JPS58200125A - Method for measuring amount of eccentricity of lens system - Google Patents

Abstract

PURPOSE:To obtain the amount of eccentricity of a lens system to be measured readily, by combining the lens system, whose amount of eccentricity is to be measured, and an optical system, whose amount of eccentricity with respect to a reference axis displaying the amount of eccentricity is known, and measuring the amount of deflection. CONSTITUTION:In the inside of a lens mounting mechanism 10, e.g. a single lens 20 is built in advance. An amount of eccentricity epsilon with respect to a reference axis B' of said single lens 20 is already known. Under the state a photograph lens LX is attached to the lens mounting mechanism 10, each surface in the photograph lens LX are measured, and each surface of the single lens 20 in the lens mounting mechanism 10 is measured at the same time. By this measurement, the amount of deflection DELTA of a reflected image I2 by each lens surface of the photograph lens LX and the surfaces of the single lens 20 is measured. In this way, the amount of eccentricity of each surface with respect to a measuring reference axis B and the eccentricity epsilon of the two surfaces of the single lens 20 can be readily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the amount of eccentricity of a lens system with respect to a specific reference axis for which the amount of eccentricity is to be displayed.

The conventional method for quantitatively measuring the amount of eccentricity of each lens surface in a lens system with a set of 1"f is the 1-tocollimation reflection method. The collimated reflection method means that each lens surface S1, S2, .
Among S3, S4, and φ No. 1, the apparent center of curvature of the surface to be measured, for example, the surface Sl, that is, the surface to be measured caused by another surface existing between the surface to be measured and the observation system. This is a method in which an index image (1) by the index I is projected at the position A of the center of curvature of the virtual image by autocollimation, and a reflected image I2 of the same size by the surface S1 is generated at the same position as A. At this time, if there is no eccentricity on all surfaces with respect to the measurement reference axis B, the reflected image I2 of the index image 11 will be on this reference axis B.
is formed, but if there is eccentricity on either side,
The reflected image I2 is at a position shifted by Δy in the Y direction perpendicular to the reference axis B and parallel to the paper surface, or by Δ2 in the Z direction perpendicular to the paper surface.
is formed. These deflection amounts Δy and Δ2 (hereinafter abbreviated as Δ
) is proportional to the eccentricity ε of each surface, so the index image ■1 projected onto the apparent center of curvature of each surface
If such a measured value of the amount of deviation Δ is obtained, the amount of eccentricity ε of each surface with respect to this measurement reference axis B can be determined by calculation.

This autocollimation method includes, for example, the so-called lens rotation method as shown in FIG. 2(a) described in Optical Industry Technology Research Association Technical Data Vol. Examples include a lens stationary system using an image rotator as shown in FIG. 2(b) described in Japanese Patent No. 9620. The former uses a light source 1 and a lens 2 along a reference axis B to sequentially project an index onto a predetermined center of curvature position of each lens surface St, S2, S3, O, . . . of the lens system to be measured. This indexing element is reflected by the corresponding lens surface of the lens system to be measured via the half mirror 3 and the imaging lens 4 to form a reflected image I of equal magnification. Then, while rotating the lens system to be measured around the reference axis B, the reflective imager 2 is reflected laterally by the half mirror 3 to form a reflected image I2 on the imaging surface 5, and the eyepiece 6
This is a method of observing the amount of deflection Δ through. In the latter case, the line of force generated by the reference target projection optical system 7 and the image rotator 8 is applied to the measuring optical system by the half mirror 9 as the reference line B, without rotating the lens system to be measured, and similar measurements can be made. The purpose is to implement the following.

The eccentricity ε in this case means the amount of deviation of the center of curvature of each spherical surface in the lens system to be measured with respect to some reference straight line. As a reference straight line for this purpose, in the case of the lens rotation method, the rotation axis B around which the measured lens system is rotated is used, and in the case of the lens stationary method, the straight line generated by the image rotator 8 is used. . However, this reference straight line is generally set independently of the lens system to be measured, and depending on how it is set, it may result in an apparently large amount of eccentricity (even though the eccentricity of the lens system to be measured is small). For example, in the above-mentioned lens rotation method, even if the lens has little eccentricity, if it is improperly mounted to the rotation axis, there will be a large deviation from the rotation axis as a whole. For example, it may have a large eccentricity ε.
As shown in Fig. 3, if the reference axis that should originally be B' is B depending on the installation method, then each lens surface S1,
S2, S3, S4. The eccentricity of φ... is El, E2,
E3, see, but the eccentricity is el, e2. e
3. It will be measured as follows. As a conventional solution to such problems, the eccentricity ε is calculated using the least squares method, for example, for the eccentricity ε once obtained.
For example, in the case of a lens made by cone pressing, you can use a hired screw used for cone pressing to attach the lens to the axis of rotation. A method of mounting is used. However, the method of finding a new straight line by calculation, as in the former method,
It has nothing to do with the eccentricity of the lens in actual use.
For example, if there is little eccentricity within the lens system, but the entire lens system is eccentric with respect to the mount, no information about this can be obtained; This method cannot be applied to lenses that do not have screws or the like, such as photographic lenses made in mass production.

