JP4928952B2 - Lens evaluation method - Google Patents

Description

  The present invention relates to a lens measurement in an optical system in which a laser beam scanned by a rotating polygon mirror or the like such as a laser beam printer is converged linearly on a photosensitive member using a long lens as an example of a measurement object. Based on the positional deviation amount obtained by executing the positional deviation amount measuring method for measuring the positional deviation amount of each position and the positional deviation amount of each tilt on the entire surface, the linearity of the long lens, The present invention relates to a lens evaluation method for evaluating the focus at each scanning position.

  As a conventional method for measuring and evaluating lens characteristics, the lens to be evaluated is attached to a jig that has a structure that can measure the lens from the front and back sides and that can measure three reference spheres from the front and back. There is one that evaluates the deviation between the axis and the optical axis of the back surface (for example, see Patent Document 1). The figure shows a conventional lens measurement and evaluation method described in Patent Document 1.

  In FIG. 20, the upper surface 101a of the lens 101 supported by the jig 111 is measured, and from the comparison with the design formula of the lens 101, the XYZ position of the measurement surface of the lens 101, the A axis with the X axis as the rotation center, Y Each value, that is, the posture of the B axis with the axis as the rotation center and the C axis with the Z axis as the rotation center is determined.

  Further, the three positioning balls 111a of the jig 111 are measured, the attitude of the jig 111 is calculated from the data on the surface of the sphere, and the attitude of the lens 101 with respect to the jig position is calculated.

  Thereafter, the jig 111 is turned upside down with the lens 101 attached. After the inversion, the back surface 101b of the lens 101 is measured in the same procedure as described above, and the three positioning spheres 111a are sequentially measured, and the attitude of the lens 101 with respect to the jig position of the lens back surface 101b is calculated from these measurement results. .

  By calculating the postures of the lens surface 101a and the back surface 101b with respect to the coordinates determined from the position of the positioning sphere 111a, the lens center deviation between the surface 101a and the back surface 101b and the inclination of the measurement surface of the lens 101 are measured and evaluated. It was.

JP 2002-71344 (6th page, FIG. 2)

  However, in the conventional configuration, the optical axis of the lens surface and the optical axis of the back surface are calculated based on the three positioning balls provided on the jig for fixing the lens. In the optical system, the overall characteristics of the optical system can be evaluated. However, the optical system that scans light by sequentially using a part of the measurement surface of the lens, etc., and evaluates the optical axis deviation at each part of the measurement surface of the lens. I can't.

  For example, it is necessary to use a long lens such as a laser beam printer to scan light in a straight line with high accuracy in a scanning optical system. However, the center position of the optical axis in the scanning direction of the lens that collects light by these optical systems changes according to the position in the scanning direction of the lens due to manufacturing errors or the like, so that the vertex position at each scanning position, that is, the optical axis The center is shifted, the laser beam is not scanned in a straight line, and the signal printed on the photoconductor is undulated from the straight line, but it cannot be evaluated by the conventional evaluation method. Similarly, the positional deviation of the focal position of the beam to the photosensitive member at each position in the scanning direction cannot be evaluated, and when transferred to paper in this state, there is a problem that the printed image is distorted or blurred, Conventionally, after assembling a laser, a polygon scanner, a lens, and the like, evaluation is performed by analyzing an actual scanning signal with a camera or the like, and the lens component level cannot be evaluated.

  Furthermore, in recent years, colorization of laser beam printers has progressed, and it is necessary to transfer four colors of red, green, blue, and black to the same spot with higher accuracy in order to reproduce the synthesized colors more precisely. However, the above-mentioned linearity and defocus characteristics for each lens of the four-color scanning optical system cannot be evaluated, and there is a problem that the cause of the lens cannot be investigated sufficiently.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a lens evaluation method for evaluating the optical characteristics at each position on the measurement surface of the lens with a single lens.

  In order to achieve the above object, the present invention is configured as follows.

According to the first aspect of the present invention, (i) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in each ABC direction of the rotation direction around each XYZ axis,
(Iii) cross-sectional measurement data of the lens obtained by sequentially extracting measurement data of the cross-section of the lens parallel to the optical axis passing through the lens by a data extraction means at a measurement pitch, and the position of (ii) Of the amount of displacement, the amount of displacement of each position and the amount of each tilt on the entire measurement surface of the lens other than the amount of displacement in two directions of translation in two directions in the plane of the lens cross section, that is, a total of three directions. Using the displacement amount, the calculation unit calculates the displacement amount in the three directions,
Based on the calculation result of the displacement amount in the three directions, the translation amount and tilt of each cross section over the entire measurement surface of the lens are obtained by the calculation unit, and the obtained parallel movement amount of each cross section There is provided a lens evaluation method characterized by evaluating characteristics of the lens based on a tilt.

