JPH08233686A - Eccentricity measuring method and measuring device of aspheric surface - Google Patents

Abstract

PURPOSE: To provide an eccentricity measuring device which enables more highly accurate measurement by a more simplified measuring mechanism in measurement of eccentricity of an aspheric surface lens. CONSTITUTION: An eccentricity measuring device is provided with a lens holding device 100 to rotatably support a lens 1 to be detected, an angular displacement detecting device 200 to detect an aspheric surface 2 of the lens 1 to be detected by using a reflected laser beam 13a reflected by an angular displacement quantity on the aspheric surface 2 and an operation control device to perform operation control of both devices 100 and 200 and operation of an eccentric quantity. The lens holding device 100 is provided with an auxiliary appliance 9 to fix the lens 1 to be detected, a rotational driving mechanism 11 to rotate the auxiliary appliance 9, a turning angle detector 12a and turning angle graduations 12b to detect a turning angle of the auxiliary appliance 9, and the angular displacement detecting device 200 is provided with an angular displacement gauge 13 to measure an angular displacement quantity, a direct acting driving mechanism 15 to move the angular displacement gauge 13 in the radial direction, a moving distance detector 16a and a moving distance detector dial 16b to detect a radial distance up to the angular displacement gauge 13 from a rotary shaft 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the amount of eccentricity of an aspherical lens used for a camera lens or the like.

[0002]

2. Description of the Related Art Recently, aspherical lenses have been adopted in various optical systems such as camera lenses for improving optical performance and miniaturization. In the case of a spherical lens, it is possible to measure the amount of eccentricity by a conventional simple method by utilizing the property of being a spherical surface. For example, the transmission eccentricity measurement method,
There is a reflection type (autocollimation type) eccentricity measurement method.
However, in an aspherical lens, since the curvature varies depending on the location of the aspherical surface, the amount of decentering cannot be measured by a simple method such as a spherical lens. Therefore, a method of measuring the eccentricity of the aspherical lens has been considered so far.

For example, as in the examples disclosed in JP-A-1-296132 and JP-A-5-196540, the paraxial portion of an aspherical lens is regarded as a spherical surface and measured by the same method as a spherical lens. Then, the position of the center of curvature of the apex of the aspherical surface is grasped, and separately from that, the displacement amount of the surface close to the outer periphery of the aspherical surface is measured using a displacement meter to grasp the inclination of the aspherical surface axis, Has been devised to obtain the eccentricity amount of.

Another method is disclosed in Japanese Patent Laid-Open No. 4-340.
As disclosed in Japanese Patent No. 406, a method has been devised in which three-dimensional measurement of an aspherical surface shape is performed, and the shape data is statistically processed to determine the amount of eccentricity of the aspherical surface.

[0005]

However, the former method requires two means for detecting both the eccentricity of the paraxial portion and the amount of displacement of the surface near the outer circumference, which complicates the structure of the eccentricity measuring device. In addition, it increases the manufacturing cost of the eccentricity measuring device. Further, in the decentering measurement of the paraxial portion, since the paraxial portion of the aspherical lens is approximately regarded as a spherical surface, an error occurs due to the fact that the lens is actually an aspherical surface, which lowers the measurement accuracy.

Further, in the former method, it is premised that the surface to be measured has an ideal shape and has no astigmatism or habit, and only information in a narrow range of the paraxial portion and the portion near the outer circumference is used. . Therefore, the obtained eccentricity may differ from the eccentricity determined from the entire aspherical surface.

Further, in the latter method, since the measurement data of the three-dimensional shape is used, the measurement time becomes long and it becomes necessary to stabilize the measurement accuracy during that time. For this reason, a large investment is required in the measuring device itself and ancillary equipment in order to guarantee the desired measuring accuracy.

An object of the present invention is to provide an eccentricity measuring method and an apparatus for eccentricity measurement of an aspherical lens whose aspherical shape is already known, which enables more accurate measurement with a simpler measuring mechanism. To do.

[0009]

The above object is to provide an eccentricity measuring device for an aspherical optical element having a rotational symmetry axis, wherein the rotational symmetry axis and a predetermined measurement reference axis are substantially coincident with each other. A holding member for fixing the optical element, an angular displacement amount detecting means for detecting an angular displacement amount which is a physical amount that changes according to the inclination angle of the aspherical surface of the aspherical optical element and its direction, and the holding member. Rotation drive means for rotating the aspherical optical element relative to the angular displacement amount detection means with the measurement reference axis as the rotation center axis,
A rotation angle detection unit that detects a relative rotation angle of the aspherical optical element with respect to the angular displacement amount detection unit that is rotated and changed by the rotation drive unit, and supports the angular displacement amount detection unit, and Radial distance adjusting means capable of displacing a supporting position in a direction perpendicular to the rotation center axis, and radial distance detecting means detecting a radial distance from the rotation center axis to a supporting position of the angular displacement amount detecting means. Storage means for storing information on the aspherical shape of the aspherical optical element, the angular displacement amount detected by the angular displacement amount detecting means, and the radial distance detecting means at the time when the angular displacement amount is detected. Using the radial distance detected by the rotation angle and the rotation angle detected by the rotation angle detection means, and the information about the aspherical shape stored in the storage means, the measurement reference axis, It is realized by the eccentric measuring apparatus characterized by having rolling a central axis and a calculation unit operable to calculate an amount of eccentricity characterizing defining the spatial positional relationship between the rotational symmetry axis of the aspheric optical element.

[0010]

In the present invention, the aspherical optical element to be measured is placed on the surface of the aspherical surface to be measured by placing the aspherical optical element to be measured in a positional relationship in which the axis of rotational symmetry and a predetermined measurement reference axis are substantially in agreement. The angular displacement amount is detected at a plurality of measurement positions having the same radial distance from the measurement reference axis and different rotation angles from a predetermined reference position with the measurement reference axis as a rotation center. Here, the angular displacement amount is a physical amount that changes according to the tilt angle and its direction at a measurement position that is one point on the aspherical surface of the aspherical optical element.

