JP2005308473A - Eccentricity measuring method and eccentricity measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentricity measuring method or the like capable of measuring the eccentricity amount of all the optical surfaces of an optical system equipped with a reflecting optical surface having power. <P>SOLUTION: This method is characterized by including a projecting process for projecting a light source 101 onto a prescribed position O by a projecting optical system 120, an imaging process for imaging a reflection image of the light source 101 on the light receiving surface of a CCD camera 114 by an imaging optical system 130, a reflection image position detection process for detecting the reflection image position I by the CCD camera 114, a light source object image distance changing process for changing the I-O distance L between the prescribed position O and the reflection image position I, a repeating measuring process for repeating the light source object image distance changing process and the reflection image position detection process in the state of two or more different I-O distances L corresponding to the number of the degree of eccentricity freedom of a reflection optical surface 12 when using a refraction optical surface 13 entered by light reflected by the reflection optical surface 12 as an optical surface to be measured, and an eccentricity amount calculation process for calculating the eccentricity amount of each optical surface based on a detection result of two or more reflection image position detection processes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an eccentricity measuring method and an eccentricity measuring apparatus suitable for an optical system, for example, an optical system having a reflective optical surface having power.

  In an optical system composed of a plurality of optical surfaces, it is desirable that the posture of each optical surface is maintained as designed after assembly. A state in which the posture of each optical surface after assembly is different from the design value is a state in which eccentricity exists. In such a state, the optical performance of the optical system is deteriorated. Degradation of optical performance due to decentering of the optical surface becomes more prominent as the optical system becomes smaller. For this reason, in an optical system, particularly a small optical system, it is important to perform decentration measurement after assembling with high accuracy. Hereinafter, in this specification, “measuring the posture of each optical surface after assembling a plurality of optical surfaces” is referred to as “assembled eccentricity measurement”. The configuration of an eccentricity measuring apparatus and an eccentricity measuring method for measuring assembled eccentricity according to the prior art are proposed in, for example, Patent Document 1 below.

  In recent years, an optical system used for a silver salt camera, a digital camera, an endoscope, a portable device, and the like is required to be thin and small. In order to satisfy this requirement, such an optical system often includes a reflective optical surface having power (refractive power) in the optical system. For this reason, an optical system (lens unit set) including a reflective optical surface having power is an object of assembly decentration measurement. As an optical system including a reflective optical surface having power, for example, a configuration in which an optical path of incident light is deflected by a predetermined angle and reflected to an optical path different from the optical path of incident light is known.

Japanese Patent Laid-Open No. 58-200237

  However, for example, in the prior art eccentricity measuring apparatus and the eccentricity measuring method proposed in Patent Document 1, it is difficult to measure the assembled eccentricity of an optical system having a reflective optical surface for the following reason. First, the reflected light from the reflecting optical surface is reflected so as to be deflected to an optical path different from the incident light as described above. Thereby, the light emitted from the measurement optical system and incident on the optical system to be measured is reflected in a direction different from that of the measurement optical system by the reflection optical surface. For this reason, the eccentricity measuring device and the eccentricity measuring method of the prior art cannot measure the amount of eccentricity of the reflective optical surface.

  Further, in the assembly eccentricity measurement, it is necessary to measure the amount of eccentricity of the optical surface on which the reflected light from the reflective optical surface having power enters. Here, the power and decentering of the reflecting optical surface affect the decentering measurement of the optical surface on which the reflected light is incident. For this reason, in particular, if the amount of eccentricity of the reflecting optical surface cannot be measured, the amount of eccentricity of the optical surfaces after the reflecting optical surface cannot be measured. As a result, in an optical system in which the position of the reflective optical surface is in the front (object side), it becomes impossible to measure the amount of eccentricity of most of the optical surfaces of the optical system to be measured. As described above, in the eccentricity measuring apparatus and the eccentricity measuring method of the prior art, it is difficult to measure the eccentricity of an optical system having a reflective optical surface, particularly a small optical system, with high accuracy.

  The present invention has been made in view of the above problems, and an eccentricity measuring method capable of measuring the amount of eccentricity of all optical surfaces of an optical system including a reflective optical surface having power with high accuracy in an assembled state, and An object of the present invention is to provide an eccentricity measuring device.

  In order to solve the above-described problems and achieve the object, according to the first aspect of the present invention, at least one reflective optical surface having power and at least one refractive optical surface on which light reflected by the reflective optical surface is incident. A decentering measurement method for measuring the decentering amount of each optical surface of an optical system to be measured having a light source for supplying illumination light or an illuminated indicator with respect to the optical surface to be measured of the optical system to be measured by a projection optical system Projection process for projecting to a predetermined position and imaging process for forming a reflected image of a light source or a reflected image of an index formed by reflected light from an optical surface to be measured on a light receiving surface of a photodetector by an imaging optical system And a reflected image position detecting step for detecting the position of the reflected image of the light source or the position of the reflected image of the index by the photodetector, and the measured optical surface of the measured optical system based on the detection result of the reflected image position detecting step. Process for calculating the amount of eccentricity The distance between the positions of the conjugate image of the light source by the projection optical system or the conjugate image of the index and the position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system is changed along the optical axis. Depending on the number of degrees of freedom of decentration of the reflecting optical surface when the light source object image distance changing step and at least one refractive optical surface on which the light reflected by the reflecting optical surface of the measuring optical system is incident are used as the measuring optical surface Thus, it is possible to provide an eccentricity measuring method including a repeated measurement step in which the light source object image distance varying step and the reflected image position detecting step are repeatedly performed in the state of two or more different light source object image distances.

