatus comprises: a reflected light sensor unit that has the annular condensed light irradiation light emitting unit that irradiates the optical element to be inspected with the annular condensed light, and generates first condensed light position data for calculating a reflection angle of an optical axis of the annular parallel light reflected by the surface of the optical element to be inspected; a transmitted light sensor unit for generating second condensed light position data for calculating a condensed point position of the light beam irradiated from the annular condensed light irradiation light emitting unit and transmitted through the optical element to be inspected; and a data processing unit for calculating the reflection angle based on the first condensing position data and calculating the condensing position of the light transmitted through the optical element to be detected based on the second condensing position data,

the data processing unit adjusts the position of the optical element based on the first data so that the lens center axis of the optical element coincides with the optical axis of the annular condensed light irradiation light emitting portion, and calculates the surface shift amount Δ of the optical element based on the condensed point position so that the optical element is not rotated₂(ii) a Alternatively, the optical element to be inspected is a lens, and the shift amount calculated based on the position of the condensed point of the transmitted parallel light beam transmitted near the center of the optical element to be inspected is set to Δ₁And using the refractive index n of the material of the optical element to be inspected, the radius of curvature r of the surface of the optical element to be inspected₁Radius of curvature r of the rear surface of the optical element to be inspected₂And calculating the surface offset amount Delta from the thickness t of the optical element to be inspected₂(ii) a Or, use

Calculating the surface offset amount Delta₂(ii) a Alternatively, the optical element to be inspected is a lens, and the refraction angle θ of the transmitted parallel light beam calculated based on the condensed point position on the transmitted light sensor portion of the transmitted parallel light beam obtained by transmitting the condensed light beam condensed at the focal point on the reflected light sensor portion side of the optical element to be inspected through the optical element to be inspected₁', refractive index n of material of the optical element to be inspected, and curvature radius r of the rear surface of the optical element to be inspected₂To calculate the amount of face shift Δ₂(ii) a Or, use

Calculating the surface offset amount Delta₂(ii) a Alternatively, three or more bundles are usedThe plural light beams are arranged at substantially equal intervals on the circumference of the ring-shaped convergent light beam instead of the ring-shaped convergent light beam; alternatively, the first optical element is formed with the plurality of holes through which the light beam passes.

(III) advantageous effects

According to the optical element characteristic measurement device of the present invention, the converging light having a ring-shaped light intensity distribution when viewed from the optical axis of the reflective light sensor section and the parallel light beam irradiated to the vicinity of the center of the test lens are simultaneously irradiated, the optical axis of the reflective light sensor section is aligned with the optical axis of the test lens, and the intensity or optical path (condensing position) of the light beam reflected on the surface of the test lens or the light beam transmitted through the test lens is analyzed, whereby the characteristic value of the test lens can be measured.

In particular, according to the optical element characteristic measurement apparatus of the present invention, the thickness of a thin test lens (thickness t to 200 μm or less) can be measured by observing the change in light intensity of a ring-shaped (wheel-shaped) image on the front and back surfaces of the test lens by an optical element having a ring-shaped (wheel-shaped) transmission hole (slit).

Further, according to the optical element characteristic measuring apparatus of the present invention, the position of the converging point of the light transmitted through the test lens is measured by adjusting the lens center axis of the test lens (the normal line of the first surface of the test lens) so as to align with the optical axis of the reflective optical sensor unit, and the amount of surface shift of the test lens can be measured without rotating the test lens.

Drawings

Fig. 1 is a schematic configuration diagram of a conventional apparatus for measuring the thickness of an optical element using two non-contact displacement meters.

Fig. 2 (a) is a structural diagram of a conventional thickness measuring apparatus for an optical element based on a single noncontact displacement meter. (B) Is a diagram showing an xyz coordinate system of the measurement apparatus shown in (A).

Fig. 3 is a diagram showing an image generated on the front surface of an optical element to be inspected and an image generated on the back surface of the optical element to be inspected when a convergent light beam is present on the front surface of the optical element in a conventional apparatus for measuring the thickness of an optical element.

Fig. 4 is a diagram showing changes in the intensity of light reflected from an optical element to be measured with respect to changes in the z-axis when a conventional converging light beam is used for measurement in a thickness measuring apparatus for an optical element based on a single non-contact displacement meter.

Fig. 5 is a detailed configuration diagram of the annular condensed light irradiation optical system that can simultaneously irradiate a condensed light having an annular light intensity distribution and a parallel light beam irradiated to the vicinity of the center of the lens to be inspected in the measurement device according to the embodiment of the present invention.

Fig. 6 is a diagram showing the shape of the optical element 34 of the annular condensed light irradiation optical system according to the embodiment of the present invention.

Fig. 7 is a detailed configuration diagram of a configuration in which an autocollimator unit is added to an annular condensed light irradiation optical system in the measuring apparatus according to the embodiment of the present invention.

Fig. 8 is a diagram showing the shape of an optical element of the reflected light detection unit according to the embodiment of the present invention.

Fig. 9 (a) is a structural diagram of an optical element thickness measurement device according to a first embodiment of the present invention. (B) The coordinates of the optical element thickness measuring device (overall structure diagram) are shown in (a) to (D). (B) The x-axis, y-axis, and z-axis of the reference plane are shown. (C) Is a diagram showing the swing angle θ x. (D) Is a diagram showing the swing angle θ y.

Fig. 10 is a diagram showing the shape of an optical element of an autocollimator unit according to a first embodiment of the present invention.

Fig. 11 is a diagram showing how the converging light is reflected on the surface of the optical element to be inspected in the apparatus for measuring the thickness of the optical element to be inspected according to the first embodiment of the present invention.

Fig. 12 is a view showing an image generated on the surface of an optical element to be inspected and an image generated on the back surface of the optical element to be inspected, when a convergent light beam having a ring-shaped (ring) light intensity is present on the surface of the optical element to be inspected, as viewed from the convergent light beam axis in the thickness measuring device for an optical element to be inspected according to the first embodiment of the present invention.

Fig. 13 is a view showing an image generated on the front surface of the optical element to be inspected and an image generated on the back surface of the optical element to be inspected, when the convergent light having a ring-shaped (ring) light intensity is present on the back surface of the optical element to be inspected, as viewed from the convergent light optical axis in the thickness measuring device for the optical element to be inspected according to the first embodiment of the present invention.

Fig. 14 (a) is a view showing an annular surface image in which a condensed point is present on the surface of the optical element to be inspected and a surface image is formed on the light receiving surface of the CCD camera in the thickness measuring device for the optical element to be inspected according to the first embodiment of the present invention. (B) The present invention is a thickness measuring device for an optical element to be inspected according to a first embodiment of the present invention, in which a converging point is present on a back surface of the optical element to be inspected, and a back surface image is formed on a light receiving surface of a CCD camera.

Fig. 15 (a) is a view showing a state in which a converging point is present inside an optical element to be inspected, and an annular front surface image in which a front surface image and a back surface image are formed on a light receiving surface of a CCD camera is partially blocked by an optical element having an annular through hole in a thickness measuring device for an optical element to be inspected according to a first embodiment of the present invention. (B) In the thickness measuring device for an optical element to be inspected according to the first embodiment of the present invention, the converging point is present near the center of the optical element to be inspected in the thickness direction, and the ring-shaped back surface image in which the front surface and the back surface image are formed on the light receiving surface of the CCD camera is cut off most of the light by the optical element having the ring-shaped passage hole.

Fig. 16 is a diagram showing a change in light intensity of reflected light from an optical element to be inspected with respect to a z-axis change when a converging beam having a light intensity in a ring shape (ring) as viewed from the optical axis of the converging beam is used and the light intensity of an image generated on the front surface and the back surface of the optical element to be inspected is measured in the thickness measuring device for the optical element to be inspected according to the first embodiment of the present invention.

Fig. 17 is a view showing a case where, in the thickness measuring apparatus for an optical element to be inspected according to the first embodiment of the present invention, when the surface of the optical element to be inspected is a convex surface (r > 0), the convergent light is incident on the optical element to be inspected having the convex surface, refracted at the surface of the optical element to be inspected, and condensed at the back surface.

Fig. 18 is a view showing a case where the converging light enters the optical element to be inspected having a convex shape when the front surface is a concave surface (r < 0) in the thickness measuring device for an optical element to be inspected according to the first embodiment of the present invention, and is refracted at the front surface of the optical element to be inspected, and is condensed at the back surface.

Fig. 19 is a view showing an image formed on the surface of an optical element to be inspected and an image formed on the back surface of the optical element to be inspected, when the converging point of the converging beam light having the light intensity of the light beam arranged along the virtual ring is present on the surface of the optical element to be inspected, as viewed from the converging beam optical axis in the thickness measuring device for an optical element to be inspected according to the second embodiment of the present invention.

Fig. 20 (a) and (B) are schematic views each showing the shape of the optical elements 61 and 62 of the apparatus for measuring the thickness of an optical element to be inspected according to the second embodiment of the present invention.

Fig. 21 is a view showing a state in which the convergent light beam enters an optical element having a flat front and back surface of the optical element to be inspected (a flat plate having a radius of curvature r ∞) and is refracted at the front surface 512a and condensed at the back surface in the thickness measuring apparatus for an optical element to be inspected according to the third embodiment of the present invention.

Fig. 22 is a diagram illustrating the definition of the amount of surface shift of the test lens measured by the apparatus for measuring the amount of surface shift of a lens according to the fourth embodiment of the present invention.

Fig. 23 is a block diagram of a lens surface displacement amount measuring apparatus according to a fourth embodiment of the present invention.