  With this configuration, depending on the light passing through a part of the lens, the difference between the shape measurement data of the measurement surface of the lens in the vicinity and the design formula is also obtained from the measurement data of the entire measurement surface of the lens. Based on the above, the deviation between the two parallel movement directions and the tilt direction in the predetermined direction is calculated for the measurement data of each part on the lens, and the optical axis position in each part of the lens can be calculated.

According to the second aspect of the present invention, according to the second aspect of the present invention, (i) the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens. XYZ measurement data point sequence above,
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in the direction of each tilt ABC in the rotation direction around each XYZ axis,
(Iii) Based on the amount of each displacement, each difference between the measurement data point sequence and the lens design formula is obtained by a calculation unit;
The measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the difference are approximated to each difference in the cross section of the measurement data of the cross section of the lens, which is sequentially extracted by the data extraction means at the measurement pitch. A product of an approximate inclination of a coefficient of a straight line or a quadratic curve or the like and an approximate radius of the measurement surface of the lens in the cross section is obtained by the calculation unit,
By calculating the product value as the displacement of the center position of the lens in the cross section by the calculation unit, the characteristics of the lens are evaluated based on the calculated displacement of the center position of the lens in the cross section. A lens evaluation method is provided.

  With this configuration, using the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine, without performing a separate comparison calculation with the lens design formula in the subsequent calculations, Using the difference between the measurement data and the design data output from the three-dimensional measuring machine and the measurement data itself, the optical axis position in each part of the lens is easily calculated according to the light passing through the part on the lens. be able to.

According to the third aspect of the present invention, according to the third aspect of the present invention, (i) the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens. XYZ measurement data point sequence above,
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
The measurement of the lens at the cross section of the lens by the measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch. The approximate radius of the surface is obtained by the calculation unit,
This approximate radius, the slope of a straight line approximated to each difference in the cross section of the extracted cross section of the lens, or the approximate slope of a coefficient such as a quadratic curve, and the approximate radius in the cross section Is obtained by the arithmetic unit,
By calculating the product value as a displacement of the center position of the lens in the cross section by the calculation unit, the characteristics of the lens are evaluated based on the calculated displacement of the lens center position in the cross section. A lens evaluation method is provided.

  With this configuration, by using the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine, the comparison calculation using the lens design formula is not performed separately in subsequent calculations. Even if the approximate radius R in each cross section changes using the difference between the measurement data output from the dimension measuring machine and the design data and the measurement data itself, the light easily passes through a part on the lens. The optical axis position in each part of the lens can be calculated.

  According to a fourth aspect of the present invention, there is provided the lens evaluation method according to the second aspect, wherein the method of calculating the approximate radius is a second-order least square method.

  According to this configuration, the calculation of the approximate radius can be easily performed by using a second-order least square method.

  According to the fifth aspect of the present invention, the displacement shape of the center position of the lens is approximated by the arithmetic unit on a plane perpendicular to the optical axis of the lens, and the displacement amount on the approximated perpendicular plane is calculated by the lens. In any one of the first to fourth aspects, the amount of displacement in the rotation direction in the perpendicular direction of the cross section is obtained by dividing by the arithmetic unit by the sag amount that is a value in the depth direction of A method for evaluating the described lens is provided.

  With this configuration, the amount of tilt obtained using the data on the entire measurement surface of the lens is used to calculate the amount of displacement of the center position and the sag amount in each cross section of the lens, The amount of tilt of the lens can be obtained with high accuracy, and the linearity of the scanning optical axis of the long lens can be evaluated with higher accuracy than in the case where the tilt is calculated only with conventional data on the entire surface.

  According to the sixth aspect of the present invention, the calculation unit calculates the displacement of the center position in each cross section of the lens on the plane perpendicular to the optical axis of the lens by approximating the vertical plane using a quadratic function. The calculation unit calculates a displacement amount on the approximated vertical plane using the calculated second-order coefficient, and calculates the calculation amount based on the sag amount that is a value in the depth direction of the lens. The lens evaluation method according to any one of the first to fifth aspects is provided in which the amount of positional deviation in the rotation direction in the perpendicular direction of the cross section is obtained by dividing by.

  With this configuration, the tilt amount obtained by using the data on the entire measurement surface of the lens is approximated by the displacement amount of the center position in each cross section of the lens and this displacement by a quadratic function, and this approximated function By obtaining the displacement amount and sag amount on the vertical surface obtained more and applying correction, there is variation data in the displacement amount of each center position, or there is deviation data caused by dust on the measurement surface, Even when an error is included in a part of the displacement amount, the tilt amount of the lens can be obtained with high accuracy, and compared with the conventional case where the tilt is calculated only from the entire data, the scanning optical axis of the long lens is calculated. Linearity can be evaluated with higher accuracy.