  According to the second aspect of the present invention, each optical surface of the optical system to be measured has at least one reflective optical surface having power and at least one refractive optical surface on which light reflected by the reflective optical surface is incident. An eccentricity measuring apparatus for measuring the amount of eccentricity, comprising: a light source that supplies illumination light or an illuminated index; a projection optical system that projects the light source or index to a predetermined position with respect to the measured optical surface of the measured optical system; An imaging optical system that forms a reflected image of a light source or a reflected image of an index on a predetermined surface, which is formed by reflected light from the measurement optical surface, and is provided in the vicinity of the predetermined surface or the predetermined surface. A position detector or a position of the reflected image of the index, a position of a conjugate image of the light source or index conjugate image by the projection optical system, and a position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system To change the distance of the light source object image, which is the distance along the optical axis And a decentering amount calculation unit for calculating the decentering amount of each optical surface constituting the optical system to be measured based on the position detection result from the photodetector. When at least one refracting optical surface on which light reflected by the reflecting optical surface of the measuring optical system is incident is used as the optical surface to be measured, the conjugate of the light source by the projection optical system depends on the number of degrees of freedom of eccentricity of the reflecting optical surface. Positions in two or more different states in which the distance of the light source object image, which is the distance along the optical axis, between the position of the conjugate image of the image or index and the position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system is changed An eccentricity measuring device can be provided that calculates the amount of eccentricity of each optical surface based on the detection result.

  According to the present invention, for example, there is an effect that the amount of eccentricity of each optical surface of an optical system including a reflective optical surface having power can be measured with high accuracy in an assembled state.

  Embodiments of an eccentricity measuring apparatus and an eccentricity measuring method according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this Example.

(Principle of eccentricity measurement)
With reference to FIG. 1 and FIG. 2, the principle of the eccentricity measurement in a present Example is demonstrated. In FIG. 1, the optical system to be measured is composed of four lens surfaces S1, S2, S3, and S4. Consider a case in which the amount of eccentricity of the lens surface S4 is measured among the lens surfaces S1, S2, S3, and S4. A projection optical system (not shown) projects a light source image of the light source at a position I1 different from the apparent center of curvature position C4 of the lens surface S4. The apparent curvature center position refers to the image position of the curvature center position, which is the design value of the lens surface S4, formed by the other lens surfaces S1, S2, and S3. The lens surfaces S1, S2, and S3 exist between the lens surface S4 and the imaging optical system (not shown).

  Then, a reflection image of the light source by the lens surface S4 that is the optical surface to be measured is formed at the position I2. If all the lens surfaces S1, S2, S3, and S4 are not decentered with respect to the measurement reference axis B, a reflected image is formed at a position on the measurement reference axis B. On the other hand, if any one of the lens surfaces S1, S2, S3, and S4 is decentered, a reflected image of the light source is formed at a position I2 in a plane orthogonal to the measurement reference axis B. For this reason, the amount of eccentricity of the lens surface S4 that is the surface to be measured can be obtained from the distance of the position I2 of the reflected image with respect to the measurement reference axis B.

  In FIG. 1, the direction perpendicular to the paper surface is defined as the x direction, and the direction parallel to the paper surface is defined as the y direction. The distances from the measurement reference axis B to the position I2 of the reflected image are referred to as shake amounts Δx and Δy (hereinafter referred to as “flow amount Δ”).

  The above will be further described using mathematical expressions by taking the configuration of the four lens surfaces S1 to S4 as an example. The amount of deflection Δ can be expressed by a function having the amount of eccentricity of each lens surface, that is, the inclination ε with respect to the measurement reference axis B as a variable. In the paraxial region, the deflection amount Δ can be expressed by a linear combination of the eccentric amounts ε of the lens surfaces S1 to S4. For this reason, the deflection amount Δ can be obtained sequentially by performing paraxial ray tracing from the lens surface S1 on the measurement optical system side (not shown). For example, in the case of an optical system to be measured having four surfaces as shown in FIG. 1, the relationship between the amount of deflection Δ and the amount of eccentricity ε can be expressed by the following equation (1).

Here, as an integer of i = 1 to 4,
Δi is the amount of deflection of the reflected image by the lens surface S _i ,
ε _i is the amount of eccentricity of the lens surface S _i ,
a ₁₁ ~a _44-specific constants each lens surface _{S i} determined by the paraxial ray tracing is well known,
Respectively.

  Further, when the optical system to be measured is composed of n lens surfaces, n rows × n columns of a column vector related to the n component deflection Δ and a column vector related to the n component eccentricity ε. Can be expressed by the determinant (2). In this way, the deflection amount Δ and the eccentricity amount ε can be related by a predetermined function f.

  For this reason, by measuring the deflection Δ for each of the lens surfaces S1 to S4 constituting the measured optical system, the eccentricity ε of each of the lens surfaces S1 to S4 with respect to the measurement reference axis B is obtained based on the function f. be able to.

  Next, a basic configuration for measuring the amount of eccentricity will be described with reference to FIG. In FIG. 2, the optical system 303 to be measured includes a lens 304 and a reflective optical surface 305. The reflective optical surface 305 has an inclination with respect to the measurement reference axis B, for example, an eccentricity ε. Here, consider a case where the amount of eccentricity ε of the reflective optical surface (surface to be measured) 305 is measured.

  The lens 302 forms a light source image at the position O by the light from the light source 301 that has passed through the beam splitter 306. The position O is a position different from the apparent curvature center position C on the measurement reference axis B of the reflective optical surface 305. Note that the lens 302 combines the functions of the projection optical system and the imaging optical system. A reflected image of the light source 301 is formed at a position I by the reflected light from the reflective optical surface 305. The lens 302 forms a reflected image on the light receiving surface 307 of the photodetector via the beam splitter 306. The imaging position exists on the measurement reference axis B when there is no eccentricity.

The deflection amount Δ (primary deflection amount) by the reflection optical surface 305 and the deflection amount Δim (secondary deflection amount) on the light receiving surface 307 are expressed by the following relationship.
Δim = β × Δ
Here, β is an imaging magnification of the lens 302 that is an imaging optical system.

  Thus, the secondary shake amount Δim is uniquely determined by the magnification of the lens 302. Therefore, the shake amount Δ can be calculated based on the magnification of the lens 302 and the shake amount Δim.