Fig. 24 is a detailed configuration diagram of a lens surface displacement amount measuring apparatus according to a fourth embodiment of the present invention.

Fig. 25 (a) and (B) are schematic diagrams showing the shapes of an optical element that converts light into a ring-shaped beam for measuring the amount of surface offset of a lens and a pinhole-type optical element, respectively, according to the fourth embodiment of the present invention.

Fig. 26 is a view showing the optical paths of the ring-shaped convergent light beam and the parallel light beam near the lens center axis when the device for measuring the amount of lens surface shift is initially set in the fourth embodiment of the present invention.

Fig. 27 is a view showing a state in which the optical axis of the reflected light beam on the first surface of the test lens is reflected as a parallel light beam not coinciding with the lens central axis in the fourth embodiment of the present invention.

Fig. 28 is a diagram showing how the optical axis of the reflected light beam on the first surface of the test lens is reflected as a parallel light beam that coincides with the lens center axis in the fourth embodiment of the present invention.

Fig. 29 is a diagram showing the shape of the ring-shaped convergent light beam irradiated from the reflective light sensor portion to the subject lens and the state of being reflected as parallel light beams on the first surface of the subject lens in the fourth embodiment of the present invention.

FIG. 30 shows a fourth embodiment of the present invention, in which the amount of surface shift Δ generated in the lens to be inspected is set on the second surface of the lens to be inspected₂Resulting in a picture of how parallel rays are refracted.

Fig. 31 is a diagram showing a state in which a convergent light beam having an optical axis coincident with a lens center axis of a lens to be inspected enters the lens to be inspected and exits the lens to be inspected as a parallel light beam inclined with respect to the lens center axis in the fourth embodiment of the present invention.

Detailed Description

The measuring apparatus of the present invention measures the size or shape characteristics of a lens to be inspected by simultaneously irradiating a convergent light beam having an annular light intensity distribution when viewed from the optical axis of a reflective light sensor section and a parallel light beam irradiated to the vicinity of the center of the lens to be inspected, aligning the optical axis of the reflective light sensor section with the optical axis of the lens to be inspected, and analyzing the intensity or optical path (for example, the position of the convergent light beam) of a light beam reflected on the surface of the lens to be inspected or a light beam transmitted through the lens to be inspected.

Here, in the measurement device according to the embodiment of the present invention, the relationship between the respective structures and the functions of the respective structures will be described in the order of propagation of the rays with respect to the annular condensed light irradiation optical system 29 that can simultaneously irradiate the condensed light having the annular intensity distribution and the parallel rays irradiated to the vicinity of the center of the lens to be inspected. Fig. 5 is a detailed configuration diagram of the annular condensed light irradiation optical system 29.

First, the light source 31 (for example, a laser diode) is disposed at a focal distance f1 of the collimator lens 32, and the light beam emitted from the light source 31 is converted into parallel light beams by the collimator lens 32. The parallel light rays are converted into parallel annular light rays 49a by the optical element 34 having the annular through-hole. Then, the parallel annular light beam 49a is converted into an annular convergent light beam 50a by the lens 35 having the focal length f2 disposed at the propagation destination, and is emitted. On the other hand, the parallel light rays 49b near the center of the optical axis are arranged in the optical element 34, and pass through the small-diameter lens 34b having the focal distance f4, and are condensed at a point N located at a distance f4 from the small-diameter lens 34 b. Then, the parallel light ray 50b is converted again into a parallel light ray by the lens 35 having the focal point distance f2 located away from the focal point distance f2 from the point N. As a result, the annular condensed light irradiation optical system 29 can simultaneously emit the annular condensed light 50a and the parallel light 50 b. The ring-shaped converging light 50a and the parallel light 50b have a common axis.

Fig. 6 shows the shape of the optical element 34. The optical element 34 is configured such that the annular component 34g is disposed inside the outer annular component 34h, and the small-diameter lens 34b having the focal distance f4 is disposed inside the inner annular component 34 g. Since the optical element 34 has the annular transmission hole 34a, the incident light is converted into the annular light having a diameter in a predetermined range and transmitted therethrough. Further, since the small-diameter lens 34b having the focal length f4 is disposed near the center of the optical element 34, the parallel light is converted into the convergent light. The optical element 34 includes an annular member 34g as a holder for supporting the small-diameter lens 34 b. Since the through hole 34a is a gap (space) existing between the outer annular component 34h and the holder component 34g, the support components 34c to 34f are disposed between the outer annular component 34h and the holder component 34 g.

In order to measure the size or shape characteristics of the subject lens using the annular condensed light irradiation optical system 29, it is necessary to analyze the reflection angle or light intensity of the light beam reflected by the annular condensed light 50a on the front surface or the back surface of the subject lens. Fig. 7 shows an example in which the reflected light detection unit 48 is provided in the annular condensed light irradiation optical system 29.

For example, in order to measure the thickness of the subject lens using the annular condensed light irradiation optical system 29, it is necessary to measure the light intensity of an annular image formed on the front surface or the back surface of the subject lens using the annular condensed light 50 a. As a specific configuration therefor, a beam splitter (half mirror) 33 is disposed between the optical element 34 and the collimator lens 32 at an angle of substantially 45 ° with respect to the optical axis. Further, a reflected light detection unit 48 is disposed at the front end of the beam splitter 33. The reflected light detection unit 48 is constituted by the optical element (for example, an annular passage hole) 39, the lens 40, and the components of the CCD camera 41 which are disposed at the end of the focal distance f3 of the lens 40 in the order of incidence of the light beam from the annular image. By analyzing the intensity distribution or the light-converging position of the reflected light input to the CCD camera 41, the angle of the reflected light with respect to the optical axis can be measured. Further, the shape characteristics of the test lens can be calculated based on the measured angle of the reflected light beam, and the optical axis of the test lens can be adjusted as described later.

The optical element 39 also functions to block the light transmitted through the small-diameter lens 34 b. As shown in fig. 8, the optical element 39 has a structure in which an inner circular part 39c is disposed at the center of an outer annular part 39b, thereby forming an annular light-transmitting hole 39a and functioning to transmit annular light having a diameter within a predetermined range with respect to incident light and to block light having a diameter other than the diameter within the predetermined range. Since 39a is a gap (space), 39b and 39c are connected by arranging the supporting members 39d to 39 g.

[ embodiment 1]

Next, as a first embodiment of the present invention, a measuring apparatus for measuring the thickness of a lens to be inspected using the annular condensed light irradiation optical system 29 described above will be described.

Fig. 9 (a) shows a configuration diagram of a thickness measuring apparatus for an optical element according to a first embodiment of the present invention.

In the first embodiment of the present invention, the thickness of the optical element to be inspected is measured by causing the convergent light beam having the light intensity in a ring shape as viewed from the optical axis to enter the optical element to be inspected, and observing the change in the light intensity of the images on the front and back surfaces of the optical element to be inspected through the optical element having the ring-shaped (wheel-shaped) transmission hole. Examples of the optical element to be inspected include a lens having a curvature on the surface, a transparent substrate, and a flat glass plate. As a first embodiment of the present invention, a measuring apparatus for measuring the thickness of a test lens having a convex surface curvature (r > 0) will be described.

Before describing the measurement method, first, two adjustments of the apparatus according to the first embodiment of the present invention will be described. Fig. 9 (B) to (D) show coordinate systems of the overall configuration diagram of the first embodiment. The optical element holder 36 on which the optical element to be inspected is mounted is provided on a rotary stage 43 having a function of adjusting the x-axis, y-axis, z-axis, swing angle θ x, and swing angle θ y of the reference plane 300. Before measuring the thickness of optical element 37, it is necessary to adjust the x-axis, y-axis, swing angle θ x, and θ y of rotation stage 43. The first adjustment is as follows: since the reference plane 300 of the optical element holder 36 to be inspected provided on the rotary stage 43 is not limited to being perpendicular to the optical axis Z of the convergent light beam, the reference plane 300 provided with the optical element holder 36 to be inspected is adjusted (adjusted to be perpendicular) so as to be perpendicular to the optical axis Z of the convergent light beam. For this adjustment, a mirror, not shown, is provided on reference plane 300 of rotation stage 43. The rocking angles θ x and θ y are adjusted so that the optical axis of the reflected light from the mirror coincides with the optical axis Z of the converging light. Such adjustment is performed at the time of initial setting of the optical element thickness measuring apparatus of the present invention. Further, when the optical element 37 to be inspected is set in the optical element holding unit 36, the second adjustment is performed. After the second adjustment, the optical axis Z of the converging light coincides with the optical axis of the optical element 37 to be inspected.

As shown in fig. 9 (a), when the first adjustment is performed, the optical system 30 of the apparatus according to the first embodiment of the present invention emits the parallel light 50b together with the measuring convergent light 50a as the rotation stage adjustment. When the parallel light 50b is emitted from the optical system 30, the parallel light 50b is reflected by a not-shown mirror provided on the rotary stage 43. The angle of the reflected light can be measured by the autocollimator unit 47 of the optical system 30. Next, the principle of measuring the angle of the reflected light will be explained. First, when reference plane 300 on which optical element holding unit 36 is provided on rotation stage 43 is perpendicular to the optical axis of the sensor unit (the optical axis of parallel light 50b irradiated to the mirror), it is reflected in the direction of incident parallel light 50 b. Then, the reflected light reaches a beam splitter (half mirror) 33 along a path reverse to the incident path. Here, a part of the reflected light is deflected to travel toward a beam splitter (half mirror) 38. Then, the reflected light is deflected by the beam splitter (half mirror) 38 and enters an autocollimator unit 47 including an optical element 44 having a transmission hole 44a, a lens 45, and a CCD camera 46. Fig. 10 shows the shape of the optical element 44 of the autocollimator unit 47.