Further, a radial distance common to the plurality of measurement positions and a rotation angle at each of the plurality of measurement positions,
The amount of angular displacement detected at each of the plurality of measurement positions,
And an eccentricity indicating a spatial positional relationship between the measurement reference axis and the rotational symmetry axis (aspherical axis) of the aspherical optical element by using information on the aspherical shape of the aspherical optical element that is given in advance. The amount is calculated.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, an example of the measuring method of the present invention will be described with reference to FIGS.

In the eccentricity measuring method of this embodiment, the lens 1 to be inspected having a known shape as shown in FIG. 1 is fixed with respect to the measurement reference axis (rotation axis) 3 to measure the lens 1 to be inspected. The amount of angular displacement that changes depending on the inclination angle of the surface of the aspherical surface 2, which is a power surface, and the direction thereof is measured at a plurality of measurement positions 4a, 4b, 4c, etc. at a predetermined radial distance from the measurement reference axis 3. . Next, the angular displacements at the plurality of measurement positions are calculated using the known shape of the aspherical surface 2 of the lens 1 to be measured and the eccentricity, and the calculation result and the measurement result are The supposition value when the best match is determined as the amount of eccentricity.

Here, FIG. 1 shows three positions, 4a, 4b, and 4c, for measuring the angular displacement amount, but the present invention is not limited to this, and there is no upper limit if there are two or more positions.

When measuring the amount of angular displacement, as shown in FIG. 2, the circumferences 5a, 5 are virtually drawn on the aspherical surface 2 where the radial distances 6a, 6b, 6c from the measurement reference axis 3 are constant.
While changing the measurement positions 4a, 4b, 4c along b, 5c, the amount of angular displacement of the surface of the aspherical surface 2 at each measurement position and the rotation from the measurement reference position 7 of the predetermined rotation angle to the measurement position. Corner 8 and are measured as a set of measurements.

Here, the angular displacement of the surface of the aspherical surface 2 is measured for each circumference having a constant radial distance from the measurement reference axis 3. That is, a plurality of measurement positions set on the one circumference, for example, measurement positions 4b, 4b ₁ , 4b ₂ , 4b _3, ... Set on the circumference 5b having a radius distance 6b.
The amount of angular displacement measured in each of the cases is used as a set of data in the eccentricity calculation processing described later.

In this embodiment, a physical quantity that represents a relative change depending on the size of the tilt angle at the measurement position and the direction of the tilt angle is defined as the angular displacement amount, and this is detected.

More specifically, for example, spot light having a fixed diameter such as laser light is irradiated from a predetermined direction to a measurement position on the aspherical surface 2, and spot light reflected from the spot is preliminarily set at a predetermined position. Angular displacement of the two-dimensional measurement coordinate value set on the light-receiving surface of the two-dimensional optical sensor, which corresponds to the position of the detection point of the reflected spot light, which is obtained by detecting with the two-dimensional optical sensor arranged. It can be used as a quantity.

In this embodiment, since the amount of angular displacement is a physical quantity representing a relative change, the two-dimensional measurement coordinate system set by the above two-dimensional optical sensor uses a plurality of measurements with a constant radial distance. As long as it is common between the positions, there is an effect that it can be arbitrarily set.

It is desirable that the measurement intervals of the rotation angle 8 are approximately equal to each other, but they need not be completely equal. Further, the plurality of radial distances from the measurement reference axis 3 are set as in 6a, 6b, and 6c in FIG. 2, and the circumferences 5a, 5b, and 5 having the radial distances are set.
Perform the angular displacement measurement on c. Also, the radius distance 6
Rotation angles 8 at a plurality of measurement positions 4a, 4b, 4c set on different circumferences like a, 6b, 6c.
Need not be equal to each other.

In FIG. 2, virtual circles having different radial distances are provided at three places, and measurement positions are set on those circles. However, the place and number of the circles provided in the present invention are set. Is not limited to this, and the radial distance and the number thereof are not limited as long as they are 2 or more.

Next, the amount of eccentricity of the aspherical surface is calculated from the amount of angular displacement and the rotation angle measured at a group of measuring positions set on the circumference with a constant radial distance, obtained as described above. An example of a calculation method will be shown.

In this example, first, assuming the value of the amount of eccentricity of the aspherical surface, it corresponds to the amount of angular displacement at the measurement position set on the circumference where the radial distance from which the measurement data was obtained is constant. A physical quantity (hereinafter, referred to as a calculation amount k) is simulated, and the radius distance is changed corresponding to the measurement data, and the calculation amount k at a different radius distance is obtained by the same method.
Next, using the calculation amount k calculated in this way and the actually measured angular displacement amount (hereinafter referred to as the measurement amount K), the sum of squares of the difference between the calculation amount k and the measurement amount K is used. The value of the amount of eccentricity that minimizes is obtained, and this is determined as the amount of eccentricity of the aspherical surface.

Hereinafter, a method of obtaining the calculation amount k at each of a group of measurement positions set on the circumference of a certain radial distance R will be described.

Generally, the eccentricity of an aspherical surface is the amount of deviation (hereinafter referred to as a shift amount) between the apex of the aspherical surface (intersection point of the aspherical surface axis and the aspherical surface) with respect to a certain reference axis, and the aspherical surface with respect to the reference axis. It can be expressed by the inclination of the axis (hereinafter referred to as the tilt amount), and the directions in which the shift amount and the tilt amount are generated.

A coordinate system as shown in FIG. 3, which will be described below, will be considered in order to represent a calculation formula used to calculate the amount of eccentricity. That is, consider a three-dimensional Cartesian coordinate system (x, y, z) in which the measurement reference axis 3 is the z-axis, and the vertex of the aspherical surface (intersection point of the aspherical surface and the aspherical surface) is the origin and the aspherical surface axis. Consider a three-dimensional Cartesian coordinate system (u, v, w) with w as the w axis.