An object of the present invention is to solve the above-mentioned problems and provide a method for measuring the amount of eccentricity of a lens system, which is capable of measuring a practically useful eccentricity with respect to a reference axis. A light beam that projects an index image onto the specified position, measures the amount of deflection from the reference axis of the image reflected by the surface to be measured in the lens system to be measured using an observation optical system, and calculates the amount of eccentricity of each lens surface. In the reflection method for measuring eccentricity, the lens system to be measured for eccentricity is measured by combining the lens system whose eccentricity is to be measured with an optical system whose eccentricity is known relative to the reference axis that displays the eccentricity to measure the amount of deflection. This method is characterized by determining the amount of eccentricity of each surface of the lens system to be measured relative to the measured lens system.

The method of the present invention will be explained in detail below based on the embodiments shown in FIG. 4 and below.

In FIG. 4, Lx is a lens system to be measured, such as a photographic lens, which has a plurality of lenses whose eccentricity is to be measured individually, and this photographic lens Lx has the same structure as the lens mount of a camera. It is attached to the lens mount mechanism 10 held by the user. A practical reference for expressing the eccentric state of the photographic lens Lll is the reference axis B', and this reference axis B' is the central axis of the lens mount mechanism IO, that is, the photographic lens Lx hits the lens mount mechanism IO. This is a line that passes through the center of the cylindrical surface 12 that regulates the position of the photographic lens Lx within a plane that is perpendicular to the flange surface 11 and orthogonal to these two lens surfaces ll. Inside this lens mount mechanism 10,
It is assumed that, for example, a single lens 20 is installed in advance, and the eccentricity ε of this single lens 20 with respect to the reference axis B' is already known. The amount of eccentricity ε of the single lens 20 with respect to the reference axis B' can be easily determined by measuring it at the same time as manufacturing the lens mount mechanism 10. Preferably, the eccentricity of the single lens 20 (is reduced to 0 by cone pressing, etc.)
It is more convenient to do so because the optical axis of the single lens 20 and the reference axis B' coincide.

For actual measurements, use the photo lens L! is attached to the lens mount mechanism 10, and at the same time the individual surfaces within the photographic lens Lx are measured.
The surface of the lens 20 is also measured at the same time.

This measurement can be carried out by any method such as the above-mentioned lens rotation method or lens stationary method. In other words, by this measurement, the amount of deflection Δ of the reflected image I2 by each lens surface of the photographic lens LX and the surface of the single lens 20 is measured. Then, the amount of eccentricity 6 of each surface with respect to the measurement reference axis B and the amount of eccentricity of the two surfaces of the single lens 20 may be determined by calculation. Therefore, if the amount of eccentricity of the two surfaces of the single lens 20 with respect to the reference axis B is determined by this measurement, the reference axis B' can be determined from this.
The relationship between and reference axis B is determined, and from reference axis B to reference axis B'
By the coordinate transformation, the eccentricity ε of each lens surface of the photographic lens Lx can be expressed as the eccentricity ε with respect to the reference axis B'.

Now, the amount of deflection Δ of the reflection imager 2 due to the first surface Si in the photographic lens Lx is expressed as (Δ(yi),
Δ(2i)), and the eccentricity ε of the first surface is (t
(yi), ε(zi)), between these, Δ(yi)=a(il) ε(yl)+a(i2) ε
(y2)+ ...+a(ii) ε(yi) Δ(zi)=a(it) ε(zl)+a(i2) e
It is known that the following relationship exists: (z2)+*-...banju, a(ii)ε(21). Here, a(
il), a(i2), ee, etc. are constants that can be calculated in advance from data of the optical system.

Therefore, each surface S1, S in the photographic lens Lx consisting of the k-plane
2, S3, ..., the amount of deflection (Δ(yl)) of the reflected image I2 regarding Sk and the two surfaces Ss and Sn of the single lens 20
, Δ(21)), (Δ(!2), Δ(22)
)) 11 * * *, (Δ(yk), Δ
(zk)) and (Δ(ym), Δ(2m)), (Δ
(yn).