(Explanation of coordinate system)
Before giving specific numerical examples, the coordinate system used in this specification will be described with reference to FIG. A case where light travels from right to left with respect to the paper surface along the optical axis AX indicated by a two-dot chain line is a reference. The signs such as the distance, the length LL, and LL ′ are positive for the amount measured from right to left with respect to the paper surface, and negative for the amount that is measured from left to right. The radius of curvature R is defined as the distance from the top V of the lens surface S to the center of curvature C. In addition, when using a coordinate system different from the definition shown in FIG. 3, the definition of a different coordinate system is mentioned each time.

(Schematic configuration of the eccentricity measuring device)
FIG. 4 shows a schematic configuration of the eccentricity measuring apparatus 100 according to the first embodiment of the present invention. The decentration measuring apparatus 100 includes a measuring optical system 150, a computer 115 serving as an eccentricity calculating unit, and a measured optical system mounting base 170. The measured optical system 160 is attached to the measured optical system mounting base 170. A prism optical system is used as the optical system 160 to be measured. This prism optical system has at least one reflecting optical surface having power and at least one refractive optical surface on which light reflected by the reflecting optical surface is incident. The configuration of the measured optical system 160 will be described later. Then, the eccentricity measuring apparatus 100 measures the amount of eccentricity of each optical surface of the optical system 160 to be measured in an assembled state. First, the configuration of the eccentricity measuring device 100 will be described, and then the principle and procedure of the eccentricity measurement will be described.

(Configuration of eccentricity measuring device)
The measurement optical system 150 includes a light source 101, a projection optical system 120, an imaging optical system 130, and a CCD camera 114 that is a photodetector. A light source 101 such as a semiconductor laser supplies illumination light for illuminating the optical system 160 to be measured. Light from the light source 101 passes through the lens 102 and enters the beam splitter 104. The lens 102 can be moved in a direction along the optical axis AX by a motor 103 which is a variable drive unit. The beam splitter 104 reflects incident light from the light source 101 and bends the optical path by 90 °. As the beam splitter 104, for example, a half mirror in which the intensity of transmitted light and the intensity of reflected light are approximately 1: 1 can be used. The light reflected by the beam splitter 104 passes through the lens 105. The lens 102 and the lens 105 constitute a projection optical system 120. The projection optical system 120 projects an image of the light source 101 at a predetermined position O with respect to the optical surface to be measured in the optical system 160 to be measured. The position O is a position different from the apparent center of curvature position of the optical surface to be measured. The apparent center of curvature position exists on the optical axis AX that coincides with the measurement reference axis B.

  Note that the indicator may be illuminated with illumination light from the light source 101. A configuration of a modified example in which the indicator is illuminated is shown in FIG. FIG. 9A shows a configuration of the illumination unit 180 when the indicator 183 is illuminated. Other configurations are the same as those shown in FIG. The light source unit 180 includes, for example, a light source 181 such as a halogen lamp, a xenon lamp, or a semiconductor laser, a condenser lens 182, and an index 183. FIG. 9-2 shows a front configuration of the pattern of the index 183. As illustrated in FIG. 9B, the index 183 includes a transmissive region in which slits are combined and a light shielding region indicated by hatching. The size t of the transmissive region pattern is approximately 1 mm. The index 183 is a secondary light source and plays the same role as the light source 101 in FIG. Then, the projection optical system 120 projects the illuminated image of the index 183 onto the position O instead of the image of the light source 101.

  Returning to FIG. The image of the light source 101 formed at the position O is projected on the optical surface to be measured. Then, a reflected image of the light source 101 (hereinafter referred to as “first reflected image”) is formed at the position I by the reflected light from the optical surface to be measured. Note that the light source 101, the projection optical system 120, and an imaging optical system 130 described later are arranged so as to be substantially coaxial with respect to the optical axis AX. Further, an interval between the position O and the position I along the optical axis AX is a light source object image distance (hereinafter referred to as “I-O distance L”). The method for taking the positive and negative signs of the IO distance L is as described in FIG. The amount of eccentricity of the optical surface to be measured is measured with reference to the measurement reference axis B. As the measurement reference axis B, for example, the optical axis AX of the measurement optical system 150 can be used as in this embodiment. Note that the measurement reference axis B may be any axis of the measurement optical system 150, for example, an axis parallel to the housing. For simplicity, the following description is based on an example in which the measurement reference axis B and the optical axis AX are matched.

  The light from the first reflected image passes through the lens 105 again. The light that has passed through the lens 105 passes through the beam splitter 104. The light that has passed through the beam splitter 104 enters the lens group 140. The lens group 140 includes three lenses 106, 107, and 108. The lens 105 and the lens group 140 constitute an imaging optical system 130. The lens 105 is used in common with the imaging optical system for the projection optical system 120. The imaging optical system 130 forms the first reflected image as a second reflected image on a predetermined surface. A CCD camera 114 corresponding to, for example, 1/3 inch, which is a photodetector, is provided on the predetermined surface or in the vicinity of the predetermined surface. Here, the predetermined surface and the light receiving surface of the CCD camera 114 are substantially matched. The CCD camera 114 captures the second reflected image. In addition, each lens structure which comprises the projection optical system 120 and the imaging optical system 130 is not restricted to the structure shown in figure, The number of lenses can be increased or decreased suitably. A computer 115 is connected to the CCD camera 114 and motors 103, 109, 110, 111, 112 and 113 which are variable drive units. The function of the computer 115 will be described later.

  The lens group 140 can be moved in a direction along the optical axis AX by a motor 112 which is a variable drive unit. By moving the lens group 140 along the optical axis AX, the first reflected image can be formed on the light receiving surface of the CCD camera 114 at a predetermined magnification. That is, the lens group 140 can change the size of the second reflected image. Furthermore, the distance between the lenses 106, 107, and 108 constituting the lens group 140 can be changed by motors 109, 110, and 111, which are variable drive units, respectively. Thus, the lens 140 is a zoom optical system. The magnification of the lens 140 is set so that the first reflected image is formed on the light receiving surface of the CCD camera 114 at a desired magnification.