The reflected light is collected on a light receiving surface of the CCD camera 46 connected to the processing unit 42 by a cable. When the reflected light is condensed at a predetermined position on the light receiving surface, the processing unit 42 determines that the reference plane 300 is perpendicular to the optical axis Z of the converging light. However, when the processing unit 42 determines that the light is not condensed at the predetermined position, the swing angle θ x and the swing angle θ y of the rotary stage 43 are changed based on the condensed position (the digitized data transmitted from the CCD camera 41), and the rotary stage 43 is adjusted so that the reflected light is irradiated to the predetermined position.

The second adjustment is performed when the optical element 37 to be inspected is set in the optical element holding unit 36. Fig. 11 shows how the converging light is reflected on the surface of the optical element to be inspected. In fig. 11, the radius of curvature of the optical element 302 to be inspected is r, and the angle between the optical axis Zr of the reflected lights 303a and 303b and the optical axis Z of the convergent light is θ₄. Thus, θ may be used₄The radius of curvature r is defined by a distance h ═ r · sin (θ)₄And/2) represents the distance h between the measurement axis (optical axis Z' of the optical element 302 to be detected) and the optical axis Z of the converging beam. Here, the processing unit 42 can drive the x-axis and the y-axis of the rotary stage 43 so that the converging beam optical axis Z coincides with the optical axis Z' of the optical element 37. In other words, the processing unit 42 can adjust the distance h to 0. In FIG. 11, the test optical system in which the convex surface is directed to the optical system 30The element 302 is provided in the optical element holder 304 to be inspected. The principle of the processing unit 42 for positioning the uppermost point T of the convex surface of the optical element 302 to be detected on the optical axis Z of the converging beam, which is the optical axis of the optical system 30, will be described below. First, as shown in fig. 11, the converging light beams 301a and 301b of the optical system 30 are used for measurement. When the converging light beams 301a and 301b are irradiated onto the optical element 302 to be detected, the light beams become parallel reflected light beams 303a and 303b and are reflected toward the lens 35. Here, when the position of the convex portion or the concave portion of the optical element 302 to be inspected coincides with the beam converging optical axis Z (reflection angle θ)₄0), the optical axes of the reflected lights 303a and 303b coincide with the optical axis Z of the convergent light beam, and therefore the spot light should be irradiated to a predetermined position on the light receiving surface of the CCD camera 46 of the autocollimator unit 47. In the autocollimator unit 47, the reflected light forms an image as a spotlight on the light receiving surface of the CCD camera 46 disposed at the focal length f5 of the lens 45. However, if the reflection angle of the optical axis of the reflected light 303a, 303b with respect to the optical axis Z of the converging beam is θ₄Then at an angle of not reflection θ₄When the value is 0, it is detected that the spot light is not irradiated at the predetermined position. Therefore, by performing adjustment so as to move in the x-axis direction and the y-axis direction with respect to rotation stage 43, it is possible to adjust the spot light to coincide with a predetermined position. The processing unit 42 is connected to the CCD camera 46 of the optical system 30 by a cable, and the spot light irradiated on the light receiving surface of the CCD camera 46 is transmitted to the processing unit 42 as digitized data. Therefore, the processing unit 42 may detect the spot light position based on the transmitted digitized data, detect a difference between the direction and distance of the measured spot light position and the predetermined spot light position, and instruct the reference plane 300 on which the optical element holding unit 36 to be inspected is provided in the x-axis direction and the y-axis direction to move relative to the rotation stage 43 based on the difference, thereby automatically adjusting the spot light position to match the predetermined position. Reflection angle theta₄The processing unit 42 can calculate the reflection angle θ based on the position of the spot light (focal point) on the light receiving surface of the CCD camera 46₄. In this case, the processing unit 42 may calculate the light intensity based on the images received by the CCD cameras 41 and 46Degree and angle theta of incident light₄And outputs and displays the data on, for example, a monitor of a PC provided in the processing unit 42.

Although the case where the optical element to be inspected 37 having a convex surface facing the optical system 30 is provided in the optical element holder 36, when the optical element to be inspected having a concave surface facing the optical system 30 is provided in the optical element holder 36, the adjustment can be performed in the same manner as described above when the position of the lowermost portion of the concave surface of the optical element to be inspected is adjusted to be located on the optical axis Z of the convergent light beam, which is the optical axis of the optical system 30.

Next, an effective method for separating an image generated on the front surface and the back surface of a thin optical element (for example, a lens having a thickness of 200 μm or less) using the ring-shaped convergent light beam 310 will be described with reference to fig. 12 to 14. Fig. 12 and 13 show images of the ring-shaped converging light 310 irradiated on the optical element 37 to be inspected provided in the optical element holder 36, which images are generated on the front and rear surfaces of the optical element 311 to be inspected. Fig. 14 shows an image formed on the light receiving surface of the CCD camera 41.

Conventionally, when the converging light 24 from the sensor unit 20 is irradiated onto the optical element 21 to be tested and the thickness of the optical element is measured, an image 204a formed by imaging with a light receiving element, not shown, of the sensor unit 20 and generated when the converging point 202 is aligned with the front surface 203a of the optical element 203 to be tested is in close proximity to or overlaps with an image 204b of the rear surface, and therefore, there is a problem that separation is difficult as shown in fig. 3.

Therefore, in the first embodiment of the present invention, as shown in fig. 12 and 13, the above-described problem is solved by using a light flux (for example, a ring or a wheel) in which the center of the convergent light flux is shielded. Fig. 12 shows that the ring-shaped (wheel-shaped) converging light 310 enters the optical element 311 to be detected, and two images are generated by the reflected light from the boundary between the front surface of the optical element 311 and the air and the boundary between the back surface of the optical element 311 and the air. These images will be explained. First, when the converging point 312 exists on the front surface 311a, the image of the front surface 311a becomes a point, a small annular back surface image 313 is formed at the boundary of the back surface, and the converging light reflected at the boundary of the back surface 311b forms an annular (annular) surface image 314 larger than that of the back surface at the front surface 311 a. In this way, the ring-shaped image 313 and the ring-shaped image 314 do not overlap and can be separated. As shown in fig. 13, when the converging point 322 is present on the rear surface 311b, the image of the rear surface 311b becomes a point and is reflected to form a small annular image 323 on the front surface 311a, and the converging light reflected at the boundary surface of the front surface 311a forms an annular (wheel-like) image 324 larger than the annular image 323 on the front surface 311a on the rear surface 311 b. In this way, since the annular image 323 and the annular image 324 do not overlap and can be separated, the annular front surface image 314 formed on the front surface 311a when the focal point 312 is present on the front surface 311a and the annular rear surface image 324 formed on the rear surface 311b when the focal point 322 is present on the rear surface 311b can be effectively separated from the other images while moving the rotary stage 43 in the z-axis direction. Therefore, in the graph showing the change in light intensity with respect to the z-axis, two maximum values (peak values) of the light intensity of the surface image 313 and the back surface image 324 can be detected with high accuracy. As a result, the thickness t of the optical element 37 can be calculated with higher accuracy based on the difference in the z-axis between the two light intensities.

Here, the imaging mode detected on the light receiving surface of the CCD camera 41 will be described. Fig. 14 (a) shows an annular surface image 402a in which the surface image 314 of fig. 12 is imaged on the light-receiving surface of the CCD camera 41. As described above, since the optical element 34 has the annular transmission hole 34a, the region in which the parallel light rays are transmitted through the transmission hole 43a and irradiated on the light receiving surface of the CCD camera 41 can be displayed as the transmission region 401c sandwiched between the outer virtual line 401a indicated by the broken line and the inner virtual line 401b indicated by the broken line in fig. 14. By designing so that the light from the surface image 314 passes through the annular transmission hole 43a of the optical element 34, the light intensity of the surface image 314 can be easily detected by the CCD camera 41 without being affected by the light intensity of another image. Similarly, fig. 14 (B) shows a ring-shaped back surface image 402B in which the back surface image 324 of fig. 13 is imaged on the light receiving surface of the CCD camera 41. Similarly, by designing the light from the back surface image 324 so as to pass through the annular transmission hole 43a of the optical element 34, the light intensity of the surface image 324 can be easily detected by the CCD camera 41 without being affected by the light intensity of another image. In this way, if the inner diameter and the outer shape of the annular transmission hole 34a are designed such that both the annular (wheel-like) condensed beam 314 formed by reflection at the boundary surface of the rear surface 311b when the condensed point 312 is present on the front surface 311a and the annular (wheel-like) condensed beam 324 formed by reflection at the boundary surface of the rear surface 311b when the condensed point 322 is present on the rear surface 311b are imaged within the range of the passing region 410c, the light intensity when the condensed point 312 is present on the front surface 311a and the light intensity when the condensed point 322 is present on the rear surface 311b can be effectively amplified and detected as the maximum value (peak value) of the light intensity change with respect to the z axis. In contrast, when the light converging point exists at a portion other than the front surface 311a or the back surface 311b, the annular front surface image 404a and the annular back surface image 404b that are imaged by the light beams from the front surface image and the back surface image have a portion that is distant from the passage area 401c as shown in fig. 15 (a), and therefore the portion does not contribute to the calculation of the light intensity, and the light intensity calculated by the processing unit 42 can be effectively reduced. In particular, when the light converging point is present at a depth from the surface of the optical element 37 to be inspected to the vicinity of the thickness t/2, if the inner diameter and the outer shape of the through hole 34 are designed so that both the annular front surface imaging image 404c and the annular back surface imaging image 404d are completely shielded from light as shown in fig. 15 (B), the z-axis positions of the maximum value and the minimum value of the light intensity change with respect to the z-axis can be effectively detected. Further, the images 403a and 403b as the focused spots are shielded by the optical element 34, and do not contribute to the light intensity.