When there is no eccentricity of the aspherical surface with respect to the measurement reference axis 3, it is assumed that the xyz coordinate system and the uvw coordinate system coincide with each other. If there is an aspheric eccentricity with respect to the measurement reference axis 3,
First, the uvw coordinate system is rotated clockwise by the angle α with the v axis as the rotation axis, and then the uvw coordinate system is rotated clockwise by the angle β with the u axis as the rotation axis, and then the origin of the uvw coordinate system is set to x.
By moving parallel to the point Q ₀ (x ₀ , y ₀ , 0) on the y plane, the eccentricity of the aspherical surface can be expressed. That is,
The shift amount and its direction can be calculated from x ₀ and y _0, and the tilt amount and its direction can be calculated from α and β.

Letting ε be the shift amount and θ ₁ be the angle formed by the direction in which the shift occurs with the x-axis,

[0029]

[Equation 1]

[0030]

[Equation 2]

If the tilt amount is φ, and the angle between the tilting direction and the x axis is θ ₂ ,

[0032]

(Equation 3)

[0033]

[Equation 4]

It becomes

The relationship between the coordinate values in the xyz coordinate system and the uvw coordinate system described above is obtained by considering the coordinate conversion in the three-dimensional space.

[0036]

(Equation 5)

[0037]

(Equation 6)

[0038]

(Equation 7)

It becomes In the uvw coordinate system, the equation expressing the shape of the aspherical surface having the axis of rotational symmetry is

[0040]

(Equation 8)

[0041]

[Equation 9]

It is expressed as Here, the function f (r) represents the shape of the aspherical surface 2 of the lens 1 to be inspected.

Next, let us consider a radius vector OP ₀ that moves in the xy plane and corresponds to a measurement position set on the circumference where the radial distance is constant, and let the length of OP _{0 be} the radial distance R. Also,
If the angle between the x-axis and the radius OP ₀ is θ, the point P ₀ (x,
y) is

[0044]

[Equation 10]

[0045]

[Equation 11]

It is

In this embodiment, the point P shown in FIG. 3 is the measurement position on the aspherical surface 2 of the lens 1 to be measured (position 4a in FIG. 2).
Etc.), and the point P ₀ is a projection of the point P on the xy plane.

Since R and θ are obtained as measured values, they are known, and x and y can be obtained by the equations (10) and (11). As shown in equations (8) and (9), w is a function of u and v, and assuming that (x ₀ , y ₀ , α, β) is known, in equations (5) and (6) There are two unknowns, u and v, and u and v can be obtained by solving equations (5) and (6) as simultaneous equations. Here, u and v are obtained by the convergence calculation method. That is, when the equation (5) is solved for u of the first term on the right side,

[0049]

(Equation 12)

[Mathematical formula-see original document] When equation (6) is solved for v of the first term on the right side,

[0051]

(Equation 13)

It becomes

Therefore, for example, from the expressions (10) and (11) and the values of R and θ at the point P, the values of x at the point P, x ₁ and y.
Y ₁ of the equations (12), (13)
By substituting u = x ₁ and v = y ₁ as initial values into, new values of u and v can be obtained. This new u, v is expressed by the equation (1
2) Repeat the operation of substituting u and v on the right-hand side of (13) and further obtaining new values of u and v, and judge that the difference between the substituted u and v and the obtained u and v can be ignored. The values of u and v are made to converge to the values below.

Next, when the maximum value of the inclination at the point P is γ, and the direction in which the maximum value of the inclination at the point P is the center makes the angle with the x-axis direction τ,

[0055]

[Equation 14]

[0056]

(Equation 15)

Is given by

From equations (14) and (15), τ is eliminated and

[0059]

[Equation 16]

Is obtained.

When both sides of the equation (7) are partially differentiated with respect to x,

[0062]

[Equation 17]

Then,

[0064]

(Equation 18)

It is Partially differentiating both sides of equation (5) with x,

[0066]

[Formula 19]

Then, when both sides of the equation (6) are partially differentiated with respect to x,

[0068]

(Equation 20)

Is obtained. When the simultaneous equations are solved by using the equation (18) in the equations (19) and (20),

[0070]

[Equation 21]

[0071]

[Equation 22]

Therefore, by substituting these into the equation (17),

[0073]

(Equation 23)

Is obtained.

Similarly, if both sides of the equation (7) are partially differentiated by y,

[0076]

[Equation 24]

Then,

[0078]

(Equation 25)

It is Partially differentiating both sides of equation (5) with y,

[0080]

(Equation 26)

## EQU12 ## When both sides of the equation (6) are partially differentiated with respect to y,

[0082]

[Equation 27]

Is obtained. When the simultaneous equations are solved by using the equation (25) for the equations (28) and (27),

[0084]

[Equation 28]

[0085]

[Equation 29]

Therefore, by substituting these into the equation (24),

[0087]

[Equation 30]

Is obtained.

From equations (8) and (9),

[0090]

[Equation 31]

[0091]

[Equation 32]

Therefore, equation (23) is added to equation (16),
Using (30), (31), and (32), (u, v,
By assuming that α, β) are known, the equation (1
In 6), the only unknown number is γ. As described above, u and v are obtained by assuming that the unknowns (R, θ, x ₀ , y ₀ , α, β) are known, and thus γ can be obtained.

Further, from equations (14) and (15), γ is eliminated and

[0094]

[Expression 33]

Then, τ can be obtained.

Next, letting ρ be the angle between the radius vector OP ₀ and the direction in which the maximum tilt occurs,

[0097]

(Equation 34)

There is a relationship of

Here, as shown in FIG. 4, the measurement reference axis 3
And γ when the aspherical axes match (no eccentricity),
Let γ ₀ and consider a straight line PA passing through the point P and parallel to the z-axis.
It is assumed that the surface normal at the point P is on the plane PC that passes through the point A and is parallel to the xy plane.

Let L be the distance between point P and point A.

