JPH06194122A - Decentering measuring device - Google Patents

Abstract

PURPOSE:To allow the deflection of transmitted light and that of reflected light to be measured simultaneously by combining the transmitted light and reflected light, coming into a beam splitter, into the same visual field, and observing it on the observation face. CONSTITUTION:Parallel light from one light source 15 is divided into two beams by a beam splitter 19. These beams are reflected on the respective mirrors 14 and made incident from the upper and lower sides of a lens to be inspected 13. The transmitted and reflected light from the lens to be inspected 13 is reflected on the beam splitter 19 so as to be guided toward an eyepiece 17. Viewed through the eyepiece 17, the transmitted light and reflected light are observed in the form of being combined in one visual field. At this time, the light spots of two beams 9, 10 describe a specific locus according to the decentered state of the detected lens 13 when the lens to be inspected 13 is rotated, and the absolute quantity of its deflection can be read by an ocular chart 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eccentricity measuring device which is required in a lens manufacturing process among optical parts.

[0002]

2. Description of the Related Art There are two types of conventional eccentricity measuring devices, a transmission type for observing the deflection of transmitted light by a lens and a reflection type for observing the deflection of reflected light.

First, a transmission type eccentricity measuring device will be described with reference to FIG. 1 (Optical element processing technology '82, Chapter II-2, Centering and Cleaning, Yuji Wakana, P.18-22, ed. The light emitted from the light source 15 is converted into parallel light by the collimator lens and is incident on the lens 13 to be inspected. The lens 13 to be inspected is set so as to rotate about the outer diameter center axis 6 with reference to the one surface 3 and the side surface 2. If the lens has eccentricity, the incident light touches in a direction different from the incident direction, so if the lens is rotated, the light source 15 observed on the observation surface 12
The locus of the image of will draw a circle. The deflection angle θ of the transmitted light is calculated from the radius of this circle, and the deflection of the lens surface is calculated based on this.

Next, a conventional reflection type eccentricity measuring device will be described with reference to FIG. 2 (same as above). The light emitted from the light source 15 passes through the beam splitter 19 and the lens system to be converged light and enters the lens 13 to be inspected. The lens 13 to be inspected is set so as to rotate about the outer diameter center axis 6 with reference to the two surfaces as in the case of the transmission type. If the lens 13 to be inspected is decentered, the light does not enter the lens surface perpendicularly, so the reflected light is touched at an angle. Light reflected from the lens surface passes through the lens system again and is reflected by the beam splitter 19 to reach the observation surface. When the lens 13 to be inspected is rotated, the image on the observation surface 12 rotates and draws a locus of a circle. The deflection angle of the reflected light can be obtained from the radius of this circle to obtain the inclination of the lens surface.

Next, a case where a meniscus lens having eccentricity is measured by a transmission type or reflection type eccentricity measuring device will be described. As shown in FIG. 3, the eccentricity of the meniscus lens is a line (optical axis) 5 connecting the centers of curvature of the concave and convex surfaces and an outer diameter center axis 6
It is defined by the deviation amount r (concentricity tolerance) and the inclination angle ε (rectangular tolerance) of the optical axis 5 on the concave surface side from the vertical. The outer diameter is 2l ₀ , the radius of curvature of the convex surface is R ₁ , and the center of curvature is O.
₁ radius of curvature of the concave surface _R2, the center of curvature and O _2. The plane 3 is inclined by an angle ε about a point E on the outer diameter center axis 6, and the distance on the optical axis between the foot of the perpendicular line drawn from E to the optical axis 5 and the surface 4 is m. The squareness tolerance is μ when the deviation of the surface 3 from the ideal vertical surface is μ

[0006]

[Formula 1] Is also represented.

The deflection angle θ of the transmitted light when light is incident from the concave side with respect to the flat surface 3 and the side surface 2 on the concave surface side is derived according to FIG.

When light is incident along the perpendicular bisector 7 of the surface 3, the spherical surface 4 is separated by a distance y (= {r-
Light is incident on a point shifted upward by (R ₂ −m) tan ε} cos ε). Assuming R ₂ >> y, the incident angle α of this light on the surface 4 is

[0009]

[Formula 2] Becomes When the refractive index of the lens is n and the refraction angle is α ', the paraxial theory holds that α = nα', so that α '= α / n.

Let ψ be the angle between the optical axis 5 and the line 8 connecting the point B and O ₁ where the line 7 and the convex surface 1 intersect.

[0011]

[Formula 3] Holds.

The angle between the bisector 7 and the normal 8 to the surface 1 is ε
-4 and the angle formed with the refracted light line 7 on the surface 4 is α-
Since α ′, the incident angle β of the ray on the surface 1 is β = ε−ψ + α−
α '.

If the emission angle when light is emitted from the surface 1 is β ′, then β ′ = nβ from paraxial theory, so β ′ =
It becomes n (ε−ψ) + (n−1) α.

Therefore, the deflection angle θ of the transmitted light is

[0015]

[Formula 4] Becomes

Next, the deflection angle τ of the reflected light when the light incident on the convex surface 1 is reflected is calculated.