Fig. 4 and 16 are graphs showing actual measurement results of the optical element 37 (lens having a thickness of 200 μm) to be inspected. As described above, fig. 4 is a graph showing the light intensity with respect to the z-axis measured using a light beam having a circular light intensity distribution in the cross section of the optical axis, that is, without using a ring-shaped (wheel-shaped) light beam. In contrast, fig. 16 is a graph showing the intensity of light with respect to the z-axis measured using the light flux of the ring-shaped (wheel-shaped) convergent light beam according to the first embodiment of the present invention. The difference between the maximum value and the minimum value of the light intensity read from the graph is "11" in fig. 4, and is "70" in fig. 16, in contrast to this. As a result, the light intensity of the images of the front surface 311a and the back surface 311b of the optical element 37 can be effectively separated, and the change in light intensity of the images from the front surface and the back surface of the optical element can be amplified and measured with respect to the z-axis. In the above-described manner, the processing unit 42 can detect the local maximum values (peaks) of the two light intensities based on the measurement data, and calculate the difference between the two local maximum values in the z-axis as the measurement value d.

However, the measured value d calculated using the optical system 30 and the processing unit 42 cannot be directly used as the thickness t of the optical element 37 to be inspected. This is because, as shown in fig. 17, the converging light beams 501a and 501b are refracted at the surface 502a of the optical element 502 to be inspected, that is, at the interface between the optical element 502 to be inspected and the air. The measurement of the position of the point a as the focal point of the surface 502a is not affected by refraction. However, the measurement of the position of the point B, which is the focal point of the back surface 502B, is affected by the refraction of the converging beam. For example, the problem is that: when the refractive index n of the optical element 502 to be measured is not considered, the converging point of the rear surface 502b is present at the point E where the converging beams 501a and 501b intersect, and the measurement value d is calculated. Therefore, in order to calculate the accurate thickness t of the optical element 37 to be inspected, it is necessary to find the condensing angle θ based on the measurement value d and the converging light beams 501a and 501b₁The numerical expression of the thickness t of the optical element 502 to be inspected is calculated based on the curvature radius r of the surface 502a of the optical element 502 to be inspected and the refractive index n of the material of the optical element 502 to be inspected.

Here, a method of calculating the numerical expression of the thickness t of the optical element (convex lens) 502 to be inspected according to the first embodiment of the present invention will be described. The surface curvature radius r (r > 0) of the optical element 502 to be inspected, the refractive index n, and the condensing angle θ of the converging light beams 501a and 501b₁Are all known as preconditions.

First, fig. 17 shows that the converging light beams 501a and 501B enter the convex optical element 502 to be detected, are refracted at the point C and the point F located in the front surface 502a of the optical element 502 to be detected, and are condensed at the point B located in the rear surface 502B.

The intersection point of the optical axes of the convergent light beams on the front surface 502a is set as point A, the convergent light beam on the back surface 502B is set as point B, and the convergent light beams 501a and 501B are folded on the front surface 502aThe positions of the beams are set to point C and point F, the center of curvature of the surface 502a is set to point D, and the intersection of the convergent beams of the surface 502a without taking refraction into account is set to point E. Thus, the length of the line segment AE is the measured value d, and the length of the line segment AB corresponds to the thickness t of the optical element. In addition, regarding the angle of the condensed light, the condensed angle is θ with respect to the optical axis Z of the condensed light as a reference₁Let the angle formed by the segment BC and the optical axis Z be theta₂The angle of a line connecting a point C or F at which the converging beams 501a and 501b intersect the surface 502a and a point D which is the center of curvature of the surface 502a is represented by θ₃. Using the above-described setting values, first, the x-coordinate of the point C, i.e., the distance e between the optical axes Z of the convergent light beams 501a and 501b and the point C is obtained using an equation of a straight line representing the line segment CE, which is the convergent light beam without taking into account refraction, and an equation of a circle representing the surface 502a of the optical element 502 to be inspected. Then, θ is obtained based on e which is the x coordinate of the point C₃F, which is the y-coordinate of point C and point F, and Δ (═ r-F). Then, θ obtained by using the snell's law₂And the x-coordinate e of the point C, g, which is the distance between the point C and the back surface 502b of the optical element 502 to be inspected, is obtained. Using the above results, the thickness t (═ g + Δ) of the test optical element 502 is calculated.

Specifically, the line CE can be expressed by equation 1, which is an equation of a straight line having a slope a and an intercept b, with a point D of the center of curvature of the optical element surface as the origin of coordinates.

[ mathematical formula 1]

y＝ax+b

The slope a and the intercept b can be expressed by expressions 2 and 3.

[ mathematical formula 2]

[ mathematical formula 3]

b＝r-d

The equation in which the point D is set as the origin of coordinates and the surface 502a of the test optical element 502 is a circle can be expressed as shown in equation 4.

[ mathematical formula 4]

The equation for calculating the X-coordinate e of the point C (expressed by X in equation 5) can be expressed as shown in equation 5, based on equations 1 and 4.

[ math figure 5]

The distance e between the point C and the optical axis Z of the convergent light beams 501a and 501b can be expressed by a formula of solution as shown in equation 6.

[ mathematical formula 6]

When the intersection point of the straight line and the circle is two points C and C' and the surface 502a is convex (r > 0), the intersection point of the straight line and the circle is defined as point C, and a solution with a positive (+) sign is used. As shown in fig. 18, when the surface is concave (r < 0), the intersection of the straight line and the circle can be set to point C', and a solution having a negative (-) sign can be used.

Then, as described below, the length e, the measured value d of the present apparatus, the refractive index n of the material of the optical element, the surface curvature radius r, and the condensing angle θ of the condensed light can be used₁The case of calculating the thickness t of the optical element 502 to be inspected will be described.

As shown in fig. 17, θ, which is an angle of a line connecting a point C, which is an intersection of the convergent light beam and the surface, and the center of curvature of the surface₃The length e and the surface curvature radius r can be expressed as in equation 7.

[ math figure 7]

F as the y-coordinate of the point CCan use theta₃And the surface curvature radius r are expressed by the following equation 8, and the distance Δ from the Y coordinate of the point C to the uppermost point a on the surface 502a of the optical element 502 to be inspected can be expressed by the following equation 9.

[ mathematical formula 8]

f＝rcosθ₃

[ mathematical formula 9]

Δ＝r-f

Furthermore, the incident angle (θ) of the surface 502a of the optical element 502 to be inspected can be determined using snell's law₁-θ₃) Angle of refraction (theta)₂-θ₃) And the refractive index n of the optical element 502 to be inspected are expressed as shown in expression 10, and expression 11 can be obtained by transforming expression 10.

[ mathematical formula 10]

sin(θ₁-θ₃)＝nsin(θ₂-θ₃)

[ mathematical formula 11]

Further, g, which is a distance from the point C to the back surface 502b of the test optical element 502, can be expressed as shown in equation 12.

[ mathematical formula 12]

The thickness t of the lens can be expressed as shown in equation 13, and can be expressed as shown in equation 14 using equations 9 to 13.

[ mathematical formula 13]

t＝g+Δ

[ mathematical formula 14]

As described above, in the first embodiment of the present invention, it can be found that: can be used forBased on the measured value d, the refractive index n of the material of the optical element to be inspected, the surface curvature radius r, and the condensing angle theta of the condensed beam₁And e is calculated by calculating a formula for calculating the thickness t of the lens of the optical element to be inspected.

The procedure for measuring the thickness t of the optical element 37 to be inspected according to the first embodiment of the present invention will be described. First, the optical axis of the optical system 30, i.e., the converging beam optical axis Z, is adjusted to be perpendicular to the reference plane 300 of the optical element holder 36. As described above, the angle between the optical axis of the optical system 30 and the reference plane 300 of the optical element holding unit is measured and adjusted by the rotary stage 43.

Next, the position of the optical element 37 to be inspected is adjusted so that the optical axis of the optical system 30 coincides with the optical axis of the optical element 37 to be inspected in the xy plane by adjusting the x axis and the y axis of the rotation stage 43. Specifically, the optical element 37 to be inspected is disposed in the optical element holder 36, and when the convergent light beam is irradiated to the optical element 37 to be inspected, the convergent light beam is converted into a parallel light beam from the surface of the optical element 37 to be reflected, passes through the optical system 30, reaches the autocollimator 47, and is imaged by the CCD camera 46. The reflection angle of the parallel light reflected from the optical element 37 to be inspected is adjusted by the x-axis and y-axis of the rotary stage 43 on which the optical element holder 37 is provided so that the spot light on the light receiving surface of the CCD camera 46 of the autocollimator unit 47 is positioned at a predetermined position with respect to the spot light that has been imaged.

Then, by moving rotary stage 43 in the z-axis direction, optical element 37 to be inspected is moved in the z-axis direction, and an annular image on the light receiving surface of CCD camera 41 is detected, converted into digitized data, and transmitted to processing unit 42. The processing unit 42 stores measurement data in which the z-axis value and the light intensity calculated based on the digitized data are associated with each other. The processing unit 42 detects the maximum values (peaks) of the two light intensities based on the measurement data, and calculates the difference between the two maximum values in the z-axis as a measurement value. Finally, the processing unit 42 calculates the refractive index n of the material of the optical element to be inspected, the surface curvature radius r, and the condensing angle θ of the condensed light based on the measured value d₁And e, the thickness t of the lens of the optical element to be detected is calculated.