According to the seventh aspect of the present invention, (i) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in each ABC direction of the rotation direction around each XYZ axis,
(Iii) measurement data of a cross section of the lens obtained by sequentially extracting measurement data of a cross section of the lens parallel to the optical axis passing through the lens by a data extraction unit at a measurement pitch;
And (ii) out of the positional deviation amount of the lens, except for the position and the tilt deviation amount in a total of three directions of two directions of translation and tilt in the plane of the cross section of the lens. Using the amount of positional deviation at each position and the amount of positional deviation of each tilt, the calculation unit calculates the position in three directions and the amount of tilt deviation.
Further, the radius parameter in the lens cross section of the lens design formula is a value of the displacement calculation amount in the lens cross section, and the measurement data points extracted in the radius parameter value and the lens cross section The optimal radius parameter of each cross section obtained by the arithmetic unit and the optimal radius parameter of each cross section over the entire measurement surface of the lens is obtained by the arithmetic unit so that the difference from the column is minimized. There is provided a lens evaluation method characterized by evaluating a characteristic of a lens based on a parameter.

  According to this configuration, the optimum radius parameter Rybf at each cross section of the lens is obtained by comparing the shape measurement data of the measurement surface of the lens in the vicinity thereof with the design formula according to the light passing through a part on the lens. Thus, the focus position of the lens at each part of the lens can be calculated.

According to the eighth aspect of the present invention, (i) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And calculating each difference between each measurement data point sequence and the design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions in the rotational directions around the XYZ axes. ,
Data extraction means for sequentially extracting the measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the difference at a measurement pitch, and each difference in the cross section of the measurement data of the extracted cross section of the lens Approximate the function with a quadratic or higher order function, obtain this quadratic coefficient, and use the arithmetic unit to calculate a value that is twice the product of this coefficient and the square of the approximate radius of the measurement surface of the lens in the cross section. The characteristic of the lens is evaluated based on the calculated arc radius deviation amount in the cross section by calculating and calculating the value as an arc radius deviation amount in the cross section by the calculation unit. A lens evaluation method is provided.

  With this configuration, the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine is used, and the comparison calculation using the lens design formula is not performed separately in the subsequent calculations. Using the difference between the measurement data output from the dimension measuring machine and the design data, and the measurement data itself, the lens focus position deviation at each part of the lens can be calculated easily according to the light passing through the part on the lens. can do.

According to the ninth aspect of the present invention, (i) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
The measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch. The square of the difference from a quadratic function The value of the coefficient that minimizes is calculated by the calculation unit,
A value that is twice the product of the coefficient and the square of the approximate radius of the measurement surface of the lens in the cross section is obtained by the calculation unit,
A lens evaluation method is provided, wherein the characteristic of the lens is evaluated based on the arc radius deviation amount in the cross section by calculating this value as the arc radius deviation amount in the cross section by the calculation unit. To do.

According to the tenth aspect of the present invention, (i) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
For the measurement data of the YZ cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the YZ cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch, a quadratic function relating to each difference The value of the coefficient that minimizes the square of the difference from is calculated by the calculation unit,
For the measurement data of the YZ cross section of the lens sequentially extracted by the data extraction means, the calculation unit calculates the value of the coefficient that minimizes the square of the difference from the quadratic function with respect to the Z coordinate,
Using the value of the coefficient calculated later, an approximate arc radius in the YZ section of the lens is calculated by the calculation unit according to the formula: approximate arc radius = 1 / (2 × coefficient),
Using the previously calculated coefficient value and the calculated approximate arc radius in the YZ section of the lens, the deviation amount of the optical axis position in the XY section is calculated using the previously calculated coefficient and the approximate arc. Calculated by the calculation unit from the equation of the product with the radius,
The calculation unit obtains a value that is twice the product of the previously calculated coefficient and the square of the approximate radius of the measurement surface of the lens in the YZ section,
A lens evaluation method is provided, wherein the characteristic of the lens is evaluated based on the arc radius deviation amount in the cross section by calculating this value as the arc radius deviation amount in the cross section by the calculation unit. To do.

  With this configuration, the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine is used, and the comparison calculation using the lens design formula is not performed separately in the subsequent calculations. Even if the approximate radius R in each cross section changes using the difference between the measurement data output from the dimension measuring machine and the design data and the measurement data itself, the light easily passes through a part on the lens. The focus position shift of the lens at each part of the lens can be calculated.