If Δ(zn) ) is measured, from the above relational expression,
A simultaneous equation is established, and by solving this simultaneous equation, the eccentricity of each surface with respect to the measurement reference axis B (ε(yl
), ε(zl)), (ε(I2), ε(22)),・
Fist..., (ε(yk), e (zk)) and (ε(ys
), e (z+a)) (ε(yn), ε(z
n)) can be known. Here, (@(ym),
ε(zm)), (@(yn), e(zn)) are the eccentricity of the single lens 2o with respect to the reference axis B, as described above, and on the other hand, the eccentricity of this single lens 2o with respect to the reference axis B' The eccentricity ε of each surface of the photographic lens Lx is the single lens 2
The coordinates can be converted to the reference axis B' which is the reference for the eccentricity of o and displayed.

As explained earlier, during conventional measurements, the photographic lens L
! However, the measurement may be made in a state where it is largely offset from the reference axis B' of a desirable practical display, and the amount of eccentricity may also appear to be large at first glance. However, if the measurement is performed using the method described in the embodiment of the present invention, the practical reference axis B' will also be measured indirectly through the single lens 20 at the same time as the photographic lens L11. As shown in Figure 3, by converting the coordinates from the measurement reference axis B to the practical reference axis B', el,
Practical eccentricity ε can be displayed as e2, e3, . . . .

Note that in the above embodiment, the lens mount mechanism 10
The optical system with a known eccentricity ε with respect to the reference axis B' to be incorporated into the lens 20 is assumed to be a single lens 20, but as long as the eccentricity ε is known, a plurality of lenses may be used. If the problem is the inclination of the entire lens with respect to the lens mount mechanism 10, and the allowable amount of parallel deviation is relatively large, only one surface of the parallel plane glass 21 or the photographic lens system itself is flat, as shown in FIG. It is best to use a lens system like this.

As explained above, the lens system according to the present invention is polarized.
The single center amount measuring method allows the amount of eccentricity of the lens system to be measured to be easily determined based on a specific reference axis on which the amount of eccentricity is to be displayed. Furthermore, according to the method of the present invention, it is possible to measure the eccentricity ε corresponding to the practical usage conditions of the lens system to be measured, so for example, the eccentricity ε of the lens system itself is small, but the mounting method is poor It can be used as a means of cause analysis in cases where imaging performance is degraded due to

[Brief explanation of the drawing]

Figure 1 is an illustration of the principle of the autocollimation reflection method, Figures 2 (a) and (b) are illustrations of the conventional measurement method, and Figure 3 shows how the amount of eccentricity changes depending on how the reference axis is taken. The explanatory diagrams, FIG. 4, and FIG. 5 are explanatory diagrams of an embodiment of the method for measuring the amount of eccentricity of a lens system according to the present invention, respectively. 1 is a light source, 2 is a lens, 3.9.11 is a half mirror, 14 is an imaging lens, 5 is an imaging surface, 6 is an eyepiece, 8
is the image rotator, 1o is the lens mount mechanism, 1
1 is a flange surface, 12 is a cylindrical surface, 20 is a single lens, 21
is a parallel plane glass, L is a lens system to be measured, LX is a photographic lens, ■ is an index, 11 is an index image, and I2 is a reflected image. drawing ,,. 12 1211 13I! 1 114! l lllISFigure 125

Claims (1)

[Claims] 1. Projecting an index image onto a pre-calculated position of the lens system to be measured, and measuring the amount of deflection from the reference axis of the image reflected by the surface to be measured in the lens system using an observation optical system. However, in the optical reflection method for measuring the amount of eccentricity of each lens surface by calculation, the lens system to be measured for which the amount of eccentricity is to be measured is an optical system whose amount of eccentricity is known with respect to the reference axis that displays the amount of eccentricity. A method for measuring the amount of eccentricity of a lens system, characterized in that the amount of eccentricity of each surface of the lens system to be measured with respect to the reference axis is determined by measuring the amount of deflection in combination. 2. The method for measuring the eccentricity of a lens system according to claim 1, wherein the optical system whose eccentricity with respect to the reference axis is known is a single lens. 3. The method for measuring the eccentricity value of a lens system according to claim 1, characterized in that the optical system has a known eccentricity with respect to the reference axis. 4. The method for measuring eccentricity of a lens system according to claim 1, wherein the lens system to be measured is a photographic lens, and the lens has an optical system whose eccentricity with respect to the reference axis is known built into a mount mechanism. .