The rays travel from left to right along line 7 as in the case of transmission. Since the surface 1 is inclined from the vertical by an angle ε-ψ with respect to the incident light ray, the reflected light is reflected at an angle twice that angle. Ie

[0018]

[Formula 5] Although the above description is based on the case where the surface 3 and the surface 2 are used as reference, the shakes of the transmitted light and the reflected light can be similarly obtained when the surface 1 and the side surface 2 are used as the reference.

[0019]

Conventional eccentricity measuring devices are either transmission type or reflection type. The shake of transmitted light and the shake of reflected light can be measured respectively.

However, when the allowable amount of eccentricity of the lens is regulated by an optical scale such as a shake of transmitted light or a shake of reflected light, the conventional method is sufficient. The conventional method is inadequate when it is defined by a mechanical scale such as the deviation r of the outer diameter center axis and the squareness tolerance μ. Because the conventional method is limited to one physical quantity that can be measured by one measurement method,
This is because the two quantities r and μ cannot be measured separately.

Alternatively, r and μ cannot be independently determined even when two conventional transmission type and reflection type measuring devices are arranged and measured. This is because the vibration that can be measured by the conventional measuring device is the absolute value of θ or τ | θ |, | τ |
This is because the uncertainty of the code remains because it is not itself.

| Θ | = (n−1) | 1 / R ₂ −1 / R ₁ || r | (4) ′ | τ | = 2 | μ / 2l ₀ −r / R ₁ | (5) ′ 5 to 8 are graphs in which r is plotted on the horizontal axis for θ and τ expressed by Equations 4 and 5, and the circumstances around this will be described.

If θ and τ can be measured by including the signs, for example, if a measured value θ ₁ of a shake of transmitted light is _first obtained, r ₁ can be uniquely obtained from FIG. 5 (equation 4).
Then, if the measured value τ ₁ of τ is obtained, it is calculated from r ₁ and τ _{1 as} shown in FIG.
Μ ₁ is uniquely obtained from (Equation 5).

However, in the conventional measurement method, for example, the shake obtained by the transmission measurement is | θ ₁ |, and therefore two corresponding values of r ₁ and -r ₁ are obtained from FIG. 7 (equation (4) ′). Further, assuming that the deflection in the reflection measurement is | τ ₁ |, from FIG. 8 (equation (5) ′), for r ₁ , two corresponding values of μ ₂ and −μ ₁ , and −r ₁
, There are two corresponding values of -μ ₂ and μ ₁ , and it is impossible to uniquely determine the values of r and μ.

The present invention has been made in view of the drawbacks of the conventional lens eccentricity measuring device, and provides an eccentricity measuring device capable of simultaneously measuring the deflection θ of transmitted light and the deflection τ of reflected light, including their signs. The purpose is to provide.

[0026]

The basic structure of the eccentricity measuring device of the present invention will be described with reference to FIG.

First, there is a base 11 for fixing the lens 13 to be inspected. This table serves as a reference plane at the time of measurement and has a mechanism for rotating about the vertical bisector 7 of the lens to be inspected.

The measuring light is assumed to be light which is incident along the axis 7 toward the lens to be inspected from two directions below and above the table 11.

A beam splitter is provided above the lens to be inspected.
19 is arranged, and the transmitted light 9 and the reflected light 10 incident on the beam splitter are combined in the same field of view and set so that they can be observed on the observation surface 12.

[0030]

[Function] When the eccentric lens 13 to be inspected is placed on the base 11, the base 11
The light incident from the lower side of the lens is swayed like a light ray 9 when passing through the lens.

On the other hand, the light incident from above the pedestal 11 is reflected by the lens surface and causes a shake like a light ray 10.

The light rays 9 and 10 are reflected by the reflecting surface of the beam splitter 19 and reach the observation surface 12. Test lens 13 stand 11
When rotated about the axis 7 by, the loci of the rays 9 and 10 projected on the observation plane 12 describe a circle.

Considering now two lenses A and B, two sets of tolerances r and μ which define the eccentricity are r _A = | r | and μ, respectively.
Let _A = | μ |, r _B = | r |, μ _B = − | μ |. The lenses A and B are examples in which the absolute values of r and μ are equal and the signs are different from each other, but they show different cross-sectional shapes as is clear from comparison between FIGS. 10 and 12. In lens A, the transmitted light and the reflected light exit on opposite sides with respect to axis 7, whereas in lens B they exit on the same side with respect to axis 7. Therefore, when the lens is rotated, in the lens A, the transmitted light and the reflected light are concentric circles on the opposite sides of the axis 7 while the concentric circles are on the same side on the lens B. Draw. By examining the movement of the locus and the radius thereof (corresponding to the absolute values of θ and τ), it is possible to determine μ and r including whether they have the same sign or different signs.

That is, from equations 4 and 5, r = θ / (n-1) (1 / R ₂ -1 / R ₂ ) (6) μ = 2l ₀ (τ / 2 + r / R ₁ ) (7) However, the signs of θ and τ may be determined so that the signs of r and μ do not conflict with the measurement results.