According to the eleventh aspect of the present invention, (i) the surface of the lens held by the lens holding jig can be measured from the surface side of the lens holding jig, and the lens holding jig is inverted so that the lens Using the lens holding jig configured to be able to measure the back surface of the lens from the back side of the holding jig and having three spheres fixed to the lens holding jig, the surface side of the lens holding jig Measuring the surface of the lens and the surfaces of the three spheres;
Next, the lens holding jig is turned upside down, and the back side of the lens and the surfaces of the three spheres are measured from the back side of the lens holding jig,
Next, the coordinate axis of the surface of the lens is calculated by a calculation unit with reference to the centers of the three spheres,
Next, the coordinate axis of the back surface of the lens is calculated by the calculation unit with reference to the center of the three spheres,
Next, the data of the front and back surfaces of the lens is synthesized with the three spheres as a reference, and the characteristics of the lens on the back surface with respect to the front surface of the lens or the front surface with respect to the back surface of the lens are evaluated. A method for evaluating a lens according to any one of the embodiments -9 is provided.

  With this configuration, it is possible to evaluate the linearity and the focus position of the lens on the back surface based on the front surface or the front surface.

  According to a twelfth aspect of the present invention, in the lens holding jig, one of the two holding parts for holding the lens of the lens holding jig is one spherical surface in the vertical direction. In the state where the front and back surfaces of the end portion of the lens are supported, the lower holding portion supports the lower surface of the end portion of the lens with two spherical surfaces, and the upper surface of the end portion of the lens is supported with one spherical surface. The lens evaluation method according to the tenth aspect is provided.

  With this configuration, the lens can be stably held and evaluated without distortion.

  As described above, according to the lens evaluation method of the present invention, the linearity in the scanning direction of the light and the focus position of the long lens as an example of the measurement object can be evaluated with high accuracy. The above-described evaluation, which could not be evaluated unless it is completed as an embedded device, is realized at the stage of a single lens without making it into a device, and the lens evaluation process is greatly streamlined.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1A is a perspective view illustrating a schematic configuration of a three-dimensional shape measuring machine capable of performing the lens evaluation method according to the first embodiment of the present invention. FIG. 1B is a diagram showing a scanning path on the upper surface of the measurement object in the lens measurement by the three-dimensional shape measuring machine in the first embodiment of the present invention. FIG. 1C is a configuration diagram showing the relationship between the measuring means and the control calculation unit of the three-dimensional shape measuring machine according to the first embodiment of the present invention.

  The shape measuring machine includes a measuring probe 3 that scans the measuring surface 1a of the measuring object 1 fixed on the surface plate 7 along the scanning path 1g (FIG. 1B), and the amount of movement of the probe 3 in the Z direction. A laser measuring optical unit 2 to be measured, a laser measuring optical unit 2 and a movable body 4 which is mounted so as to be movable in the Z direction and which can be moved on a surface plate 7, together with the movable body 4 An XY stage that can move the measurement probe 3 in the XY directions and includes the X stage 5 and the Y stage 6, and a control calculation unit 90 that performs various calculation operations based on measurement information from the laser measuring optical unit 2. And a display device 95 such as a monitor for displaying measurement results and calculation results.

  The control calculation unit 90 includes a control unit 91 that performs various operation controls, a data extraction unit 92 that performs data extraction, data obtained by measurement by the measurement unit 89, a design formula of the lens 1, and a calculation result. A memory 93 that stores data and the like, and a deviation amount evaluation means 94 that evaluates the deviation amount and the like are provided. Each is controlled. The deviation amount evaluation means 94 includes an arithmetic unit 94a that performs various arithmetic operations and an evaluation unit 94b that evaluates the characteristics of the lens 1. As will be described in detail later, the measurement data point sequence and the lens 1 are described in detail. Using this design formula, the design formula of the lens 1 and the coordinate deviation amount of the measurement data point sequence are evaluated.

  The probe 3 and the laser measuring optical unit 2 function as measuring means (measuring device) 89 that measures shape coordinate data in the XYZ directions on the measuring surface 1a of the lens 1.

  In FIG. 1A, the moving body 4 on which the laser measuring optical unit 2 and the probe 3 are mounted is moved in the XY directions by the X stage 5 and the Y stage 6, and the probe 3 is an example of the measurement object 1 fixed on the surface plate 7. It moves in the Z direction along the measurement surface 1a of the long lens. The laser measuring optical unit 2 measures the amount of movement of the probe 3 in the Z direction by a known optical interference method or the like. Therefore, this shape measuring machine scans the measurement probe 3 on the measurement surface 1a of the lens 1 in the X and Y directions by the X stage 5 and the Y stage 6 so that the Z coordinate data at the XY coordinate position of the measurement probe 3 is obtained. The measuring unit 89 measures the shape of the measurement surface 1a based on the Z coordinate data column.