[0101]

[Equation 35]

[0102]

[Equation 36]

And also,

[0104]

(37)

Therefore, assuming that the distance between points B and C is k, from equations (35), (36) and (37),

[0106]

(38)

It becomes:

As described above, the calculation amount k corresponding to the angular displacement amount measured at a plurality of measurement positions set on the circumference with a constant radial distance is the eccentricity amount (x ₀ , y ₀ , α, β). ), The radial distance R can be made constant, and the rotation angle θ can be used as a variable for calculation.

In the present embodiment, a new calculation amount k is obtained by changing the radial distance R in correspondence with measurement positions having different radial distances R and by the same method as above.

Hereinafter, the calculation amount k obtained as described above
A method of obtaining the amount of eccentricity from the measured amount K and the measured amount K will be described.

Here, as a means for measuring the amount of angular displacement, for example, an eccentricity measuring device to be described later, a laser light source held at a predetermined position with respect to the lens 1 to be measured is used to form an aspherical surface of the lens 1 to be measured. The laser beam is irradiated onto the laser beam 2 and the laser beam reflected by the aspherical surface 2 is received by the two-dimensional position sensor.

According to such an angular displacement amount measuring means, a measurement data string (θi, which is a value of the displacement amount and the rotation angle at the measurement position set on the virtual circumference of a certain radial distance R).
Zi) {i = 1 to n} is obtained. By using this data sequence and using the nonlinear least squares method in which the eccentricity amount (x ₀ , y ₀ , α, β) is the unknown number, the value of the eccentricity amount that is the value of the unknown number can be obtained. Here, n is the number of measurement positions set on the virtual circumference of a certain radial distance R, that is, the number of measurement data obtained at a certain radial distance P.

The measurement data Ki of the angular displacement amount is the value of the measurement amount defined above, and is specifically obtained as follows.

The laser light emitted from the laser light source and reflected by the aspherical surface 2 at each of a plurality of measurement positions set on a virtual circumference having a certain radius R is represented by x
A two-dimensional coordinate system, which is arranged so as to be parallel to the y plane (see FIG. 3), detects on the light-receiving surface of the two-dimensional position sensor and is installed on the light-receiving surface corresponding to the position detection. Find the coordinate position.

Next, the position of the least mean square center with respect to all the coordinate positions is found from the coordinate positions found at all the angular displacement measurement positions, and the least mean square center of the found least square mean is calculated. The distance between the position and each coordinate position is calculated.

Finally, an arithmetic mean value for all the obtained distances is calculated, and a value obtained by dividing the distance at each of a plurality of measurement positions having the same radial distance R by the arithmetic mean value is calculated. , And let this be Ki.

The residual function Fi used in the nonlinear least squares method used in this embodiment is

[0118]

[Formula 39]

[0119]

(Equation 40)

Is given by Here, k (θi) is a calculation amount obtained by the above-described calculation method, and is a calculation for the radial distance R and the rotation angle θi when a certain eccentricity amount (x ₀ , y ₀ , α, β) is given. The value of the quantity k.

The nonlinear least squares method that can be used in this embodiment includes the Newton-Raphson method, the Gauss-Newton method, the Levenberg-Marquardt method, and the improved methods thereof, which can be selected. is there.

The unknowns (x ₀ ,
In order to correctly obtain y ₀ , α, β), a measurement data string (θi, Ki) for two or more radial distances R is required. The reason will be described below.

When the values of the calculation amount ki and the measurement amount Ki are plotted on the ordinate and the values of the rotation angle are plotted on the abscissa, the calculation amount and the measurement amount at each measurement position have a period of 2π like a sine curve. It changes along a changing curve.

In the present embodiment, conceptually speaking, the amount of eccentricity is determined so that the curve corresponding to the measurement amount fits the curve corresponding to the calculation amount. However, when only the measurement data at one radial distance R is used, the square of the residual function Fi described above is obtained in a combination of eccentricity amounts different from the true eccentricity amount (x ₀ , y ₀ , α, β). The sum may be minimal. In the nonlinear least squares method,
This is because it is determined that the combinations of unknowns (eccentricity) that minimize the sum of squares of the residual function Fi have converged in the combinations of unknowns that produce the above-described minimum. By using the measurement data obtained at two or more radial distances R, it is possible to avoid this problem.

If the aspherical shape of the lens 1 to be inspected has no geometric deviation, the measurement data string for the two radial distances R is sufficient. By using a measurement data string for three or more (the larger the better) radial distance R, the amount of eccentricity considering the shape of the entire aspherical surface, that is, the position of the aspherical surface axis, can be obtained. Therefore, depending on the degree of geometric deviation of the aspherical shape. Good to choose.

In this embodiment, as the angular displacement measuring means,
Although the method of irradiating the aspherical surface 2 of the laser beam and receiving the reflected light by the two-dimensional position sensor is adopted and the light receiving surface is arranged perpendicular to the measurement reference axis 3, it can be used in the present invention. The arrangement position of the light receiving surface of the two-dimensional position sensor is not limited to this.

For example, the light-receiving surface of the two-dimensional position sensor can be arranged perpendicularly to the reflected light from the aspherical surface 2 or perpendicular to the normal line of the aspherical surface 2 at the observation position. Is. However, when changing the arrangement of the light-receiving surface, a measurement value that does not correspond to the above equation (38) can be obtained as the measurement quantity. Need to ask.

Next, an embodiment of the decentering measuring apparatus for an aspherical lens to which the present invention is applied will be described.

The eccentricity measuring apparatus of this embodiment is shown in FIGS.
As shown in FIG.
A lens holding device 100 that rotatably supports the lens
The amount of angular displacement of the aspherical surface 2 of the lens 1 to be inspected is reflected by the laser light 13
An angular displacement detection device 200 that detects a using a, and an arithmetic control device 300 that controls the operation of both devices and calculates the eccentricity amount.
Have and.

The lens holding device 100 has a cylindrical work 9, the end of which is in contact with the surface on the opposite side of the aspherical surface 2 which is the surface to be measured of the lens 1 to be inspected. The lens 1 to be inspected is fixed to the employment 9 by the mechanism. When the weight of the lens 1 to be inspected is large and the frictional force between the portion to be in contact with the lens 1 to be inspected 9 is sufficiently large, the frictional force is utilized to require the fixing mechanism for the lens 1 to be inspected as described above. It is also possible to adopt a structure that does not.