  Furthermore, the motor 113 which is a variable drive unit moves the entire measurement optical system 150 along the optical axis AX. Thereby, the space | interval of the to-be-measured optical system 150 and the to-be-measured optical system 160, ie, a working distance, can be adjusted. In this way, for example, the working distance can be adjusted according to the radius of curvature of the optical surface to be measured.

(Details of the eccentricity measurement principle)
Next, the details of the principle of the eccentricity measuring method of the present invention will be described with reference to FIGS. FIG. 5 shows the optical system 125 to be measured. The measured optical system is a small optical system composed of the prism 10 and the lens 20. The prism 10 has three optical surfaces including a first surface 11, a second surface 12, and a third surface 13 in order from the incident side. The lens 20 has two optical surfaces, a fourth surface 14 and a fifth surface 15. The first surface 11 of the prism 10 has a negative (concave) refractive power (hereinafter referred to as “negative power”), and the second surface 12 has a positive (convex) refractive power (hereinafter referred to as “positive power”). The third surface 13 is a refracting surface having positive power. The prism 10 has a positive power as a whole. As a result, the prism 10 condenses the incident light beam and deflects the optical path by bending it by approximately 90 °.

The reflected light from the second surface 12 of the prism 10 is deflected by approximately 90 ° in the optical path, and therefore does not return to the measurement optical system side. For this reason, as described above, the eccentricity measuring device of the prior art cannot measure the eccentricity of the second surface 12. This corresponds to the fact that the equation of the second row component cannot be obtained in the above equation (2). Thus, for the number of eccentricity epsilon _n is unknown, the number of independent equations for missing one, it becomes impossible to determine all of the eccentricity epsilon _n.

  The amount of eccentricity of the second surface 12 contributes to the amount of deflection Δ on the optical surface after the third surface 13. In other words, the amount of deviation Δ between the third surface 13 and the fourth surface 14 includes information on the amount of eccentricity of the second surface 12. Here, it is assumed that the first IO distance L and the second IO distance L are different from each other. Then, at each IO distance, the degree of contribution of the eccentric amount of the second surface 12 to the deflection amount Δ on the optical surface after the third surface 13 is different at each IO distance.

  In consideration of these, by detecting the deflection amount Δ at the first IO distance and the second IO distance L on any optical surface after the third surface 13, one predetermined optical surface is obtained. Two mutually independent equations can be obtained for the surface. In addition, if the number of measurements with different I-O distances L is further increased, in principle, equations independent of each other can be obtained for one optical surface by the number of times of measurement of different I-O distances.

(Degree of freedom of reflection optical surface)
Next, with reference to FIG. 6, the degree of freedom of decentering that the reflecting optical surface has will be described. In the three-axis coordinate system in which the x axis, the y axis, and the z axis are orthogonal to each other, the xy plane including the origin ORG and the plane of the second plane 12 are matched. At this time, the second surface 12 has an x-axis tilt ε _y , a y-axis tilt ε _x , a z-axis tilt ε _z , an x-axis direction shift δ _x , a y-axis direction shift δ _y , and a z-axis direction shift δ _z. 6 independent degrees of freedom. Further, how to obtain positive and negative signs of the eccentricity in the x-axis tilt ε _y , the y-axis tilt ε _x , and the z-axis tilt ε _z are shown in the three coordinate systems COR on the left in FIG.

  Therefore, when measuring the amount of eccentricity of the optical system 125 shown in FIG. 5, for example, on the third surface 13, there are seven states of the first IO distance L to the seventh IO distance L. The amount of deflection Δ is detected. As a result, the same number of independent equations as the number of unknown eccentric degrees of freedom can be obtained. Specifically, with respect to the five optical surfaces of the first surface 11 to the fifth surface 15, the amount of eccentricity is calculated using the following equations (3) and (3 ').

However, each parameter indicates the following contents.
ε _1x : Tilt x component of the first surface 11 ε _1y : Tilt y component of the first surface 11 ε _2x : Tilt component around the y axis of the second surface 12 ε _2y : Tilt component around the x axis of the second surface 12 ε _2z : Z-axis tilt component δ _{2x of} the second surface 12: x-axis direction shift component δ _{2y of} the second surface 12: y-axis direction shift component δ _{2z of} the second surface 12: z-axis direction shift component of the second surface 12 ε _3x : tilt x component of the third surface 13 ε _3y : tilt y component of the third surface 13 ε _4x : tilt x component of the fourth surface 14 ε _4y : tilt y component of the fourth surface 14 ε _5x : fifth surface 15 of the tilt x component epsilon _5y: tilt y component of the fifth surface 15 delta _{1_X:} reflection image deflection amount of the x component delta _{1_Y} of the first surface 11: y component of the reflected image deflection amount of the first surface ₁₁ Δ 3a_x: No. 3 surface 13 of the first I-O distance x component of the reflected image deflection amount in a state of _L Δ 3a_y: 3 13 of the first I-O distance y components of the reflected image deflection amount in a state of _L Δ 3b_x: x component of the reflected image deflection amount in a state of the second I-O distance L of the third surface ₁₃ Δ 3b_y: No. Reflected image shake amount y component Δ _{3c_x of} the third surface 13 in the second IO distance L state: Reflected image shake amount x component Δ _{3c_y of} the third surface 13 in the third IO distance L state : Y component Δ _{3d_x} of the reflected image shake amount in the state of the third IO distance L of the third surface 13: x component of the reflected image shake amount of the third surface 13 in the state of the fourth IO distance L Δ _{3d_y} : y component of the reflected image shake amount in the state of the fourth IO distance L of the third surface 13 Δ _{3f_x} : Reflection image shake amount of the third surface 13 in the state of the fifth IO distance L x component Δ _3f — y: y component Δ _{3g —} x of reflected image deflection in the state of the fifth IO distance L of the third surface 13: third surface 13 x component Δ _{3g_y} of reflected image deflection in the state of the sixth IO distance L: y component Δ _{3h_x} of reflected image deflection in the state of the sixth IO distance L of the third surface 13: 3 surface 13 of the seventh I-O distance L in the state in the reflected image deflection amount of the x-component _{Δ 3h_y:} third surface 13 of the seventh I-O distance y component delta _{4_X} of the reflected image deflection amount in a state L : fourth surface 14 of the reflected image deflection amount of the x component delta _{4_Y:} fourth surface 14 of the reflected image deflection amount of the y component delta _{5_X:} x component of the reflected image deflection amount of the fifth surface 15 delta _{5_Y:} fifth surface 15 Y component of reflected image shake amount of