  At this time, the upper surface (measurement surface) 1a of the measurement object 1 is measured by the measurement probe 3 of the measurement means 89 in the scanning path 1g of the measurement probe 3 shown in FIG. 1B, and the measurement data of the XYZ coordinates on the measurement surface 1a is obtained. Measurement means 89 obtains. For example, as an example of the measuring object 1, a lens having an effective area of 70 mm in the X-axis direction and 4 mm in the Y-axis direction, data is scanned at a 0.5 mm pitch when scanning in the X-axis direction and at a 0.5 mm pitch when scanning in the Y-axis direction. When taken in by the measuring means 89, the shape measuring result on the measuring surface 1a of the lens 1 as shown in FIG. Here, as an example, it is assumed that the measurement object 1 is asymmetric in the XY axis direction, and both the XZ cross section and the YZ cross section are non-circular arcs (aspheric surfaces).

  This measurement data evaluation method will be described with reference to FIG.

  First, as described above, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is obtained by the measurement means 89 that measures the shape coordinate data in the XYZ directions on the measurement surface 1a of the lens 1 (step A1).

Next, using the measurement data point sequence obtained by the measurement means 89 and the design formula of the lens 1 stored in advance in the memory 93, the measurement data points for the design formula of the lens 1 at the same point in XY coordinates. The sum of squares of the differences between the respective points in the column is obtained by the calculation unit 94a of the deviation amount evaluation means 94, the XYZ horizontal movement of the measurement data is executed by the calculation unit 94a of the deviation amount evaluation means 94, and each X, Y, Z A, B, and C which are rotational directions around the axis are rotated by the calculation unit 94a of the deviation amount evaluation means 94, and the calculation is the position deviation amount at each position where the square sum is minimized and the position deviation amount at each tilt. The values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ are calculated by the calculation unit 94a of the deviation amount evaluation means 94 (step A2). Here, the XYZ horizontal movement means that the coordinates of the measurement data are moved so as to match the XYZ coordinates of the design data. When the lens 1 is installed in the measuring apparatus, it is not easy to install the lens 1 at the center of the XYZ coordinates of the measuring apparatus on the order of 1 mm or less. Similarly, it is not easy to install the angle in the ABC axis direction parallel to the coordinates of the measuring device. Therefore, the lens 1 is installed in the measuring apparatus with a certain degree of accuracy (1 mm or less, 3 degrees or less), and the measurement result is used so that the XYZ coordinate axis of the lens 1 becomes an ideal coordinate. By calculating the amount of deviation and offsetting the measurement result, 0 of the measurement data overlaps with 0 of the lens design.

  Next, measurement data of a predetermined cross section of the lens 1 (a cross section of the lens 1 parallel to the optical axis passing through the lens 1) is sequentially extracted by the data extraction unit 92 at a predetermined pitch (measurement pitch). Specifically, the measurement data point sequence in the XYZ direction of the YZ section of the lens 1 is sequentially extracted by the data extraction unit 92 at a pitch of 0.5 mm in the X-axis direction to obtain measurement data of each YZ section (step A3). ). Here, the predetermined cross section is a cross section of the lens shape to be evaluated, which is a cross section cut in a direction parallel to the optical axis passing through the lens 1, and in this embodiment is an XZ cross section or a YZ cross section. is there. Therefore, the predetermined cross section can be said to be a cross section of the lens 1 parallel to the optical axis passing through the lens 1, or an XZ cross section or a YZ cross section in the present embodiment. The predetermined pitch means, for example, an interval of about 5 to 100 scanning lines, and the measurement pitch in the scanning direction is 100 to 400 points. The number of scan lines is proportional to the measurement time. The number of scanning lines and the measurement pitch are determined in consideration of the poor lens shape (small number of scanning lines and pitch for lenses with good finish) and measurement tact (increasing the measurement time increases). can do. Therefore, it can be said that the predetermined pitch is a measurement pitch according to the degree of finish of the lens surface shape.

Next, with respect to the measurement data of each YZ section extracted by the data extraction means 92, among the displacement amount obtained in the step A2, two parallel movement directions in the YZ direction and the X axis in the plane of the YZ section are obtained. Except for the total amount of misalignment of the surrounding tilt A in three directions, the misalignment amount of each position and the misalignment amounts X ₁ , B ₁ , C ₁ of each tilt on the entire measurement surface 1a of the lens ₁ are used. , Misalignment amounts Y _i , Z _i , A _{i in the} three directions that minimize the sum of squares of the difference between the measurement data and the design shape data (to distinguish from the previous calculated values Y ₁ , Z ₁ , A _1, etc. , Y _p i, Z _p i, and A _p i) are calculated by the calculation unit 94a of the deviation amount evaluation means 94, and the calculation result of the positional deviation amount Y _{j in} the three directions and the X coordinate position X _j are obtained. According to each cross section, the controller 91 sequentially stores the data in the memory 93 ( Step A4). Here, i means 1, 2,..., J and the measured values taken at regular intervals. For example, when i = 1, 2,. The quantities Y _p i, Z _p i, A _p i are (Y _p 1, Z _p 1, A _p 1), (Y _p 2, Z _p 2, A _p 2),..., (Y _p j, Z _p j, A _p j). However, j means that there are 1 to j evaluation data.