[ embodiment 2]

Next, a second embodiment of the present invention will be explained. In the second embodiment, instead of one annular light beam, a plurality of light beams, for example, four light beams shown in fig. 19 are arranged so as to be included in a cross section of a virtual annular pattern, whereby the present invention can be implemented. When the converging point 320 is present on the front surface 311a of the optical element 311 to be inspected, an image composed of four back surface images 333a, 333b, 333c, and 333d is formed, and an image composed of 334a, 334b, 334c, and 334d is formed by reflecting on the front surface 311 a. In fig. 19, four light beams 331a, 331b, 331c, and 331d are used, but two or more light beams are sufficient, and the number of light beams is not limited. The arrangement of the convergent light beams in the region sandwiched between the outer and inner peripheries 335a and 335b of the virtual annular pattern is not necessarily fixed in the directions of 0 °, 90 °, 180 °, and 270 ° with reference to the center point of the virtual annular pattern, and any direction may be selected without limitation. The distribution of the light intensity or the light amount of each light ray is not limited to the same, and an arbitrary distribution ratio may be selected. In addition, in order to correspond to the four-beam converging light used in the second embodiment, an optical element 61 having four circular passage holes as shown in fig. 20 (a) may be used instead of the optical element 34 of fig. 6, and an optical element 62 having four circular passage holes as shown in fig. 20 (B) may be used instead of the optical element 39 of fig. 8. As shown in fig. 20 (a), the optical element 61 has the following structure: the small-diameter lens 61b is disposed at the center of the circular holder 61a, and the through holes 61c to 61f are disposed in the directions of 0 °, 90 °, 180 °, and 270 ° with the center as a reference point. As shown in fig. 20 (B), the optical element 62 has the following structure: the holes 62b to 62e are arranged in the directions of 0 °, 90 °, 180 °, and 270 ° with the center of the circular bracket 62a as a reference point. The position and diameter of each of the passage holes may be designed in accordance with the number and arrangement of the beams of light used for measurement.

[ embodiment 3]

Next, a third embodiment of the present invention will be explained. In the third embodiment, forA method of calculating the thickness t of the optical element 512 to be inspected when the optical element 512 to be inspected is a flat plate (r ∞). Fig. 21 is a diagram showing a state in which the converging light beams 501a and 501b enter an optical element whose front and back surfaces of the optical element 512 to be inspected are flat, are refracted at the front surface 512a, and are condensed at the back surface 512 b. Regarding the angle of the condensed light, the condensed angle is θ with respect to the optical axis Z of the condensed light₁Let the angle of refraction on the surface be theta₆。

Using the snell's law, theta₁And theta₆Is expressed as shown in equation 15, and when equation 15 is modified, θ is expressed₆Can be expressed as shown in equation 16.

Assuming that i is the x-coordinate of the intersection point of the converging light beams 501a and 501b and the surface 522a, i.e., the distance between the optical axis Z of the converging light beams 501a and 501b and the intersection point, and d is the distance between the converging point of the converging light beams not considering refraction and the surface 522a, θ is₁Can be expressed as shown in equation 17.

[ mathematical formula 15]

sinθ₁＝nsinθ₆

[ mathematical formula 16]

[ mathematical formula 17]

i＝dtanθ₁

The thickness t of the flat plate can be expressed as shown in expression 19 using expressions 17 and 18.

[ mathematical formula 18]

[ math figure 19]

As described above, the optical element thickness measuring device (optical element) according to the present inventionCharacteristic measuring device), based on the measured value d, the refractive index n of the material of the optical element, and the condensing angle theta of the condensing light₁The thickness t of the flat plate is calculated.

In contrast to the above example, the following method is explained: the measurement value d is measured with respect to the optical element 522 to be inspected having a refractive index n and a known thickness t with its front surface parallel to the rear surface, whereby the condensing angle θ of the condensed light beam, which is a set value inherent to the optical element thickness measuring apparatus of the present invention, is determined₁. The optical element 522 to be inspected may be, for example, a glass plate.

sinθ₁、sinθ₆The expression can be expressed as the expressions 20 and 21, respectively, and the relationship expressed by the expression 22 is found by substituting the expressions into the expression 15.

[ mathematical formula 20]

[ mathematical formula 21]

[ mathematical formula 22]

In addition, when equation 22 is modified, i can be expressed as shown in equation 23, and when equation 17 is used, θ can be expressed₁Can be expressed as shown in mathematical formula 24.

[ mathematical formula 23]

[ mathematical formula 24]

As described above, in the optical element thickness measuring apparatus (optical element characteristic measuring apparatus) according to the present invention, the light collection angle θ of the collected light can be calculated from the measured value d, the refractive index n of the material of the optical element, and the known thickness t of the optical element₁. Due to the angle of convergence theta₁Is a setting value inherent to the optical element thickness measuring apparatus of the present invention, and is determined by obtaining the light converging angle θ inherent to the apparatus₁The inspection work of the system adjustment device or the like of (3) can be used for the calibration of the optical element thickness measuring apparatus of the present invention.

[ embodiment 4]

The lens surface deviation measuring device (optical element characteristic measuring device) of the present invention is a device comprising: the light intensity distribution of the convergent light is annularly observed from the optical axis of the reflective light sensor unit, and the parallel light is irradiated to the vicinity of the center of the lens to be detected, and the position of the convergent point of the light transmitted through the lens to be detected is measured by adjusting the lens center axis of the lens to be detected (the normal line of the first surface of the lens to be detected) so as to match the optical axis of the reflective light sensor unit, thereby measuring the amount of surface displacement of the lens to be detected without rotating the lens to be detected.

First, the amount of surface displacement of the lens to be inspected (optical element to be inspected) measured by the apparatus for measuring the amount of surface displacement of the lens (optical element characteristic measuring apparatus) of the present invention is shown in fig. 22 and defined. As shown in fig. 22, in the lens surface displacement measuring apparatus of the present invention, the lens 20 to be inspected is disposed on the lens holding frame 112. The upper surface of the lens holder 111 to be inspected is set as a reference plane LS. Further, as shown in fig. 22, the following configuration is adopted: the normal LN1 of the first surface 20a of the test lens perpendicular to the reference plane LS has a first surface center (center point of the first surface) CN1, and the normal LN2 of the second surface 110b of the test lens perpendicular to the reference plane LS has a second surface center (center point of the second surface) CN 2. The reference plane LS can be secured by a configuration in which the lens holder support carrier unit 23 supports the lens holding unit 111 to be inspected for holding the lens holder 22.

At this pointIn the arrangement, the distance between the normal line of the first surface (front surface) 110a of the test lens and the normal line of the second surface (back surface) 110b of the test lens, which are perpendicular to the reference plane LS, is defined as the surface shift amount Δ₂. In the embodiment of the present invention, the normal line LN1 of the first surface 110a of the test lens is defined as the lens center axis of the test lens.

Fig. 23 shows a block diagram of a lens surface displacement amount measuring device (optical element characteristic measuring device) according to a fourth embodiment of the present invention. The following is a schematic description of the structure of the lens surface displacement amount measuring apparatus using a block diagram.

As shown in fig. 23, a lens surface displacement amount measuring apparatus 120 of the present invention includes: a lens-to-be-inspected holding frame 121 for setting a lens-to-be-inspected 121 a; a lens holder holding mechanism stage 122 that holds the lens holder 121 to be inspected, moves in the 3-axis direction, and is fixed to a table that is rotatable (tiltable) along two axes; a reflective light sensor section 123 having a reflective light sensor section autocollimator 123b that measures an angle of a light beam reflected by the test lens 121a from the light source 123a with respect to an optical axis; a transmitted light sensor unit 124 having a transmitted light sensor unit autocollimator 124a and a light sensor unit 124b that measure the angle of the optical axis of the light beam transmitted through the test lens 121 a; a transmissive photosensor section holding mechanism stage section 124c that moves the transmissive photosensor section 124 in the 3-axis direction and is fixed to a table that is rotatable (tiltable) along two axes; a data processing unit 125 that calculates the amount of surface shift of the test lens 121a based on the outputs of the reflective photosensor autocollimator 123b, the transmissive photosensor autocollimator 124a, and the photosensor 124 b; and a monitor 26 for displaying the plane offset amount calculated by the data processing unit 125.

Next, a detailed configuration diagram of the lens surface shift amount measuring apparatus 30 will be described with reference to fig. 24.

The lens surface displacement amount measuring device 130 is composed of: a part 130a with 5-axis (X, Y, Z, chi, etc.),

) A movable lens holder holding mechanism stage part 131c, the lens holder holding mechanism stage part 131c having a reference plane for holding a lens holder 131b to be inspected to which a lens 131a to be inspected is fixed; a reflected light sensor unit 130b that irradiates the subject lens 131a with the ring-shaped convergent light and incorporates an autocollimator function of measuring an angle of the reflected light from the first surface of the subject lens with respect to the lens center axis; a transmitted light sensor unit 130c incorporating a function of detecting a position of a condensed point of a transmitted light beam transmitted through the lens 131a to be inspected with a parallel light beam irradiated simultaneously with the annular condensed light beam from the reflected light sensor unit 130b and an autocollimator function of measuring an angle of the transmitted light beam with respect to a lens center axis; can be divided into 5 axes (X, Y, Z, chi,) A movable stage 139 that holds the transmissive optical sensor unit 130 c; the data processing unit 130d and the display unit 30e have a function of calculating the surface shift amount from the measurement processing of each autocollimator and the focal point position data, and a function of calculating the surface shift amount from the angle of the transmitted light. The lens holder holding mechanism stage 131c includes a lens holding unit to be inspected (not shown) having a reference plane, and a rotary stage may be used.

