JP2002055023A - Refractive index measuring instrument for lens to be inspected - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractive index measuring instrument for a lens to be inspected, which can easily and speedily measure the refractive index of the object lens nondestructively. SOLUTION: This refractive index measuring instrument for the lens to be inspected has a lens support 7, which supports a lens TL to be inspected so that the measurement light beam emitted by a light source part 1 is made incident on the front surface of the lens TL to be inspected almost vertically; a projection angle detection sensor 3 which receives the measurement light beam refracted by the reverse surface of the lens TL and detects a projection angle ε to the optical axis of the measurement optical path SO; an angle measurement system 16, which projects angle measurement light toward an intersection X from the direction opposite to the traveling direction of the measurement light beam along the optical axis O; a reflection angle detection sensor 22, which receives the reflected light at the intersection X of the angle measurement light and detects the reflection angle that the optical axis O and the reflection direction of the reflected light contain; and a refractive index arithmetic circuit 15 which computes the refractive index of the lens TL, according to the projection angle obtained by the projection angle detection sensor 3 and the reflection angle obtained by the reflection angle detection sensor 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the refractive index of a test lens (eyeglass lens), which can easily and quickly inspect the refractive index of the test lens (non-destructive).

[0002]

2. Description of the Related Art Conventionally, measurement of the refractive index of a test lens has
A test prism 1A having a known apex angle σ is prepared as shown in FIG. 1 using the same material as the material used for the test lens, and a measuring beam is made incident on the test prism 1A to measure the minimum deflection angle μ. Then, according to the following equation, the refractive index n of the material
Asking has been done. n = (sin (μ + σ) / 2) / (sin (σ / 2)) Further, the refractive power of the lens to be measured in the air is obtained using a lens meter. Immersed in the liquid, and determine the refractive power of the test lens in the liquid. The ratio of the refractive power of the test lens in the liquid to the refractive power of the test lens in the air is used to determine the refractive power of the test lens. The refractive index n of the material is also obtained.

Further, instead of immersing a test lens in a liquid, the refractive power in a state in which a transparent silicone rubber having a known refractive index is pressed against the surface of the test lens is determined, and the refractive power in air is determined. The refractive index n of the lens to be inspected is also determined from the ratio of the refractive power of the lens to be inspected to the refractive power of the lens pressed against the silicone rubber.

[0004]

However, in the method of preparing the test prism 1A and measuring the refractive index n of the lens to be measured, the refractive index must be obtained by destroying the lens to be measured. There is a problem that the refractive index n of the test lens cannot be measured.

On the other hand, the refractive power of the test lens in air is measured using a lens meter, and then the test lens is immersed in a liquid to measure the refractive power in the liquid. A method of measuring the refractive index n of the test lens from the ratio of the power to the refractive power in the air, using a silicon rubber having a known refractive index, and pressing the silicon rubber against the test power. The method of measuring the refractive power of the lens and measuring the refractive index of the lens from the ratio is a non-destructive method of measuring the refractive index n of the lens.
Can be measured nondestructively, but there is a problem that the measurement becomes complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-destructive, easy-to-destructive and non-destructive method for inspecting the refractive index of a lens. An object of the present invention is to provide a refractive index measuring device.

[0007]

According to a first aspect of the present invention, there is provided an apparatus for measuring the refractive index of a lens to be inspected, such that a measuring light beam emitted from a light source section is incident substantially perpendicularly to the front surface of the lens to be inspected. A lens support that is provided in the measurement optical path of the test lens and is in contact with the front surface of the test lens to support the test lens, and is provided at a position opposite to the light source unit with the lens support as a boundary. An emission angle detection sensor for receiving a measurement light beam that has been refracted by the back surface of the test lens and detecting an emission angle of the measurement light path with respect to the optical axis; and light from the back surface of the test lens and the measurement light path. From the direction opposite to the direction of travel of the measurement light beam toward the intersection point and along the optical axis to determine the angle between the normal set to the tangent plane at the intersection with the axis and the optical axis of the measurement optical path. Angle at which angle measurement light is emitted A constant optical system, a reflection angle detection sensor that receives reflected light at the intersection of the angle measurement light and detects a reflection angle between an optical axis of the measurement optical path and a reflection direction of the reflected light, and the emission angle detection A refractive index calculation circuit configured to calculate a refractive index of the lens to be measured based on an exit angle obtained based on a sensor and a reflection angle obtained based on the reflection angle detection sensor.