  Next, the controller 91 performs the sequence of (Step A3) and (Step A4) on the entire measurement surface 1a of the lens 1 (Step A5).

Next, based on the calculation result of the displacement amount in the three directions, in other words, the calculated X coordinate position X _j and the displacement amount Y _pj are displayed on the display device 95 by the control unit 91, and the displayed graph is displayed. Based on the above, the characteristic of the lens 1, that is, the deviation of linearity from the design center position of the lens 1 in the XY cross section is evaluated by the evaluation unit 94b of the deviation amount evaluation means 94 (step A6). That is, based on the calculation result of the amount of displacement in the three directions, the amount of translation and tilt of each cross section over the entire measurement surface 1a of the lens 1 is obtained by the arithmetic unit 94a. The characteristics of the lens 1 are evaluated by the evaluation unit 94b of the shift amount evaluation means 94 on the basis of the parallel movement amount and tilt of each cross section thus obtained. The optical axis of the lens 1 can be calculated by the calculation unit 94a of the deviation amount evaluation means 94, and the linearity of the long lens 1 with a single lens can be evaluated.

  FIG. 4 shows an example of the calculation result displayed on a graph. For example, in the lens 1 used for a laser beam printer or the like that scans a laser beam in a straight line and irradiates the photosensitive member, if the graph displayed by the calculation result is closer to a straight line, higher quality printing can be performed. Judgment can be made.

  According to the configuration of the first embodiment, the shape coordinate data in the XYZ directions on the measurement surface 1a of the lens 1 is first measured by the measurement unit 89 to be measured on the measurement surface 1a of the lens 1. Obtain a measurement data point sequence. Next, by using the measurement data point sequence and the design formula of the lens 1, the shift amount evaluation means 94 evaluates the shift amount between the design formula of the lens 1 and the coordinate position of the measurement data point sequence. Next, measurement data of a predetermined cross section of the lens 1 is sequentially extracted by the data extraction unit 92 at a predetermined pitch. Next, (i) an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 obtained by the measurement unit 89, and (ii) an XYZ position and each XYZ axis in the XYZ coordinate system obtained by the deviation amount evaluation unit 94 The position extraction amount of each position and the position displacement amount of each tilt in each ABC direction of the surrounding rotation direction, and (iii) measurement data of a predetermined cross section of the lens are sequentially extracted by the data extraction means 92 at a predetermined pitch. The measurement data of the predetermined cross section is used, and the positional deviation amount of (ii) other than the positional deviation amount in the total three directions of the two parallel movement directions and the tilt in the plane of the predetermined cross section, Using the amount of displacement at each position and the amount of displacement at each tilt on the entire measurement surface 1a of the lens 1, the amount of displacement in the three directions is calculated by the calculation unit 94a. Next, based on the calculation result of the positional deviation amount in the three directions, it is sequentially stored in the memory 93 according to each cross section, and the parallel movement amount and tilt of each cross section over the entire measurement surface 1a of the lens 1 are calculated. The characteristic of the lens 1 is evaluated by the deviation amount evaluation means 94 based on the calculated parallel movement amount and tilt of each cross section. With this configuration, the optical axis of the lens 1 can be calculated by the calculation unit 94a at each part in the measurement surface 1a of the lens 1, and the linearity of the long lens 1 as a single lens is evaluated. can do.

  In the first embodiment, the measurement pitch in the XY direction is 0.5 mm. However, the present invention is not limited to this value, and the same effect can be obtained. Good.

(Second Embodiment)
Hereinafter, a lens evaluation method according to the second embodiment of the present invention will be described with reference to FIG. As in the first embodiment, first, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement means 89 of the three-dimensional shape measuring machine capable of performing the lens evaluation method (step B1).

Next, using the measurement data point sequence obtained by the measurement means 89 and the design formula of the lens 1 stored in advance in the memory 93, the measurement data points for the design formula of the lens 1 at the same point in XY coordinates. The sum of squares of the differences between the respective points in the column is obtained by the calculation unit 94a of the deviation amount evaluation means 94, the XYZ horizontal movement of the measurement data is executed by the calculation unit 94a of the deviation amount evaluation means 94, and each X, Y, Z A, B, and C, which are rotational directions around the axis, are rotated by the calculation unit 94a of the deviation amount evaluation means 94, and a positional deviation amount at each position in the XYZ directions and a positional deviation amount at each tilt at which the square sum is minimized. The calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ are calculated by the calculation unit 94a of the deviation amount evaluation means 94 (step B2).