The lens holding device 100 further includes a rotary bearing shaft 10a to which the worker 9 is fixed and a rotary bearing shaft 10a.
A rotary drive mechanism 11 having a motor or the like for rotating the rotary shaft 3 as a central axis, a rotary bearing 10b for rotatably supporting the rotary bearing shaft 10a, and a base 17 for fixing the rotary bearing 10b. For the rotary bearing shaft 10a and the rotary bearing 10b, various types of rotary bearing mechanisms such as rolling bearings and static pressure air bearings can be used.

The lens holding device 100 further has a rotation angle detector 12a such as a rotary encoder and a rotation angle scale 12b for detecting the rotation angle of the lens 1 to be measured. In the present embodiment, the rotation angle scale 12b is attached to the rotating portion from the output shaft of the rotation drive mechanism 11 to the employment 9, and the rotation angle detector 12a for reading the scale of the rotation angle scale 12b is the base 17 or the like. It is attached to the fixed part of.

The angular displacement detecting device 200 includes an angular displacement meter 13 for measuring the amount of angular displacement described in the above embodiment and an angular displacement meter 13.
Of the linear bearing moving base 14a and the linear bearing guide 14b for holding the lens 1 under test so that the position of the lens 1 can be adjusted in the radial direction of the employee 9, and the linear motion driving the linear bearing moving base 14a. And a drive mechanism 15.

As the direct drive mechanism 15, various direct drive mechanisms such as a manual feed screw method, a feed screw method using a rotary drive device such as a motor, and a method of directly driving the direct bearing moving base by hand are used. You can A clamp mechanism may be provided between the linear motion bearing moving base 14a and the linear motion bearing guide 14b, if necessary. Linear motion bearings 14a, 14
As the b, various types of linear motion bearings such as a rolling bearing, a sliding bearing, and a static pressure air bearing can be used.

The angular displacement detecting device 300 further includes a moving distance detector 16a and a moving distance detector scale plate 1 for detecting the measurement radius distance from the rotary shaft 3 to the angular displacement meter 13.
6b. The moving distance detector scale plate 16b is attached to the base 17 via, for example, an arm member so as to be fixed to the base 17.

Here, although an optical linear scale mechanism is used as the moving distance detector 16a and the moving distance detector scale plate 16b, a magnetic linear scale mechanism, a laser displacement meter, a laser interferometer are used. It is also possible to use other moving distance detectors such as a long device and displacement gauges.

The angular displacement meter 13 is, for example, as shown in FIG. 7, a laser light source 131 for irradiating a laser beam having a predetermined diameter in parallel with the rotation axis 3 and a laser beam reflected and returned on the aspherical surface 2. Measuring the two-dimensional spot position of the light 13a,
2 with a light-receiving surface arranged so as to be orthogonal to the rotation axis 3
A laser light reflection detector having a dimensional position sensor 132 can be used. As the position sensor 132,
For example, while detecting light, such as a two-dimensional semiconductor position detection device that applies a photodiode, a two-dimensional CCD, etc.,
Various optical elements that can measure the two-dimensional position of the detected light are available.

In the above structure, since the laser beam is applied to the aspherical surface 2 in parallel to the rotation axis 3 serving as the measurement reference axis, the distance from the rotation axis 3 to the irradiation port of the laser light source 131 and the aspherical surface 2 are different. The radial distance at the measurement position of the angular displacement amount of is in agreement. Further, the distance from the rotary shaft 3 to the irradiation port of the laser light source 131 can be measured with high accuracy by the moving distance detector 16a. Therefore, according to the angular displacement meter 13 having the above configuration,
There is an advantage that a measurement error in the finally obtained amount of eccentricity is unlikely to occur.

Further, the two-dimensional position sensor 13 for the reflected laser light 13a according to the inclination angle of the aspherical surface 2 at the measurement position.
The incident point on 2 changes. Therefore, the area of the light receiving surface of the two-dimensional position sensor 132 may be increased, or the installation position of the light receiving surface may be moved in parallel so that the reflected laser light 13a can be always received.

The arithmetic and control unit 300 inputs and outputs the shape data of the aspherical surface 2 of the lens 1 to be measured, which has been measured in advance and is known, and outputs the obtained decentering amount.
A storage unit 24 for storing the input shape data of the aspherical surface 2, an interface 21 and a reading unit 22 for reading the measurement data from the movement distance detector 16a, the angular displacement meter 13 and the rotation angle detector 12a. The calculation unit 23 for obtaining the amount of eccentricity of the lens 1 to be measured from the measured data stored and the stored aspherical surface shape data, and the rotation drive mechanism 11
And a control unit 26 that controls the operation of the linear drive mechanism 15.

Next, the operation of the eccentricity measuring apparatus of this embodiment will be described.

First, as a measurement preparation, the lens 1 to be inspected is fixed on the employment 9, and the aspherical surface 2 which is the surface to be measured is fixed to the opposite side of the employment 9. Furthermore, using the linear drive mechanism 15,
The angular displacement meter 13 is moved to a predetermined radial distance on the aspherical surface 2, and the laser beam 13a of the angular displacement meter 13 is applied to the aspherical surface 2 of the lens 1 under test in a state in which the amount of angular displacement can be detected.

Next, a series of measurement processing described below is started. In this measurement process, data is taken in according to the procedure shown in the flowchart of FIG. 8, and the amount of eccentricity is obtained from the taken data.

At step 81, aspherical surface shape data such as an aspherical surface coefficient relating to the shape of the aspherical surface 2 of the lens 1 to be inspected, which is stored in advance in the storage section 24, is read out. The aspherical shape is
For example, it is represented by the following formula.

[0145]

[Formula 41]

The storage unit 24 stores, as data, the form of the above equation, the curvature that defines the above equation, and the value of each coefficient.

At step 82, the moving distance detector 16a
The detected value of is taken as the radial distance R defined in the above embodiment into the arithmetic unit 23 via the interface 21 and the reading unit 22.