[0035]

EXAMPLE An example of the present invention is shown in FIGS. In the optical system shown in FIG. 14, the parallel light emitted from one light source 15 is split into two light beams by the beam splitter 19 and reflected by the mirror 14,
Light is incident from above and below the lens 13 to be inspected. The light transmitted and reflected from the lens 13 to be inspected is reflected by the beam splitter and enters the eyepiece lens 17. When viewed through the eyepiece, transmitted light and reflected light are observed in a combined form in one visual field.

When the lens to be inspected is rotated, the two light spots take either of the loci shown in FIG. 11 or 12 depending on the degree of eccentricity of the lens, and the absolute amount of the shake can be read by the eyepiece chart 16. . By measuring the absolute values | θ | and | τ | of the two read shakes and the sign, the mechanical eccentricity amounts r and μ can be obtained from the equations (6) and (7).

Unlike the case of FIG. 14, the optical system shown in FIG. 15 uses two light sources. However, there are few optical elements such as mirrors and beam splitters, and the optical system is simple. The light emitted from the two light sources enters the lens to be inspected, becomes transmitted light and reflected light, respectively, enters the beam splitter, and is combined into one visual field. The amount of eccentricity of the lens is obtained by following the same procedure as in the embodiment shown in FIG.

Since the transmitted light intensity is stronger than the reflected light intensity, in order to make the brightness of the two light spots to be observed the same, the dimming filter 18 is inserted on the transmission side in both of the two examples. Is losing its strength.

[0039]

Although the conventional eccentricity measuring device is either a transmission type or a reflection type, the eccentricity measuring device of the present invention has the function of two transmission type and two reflection type. Moreover, if either the transmitted light or the reflected light is blocked, the conventional reflection type,
Alternatively, it can be used as a transmission type eccentricity measuring device.

Conventionally, it was possible to measure either the absolute value of the deflection of the transmitted light or the absolute value of the deflection of the reflected light with one measuring device. However, the apparatus of the present invention can measure the two fluctuations including the sign. As a result, it has become possible to uniquely measure the eccentricity of the lens, which is defined by two mechanical tolerances: the deviation of the outer diameter center axis with respect to the optical axis and the inclination of the principal surface.

2 was left unclear in the conventional method
The greatest advantage of the present invention is that it is possible to determine the relationship between the three deviation directions.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system of a conventional transmission type eccentricity measuring device.

FIG. 2 is a diagram showing an optical system of a conventional reflection type eccentricity measuring device.

FIG. 3 is a sectional view of a meniscus lens.

FIG. 4 is a diagram for explaining the shake of transmitted light and reflected light when the plane 3 of the meniscus lens is used as a reference.

FIG. 5: Deflection θ of transmitted light when axis deviation r is changed
The graph which shows the change of.

FIG. 6 is a graph showing changes in the deflection τ of reflected light when the axis deviation r and the surface inclination μ are changed.

FIG. 7 is a graph showing changes in | θ | with respect to r when a conventional transmission measurement device is used.

FIG. 8 is a graph showing changes in | τ | with respect to r and μ when a conventional reflection type measuring apparatus is used.

FIG. 9 is a graph showing an optical system of the eccentricity measuring device of the present invention.

FIG. 10 is a diagram showing how the transmitted light and reflected light fluctuate with respect to a lens having r> 0 and μ> 0.

FIG. 11 is a diagram showing how trajectories of transmitted light and reflected light are observed when a lens having r> 0 and μ> 0 is observed by the eccentricity measuring device of the present invention.

FIG. 12 is a diagram showing how the transmitted light and reflected light fluctuate with respect to a lens having r> 0 and μ <0.

FIG. 13 is a diagram showing how trajectories of transmitted light and reflected light are observed when a lens having r> 0 and μ <0 is observed by the eccentricity measuring device of the present invention.

FIG. 14 is a diagram showing an optical system in which one light source is divided into two light beams in an embodiment of the present invention.

FIG. 15 is a diagram showing an optical system using two light sources in an embodiment of the present invention.

[Explanation of symbols]

1 ... Convex part of meniscus lens 2 ... Side part of lens 3 ... Plane part of concave side of meniscus lens 4 ... Concave part of meniscus lens 5 ... Optical axis 6 ... Central axis of outer diameter 7 ... Two perpendicular to surface 3 in cross section Equidistant line 8 ... A line connecting a point B where the line 7 intersects the surface 1 and the center of curvature O _{1 of the} surface 9 ... Transmitted light 10 ... Reflected light 11 ... Rotating stage 12 holding the lens ... Observation surface 13 ... Lens 14 ... Mirror 15 ... Light source 16 ... Eyepiece chart 17 ... Eyepiece 18 ... Neutral filter 19 ... Beam splitter

Claims (1)

[Claims] 1. A device for measuring the eccentricity of a lens by observing the deflection of vertically incident light when the lens is rotated about the vertical bisector of the reference plane as a central axis, and the device is the same axis as the rotation axis. It has a means for injecting two light fluxes traveling in opposite directions toward both surfaces of the lens, and a means for observing the transmitted light of one light ray and the reflected light of the other light ray in the same visual field. An eccentricity measuring device characterized by the above.