According to a second aspect of the present invention, there is provided an apparatus for measuring a refractive index of a lens to be detected, which calculates the refractive index by detecting the exit angle when the reflection angle becomes a constant value.

According to a third aspect of the present invention, there is provided an apparatus for measuring a refractive index of a test lens, wherein the refractive index is calculated by detecting the reflection angle when the exit angle becomes a constant value.

According to a fourth aspect of the present invention, there is provided an apparatus for measuring a refractive index of a lens to be inspected, wherein a half mirror for reflecting the angle measuring light toward the lens to be inspected is provided between the lens support and the exit angle detecting sensor. Have been.

According to a fifth aspect of the present invention, there is provided an apparatus for measuring a refractive index of a lens to be inspected, wherein the number of the reflection angle detection sensors is two, and one of the reflection angle detection sensors is shared by the emission angle detection sensor, The other of the detection sensors is disposed outside the measurement optical path, and the oblique half mirror has a function of reflecting the reflected light toward the other reflection angle detection sensor, and the other reflection angle detection sensor is equivalent. When it is considered that the two reflection angle detection sensors are arranged in the measurement optical path, the optical distances of the two reflection angle detection sensors from the lens support on the optical axis of the measurement optical path are different from each other. Features.

According to a sixth aspect of the present invention, there is provided an apparatus for measuring a refractive index of a lens to be inspected, wherein the reflection angle detection sensor and the emission angle detection sensor are shared, and a parallel flat surface is provided between the lens support and the emission angle detection sensor. It is characterized in that a face plate is provided.

According to a seventh aspect of the present invention, there is provided an apparatus for measuring a refractive index of a lens to be inspected, which receives the light reflected on the front side of the lens to be inspected, and the front side of the lens to be inspected is positioned on the optical axis of the optical path of the measurement. It is characterized in that a checking optical system for checking whether or not it is maintained vertically is provided.

[0014]

FIG. 2 is a view showing a measuring optical system of a measuring apparatus used for measuring the refractive index of a lens to be measured. In FIG. 2, reference numeral 1 denotes a light source unit (for example, LED), 2 denotes a slit plate, and 3 denotes a line sensor.

A pinhole plate 4 and a projection lens 5 are provided between the light source 1 and the slit plate 2. Light source unit 1
If the luminance unevenness is large, a diffusion plate (not shown) is arranged between the light source unit 1 and the pinhole plate 4. An imaging lens 6, a lens support 7, and an oblique half mirror 8 are disposed between the slit plate 2 and the line sensor 3. The test lens TL is in contact with the lens support 7.

The projection lens 5 serves to keep the pinhole plate 4 and the imaginary contact surface 8 of the test lens TL in a conjugate relationship, and the projection lens 5 applies a measurement light beam passing through the pinhole plate 4 and the slit plate 2 to the measurement light beam. Then, a secondary light source image is formed on the lens TL to be measured.

As shown in FIG. 3, slits 2a, 2b and 2c are formed in the slit plate 2. That slit 2
a extends in a direction crossing the optical axis O.
The slits 2b and 2c are formed point-symmetrically with the optical axis O as the origin on both sides of the slit a.

The slit plate 2 and the line sensor 3 are provided at conjugate positions with respect to the imaging lens 6, and when the lens TL to be inspected is not set on the measurement optical path SO, the slit image of the slit plate 2 causes the line sensor 3 to move. It is projected on a predetermined position in the plane Q including the image.