The light source unit 132 includes a light source (e.g., a laser diode) 132a and a lens (focal length f2)132b, and emits parallel light beams. An optical element 133 is disposed in the reflective light sensor unit 130b, and the optical element 133 converts the light beam irradiated from the light source unit 132 into an annular light beam and a condensed light beam. Then, the ring-shaped light beam is converted into a converging light beam, and a lens (focal length f4)134 for converting the light beam converged at the point C into a parallel light beam is disposed to irradiate the lens 131a to be inspected. An optical element (pinhole) is arranged immediately before the light beam reflected from the lens 131a to be inspected to the reflective optical sensor section autocollimator section 136 enters. The shapes of the optical elements 133 and 135 are shown in fig. 25 (a) and (B), respectively. The optical element 133 is configured such that the inner annular member 133g is disposed at the center of the outer annular member 133h, thereby forming an annular transmission hole 133a and transmitting an annular light beam having a diameter within a predetermined range with respect to the incident light. Further, a small-diameter lens 133b having a focal length f5 is disposed near the center, and has a function of converging parallel light rays. Further, an annular member 133g is disposed as a holder for holding the small-diameter lens 133b, and the support members 133c to 133f are disposed because a space is provided between the holder member 133g and the holder member 133h as a through hole 133 a. The optical element 135 is configured such that a transmission hole 135a through which light passes is disposed at the center of the outer holder 135 b.

First, since the reference plane LS of the lens holder 131b to be inspected is adjusted to be perpendicular to the optical axis of the reflective light sensor unit 130b, a plane mirror (not shown) is provided on the reference plane LS of the lens holder 131b to be inspected. The parallel light beam emitted from the reflective light sensor unit 130b is reflected, and the angle of the reflected light beam is measured by the reflective light sensor unit autocollimator 136 including the lens (focal length f7)136a and the reflective light sensor unit light-receiving device 136b in the reflective light sensor unit 130 b. Then, the angle of the lens holder holding mechanism mount portion 131c is adjusted to 0 degree with respect to the optical axis of the reflective light sensor portion 30 b.

Next, the origin of the transmitted-light sensor section autocollimator 138 and the transmitted-light sensor section optical system 137 (light receiving element for detecting the condensing point position) of the transmitted-light sensor section 130c is set by adjusting the position on the XY plane of the transmitted-light sensor section 130c with respect to the optical axis of the reflected-light sensor section 130 b.

In the initial setting of the device for measuring the amount of surface displacement of a lens according to the fourth embodiment of the present invention, a plano-convex lens is used as the adjusting lens 142. At this time, fig. 26 shows the optical paths 146 of the ring-shaped converging light 145a, the ring-shaped reflected light 145b, and the parallel light transmitted through the vicinity of the lens center axis. The adjustment lens 142 is provided on the subject lens holder 143 such that the convex surface of the adjustment lens 142 faces the reflective light sensor section 141 a. The image data sent from the transmitted-light sensor section autocollimator (not shown) and the transmitted-light sensor section light receiving device (not shown) in the transmitted-light sensor section 141b is processed by the data processing section 141c, and the transmitted-light sensor section holding mechanism stage 144 is adjusted in the Z-axis direction so that the focused point image has the minimum area while the image obtained by the above-described processing is observed by the monitor 141 d. Since the adjustment lens 142 is a plano-convex lens, the converging point of the transmitted light beam is reliably located on the lens center axis, and therefore, the XY position, which is the origin of the reflected light sensor unit 141a and the transmitted light sensor unit 141b, can be fixed by using the position on the light receiving element of the transmitted light sensor unit autocollimator (not shown) and the light sensor unit (not shown) as the origin and storing the position in the data processing unit 140 c. The central lens axis (of the adjusting lens 42) is aligned with the optical axis of the reflective light sensor section 141a in the above-described order, and the optical path 146 of the parallel light beams is irradiated to the vicinity of the lens center (of the adjusting lens 142).

As described above, the optical axis of the reflective light sensor unit 130b and the reference plane LS of the lens holder (not shown) holding the lens holder 131b are adjusted to be perpendicular to each other. Further, a plane mirror is provided on the lens holder 131b to be inspected, and reflects the parallel light beams irradiated from the reflective light sensor unit 130 b. Then, the angle with respect to the optical axis is measured by the reflective optical sensor section autocollimator 36 of the reflective optical sensor section 30 b. Based on the measured angle, the angle of a lens holding unit (not shown) holding the lens holding frame 131b to be inspected is adjusted to 0 degree with respect to the optical axis of the reflective light sensor unit 130 b. The lens holder 131b holds the lens holder to be inspected, and the reference plane LS is formed in the same manner as the lens holder 111.

The optical axis alignment in advance for measuring the amount of surface shift of the test lens 131a using the lens surface shift amount measuring device 130 of the present invention and the position adjustment in the Z-axis direction of the test lens holding frame holding portion 131b will be briefly described below. The angle of the reflected light beam from the test lens 131a is measured by the autocollimator 136 of the reflective light sensor unit 130b, and the position in the XY plane of the lens holder holding mechanism stage 131c holding the test lens holding unit 131b is adjusted so that the measured angle is 0 degree, whereby the optical axis of the reflective light sensor unit 130 (the optical axis of the annular convergent light beam irradiated from the reflective light sensor unit 130 b) can be made to coincide with the lens center axis.

Here, in the fourth embodiment of the present invention, fig. 27 shows a state in which the optical axis of the reflected light beam of the test lens is not reflected as a parallel light beam that matches the central axis of the first surface of the test lens, that is, an unadjusted state. Fig. 28 shows a state in which the optical axis of the reflected light beam of the test lens is reflected as a parallel light beam that coincides with the central axis of the first surface of the test lens, i.e., an adjusted state.

First, the lens 150 is mounted on the lens holding frame 151 (lens holding frame dedicated to the lens to be inspected) and set on the reference plane LS of the lens holding unit (not shown).

Next, by adjusting the subject lens holder 131b in the Z-axis direction, the converging point position FP1 at which the annular converging light beams 152a and 152b irradiated from the reflective light sensor unit 130b converge is moved to an intermediate position between the subject lens first surface 150a and the spherical center CN1 of the subject lens first surface 150 a. As a result, the reflected light beams 152c and 152d from the first surface 150a of the detection lens are made parallel beams, and return to the reflective light sensor section 30b to be incident thereon. The parallel light rays are further reflected at 90 degrees at the half mirror 32c, and enter the reflective photo-sensor portion autocollimator portion 136 of the reflective photo-sensor portion 130 b. The reflected light sensor section autocollimator section 136 can measure the angle θ between the parallel light beam and the lens center axis (the normal to the first surface of the lens to be inspected)₀. And based on the angle theta₀The position FP1 of the converging point at which the converged light beam is converged and the in-plane XY shift amount of the lens holder 131b from the lens center axis (normal to the first surface of the subject lens) LZ can be calculated. Based on the XY shift amount, the lens holder holding mechanism stage portion 131c is moved in the XY plane and adjusted so that the lens center axis coincides with the optical axis of the lens surface shift amount measuring device, that is, the optical axis of the annular convergent light. With this adjustment, the parallel light beams simultaneously irradiated from the reflective photosensor section 130b are made to be parallelThe light is irradiated in parallel with the lens center axis or is irradiated near the center of the subject lens 131 a.

Further, since the adjustment is performed so that the optical axis of the parallel light beam irradiated from the reflective photo-sensor portion 130b and the ring-shaped convergent light beam simultaneously with the ring-shaped convergent light beam coincides with the optical axis of the ring-shaped convergent light beam, the device 130 for measuring the amount of surface deviation of a lens according to the fourth embodiment of the present invention can align the optical axes of the lens holder holding portion 131b and the transmissive photo-sensor portion 130c to be inspected with the optical axis of the entire device for measuring the amount of surface deviation of a lens by adjusting the respective stage mechanisms (the lens holder holding mechanism stage portion 131c and the transmissive photo-sensor portion holding mechanism stage portion 139) with the optical axis of the parallel light beam irradiated from the reflective photo-sensor portion 130b as a reference axis.

First, the lens holder holding mechanism carrier part 131c is moved in the Z-axis direction so that the converging point FP1 of the annular converging light (converging light) irradiated by the reflective light sensor part 130b is located between the spherical center CN1 of the first surface of the lens to be detected and the first surface 150a of the lens to be detected. In this state, the lens holder holding mechanism stage 131c is not adjusted in the XY plane, and as shown in fig. 27, the optical axes LF of the converging beams 152a and 152b and the central axis (the normal to the first surface of the lens to be inspected) LZ of the lens are separated by a distance (XY shift amount) L₁Off, the reflected rays 152c, 152d are tilted with respect to the central axis LZ of the lens. Here, the adjustment is performed by moving the lens holder holding mechanism stage part 131c in the XY plane so that the reflected light beams 152c and 152d from the lens first surface 150a become light beams parallel to the central axis (normal line of the first surface of the subject lens) LZ of the lens. For example, let r be the radius of curvature of the first surface of the lens to be inspected₁Then distance (XY offset) L₁As shown in equation 25.