Next, each difference Zd between each measurement data point sequence and the design formula of the lens 1 is obtained based on each displacement amount. That is, the position shift amount of each position in the XYZ directions and the position shift amounts X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ of each tilt are coordinated by the arithmetic unit 94a using a determinant or the like. For the converted measurement data, {(measurement data) − (design data)} at the same point in the XY coordinates using the design data obtained for each position and each tilt using the design formula of the lens 1 The Z value Zd _i is sequentially calculated by the calculation unit 94a of the deviation amount evaluation means 94, and is stored in the memory 93 by the control unit 91 as the X coordinate position X _i , the positional deviation amount Y _pi , and the positional deviation amount Zd _i (step 93). B3).

  Next, FIG. 6 shows an example in which the data point sequence that is the calculated displacement amount is plotted on the display device 95 by the control unit 91 in a graph. In FIG. 6, the value in the Z-axis direction is a value of Zd = {(measurement data) − (design formula)} at the same point in the XY coordinates.

Next, the measurement data of the predetermined cross section of the lens 1 and the difference Zd are sequentially extracted by the data extraction means 92 at a predetermined pitch. Specifically, XYZ measurement data point sequences of the YZ cross section of the lens 1 are sequentially extracted by the data extraction unit 92 at a pitch of 0.5 mm in the X-axis direction. That is, a data string (Y _i , Zd _i ) at the j-th position in the X-axis direction (where i = 1 to 9, j is measurement data of 9 points 1 to 9, and these 9 points are Are sequentially extracted by the data extraction means 92 to obtain a measurement data string of each YZ section (step B4). Note that the maximum value of i is 9 in the measurement example in FIG. 6, an area of ± 2 mm in the Y direction is measured at a pitch of 0.5 mm, and the number of scanning lines is 4 / 0.5 + 1. It is because it becomes = 9. Here, data is handled in a two-dimensional array. When the array in the Y-axis direction is represented by i, the X-axis direction is represented by j. If a sequence of coordinate values measured by XYZ is stored in a two-dimensional array according to the arrangement of measurement points, X (i, j), Y (i, j), and Z (i, j) These are arranged on the actual XY (ij) plane.

Next, with respect to the measurement data string i of each YZ section extracted by the data extraction unit 92, the coefficients a _j and b that minimize the square of the difference from the quadratic function of Zd = a * Y * Y + b * Y + c. The values of _j and c _j are calculated by the calculation unit 94a of the deviation amount evaluating means 94, and stored in the memory 93 by the control unit 91 together with the value of the X coordinate position _Xj (step B5).

  Next, the controller 91 performs the sequence of (Step B4) and (Step B5) on the entire measurement surface 1a of the lens 1 (Step B6).

Next, a straight line approximated to each difference Zd in the cross section of the measurement data of the predetermined cross section obtained by sequentially extracting the measurement data of the predetermined cross section of the lens and the difference Zd by the data extraction unit 92 at a predetermined pitch. Or the approximate slope of the coefficients such as a quadratic curve and the approximate radius R of the measurement surface 1a of the lens 1 in the cross section is obtained by the calculation unit 94a. Specifically, using the value of the coefficient b _j at the calculated X coordinate position X _j and the approximate arc radius R of the lens 1 in the YZ section, the amount of deviation of the optical axis position in the XY section ΔY _j is calculated by the calculation unit 94a of the deviation amount evaluation means 94 using the equation _: ΔY _j = b _j * R (step B7). Here, if Y = 0 is the center of the optical axis, ΔY _j is the optical axis center.

  Here, the content of the calculation formula will be briefly described with reference to FIGS. 7A and 7B.

The apex position in the Y-axis direction of the design data of the lens 1 is y ₀ and the shape of the lens 1 is f ₀ (y).

Moreover, the vertex position of the Y-axis direction of the measuring surface 1a of the lens 1 is processed deviates from the Y axis center and y _1, the measurement data and f _{1 (y).}

When an arc of radius R is approximated by a quadratic function,
f ₀ (y) = 1 / (2R) * (y−y ₀ ) ² + c
f ₁ (y) = 1 / (2R) * (y−y ₁ ) ² + c ′
Then, when {(measurement data) − (design data)} is obtained by the calculation unit 94a of the deviation amount evaluation means 94,
f ₁ (y) −f ₀ (y) = ΔY * (y ₀ −y ₁ ) / R + c ″
And approximated by straight line data.

That is, the YZ cross-sectional data of the aligned data is linearly approximated by the calculation unit 94a of the deviation amount evaluation unit 94, and the approximate inclination b _j = (f ₁ (y) −) by the calculation unit 94a of the deviation amount evaluation unit 94. By multiplying f ₀ (y)) / (y ₀ −y ₁ ) by the design radius R, it can be mathematically explained that the center shift amount dY (shift amount ΔY _j of the optical axis position) can be calculated (here. 7B, see two triangles A and B. From the triangle similarity, y / (2R) = z / y z = y ² / (2R)).