The terms Bi and Bi ′ (i = 1 to 10) on the right side are constant terms. The constant terms Bi and Bi ′ are terms having numerical values other than 0 when an eccentric amount that is a design value is intentionally given in advance. Furthermore, the coefficients a _{11 to} a ₁₀₇ and a ₁₁ ′ to a ₁₀₇ ′ on the right side can be obtained from design value data such as the radius of curvature, the surface interval, and the medium refractive index of each optical surface of the optical system 125.

  The second to eighth lines of the expressions (3) and (3 ′) indicate calculation expressions based on measurements at seven different IO distances L with respect to the third surface 13. The significance of the second to eighth lines of the expressions (3) and (3 ′) will be described. The second line is an equation for calculating the tilt component around the y-axis of the second surface 12 based on the measurement at the first IO distance L with respect to the third surface 13. The third line is an equation for calculating a tilt component around the x-axis of the second surface 12 based on the measurement at the second IO distance L with respect to the third surface 13. The fourth line is an equation for calculating a tilt component around the z-axis of the second surface 12 based on the measurement at the third IO distance L with respect to the third surface 13. The fifth line is an equation for calculating the x-axis direction shift component of the second surface 12 based on the measurement at the fourth IO distance L with respect to the third surface 13. The sixth line is an equation for calculating the y-axis direction shift component of the second surface 12 based on the measurement at the fifth IO distance L with respect to the third surface 13. The seventh line is an equation for calculating the z-axis direction shift of the second surface 12 based on the measurement at the sixth IO distance L with respect to the third surface 13. The eighth line is an equation for calculating the tilt x component of the third surface 13 based on the measurement at the seventh IO distance L with respect to the third surface 13. As described above, the decentering amounts of all the optical surfaces of the optical system 125 to be measured can be measured.

  When the change amount of the I-O distance L is small, the change amount of the contribution of the eccentric amount of the second surface 12 to the deflection amount Δ of any optical surface after the third surface 13 may be small. In this case, the amount of deflection Δ is detected on the third surface 13 to the fifth surface 15 with a total of seven IO distances L, rather than measuring with respect to the third surface 13 with the seven IO distances L. It is desirable to do. Further, when two or more measurements are performed on the same optical surface, the I-O distance L is made different from each other.

In addition, the second surface 12 may have a spherical shape and the amount of eccentricity may be relatively small. In such a case, in FIG. 6, the tilt about the x-axis ε _y and the y-axis direction shift δ _y can be treated as the same eccentric component. Similarly, the y-axis tilt ε _x and the x-axis direction shift δ _x can be treated as the same eccentric component. In this case, since the tilt ε _z around the z axis does not need to be considered, the number of effective eccentric degrees of freedom is three. As a result, a total of four (= 3 + 1) IO distance L deflection amounts Δ may be detected on the third surface 13 to the fifth surface 15. However, when two or more measurements are performed on the same surface, the I-O distance L is made different from each other.

  Thus, when the number of refractive optical surfaces on which reflected light from the reflecting optical surface is incident is n (n is an integer), and the number of independent effective eccentric degrees of freedom of the reflecting optical surface is m (m is an integer). On the refractive optical surface on which the reflected light from the reflective optical surface is incident, the deflection amount Δ may be detected with a total of m + n IO distances. However, when two or more measurements are performed on the same optical surface, the I-O distance L is made different from each other.

It is important to set an appropriate IO distance L for any optical surface. The determination of how much distance is appropriate as the IO distance L is based on the matrix components a _{11 to} a ₁₀₇ and a ₁₁ ′ to a ₁₀₇ ′ on the right side of the equations (3) and (3 ′). Determine. Preferably, it is desirable to set the I-O distance L so that the components in the same column in each row of the formulas (3) and (3 ′) have different values as much as possible.

  If it is desired to measure the approximate amount of eccentricity with slightly low accuracy, the number of m + n measurement states can be appropriately reduced. However, in order to obtain the amount of eccentricity of all optical surfaces, it is necessary to perform at least 1 + n measurements.

  In order to make the IO distance L different, the lens 102, the lens group 140, and the measurement optical system 150 in FIG. 4 can be moved in the direction along the measurement reference axis B.

(Numerical data of measured optical system)
Next, the optical system to be measured will be described based on specific numerical data. FIG. 7 shows a cross-sectional configuration of the optical system 160 to be measured. The optical system 160 to be measured is a prism optical system, and the basic configuration is the same as that of the prism 10 described in FIG. The first surface 11 of the optical system 160 to be measured is a spherical surface having a negative power, the second surface 12 is a reflecting optical surface, a spherical surface having a positive power, and the third surface 13 is a spherical surface having a positive power. The optical system 160 to be measured has a positive power as a whole and has a condensing function.

  Table 1 shows numerical data of the optical system 160 to be measured. r1, r2, and r3 are the radii of curvature of the optical surfaces, d1 and d2 are the surface spacings between the optical surfaces, and n1 and n2 are the refractive indices at the measurement light source wavelength (λ = 587.56 nm), respectively. The unit of curvature radius and surface interval is mm. In addition, as shown in FIG. 7, the signs of the radius of curvature and the surface spacing follow coordinate systems COR1, COR2, and COR3 that are different for each optical surface.

(Table 1)
First surface 11 r1 = -221.6183 d1 = 10 n1 = 1.84666
Second surface 12 r2 = -153.7985 d2 = -10 n2 = 1.84666
Third surface 13 r3 = 138.0552

(Eccentricity measurement procedure)
Next, the following procedures (A) to (I) for measuring the amount of eccentricity of the optical system 160 to be measured in this embodiment will be described.
(A) First, the above-described measured optical system 160 is attached to the measured optical system mounting base 170.