[ mathematical formula 25]

That is, the angle θ is measured by the autocollimator of the reflective photosensor section₀. And, at the angle theta₀The optical axis of the reflective light sensor unit 130b can be adjusted to coincide with the lens center axis LZ, that is, the distance L can be adjusted by adjusting the lens holder holding mechanism mount 131c of the lens holder 131b to be inspected to 0 degree ₁0. By such adjustment, as shown in fig. 28, the optical axes of the parallel light beams 162c and 162d reflected by the converging light beams 162a and 162b can be made to coincide with the central axis of the first surface of the subject lens on the first surface 150a of the subject lens.

Fig. 29 shows the shape of the annular convergent light beam 180a irradiated from each of the reflective light sensor units 130b and 141a to the subject lens 150 and the annular intensity distribution 180 b. As shown in fig. 29, the light beam has an annular intensity distribution 180b on a plane perpendicular to the optical axis of the converging light beam 180 a. The first surface 150a of the test lens is reflected as a parallel light ray 181a maintaining a ring-shaped intensity distribution 181 b.

The initial setting method of the present apparatus 130, particularly the adjustment of the optical axis angle of the light transmitted through the optical sensor unit 130c, of the lens surface displacement amount measuring apparatus according to the fourth embodiment of the present invention will be described. First, the optical axis of the light transmitted through the photosensor section 130c is based on the optical axis of the light irradiated from the reflective photosensor section 130 b. Therefore, the light beam from the reflective optical sensor section 130b is converted into a parallel light beam by the lens 138a, and the parallel light beam is incident on the transmissive optical sensor section optical system 137. Then, the light is condensed by the lens 137a in the transmitted light sensor section optical system 137 to the transmitted light sensor section light receiving device 137b, and the angle of the parallel light is measured. Finally, the transmitted-light sensor unit holding mechanism stage part 139 of the transmitted-light sensor unit 130c is moved based on the angle of the parallel light rays, and the angle of the optical axis of the transmitted-light sensor unit 130c is adjusted to 0 degree. The transmissive optical sensor section holding mechanism stage 139 may be a rotary stage.

Next, the device 30 for measuring the amount of surface displacement using the lens of the present invention is set to the refraction angle θ of the transmitted light beam of the lens 150 to be inspected shown in FIG. 30₁The measured value of (2), calculating the surface shift amount Delta of the lens to be inspected₂The method of (3) is briefly described. Parallel rays parallel to the central axis of the lensLi is incident on the test lens 150, and the surface shift amount Delta generated in the test lens 150 on the second surface 150b of the test lens₂The appearance of the resulting parallel ray Li is shown in fig. 30.

First, to measure the angle θ of refraction as shown in FIG. 30₁A transmission optical sensor section optical system 137 is used. The transmitted light sensor section optical system 137 is composed of a lens (focal length f11)137a and a transmitted light sensor section light receiving device 137 b. The light beam transmitted through the test lens 150 is once condensed at the point D as shown in fig. 24, and then becomes parallel light by the action of the lens (focal length f10)138a, and passes through the half mirror 138 c. Then, the light beam is condensed by the action of the lens (focal length f11)137a in the light receiving device 137b of the light sensor section. Therefore, the position of the condensed point can be detected by the transmitted light sensor portion light receiving device 137 b. In the transmissive optical sensor section optical system 137, as shown in fig. 24, the position of the spot D and the position of the converging point have an imaging relationship. As described above, the data processing unit can measure θ based on the XY position data of the condensed point position₁。

Specifically, a distance B from the lowest point on the second surface of the subject lens to the focal point (hereinafter referred to as "back focus distance B" or simply "B") is calculated using a calculation formula as described below. Then, the XY position of the converging point of the parallel light rays is measured at the focal position of the subject lens 150, and the origin is set on the lens center axis LZ based on the XY position to calculate the shift amount Δ₁. Then, the offset amount Δ is used₁And a back focal length B for calculating an angle theta of refraction of the incident parallel light beam of the laser light transmitted through the second surface 150B of the lens 150 with the lens center axis LZ as a reference₁. Finally, a line connecting the intersection point of the incident laser parallel light Li and the second surface 150b and the spherical center (center of curvature) CN2 of the second surface is defined as a line L, and an angle θ of the line L based on the lens center axis LZ is calculated using snell's law₂。

Specifically, a distance B (hereinafter referred to as "back focus distance B" or simply "B") from the lowest point on the second surface of the subject lens to the focal point is calculated using a calculation formula as described below. And, in the quiltDetecting the focal position of the lens 150, measuring the XY position of the focal point of the parallel light, setting the origin on the lens center axis LZ based on the XY position, and calculating the shift amount Delta₁. Then, the offset amount Δ is used₁And a back focal length B for calculating an angle theta of refraction of the incident parallel light beam of the laser light transmitted through the second surface 150B of the lens 150 with the lens center axis LZ as a reference₁. Finally, a line connecting the intersection point of the incident laser parallel light Li and the second surface 150b and the spherical center (center of curvature) CN2 of the second surface is defined as a line L, and an angle θ of the line L based on the lens center axis LZ is calculated using snell's law₂。

Then, the surface shift amount Δ of the lens 150 to be inspected₂The specific calculation method of (2) will be explained. In the device 130 for measuring the amount of surface displacement of a lens according to the fourth embodiment of the present invention, the amount of surface displacement Δ is measured₂The parameters required for the calculation of (a) are as follows.

n: refractive index of material of inspected lens

r₁: radius of curvature of first surface of lens to be inspected

r₂: radius of curvature of second surface of lens to be inspected

t: thickness of inspected lens

The parameters are set in the data processing unit 130d, for example. The lens surface shift amount measuring device 130 of the present invention measures the surface shift amount Δ using the transmitted light beam near the center of the test lens 131a₂. Therefore, since the transmitted light beam is transmitted on the paraxial region of the subject lens, the following calculation is performed by paraxial approximation.

First, the thickness t, the refractive index n, and the first surface curvature radius r of the inspected lens 150 are used₁Second surface radius of curvature r₂The back focal length B of the test lens 150 can be calculated by the following equation 26.

[ mathematical formula 26]

Then, the laser beam transmitted through the second surface of the inspected lens 150 enters the parallel lightThe angle of refraction is set to theta based on the central axis of the lens₁. Angle theta₁Geometry-based configuration using an offset Δ₁And the back focal length B is expressed as shown in equation 27.

[ mathematical formula 27]

A line connecting an intersection LN2 of the incident parallel laser beam and the second surface and the center of curvature CN2 of the second surface is defined as a line L. Further, the angle θ of the line L with respect to the lens center axis LZ can be calculated using snell's law as shown in fig. 4₂. As a result, the angle θ of the line L based on the lens center axis LZ is modified from the equation 28₂Can be expressed by the expression shown in formula 29.

[ mathematical formula 28]

nθ₂＝θ₂+θ₁

[ mathematical formula 29]

Then, θ is erased by using the above-mentioned formula 29₁Equation 27 is modified as shown in equation 30.

[ mathematical formula 30]

Here, the amount of plane shift Δ₂The configuration according to the geometry is represented as shown in mathematical formula 31.

[ mathematical formula 31]

Δ₂＝r₂θ₂

Equation 30 can be substituted into equation 31, and the transformation can be performed as shown in equation 32.

[ mathematical formula 32]

If B is eliminated from equation 32 using equation 26 in which B is expressed as a parameter, equation 33 is obtained, and the amount of focal point shift Δ is used₁The curvature r of the first surface of the lens to be inspected₁Second surface curvature r of the lens to be inspected₂Design parameters such as the lens thickness t of the lens to be inspected and the refractive index n of the lens to be inspected can calculate the plane offset amount Delta of the first surface and the second surface of the lens to be inspected₂。

[ mathematical formula 33]

The amount of surface shift Δ is calculated using equation 33₂In the case of (3), the lens to be inspected can be measured by either a convex lens or a concave lens.

In the lens surface shift amount measuring apparatus 130 of the present invention, the surface shift amount Δ can be calculated using the ring-shaped convergent light beam₂. At this time, the converging point of the annular converging beam is spread from a focal point FF (hereinafter, referred to as "front focal point") located on the first surface side (the reflective light sensor side) of the detection target lens. Then, the angle θ of the transmitted light beam transmitted through the test lens 150 is measured with respect to the lens center axis LZ₁' to calculate the amount of plane shift Delta₂The method of (1) is explained. Fig. 31 shows a case where the convergent light beam whose optical axis coincides with the lens center axis LZ of the test lens 150 is incident on the test lens 150 and is emitted from the test lens 150 as a parallel light beam LB inclined with respect to the lens center axis LZ.

By substituting the above-mentioned equation 28 into equation 31, the surface shift amount Δ can be expressed as shown in equation 34₂. Wherein, in FIG. 31, θ is replaced with₁、θ₂Using theta₁′、θ₂′。

[ mathematical formula 34]

Using equation 34, θ can be expressed by₁' calculating the amount of plane offset Delta₂。θ₁' is an angle between the parallel light beam LB emitted from the second surface 150b of the test lens and the lens central axis LZ. Therefore, θ can be measured using the transmitted light sensor section 130c₁'. In the transmitted light sensor section autocollimator 138, since the lens center axis LZ is 0 degree as a reference, θ is obtained as a measurement value by the transmitted light sensor section autocollimator 138₁'. The transmitted light sensor section autocollimator 138 is composed of a lens (focal length f10)138a, a transmitted light sensor section light receiving device 138b, and a half mirror 138 c. With this configuration, the parallel light beam LB transmitted through the test lens 150 is condensed by the lens (focal length f10)138a via the half mirror 138c at the transmitted-light sensor portion autocollimator light-receiving device 138 b. Therefore, the position of the condensed point can be detected by using the transmitted light sensor section autocollimator light-receiving device 138 b. Finally, based on the XY position data of the condensed point position, the data processing part can measure theta₁'. The amount of surface shift Δ is calculated using equation 10₂In the case of (3), the lens to be inspected is limited to the convex lens.