Further, while the motor of the rotary drive mechanism 11 is being rotated by a command from the control unit 26, the lens 1
The output θi of the rotation angle detector 12a and the output Ki of the angular displacement meter 13 are fetched into the arithmetic unit 23 via the interface 21 and the reading unit 22 a plurality of times during one rotation of. It should be noted that the output of the rotation angle detector 12a and the output of the angular displacement meter 13 are taken into the arithmetic unit 23 at substantially equal intervals, but the intervals need not be accurate.

Furthermore, after the measurement at a certain radius distance R is completed, the linear displacement drive mechanism 15 is used to
Is moved to change the radial distance R, laser light is irradiated from the angular displacement meter 13 to a state where the angular displacement amount can be measured, and the moving distance detector 16a, the angular displacement meter 13, and the rotation angle detection are performed in the same procedure as described above. The output of the container 12a is supplied to the interface 21
Also, it is taken into the arithmetic unit 23 via the reading unit 22.

As the measurement position on the aspherical surface 2, it is necessary to measure on at least two different measurement radii R as described above. Moreover, since more information can be obtained from the surface to be measured by increasing the number of measurement positions, it is possible to more accurately measure the eccentricity amount.

In step 83, using the aspherical surface shape data read in step 82 and the measurement data of each detector taken in in step 81, the arithmetic unit 23 determines the rotation axis 3 and the aspherical surface axis. The spatial positional relationship of, that is, the amount of eccentricity from the measurement reference axis (= rotation axis) 3 is calculated. As the calculation method, the eccentricity measurement method described in the above embodiment is used. That is, using the least squares method, the measurement amount Ki corresponding to the amount of angular displacement at each measurement position on the aspherical surface 2 detected by the two-dimensional position sensor 132 and the calculation calculated corresponding to the measurement amount Ki. In order to minimize the sum of squares of the residual function Fi obtained from the quantity ki and the unknowns (x ₀ , y ₀ , α,
The value of β) is determined and these are taken as the eccentricity amount.

The calculation amount ki is a value assumed by the least-squares method for unknowns (x ₀ , y ₀ , α, β) to be obtained as the eccentricity amount, the radial distance R of the measurement position and the rotation angle θi of the measurement position. , The stored aspherical surface shape data f (r) is used to calculate using the formula described in the above embodiment shown in FIG. In the following description, the equation numbers and the symbols of variables are the same as those used in the above embodiment.

In the calculation of the calculation amount ki, from the measurement data θi and the measurement radius distance R (901), equations (10) and (1
1) is used to calculate the values of x and y, and the calculated values x and y
And the values x ₀ , y ₀ , α, β, which are assumed by the method of least squares,
And aspherical surface shape data f (r) (902), using equations (8), (9), (12), and (13), uv
The coordinate value (u, v) of the measurement position in the w coordinate system is obtained. Further, the coordinate values (u, v), the values α, β assumed by the least square method, and the aspherical surface shape data f (r) (90
3) and the formulas (16), (23) and (30) to (3).
2) is used, the maximum value γ of the inclination of the aspherical surface 2 at the measurement position is calculated using Equations (23) and (30) to (33). Angle τ
To calculate. The calculated value τ and the measurement data θi (9
05) and equation (34) is used to calculate ρ, which is the angle formed by AB and AC, as shown in FIG. 4, and the measured radius distance R and aspherical surface shape data f (r) (904) are calculated. And from
The maximum value γ ₀ of the inclination of the aspherical surface 2 at the measurement position when there is no eccentricity is calculated.

Finally, the maximum value γ of these calculated slopes
And γ ₀ and the angle ρ, a calculation amount ki (907) that is a distance between the point B and the point C as shown in FIG. 4 is virtually set at the measurement position (point P in FIG. 4). , Equation (38) is used.

In step 84, the value of (x ₀ , y ₀ , α, β) that minimizes the sum of squares of the residual function Fi obtained by the calculation process in step 83 is used as the eccentricity amount, and the display device is displayed. ,
Output to an output device such as a printer or plotter provided in the input / output unit 25.

Although only one angular displacement meter 13 is used in this embodiment, the number of angular displacement meters 13 usable in the present invention is not limited to this, and, for example, a plurality of angular displacement meters 13 are installed. However, it is also possible to simultaneously measure the angular displacement amounts on the circumference of the aspherical surface 2 at a plurality of radial distances R and to take the measured data into the calculation unit 23.

Further, in this embodiment, the displacement gauge 13 having the two-dimensional position sensor 132 arranged so that the normal line direction of the light receiving surface is parallel to the rotation axis (measurement reference axis) 3 (see FIG. 7).
However, the configuration of the angular displacement meter 13 that can be used in the present invention is not limited to this.

For example, as shown in FIG. 10, the light receiving surface is
It is also possible to use the angular displacement meter 13 having the two-dimensional position sensor 132 arranged so as to be substantially perpendicular to the reflected laser light 13a reflected by the aspherical surface 2.

According to the configuration of the angular displacement meter 13 as described above,
Similar to the angular displacement meter 13 of FIG. 7, the laser light is directed to the aspherical surface 2.
Since the irradiation is performed in parallel with the rotation axis 3 serving as the measurement reference axis, the radial distance at the measurement position on the aspherical surface 2 is calculated by the moving distance detector 1
6a makes it possible to perform measurement with high accuracy and reduce the measurement error of the finally obtained eccentricity amount.

Further, for the reflected laser light 13a, 2
Since the light receiving surface of the three-dimensional position sensor 132 is almost vertical,
There is a feature that the position detection sensitivities are equal in the radial direction at the measurement position and in the direction perpendicular to it.

Further, as the angular displacement meter 13, for example, FIG.
As shown in FIG. 2, a laser light source 131 that irradiates a laser beam substantially perpendicularly to the aspherical surface 2, and a two-dimensional position sensor 132 that detects the spot position of the reflected laser beam 13a that is reflected on the aspherical surface 2 and returns. The configuration may include a polarization beam splitter 133 and a λ / 4 plate 134 provided in the optical path between the laser light source 131 and the two-dimensional position sensor 132.