The front surface (convex surface) TLa of the lens to be measured TL is in contact with the lens support 7. This lens support 7
Is formed in an annular shape, and the test lens TL is uniformly pressed against the lens support 7 so that the front surface TLa of the test lens TL can be held substantially perpendicular to the measurement optical axis O. It is also possible to use a lens holder (not shown) to uniformly press the test lens TL against the lens support 7 from the rear surface TLb side of the test lens TL with a constant load.

When the test lens TL is inserted into the measurement optical path SO, the conjugate relationship between the slit plate 2 and the surface Q including the line sensor 3 is shifted. However, by reducing the diameter of the pinhole 4a of the pinhole plate 4, the focus is reduced. Since the depth can be increased, blurring of the slit image of the slit plate 2 in the plane Q including the line sensor 3 can be prevented.

The optical axis O1 of the test lens TL and the measuring optical path SO
Is coincident with the optical axis O, the position of the slit image on the plane including the line sensor 3 is the same as the position of the slit image before the test lens TL is inserted, and does not change.

When the test lens TL is moved in the direction of arrow AA, as shown in FIG. 4, the slit images 2a 'to 2c'
Moves in the direction in which the pixels 3a of the line sensor 3 are arranged (the direction of arrow BB). The slit images 2a 'to 2c' move in a direction opposite to the moving direction of the test lens TL when the test lens TL is a convex lens, and move in the same direction as the moving direction of the test lens TL when the test lens TL is a concave lens. I do.

At this time, as shown in FIG. 5, the peak intervals L1 and L2 of the detection outputs Q1 to Q3 output from the pixel 3a based on the slit images 2a 'to 2c' formed on the line sensor 3 are equal. While maintaining the slit image 2
a ′ to 2c ′ move in the direction of arrow BB.

When the test lens TL is moved in a direction perpendicular to the plane of the drawing on a plane perpendicular to the plane of the drawing, the slit images 2a 'to 2c' are arranged as shown in FIG. Direction perpendicular to the direction (direction of arrow CC)
And the slit image 2 formed on the line sensor 3
The peak intervals L1 and L2 of the detection outputs Q1 to Q3 output from the pixel 3a based on a 'to 2c'
When a ′ to 2c ′ move to the right as a whole, L1 <L2 as shown in FIG. 7, and when the slit image moves to the left as a whole, L1> L2 as shown in FIG.
Peak interval L between detection outputs Q1 to Q3 of line sensor 3
1, L2 and the moving directions of the slit images 2a 'to 2c' can be used to detect the moving directions of the lens TL in the vertical and horizontal directions with respect to the measurement optical path SO. The detection outputs Q1 to Q3
Is input to the refractive index calculation circuit 15 shown in FIG.

The refractive index calculating circuit 15 detects the detection outputs Q1 to Q1.
The moving direction and the moving amount of the test lens TL are calculated based on Q3, and the moving direction and the moving amount are graphically displayed on a monitor (not shown).

The optical distance d from the vertex 7a of the lens support 7 to the surface Q of the line sensor 3 is known by optical design. Accordingly, the exit angle ε can be obtained from the moving amount h1 of the image on the line sensor 3, and the line sensor 3 detects the slit image and detects the exit angle ε formed by the exit ray with respect to the optical axis O. Play a role. It is sufficient that the movement amount h1 is detected only for the slit image 2a '.

That is, since the front surface TLa of the test lens TL is maintained on the lens support 7 so as to be perpendicular to the optical axis O, the measurement light beam is not refracted at the front surface TLa of the test lens TL. It goes straight toward the back surface TLb, and receives a refraction action on the back surface TLb.

Therefore, assuming that the angle formed by the measurement light beam with respect to the normal line N on the back surface TLb is θ, sin (θ) = n · sin (θ−ε) based on Snell's law. If the angle θ formed by the measurement light beam with respect to the normal line N (the angle formed by the normal line N with respect to the optical axis O) can be measured, the refractive index n of the test lens TL can be obtained. Here, the normal line N is a perpendicular line perpendicular to a tangent plane including an intersection X between the back surface TLb of the lens TL to be measured and the optical axis O.