(B) For example, the following measurement condition data is input to the computer 115 that also functions as the eccentricity calculation unit.
(1) The radius of curvature r of the optical system 160 to be measured, the surface spacing d, the refractive index n,
(2) Mounting position and mounting direction of the measurement optical system 160,
(3) Degree of freedom of the second surface 12 that is a reflective optical surface,
(4) Which optical surface is to be measured at two or more different IO distances L?
In the present embodiment, there are three independent degrees of freedom of eccentricity of the second surface 12, that is, a tilt around the y axis, a tilt around the x axis, and a shift in the z axis direction. For this reason, eccentricity measurement is performed on the third surface 13 at four (= 3 + 1) different I-O distances L.

  (C) The computer 115 performs paraxial ray tracing based on the input numerical data listed in Table 1. Based on the paraxial ray tracing result, the apparent curvature center position, the optimum value of the IO distance L, and the matrix coefficients a and a ′ of the function f are calculated for each of the optical surfaces 11, 12, and 13. The matrix coefficients a and a ′ to be calculated are the first row, the second row, the third row, the seventh row, and the eighth row of the equations (3) and (3 ′) described above in the measurement principle. Corresponds to the eye component. Specific numerical data of the matrix coefficients a and a ′ are shown in the following expressions (4) and (4 ′).

  However, the unit of the eccentric amount tilt ε is “minute”, and the unit of the shift δ and the deflection amount Δ is “mm”. Table 2 shows the value of the IO distance L in each state.

(Table 2)
The first row of the equations (4) and (4 ′) (first IO distance L with respect to the first surface 11) L = 0.0
The second row of the expressions (4) and (4 ′) (first IO distance L with respect to the third surface 13) L = 0.496
The third row of the expressions (4) and (4 ′) (second IO distance L with respect to the third surface 13) L = −25.959
The fourth row of the expressions (4) and (4 ′) (the third IO distance L with respect to the third surface 13) L = −62.305
The fifth row of the expressions (4) and (4 ′) (fourth I-O distance L with respect to the third surface 13) L = 124.760

  (D) Further, the computer 115 calculates the reflection magnification of each of the optical surfaces 11, 12, and 13 and the imaging magnification of the imaging optical system 130. Then, when measuring each optical surface, the computer 115 outputs a predetermined control signal to the motors 103, 109, 110, 111, 112, 113 in accordance with the calculation result in (C). With this predetermined control signal, the projection optical system 120, the imaging optical system 130, the lens group 140, the lenses 106, 107, 108, and the measurement optical system 150 are set to a predetermined focus position and imaging magnification. That is, each of the motors 103, 109, 110, 111, 112, and 113 has the measurement optical system 150, the projection optical system 120, and the imaging optical system 130 so as to obtain a predetermined focus position and imaging magnification according to the control signal. Control the position and zoom ratio. Note that the position of the light source 101 and the CCD camera 114 (photodetector) in the direction along the measurement reference axis B can be controlled by controlling the position of the entire measurement optical system 150.

  (E) Following the above calculation, the computer 115 performs a projection process. In this projection process, the projection optical system 120 projects the light source 101 that supplies illumination light. Initially, the first surface 11 of the optical system 160 to be measured is the optical surface to be measured. Therefore, the light source 101 is projected onto the predetermined position O with respect to the first surface 11. Instead of the light source 101, an illuminated indicator may be used. By this projection process, a reflected image (first reflected image) of the light source 101 is formed by the reflected light from the first surface 11.

  (F) Next, in the imaging step, the reflected image of the light source 101 is imaged on the light receiving surface of the CCD camera 114 as a photodetector by the imaging optical system 130. As a result, a second reflected image is formed.

  (G) In the reflected image position detecting step, the position of the reflected image of the light source 101 is imaged (detected) by the CCD camera 114 which is a photodetector. Then, based on the captured image, a secondary shake amount Δim is calculated.

  (H) Next, in the eccentric amount calculating step, the eccentric amount of the first surface 11 is calculated based on the detection result of the reflected image position detecting step. Specifically, the computer 115 captures the secondary deflection amount Δim of the first surface 11 as a digital signal. Further, based on the function f of the first surface 11 expressed by the equations (4) and (4 ′), the secondary deflection amount Δim, and the imaging magnification of the imaging optical system 130, the first surface 11. The amount of eccentricity is calculated. Subsequently, the second surface 12 is measured.

  (I) In the light source object image distance varying step, the light source object image distance, that is, the I-O distance L is changed. The light source object image distance is the distance along the optical axis AX between the position O of the conjugate image of the light source 101 by the projection optical system 120 and the position I of the conjugate image of the CCD camera 114 (light receiving surface) by the imaging optical system 130. It is. When the first IO distance L is set in the light source object image distance varying step, the reflected image position detecting step is performed at the IO distance L. Next, the second IO distance L is set in the light source object image distance varying step, and the reflected image position detecting step is performed at this IO distance L. A plurality of such measurements are performed in a repeated measurement process. Thus, in the light source object image distance varying step, the reflected image position detecting step is performed on the refractive optical surface on which the light reflected by the reflecting optical surface is incident, according to the number of degrees of freedom (3) of the eccentricity of the reflecting optical surface. Repeat for two or more different IO distances L.

  Here, the number of degrees of freedom of eccentricity of the second surface 12 is three, and the number of the third surfaces 13 on which the reflected light from the second surface 12 is incident is one. Therefore, there are a total of four unknowns (= 3 + 1). Therefore, measurement is performed at four different IO distances L. Specifically, for the third surface 13, the first IO distance L, the second IO distance L, the third IO distance L, and the fourth IO distance L The deflection amount Δim is calculated for each of four different IO distances L. Thereby, all the eccentric amounts of the optical surfaces 11, 12 and 13 of the optical system 160 to be measured can be measured.