Here, linearly polarized laser light is used as the irradiation light from the laser light source 131. The linearly polarized laser light is transmitted to the polarization beam splitter 133 and the λ / 4 plate 134.
And are passed in order to make circularly polarized light. The circularly polarized reflected laser light 13 a is reflected on the aspherical surface 2 and is again reflected by the λ / 4 plate 1.
By passing through 34, linearly polarized light orthogonal to the laser light emitted from the laser light source 131 is formed. For this reason,
The optical path of the reflected laser light 13a that has passed through the λ / 4 plate 134 is bent at a right angle by the polarization beam splitter 133,
It is incident on the two-dimensional position sensor 132 whose light receiving surface is arranged at a position perpendicular to the optical path of the irradiation laser beam.

According to the configuration of the angular displacement meter 13 as described above,
Similar to the angular displacement meter 13 of FIG. 10, since the light receiving surface of the two-dimensional position sensor 132 is substantially perpendicular to the reflected laser light 13a, the position is different between the radial direction at the measurement position and the direction perpendicular thereto. It has the characteristic that the detection sensitivities are equal.

Further, the two-dimensional position sensor 13 is controlled by controlling the angle of the entire angular displacement meter 13 with respect to the aspherical surface 2 so that the laser beam is irradiated almost vertically onto the aspherical surface 2.
It is possible to prevent the position of the reflected laser beam 13a that is incident on the beam 2 from being dispersed too much.

In the configuration of FIG. 11, the laser light is emitted at a certain angle with respect to the measurement reference axis 3, so that the laser light source 13 can be formed depending on the shape of the aspherical surface 2 and the amount of eccentricity.
Even if the position of 1 does not change, the radial distance at the measurement position may not be constant. In such a case, it is advisable to provide a means for independently detecting the radial distance at the measurement position where the laser light is irradiated.

Further, in the present embodiment, by providing a detector (not shown) for detecting the displacement amount of the outer diameter portion 18 of the lens 1 to be tested due to the rotation of the lens 1 to be tested, the measurement reference axis 3 and the object to be measured are provided. An eccentricity with the outer diameter of the inspection lens 1 can be obtained. According to such a configuration, the measurement reference axis 3 obtained in the above
It is possible to know the spatial positional relationship (eccentricity amount) of the aspherical surface axis with respect to the outer diameter of the lens 1 to be tested by using the spatial positional relationship (eccentricity amount) between the aspherical surface and the aspherical surface. Further, the spatial positional relationship of the aspherical surface axis with respect to the outer diameter of the lens 1 to be inspected can also be obtained by adding a structure in which the outer diameter portion 18 of the lens 1 to be inspected is used as a reference or a structure for fixing the same. It is possible to get directly.

According to this embodiment, the angular displacement meter, which is means for obtaining the amount of eccentricity of the aspherical surface, measures the angular displacement of the surface of the aspherical surface 2 at a predetermined radial distance from the measurement reference axis. It only performs the detection and does not require a separate mechanism for paraxial eccentricity measurement. Therefore, the structure of the eccentricity measuring device can be greatly simplified, and the manufacturing cost of the eccentricity measuring device can be reduced.

Furthermore, according to this embodiment, the number of measurement positions having different radial distances can be increased by performing a very simple operation of moving the angular displacement meter in the radial direction with respect to the measurement reference axis. I can. For this reason, the amount of information obtained can be easily brought close to the information on the entire surface of the aspherical surface, so that the measurement error of the amount of eccentricity should be made smaller even on an aspherical surface having geometric deviation such as as and habit. Is possible.

Further, according to the present embodiment, the angular displacement is measured by knowing the relative change of the angular displacement between a plurality of measurement positions set on the circumference having a constant radial distance. well,
Furthermore, there is no need for an absolute relationship between measurement positions with different radial distances. Therefore, stability of measurement accuracy is required only for the time required for measurement with one radial distance.
Since the measurement time at this one radial distance can usually be shortened, according to the present embodiment, it is possible to provide a measuring device that is resistant to environmental changes and has high measurement accuracy.

[0170]

According to the present invention, when measuring the eccentricity of an aspherical lens, not only can the structure of the device be greatly simplified, but also the measurement accuracy and the eccentricity of the aspherical surface can be improved. Can be provided.

[0171]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a cross section and a measurement position of an aspherical lens to be tested in order to explain an example of an eccentricity measuring method according to the present invention.

FIG. 2 is an explanatory diagram showing an upper surface of a lens to be inspected shown in FIG. 1 and measurement positions on the upper surface.

FIG. 3 is an explanatory diagram showing two coordinate systems used in a calculation method used in an embodiment of the eccentricity measuring method according to the present invention.

FIG. 4 is an explanatory diagram for explaining a relationship among variables used in the calculation method of FIG.

FIG. 5 is an explanatory diagram showing a part of the configuration of an embodiment of the eccentricity measuring device according to the present invention.

FIG. 6 is a block diagram showing a part of the configuration of an embodiment of the eccentricity measuring device according to the present invention.

FIG. 7 is an explanatory diagram showing an example of the configuration of the angular displacement meter of the embodiment of FIG.

8 is a flowchart showing a processing operation in the embodiment of FIG.

9 is an explanatory diagram showing the relationship between variables and expressions used in the arithmetic processing in step 83 of FIG.

FIG. 10 is an explanatory diagram showing another example of the configuration of the angular displacement meter in the embodiment of FIG.

FIG. 11 is an explanatory diagram showing another example of the configuration of the angular displacement meter in the embodiment of FIG.