As shown in FIGS. 2 and 9, the measuring optical system is provided with an angle measuring optical system 16 for obtaining an angle θ between the optical axis O and a normal line N. The angle measuring optical system 16 has a function of measuring the reflection angle of the angle measuring light P ′ incident along the optical axis O at the intersection X between the rear surface TLb of the lens TL to be measured and the optical axis O.

The angle measuring optical system 16 comprises a light source 17, a pinhole plate 18, a projection lens 19, a slit plate 20, and an imaging lens 21. The pinhole plate 18 and the back surface TLb of the test lens TL are conjugate with respect to the projection lens 19. The slit plate 20 has one slit 20a at the center.

The optical axis O2 of the angle measuring optical system 16 is conjugate with the optical axis O with respect to the oblique half mirror 8, and the optical axis O2
And the optical axis O are optically coincident with each other.

The angle measuring light P ′ emitted from the light source unit 17 of the angle measuring optical system 16 is guided to the oblique half mirror 8 via the pinhole plate 18, the projection lens 19, the slit plate 20, and the imaging lens 21. I will The angle measurement light P ′ is reflected by the oblique half mirror 8, travels along the optical axis O, and is guided to the back surface TLb of the test lens TL.

A light source image of the pinhole plate 18 is formed on the back surface TLb of the test lens TL at the intersection X by the angle measurement light P '. The reflected light P ″ reflected at the intersection X of the test lens TL is guided to the oblique half mirror 8, a part of the reflected light P ″ passes through the oblique half mirror 8, and the remaining reflected light is The light is reflected by the oblique half mirror 8.

A line sensor 22 is provided in the direction of reflection of the remaining reflected light. This line sensor 22
Is that the line sensor 22 is equivalent to its measurement optical path SO
Is on the optical axis O, the optical distance d 'from the back surface TLb of the test lens TL to the line sensor 22 is equal to the surface Q of the line sensor 3 from the back surface TLb of the test lens TL.
Is different from the optical distance d. here,
d ′> d.

The intermediate position MP between the line sensor 3 and the line sensor 22 and the slit plate 20 are conjugate with respect to the imaging lens 21, and the line sensor 3 and the line sensor 22 have slit images 20a 'and 20a "of the slit 20a. The slit images 20a 'and 20a "extend in a direction perpendicular to the arrangement direction of the pixels of the line sensors 3 and 22.

The slit image 20a 'based on the reflected light P ",
The image heights of the 20a ″ on the line sensors 3 and 22 are denoted by h2 and h3, respectively. When the reflection angle between the measurement light P ′ and the reflected light P ″ is δ, the light enters and reflects from the normal N. According to the principle of the law, δ = 2θ.

Further, the relational expression of tan2θ = (h3−h2) / (d′−d) holds according to the tangent formula of the triangle.

Therefore, by measuring the reflection angle δ using the angle measuring optical system 16 and the line sensors 3 and 22,
The refractive index of the test lens TL can be measured, and the line sensors 3 and 22 play a role as a reflection angle detection sensor that detects the reflection angle δ in cooperation.

Here, as shown in FIG. 9, a monitor (not shown) is used to maintain the perpendicularity of the front surface TLa of the lens TL to be measured to the optical axis O and to keep the reflection angle δ at a constant value. Inspecting the lens TL by hand while following the instructions while watching
Is moved and decentered, and the exit angle ε when the reflection angle δ is a constant value is measured. As a result, the arithmetic circuit 15 performs an arithmetic operation, and the refractive index n of the lens TL is determined. The measurement of the exit angle ε is performed by pressing a measurement button (not shown) to cause the light source unit 1 to emit light when the reflection angle δ is displayed on the monitor as a constant value. Has reached a constant value by a refractive index calculation circuit 15 (not shown), and the light source unit 1 automatically emits light to execute.

In this case, the emission angle ε is measured with the reflection angle δ being a fixed value (fixed value).
Is measured, and the reflection angle δ is measured, whereby the refractive index n of the test lens TL can be obtained.