  As described above, the measurement is performed in four states with different I-O distances L on the third surface 13, so that all the optical surfaces 11, 12, 13 including the reflective optical surface having power (second surface 12) are included. Can be measured with high accuracy in a state where the optical system 160 to be measured is assembled.

  Next, an eccentricity measuring method according to Embodiment 2 of the present invention will be described with reference to FIG. The configuration of the eccentricity measuring apparatus used for the eccentricity measurement is the same as that of the eccentricity measuring apparatus 100 described in the first embodiment. The present embodiment is a decentering measurement method when the configuration of the optical system 200 to be measured is different from that of the first embodiment. In addition, about the same procedure as the eccentricity measuring method demonstrated in Example 1, the overlapping description is abbreviate | omitted and it demonstrates focusing on a different procedure.

  FIG. 8 shows a cross-sectional configuration of a measured optical system 200 to which the eccentricity measuring method according to the present embodiment is applied. In a reflective optical system including a reflective optical surface having power, a shape different from a spherical surface, for example, an anamorphic aspherical shape, a free-form surface shape, or the like may be used in order to reduce optical aberration. In such a shape different from the spherical surface, that is, a so-called aspherical shape, the curvature radius of the optical surface may not be uniquely defined. In this embodiment, when the optical surface has a free-form surface shape, the eccentricity measurement can be performed with high accuracy.

  As shown in FIG. 8, the measured optical system 200 includes two prisms 30 and 40. The first surface 21, the second surface 22, the third surface 23, the fourth surface 24, the fifth surface 25, the sixth surface 26, and the seventh surface 27 constituting the two prisms 30 and 40 are all optical having power. Surface. The second surface 22, the third surface 23, and the sixth surface 26 are free-form reflecting optical surfaces. The degrees of freedom of eccentricity of the second surface 22, the third surface 23, and the sixth surface 26 are the x-axis tilt, the y-axis tilt, the z-axis tilt, the x-axis direction shift, and the y-axis direction shift. There are a total of six with a shift in the z-axis direction.

  The free-form surface shape is a shape defined by the following equation (5). The z axis in equation (5) is the axis of the free-form surface.

Here, the first term of the equation (5) is a spherical term, and the second term is a free-form surface term.
C: curvature of vertex,
k: Conic constant (conical constant),
r = (X ² + Y ² ) ^1/2 ,
N: A natural number of 2 or more.

ただし、Ｃｊ(ｊは２以上の整数)は係数である。

However, Cj (j is an integer of 2 or more) is a coefficient.

  The first surface 21, the fourth surface 24, the fifth surface 25, and the seventh surface 27 are spherical refractive optical surfaces. The second surface 22, the third surface 23, and the sixth surface 26 are reflective optical surfaces. This reflective optical surface is a surface that deflects and reflects the optical path of incident light. For this reason, the deflection amount Δ cannot be detected from the reflected light itself from the second surface 22, the third surface 23, and the sixth surface 26. Accordingly, as described in the first embodiment, seven different IO distances (= 6 of degrees of freedom + number of optical surfaces 1) on each of the optical surfaces on which the reflected light from each reflecting optical surface is incident. Measure at L.

  Specifically, in order to measure the amount of eccentricity of the second surface 22 and the amount of eccentricity of the fourth surface 24, the fourth surface 24 is measured at first to seventh different IO distances L. . Further, in order to measure the amount of eccentricity of the third surface 23 and the amount of eccentricity of the fifth surface 25, the measurement is performed on the fifth surface 25 at different 1 ′ to 7 ′ IO distances L. Further, in order to measure the amount of eccentricity of the sixth surface 26 and the amount of eccentricity of the seventh surface 27, the measurement is performed on the seventh surface 27 in the state of different I—O distances L from 1st to 7th. .

  Further, as described in the first embodiment, numerical data of the radius of curvature r, the surface interval d, and the refractive index n of the optical system 200 to be measured are input to the computer 115. At this time, for the second surface 22, the third surface 23, and the sixth surface 26, the local curvature radii in the yz plane and the xz plane (see FIG. 7) are input. The local radius of curvature refers to the radius of curvature of the surface near the center of the region where the light beam intersects the reflective optical surface or refractive optical surface. The local curvature radius may be different between the yz plane and the xz plane. In this case, both the radius of curvature in the yz plane and the radius of curvature in the xz plane are used. However, if both radii of curvature are used, the IO distance L of the yz plane and the IO distance L of the xz plane are different. For this reason, the position of the projection optical system 120 differs between the yz plane and the xz plane. Therefore, it is desirable to detect the secondary shake amount Δim separately for the y component and the x component. In some cases, it may be sufficient to measure the approximate amount of eccentricity with a slightly reduced measurement accuracy. In such a case, sufficient measurement is possible using only the local curvature radius of the yz plane or the xz plane.

  It is also possible to perform eccentricity measurement with higher accuracy. In that case, instead of using the expressions (3) and (3 ′) or the expressions corresponding to the expressions (4) and (4 ′), it is based on design values or actual measured values of shapes by other measuring instruments. It is desirable to directly determine the amount of eccentricity using a real ray trace.

  When using the real ray trace, in addition to numerical data such as the radius of curvature r, the distance d, and the refractive index n of each optical surface, the surface shape data of the second surface 22, the third surface 23, and the sixth surface 26 are calculated by a computer. 29. As the surface shape data, design value data or measured value data is used. By using the calculation result of the real ray trace, the amount of eccentricity can be calculated with higher accuracy.

  Next, in the reflected image position detection step, the CCD camera 114 detects the secondary shake amount Δim or the light intensity distribution of the reflected image. Then, for example, the detected second-order deflection amount Δim is set as a target value (target), and optimization calculation using the least square method or the like is performed using the amount of eccentricity of each optical surface of the optical system 200 to be measured as a variable. Thereby, the amount of eccentricity of each optical surface can be calculated with higher accuracy.