[Explanation of symbols]

1 ... Lens to be inspected 2 ... Aspherical surface 3 ... Measurement reference axis (rotation axis) 4a, 4b, 4c ... Angular displacement measurement position 5a, 5b, 5c ... · Locus of angular displacement measurement position 6a, 6b, 6c ··· Radial distance from measurement reference axis of angular displacement measurement position 7 · · · Measurement reference position of rotation angle of angular displacement measurement position 8 · · ..Rotation angle of angular displacement measurement position 9 .... Employment of lens to be inspected 10a ... Rotary bearing shaft 10b ... Rotary bearing 11 ... Rotation drive mechanism (motor) 12a ... Rotation angle detector (rotary encoder) 12b ... Rotation angle detector scale plate 13 ... Angular displacement meter 13a ... Reflected laser light reflected by aspherical surface 14a ... Linear bearing Moving base 14b ... ・ Linear bearing guide 15 ・ ・ ・ ・ Linear drive mechanism 16a ・ ・ ・ ・ Movement distance detection Output device 16b ・ ・ ・ ・ Movement distance detector scale plate (linear scale) 17 ・ ・ ・ ・ Measuring device base 18 ・ ・ ・ ・ Outer diameter part of the lens under test

Claims (8)

[Claims] 1. An eccentricity measuring device for an aspherical optical element having a rotational symmetry axis, comprising: a holding member for fixing the aspherical optical element in a state where the rotational symmetry axis and a predetermined measurement reference axis are substantially coincident with each other. An angular displacement amount detection unit that detects an angular displacement amount that is a physical amount that changes according to an inclination angle of the aspherical surface of the aspherical optical element and its direction, and the aspherical optical element via the holding member, A rotation driving unit that relatively rotates with respect to the angular displacement amount detecting unit with the measurement reference axis as a rotation center axis, and the aspherical surface with respect to the angular displacement amount detecting unit that changes by being rotated by the rotation driving unit. A rotation angle detecting means for detecting a relative rotation angle of the optical element, and a radial distance adjustment for supporting the angular displacement amount detecting means and enabling the support position to be displaced in a direction perpendicular to the rotation center axis. A step, a radial distance detecting means for detecting a radial distance from the rotation center axis to a supporting position of the angular displacement amount detecting means, a storage means for storing information about an aspherical shape of the aspherical optical element, An angular displacement amount detected by the angular displacement amount detection means, a radial distance detected by the radial distance detection means at the time when the angular displacement amount is detected, and a rotation angle detected by the rotation angle detection means, An eccentric amount that defines a spatial positional relationship between the rotation center axis that is the measurement reference axis and the rotational symmetry axis of the aspherical optical element by using the information about the aspherical surface shape stored in the storage unit. An eccentricity measuring device comprising: 2. The calculation device according to claim 1, wherein the calculation means uses information about the aspherical surface shape, the radial distance and the relative rotation angle, and the assumed value of the eccentricity amount,
An angular displacement amount calculation unit for calculating the value of the angular displacement amount at the measurement position detected by the angular displacement amount detection unit, a measured value detected by the angular displacement amount detection unit, and the measured value By the least squares method using the difference from the corresponding calculated value of the angular displacement amount calculation unit, the hypothetical value of the eccentricity amount that minimizes the sum of squares of the residuals is calculated, and the calculated eccentricity amount is calculated. An eccentricity measuring device having a value of eccentricity determining unit. 3. The angular displacement detecting means according to claim 1, wherein the angular displacement detecting means is supported by the radial distance adjusting means at a predetermined supporting position, and the aspherical surface is driven by the rotational driving means. An eccentricity measuring device characterized by detecting an angular displacement amount at a plurality of measurement positions having the same radial distance and different relative rotation angles, which are set by relatively rotating an optical element. 4. The angular displacement amount detecting means according to claim 1, wherein the light source unit emits light to a measurement position on the aspherical surface of the aspherical optical element, and the reflected light reflected at the measurement position is detected. An eccentricity measuring device, comprising: a light receiving section having a light receiving surface for detecting the two-dimensional coordinate position on the light receiving surface where the reflected light is detected. 5. The light source unit according to claim 4, wherein the light source unit irradiates the light in parallel with the rotation center axis, and the light receiving unit has the light receiving surface in a direction normal to the light receiving surface. An eccentricity measuring device, wherein the eccentricity measuring device is arranged so as to be parallel to a rotation center axis. 6. An eccentricity measuring method for an aspherical optical element having a rotational symmetry axis, wherein the aspherical optical element is placed in a positional relationship in which the rotational symmetry axis and a predetermined measurement reference axis are substantially coincident with each other. Located on the aspherical surface to be measured of the aspherical optical element placed in a relationship, the radial distance from the measurement reference axis is the same, and from a predetermined reference position with the measurement reference axis as the center of rotation. Rotation angles are different from each other, at a plurality of measurement positions, an angular displacement amount that is a physical quantity that changes according to the inclination angle of the aspherical surface and its direction is detected, and a radial distance at the plurality of measurement positions, and the plurality of measurement positions. The spatial position of the measurement reference axis and the rotational symmetry axis of the aspherical optical element by using the rotation angle and the angular displacement amount at each of the measurement positions and the information about the aspherical shape of the aspherical optical element. Eccentricity that represents a relationship Eccentricity determination method characterized by determining by calculation. 7. The amount of angular displacement detected at each of the plurality of measurement positions by using the information on the aspherical surface shape, the radial distance, and the rotation angle in the calculation of the eccentricity amount. The value of the physical quantity corresponding to, is calculated by assuming the value of the eccentricity, the calculation result, and the measured value of the angular displacement corresponding to the calculation result is used when the best match. An eccentricity measuring method, wherein the assumed value of the eccentricity amount is set to the value of the eccentricity amount. 8. The calculation of the eccentricity amount according to claim 6, wherein the plurality of measurement positions are calculated by using the information about the aspherical surface shape, the radial distance and the rotation angle, and the assumed value of the eccentricity amount. The value of the amount of angular displacement at each of the above is calculated, and the sum of squares of the residual function is calculated by the least square method using the residual function that represents the difference between the calculation result and the measurement result obtained at the plurality of measurement positions. An eccentricity measuring method, characterized in that a hypothetical value of the eccentricity amount to be minimized is obtained and used as the value of the eccentricity amount.