In the embodiment of the invention shown in FIGS. 2 and 9,
To measure the reflection angle δ, two line sensors 3, 22
However, as shown in FIG. 10, a parallel plane plate 23 is provided in the measurement optical path SO, and reflected light P ″ is reflected by a front surface 23a and a rear surface 23b of the parallel plane plate 23, respectively, and a line is formed. The sensor 3 may be configured to receive the slit images 20a ′ and 20a ″ based on the reflected light P ″.

At this time, assuming that the thickness of the parallel plane plate 23 is D, the reflected light P ″ reflected by the rear surface 23b and the front surface 23a of the parallel plane plate 23 and the rear surface 23
Since a double optical path length difference 2D is generated between the reflected light P ″ and the reflected light P ″ that has passed through b, the relational expression of tan2θ = (h3−h2) / 2D is established.

When the measurement is performed when the reflection angle δ is substantially constant, an antireflection coat is provided at a portion 23c where the reflected light P ″ on the front surface 23a of the parallel flat plate 23 is incident, and the reflection on the rear surface 23b is performed. A half mirror coat is provided at a portion 23d where the light P "partially transmits and the remaining reflected light P" is reflected, and a total reflection coat is provided at a portion 23e of the front surface 23a where the reflected light P "is reflected. , Loss of the reflected light P ″ can be prevented.

In the above embodiment of the present invention, the slit images 20a ', 20a based on the reflected light P "depend on the thickness of the lens TL to be measured (the distance from the front surface TLa to the rear surface TLb).
Since the image height of a ″ on the line sensor changes, the reflection angle δ is measured using the two slit images 20a ′ and 20a ″. When measuring the angle θ of the test lens TL, which is almost fixed, if the distance d from the lens support 7 to the line sensor 3 is designed to be large enough to ignore the thickness of the test lens TL, one slit image 20a ′ can be used to measure the reflection angle δ.

FIG. 11 is an explanatory view of a confirmation optical system 23 for confirming whether or not the front surface TLa of the test lens TL is disposed perpendicular to the optical axis O. The confirmation optical system 23 is a half mirror. 24, an imaging lens 25, and an image receiving element 26. The measurement light beam is the front surface TLa of the test lens TL.
, A part thereof is reflected, and the rest is transmitted toward the back surface TLb.

The measurement light beam reflected by the front surface TLa of the test lens TL is reflected by the half mirror 24 and guided to the imaging lens 25. When the image receiving element 26 is an area sensor, the imaging lens 25 moves the front surface TLa to the image receiving element 26.
When the image receiving element 26 is a line sensor, it is held in a conjugate relationship with the slit plate 2. Accordingly, when the image receiving element 26 is an area sensor, a light source image is formed by the measurement light beam reflected on the front surface TLa, and when this is a line sensor, the light source image is formed on the front surface TLa.
The slit images 2a ′ to 2
c ′ is formed.

When the front surface TLa of the test lens TL is held perpendicular to the optical axis O, the center point 2
6a, the center of the light source image or the slit image is located, but if the front surface TLa of the lens to be inspected TL is inclined with respect to the optical axis O, the light source image or the slit image is shifted to the center point in proportion to the inclination. 26a. Therefore, the image receiving output of the image receiving element 26 is input to the refractive power calculation circuit 15 to calculate the amount of deviation from the center point 26a, and the moving direction of the lens TL to be displayed may be displayed on a monitor (not shown). good.

In the above, the measurement of the refractive index has been described in the embodiment of the present invention. However, if the light source unit 1 capable of obtaining a light beam of three wavelengths is used, the Abbe number of the lens TL to be measured can be measured. Can be. For details of this principle, refer to Japanese Patent Application No. 2000-190415.

[0049]

As described above, the present invention has an effect that the refractive index of the test lens can be measured nondestructively and simply and quickly.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for measuring a refractive power using a test prism.

FIG. 2 is a diagram showing a measurement optical system of a device for measuring the refractive index of a lens to be inspected according to the present invention.

FIG. 3 is a plan view of the slit plate shown in FIG. 2;

FIG. 4 is an explanatory diagram of a slit image formed on a line sensor provided on a measurement optical path shown in FIG. 2;

FIG. 5 is an explanatory diagram of a peak interval of a detection output output from the line sensor shown in FIG.