  Further, in the present embodiment, even when the first surface 21, the fourth surface 24, the fifth surface 25, and the seventh surface 27 have shapes different from spherical surfaces, that is, aspherical shapes, the eccentricity can be measured by the same procedure. As described above, according to the second embodiment, even if the optical system under measurement 200 includes a plurality of reflective optical surfaces and an optical surface having a free-form surface other than a spherical surface, all the optical surfaces including the reflective optical surfaces are included. The amount of eccentricity of the optical surface can be measured with high accuracy in a state where the optical system is assembled.

  As described above, the eccentricity measuring method and the eccentricity measuring apparatus according to the present invention are useful for assembly eccentricity measurement, particularly for measuring the amount of eccentricity of all optical surfaces of an optical system including a reflective optical surface having power. is there. Although the present invention has been described based on the above embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

It is a figure explaining the eccentricity measurement principle in Example 1. FIG. It is another figure explaining the eccentricity measurement principle in Example 1. FIG. It is a figure explaining how to take the code about length etc. It is a figure which shows schematic structure of the eccentricity measuring apparatus which concerns on Example 1. FIG. It is a figure explaining the structural example of a to-be-measured optical system. It is a figure explaining the kind of eccentricity of a to-be-measured optical system. It is another figure explaining the structural example of a to-be-measured optical system. FIG. 10 is still another diagram illustrating a configuration example of an optical system to be measured in Example 2. It is a figure which shows schematic structure of the light source unit using a parameter | index. It is a figure which shows the front structure of a parameter | index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Eccentricity measurement optical system 101 Light source 102, 105, 106, 107, 108 Lens 103, 109, 110, 111, 112, 113 Motor 104 Beam splitter 114 CCD camera 115 Computer 120 Projection optical system 130 Imaging optical system 150 Measurement optical system 160 Optical system to be measured 170 Mounting base B Measurement reference axis AX Optical axis S1, S2, S3, S4 Lens surface I, O Position C Position of apparent curvature center 301 Light source 302 Lens 303 Optical system to be measured 304 Lens 305 Reflective optical surface 306 Beam splitter 307 Light receiving surface 10 Prism 20 Lens 11, 12, 13, 14, 15 Each optical surface 200 Optical system to be measured 21, 24, 25, 27 Refractive optical surface 22, 23, 26 Reflective optical surface 180 Light source unit 181 Light source 182 Condensation Lens 183 index

Claims (5)

An eccentricity measuring method for measuring an eccentricity amount of each optical surface of an optical system to be measured having at least one reflective optical surface having power and at least one refractive optical surface on which light reflected by the reflective optical surface is incident. And
A projection step of projecting a light source for supplying illumination light or an illuminated indicator onto a predetermined position with respect to the optical surface to be measured of the optical system to be measured by a projection optical system;
An image forming step of forming an image of the reflected image of the light source or the reflected image of the index formed by reflected light from the optical surface to be measured on the light receiving surface of the photodetector by an imaging optical system;
A reflected image position detecting step of detecting the position of the reflected image of the light source on the light receiving surface or the position of the reflected image of the index by the photodetector;
Based on the detection result of the reflected image position detection step, an eccentricity amount calculating step for calculating an eccentricity amount of the optical surface to be measured of the optical system to be measured, and a conjugate image of the light source or a conjugate of the index by the projection optical system A light source object image distance varying step for changing a light source object image distance, which is an interval along the optical axis between the position of the image and the position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system;
When at least one of the refractive optical surfaces on which the light reflected by the reflective optical surface of the optical system to be measured is incident is the optical surface to be measured, A decentering measurement method comprising: a repetitive measurement step of repeatedly performing a light source object image distance varying step and the reflected image position detecting step in a state of two or more different light source object image distances. The number of the refractive optical surfaces on which the light reflected by the reflective optical surface of the optical system to be measured is incident is n (n is an integer), and the number of independent degrees of eccentricity of the refractive optical surface is m (m is an integer). )
With the refractive optical surface on which the light reflected by the reflective optical surface of the optical system to be measured is incident as the optical surface to be measured, the repetitive measurement step is performed in the state of n + m different light source object image distances,
The eccentricity measuring method according to claim 1, wherein the reflected image position detecting step is performed with two or more different light source object image distances on the same optical surface to be measured. The optical system to be measured has a free-form optical surface that is a shape different from a spherical surface,
The eccentricity measuring method according to claim 1, wherein the light source object image distance is determined based on a radius of curvature in a predetermined region of the free-form surface shape.   The eccentricity measurement according to any one of claims 1 to 3, wherein in the eccentricity calculation step, a calculation result of a real ray trace based on design value data or actual measurement value data on the optical surface to be measured is used. Method. An eccentricity measuring device that measures the amount of eccentricity of each optical surface of an optical system to be measured, having at least one reflective optical surface having power and at least one refractive optical surface on which light reflected by the reflective optical surface is incident. And
A light source that provides illumination light or an illuminated indicator;
A projection optical system that projects the light source or the index onto a predetermined position with respect to the optical surface to be measured of the optical system to be measured;
An imaging optical system that forms a reflected image of the light source or a reflected image of the index on a predetermined surface, which is formed by reflected light from the optical surface to be measured;
A photodetector that is provided in the vicinity of the predetermined surface or the predetermined surface and detects the position of the reflected image of the light source or the position of the reflected image of the index;
A light source that is an interval along the optical axis between the position of the conjugate image of the light source or the conjugate image of the index by the projection optical system and the position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system A variable drive for changing the object image distance;
An eccentric amount calculation unit that calculates an eccentric amount of each optical surface constituting the optical system to be measured based on a position detection result from the photodetector;
The decentering amount calculation unit has a degree of freedom of decentering of the reflective optical surface when at least one refractive optical surface on which light reflected by the reflective optical surface of the optical system to be measured enters is the optical surface to be measured. Depending on the number of the optical axis, the position of the conjugate image of the light source or the conjugate image of the index by the projection optical system and the position of the conjugate image of the light receiving surface of the photodetector by the imaging optical system are along the optical axis. An eccentricity measuring apparatus that calculates an eccentricity amount of each optical surface based on the position detection results in two or more different states in which the light source object image distance, which is an interval, is changed.

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