As described above, according to the device for measuring the amount of surface deviation of a lens in accordance with the fourth embodiment of the present invention, the converging light beam having a ring-shaped light intensity distribution when viewed from the optical axis of the reflective light sensor unit and the parallel light beam irradiated in the vicinity of the center of the test lens are simultaneously irradiated, the lens center axis of the test lens (the normal line of the first surface of the test lens) is adjusted so as to coincide with the optical axis of the reflective light sensor unit, and the converging point position of the light beam transmitted through the test lens is measured, whereby the amount of surface deviation of the test lens can be measured without rotating the test lens.

As described above, the angle θ of the transmitted light beam transmitted through the lens to be inspected is used₁' amount of plane offset Δ₂In the method of calculating (1), the angle between the direction of the transmitted light beam transmitted through the lens to be inspected and the lens center axis is measured by irradiating the diffused light beam from the front focal point position of the lens to be inspected, whereby the amount of surface shift of the lens to be inspected can be measured without rotating the lens to be inspected.

According to the lens surface shift amount measuring device of the present invention, since the rotation mechanism of the lens to be inspected is not required, the device has a simpler configuration than the conventional device, and the measuring time can be shortened.

Although the embodiments of the present invention have been described, the above embodiments are presented as examples, and are not intended to limit the scope of the invention. Various omissions, substitutions, and changes may be made in the novel embodiments without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the scope of claims and the scope equivalent thereto.

Industrial applicability

The present invention simultaneously irradiates a convergent light beam having a light intensity distribution in a ring shape when viewed from an optical axis of a reflective light sensor unit and a parallel light beam irradiated to the vicinity of the center of a lens to be inspected, and is suitable for measuring a characteristic value of the lens to be inspected. In particular, the present invention can be applied to a device for measuring the thickness of a thin test lens of 200 μm or less, or to a device for measuring the amount of surface shift of a lens as follows: after the adjustment is performed to align the lens center axis of the subject lens (the normal line of the first surface of the subject lens) with the optical axis of the reflective light sensor unit, the position of the converging point of the annular converging light beam transmitted through the subject lens or the parallel light beam irradiated to the vicinity of the center of the subject lens is measured, and the amount of surface shift of the subject lens can be measured without rotating the subject lens.

Description of the reference numerals

29 annular beam-converging optical system

30 optical system

31 light source (for example, laser diode)

32 collimating lens

33 semi-reflecting mirror

34 optical element

34a ring-shaped through hole

34b small diameter lens

39 optical element

40 lens

41 CCD camera

42 treatment part

43 rotating stage

44 optical element

45 lens

46 CCD camera

47 autocollimator part

48 reflected light detection unit

50a bundle light

50b parallel light

110 detected lens 10

110a first side 10a

110b second side 10b

111 lens holding part to be inspected

112 lens holding frame

113 lens holder holding carrier part

Surface offset measuring device for 120 lens

121 lens holder to be inspected

122 lens holder holding mechanism carrier part

123 reflective optical sensor unit

123a light source

123b reflective photosensor section autocollimator

124 transmitted light sensor part

124a transmission photosensor section autocollimator

124b light sensor part

124c through the photosensor holding mechanism carrier part

125 data processing part

126 monitor

Surface offset measuring device for 130 lens

130a detected part

130b reflective optical sensor unit

130c through the photosensor part

130d data processing section

130e display part

131a lens to be inspected

131b lens holder to be inspected

131c lens holder holding mechanism

132 light source unit

132a light source (e.g., laser diode)

132b lens (focal distance f2)

132c half mirror

133 optical element 33

134 lens (focal distance f4)

135 optical element (e.g., pinhole)

136 reflection photosensor auto-collimator

136a lens (focal distance f7)

136b reflective optical sensor unit light receiving device

137 transmitted light sensor part optical system

137a lens (focal distance f11)

137b transmitted through the photosensor part

138-transmission light sensor portion autocollimator

138a lens (focal distance f10)

138b automatic collimator light receiving device of light transmitting sensor

138c half mirror

139 transmission optical sensor holding mechanism carrier part

141a reflective photosensor part

141b transmitted light sensor unit

141c data processing unit

141d monitor

142 lens for adjustment (plano-convex lens)

143 test lens holder

144 transmission optical sensor part holding mechanism carrier part

145a ring-shaped light beam converging device

145b annular reflected light

146 optical path.

Claims (9)

1. An optical element characteristic measurement device comprising an annular condensed light irradiation light section for irradiating an optical element to be tested with condensed light having an annular light intensity distribution on a plane perpendicular to an optical axis and parallel light having a center of the light intensity distribution on the optical axis,

a surface of the optical element to be detected on the side of the annular beam converging light irradiation light portion is a front surface, and an opposite side of the front surface is a back surface,

measuring the shape characteristics of the optical element by analyzing the intensity of the light reflected or transmitted from the front surface or the back surface of the optical element or the optical path of the light,

the optical element characteristic measurement device is provided with:

a reflected light detection unit that irradiates the optical element to be inspected with the annular convergent light, forms an image of a first annular image generated on a front surface of the optical element to be inspected and an image of a second annular image generated on a rear surface of the optical element to be inspected on a light-receiving surface, and generates data for calculating light intensities of the first annular image and the second annular image; and

a processing unit that calculates a thickness of the optical element to be inspected based on a change in the light intensity with respect to a distance in which the optical element to be inspected moves in the optical axis direction,

the optical element to be detected is a lens,

two maximum values of the change in light intensity of the first annular image and the second annular image based on the data are detected, and the difference between the moving distances of the optical element to be inspected corresponding to the two maximum values is used to measureA value d, a refractive index n of a material of the optical element to be inspected, a radius r of curvature of the optical element to be inspected, and a condensing angle θ of the condensed beam light, which is an angle formed by a center point of the radius r of curvature and the optical axis and the condensed beam light₁Calculating the thickness t of the lens of the optical element to be inspected,

the slope a and the intercept B of a line segment BC connecting a point C at which the annular convergent light beam on the front surface of the optical element to be inspected refracts and an annular convergent point B on the rear surface of the optical element to be inspected:

b＝r-d，

and use

Calculating a distance e between the point C and the optical axis of the annular convergent light beam, wherein when the curvature radius r is positive, that is, when the optical element to be inspected is convex, the signs of the distance e in the same order of the two signs take positive values, and when the curvature radius r is negative, that is, when the optical element to be inspected is concave, the signs of the distance e in the same order of the two signs take negative values, and using the values

And calculating the thickness t of the lens of the optical element to be detected.

2. The optical element characteristic measurement device according to claim 1, wherein the annular condensed light irradiation light portion includes a light source, a first optical element, and a first lens,

the light source, the first optical element, and the first lens are arranged in this order along the optical axis,

the first optical element is formed with an annular gap perpendicular to the optical axis, and a first lens having a diameter smaller than a diameter inside the annular gap is disposed.

3. The optical element characteristic measurement device according to claim 1, comprising:

a reflected light sensor unit that has the annular condensed light irradiation light emitting unit that irradiates the optical element to be inspected with the annular condensed light, and generates first condensed light position data for calculating a reflection angle of an optical axis of the annular parallel light reflected by the surface of the optical element to be inspected;

a transmitted light sensor unit for generating second condensed light position data for calculating a condensed point position of the light beam irradiated from the annular condensed light irradiation light emitting unit and transmitted through the optical element to be inspected; and

a data processing unit that calculates the reflection angle based on the first condensing position data and calculates the condensing position of the light transmitted through the optical element to be inspected based on the second condensing position data,

the data processing unit adjusts the position of the optical element to be detected based on the first light-condensing position data so that the lens center axis of the optical element to be detected coincides with the optical axis of the annular condensed light irradiation light-emitting portion, and calculates the amount of surface shift Δ of the optical element to be detected based on the light-condensing position data so that the optical element to be detected is not rotated₂。

4. The optical element characteristic measurement device according to claim 3, wherein the optical element to be inspected is a lens,

the offset amount calculated based on the position of the converging point of the transmitted parallel light beam transmitted near the center of the optical element to be detected is set as delta₁And using the refractive index n of the material of the optical element to be inspected, the radius of curvature r of the surface of the optical element to be inspected₁Radius of curvature r of the back surface of the optical element to be inspected₂To therebyAnd the thickness t of the optical element to be inspected to calculate the surface shift amount Delta₂。

5. The optical element characteristic measuring apparatus according to claim 4, wherein

Calculating the surface offset amount Delta₂。

6. The optical element characteristic measurement device according to claim 3, wherein the optical element to be inspected is a lens,

a refraction angle θ of a transmitted parallel light ray calculated using a condensed light condensed to a focus on the side of the reflective light sensor of the optical element to be detected and transmitted through the optical element based on the condensed point position of the transmitted parallel light ray on the transmitted light sensor₁', refractive index n of material of the optical element to be inspected, and curvature radius r of the rear surface of the optical element to be inspected₂To calculate the amount of face shift Δ₂。

7. The optical element characteristic measuring apparatus according to claim 6, wherein

Calculating the surface offset amount Delta₂。

8. The optical element characteristic measurement device according to any one of claims 1 to 7, wherein an annular convergent light beam in which three or more light beams are arranged at substantially equal intervals on a circumference is used instead of the annular convergent light beam.

9. The optical element characteristic measurement device according to claim 2, wherein the first optical element is formed with a plurality of holes through which a plurality of three or more light beams, instead of the annular convergent light beam, pass.

Images