FIG. 6 is an explanatory view of a slit image formed on a line sensor provided on a measurement optical path when the test lens shown in FIG. 2 is moved perpendicularly to the optical axis in a plane perpendicular to the paper surface. It is.

FIG. 7 is an explanatory diagram for explaining a peak interval of a detection output output from a line sensor when the slit image shown in FIG. 6 moves to the right.

FIG. 8 is an explanatory diagram for explaining a peak interval of a detection output output from the line sensor when the slit image shown in FIG. 6 moves to the left.

FIG. 9 is an explanatory diagram of a principle of detecting a reflection angle using the measurement optical system shown in FIG. 2;

FIG. 10 is a diagram showing a modification of the measuring optical system of the refractive index measuring device for the lens to be inspected shown in FIG.

FIG. 11 is a diagram illustrating a measurement optical system including a confirmation optical system for confirming whether or not a test lens is disposed perpendicular to an optical axis of a measurement optical path.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source part 3 ... Exit angle detection sensor 7 ... Lens support 15 ... Refractive index calculation circuit 16 ... Angle measurement optical system 22 ... Reflection angle detection sensor s ... Exit angle N ... Normal line O ... Optical axis X ... Intersection TL ... Inspection lens SO… Measurement optical path

Claims (7)

[Claims] 1. A measurement light beam generated from a light source unit is provided in a measurement optical path of a lens to be measured so that the measurement light beam is incident on the front surface of the lens to be measured substantially perpendicularly. A lens support that supports the lens to be inspected, and receives the measurement light beam that is provided at a position opposite to the light source unit with respect to the lens support and that is refracted by the back surface of the lens to be inspected. An emission angle detection sensor for detecting an emission angle with respect to the optical axis of the optical path, a normal line established on a tangent plane at an intersection of the back surface of the lens to be measured and the optical axis of the measurement optical path, and an optical axis of the measurement optical path. An angle measuring optical system that projects angle measuring light from the direction opposite to the traveling direction of the measuring light beam toward the intersection and along the optical axis to obtain the angle to be performed, and the intersection of the angle measuring light Receiving the reflected light at A reflection angle detection sensor for detecting a reflection angle between the optical axis of the measurement optical path and the reflection direction of the reflected light; an emission angle obtained based on the emission angle detection sensor; and a reflection angle obtained based on the reflection angle detection sensor A refractive index calculating circuit that calculates the refractive index of the test lens based on
A refractive index measuring device for a test lens, comprising: 2. The apparatus according to claim 1, wherein the refractive index is calculated by detecting the exit angle when the reflection angle becomes a constant value. 3. The apparatus according to claim 1, wherein the refractive index is calculated by detecting the reflection angle when the emission angle becomes a constant value. 4. The refraction of the lens according to claim 1, wherein a half mirror for reflecting the angle measurement light toward the lens to be measured is provided between the lens support and the exit angle detection sensor. Rate measuring device. 5. The apparatus according to claim 1, wherein the number of the reflection angle detection sensors is two, one of the reflection angle detection sensors is shared with the emission angle detection sensor, and the other of the reflection angle detection sensors is disposed outside the measurement optical path, The oblique half mirror has a function of reflecting the reflected light toward the other reflection angle detection sensor,
When it is considered that the other reflection angle detection sensors are equivalently disposed in the measurement light path, the optical signals from the lens support on the optical axis of the measurement light paths of the two reflection angle detection sensors The apparatus according to claim 1, wherein the distances are different from each other. 6. The apparatus according to claim 1, wherein the reflection angle detection sensor and the emission angle detection sensor are shared, and a parallel flat plate is provided between the lens support and the emission angle detection sensor. 4. The apparatus for measuring the refractive index of a test lens according to claim 1. 7. A method for receiving reflected light reflected on the front side of the lens to be tested and confirming whether the front surface of the lens to be tested is maintained perpendicular to the optical axis of the measurement optical path. The apparatus according to claim 1, further comprising an optical system.