Next, the sequence of (step B7) is performed on the entire measurement surface 1a of the lens 1 for each X coordinate position _Xj by the control unit 91 (step B8).

Next, the calculation unit 94a calculates the value of the product as the displacement of the center position of the lens 1 in the cross section, so that the calculated displacement of the center position of the lens 1 in the cross section is calculated. The characteristics of the lens 1 are evaluated. Specifically, a graph is displayed on the display device 95 by the control unit 91 with respect to the calculated X coordinate position X _j and the displacement of the center position of the lens 1, that is, the deviation amount ΔY _j of the optical axis position, and based on the displayed graph. Then, the characteristic of the lens 1, that is, the lens linearity in the scanning direction in the XY cross section is evaluated by the evaluation unit 94b of the deviation amount evaluation means 94 (in other words, the lens linearity is determined in Step B7, Step B8, Step B9) (Step B7 to Step B9). As the calculation result, an output similar to the form shown in FIG. 4 is obtained.

  With the configuration according to the second embodiment, the difference between the shape measurement data output from a conventional measuring machine such as a three-dimensional shape measuring machine and the design shape data (design data) stored in the memory 93 or the like is obtained. By using the difference between the measurement data output from the measuring means 96 of the three-dimensional shape measuring machine and the design data, and the measurement data itself, without using a separate comparison calculation in the lens design formula in the subsequent calculations. In addition, in accordance with the light passing through a part on the lens 1, the shift of the optical axis position in each part of the lens 1 (in other words, the displacement of the center position of the lens) can be calculated. Therefore, the characteristics of the lens can be evaluated based on the calculated displacement of the center position of the lens in the cross section.

In the second embodiment, the positional deviation amounts Y _pi and Zd _i data are approximated by a quadratic function, but may be approximated by a linear function or a function of third or higher order. Obtainable.

(Third embodiment)
The lens evaluation method according to the third embodiment of the present invention will be described below with reference to FIG. As in the first embodiment, first, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement means 89 of the three-dimensional shape measuring machine capable of performing the lens evaluation method (step C1).

Next, using the measurement data point sequence obtained by the measurement means 89 and the design formula of the lens 1 stored in advance in the memory 93, the measurement data points for the design formula of the lens 1 at the same point in XY coordinates. The sum of squares of the differences between the respective points in the column is obtained by the calculation unit 94a of the deviation amount evaluation means 94, the XYZ horizontal movement of the measurement data is executed by the calculation unit 94a of the deviation amount evaluation means 94, and each X, Y, Z A, B, and C, which are rotational directions around the axis, are rotated by the calculation unit 94a of the deviation amount evaluation means 94, and a positional deviation amount at each position in the XYZ directions and a positional deviation amount at each tilt at which the square sum is minimized. The calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ are calculated by the calculation unit 94a of the deviation amount evaluation means 94 (step C2).

Next, the XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means 94 for evaluating the design shift of the lens 1 and the coordinate shift amount of the measurement data point sequence, and the respective ABC directions of the rotation directions around the XYZ axes, Based on the positional deviation amount of each position and the positional deviation amount of each tilt, each calculation unit 94a obtains each difference Zd between each measurement data point sequence and the design formula of the lens 1. Specifically, the coordinate conversion is performed by the calculation unit 94a using the positional deviation amount of each position in the XYZ directions and the positional deviation amounts X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ of each tilt. For the measurement data, using the design data obtained for each position and each tilt using the design formula of the lens 1, Z of {(measurement data)-(design data)} at the same point in the XY coordinates is used. The value Zd _i is sequentially calculated by the calculation unit 94a of the deviation amount evaluation means 94, and is stored in the memory 93 by the control unit 91 as the X coordinate position X _i , the positional deviation amount Y _pi , and the positional deviation amount Zd _i (step C3).

Next, the measurement data of the predetermined cross section of the lens 1 and the difference Zd are sequentially extracted by the data extraction means 92 at a predetermined pitch. Specifically, XYZ measurement data point sequences of the YZ cross section of the lens 1 are sequentially extracted by the data extraction unit 92 at a pitch of 0.5 mm in the X-axis direction. That is, the data string (Y _i , Zd _i ), (Y _i , Z _i ) at the j-th position in the X-axis direction (where i = 1 to 9, j is 9 points of measurement data from 1 to 9) These are calculated using the nine points) by the data extraction means 92 in order to obtain a measurement data string for each YZ section (step C4). Note that the maximum value of i is 9 in the measurement example in FIG. 6, an area of ± 2 mm in the Y direction is measured at a pitch of 0.5 mm, and the number of scanning lines is 4 / 0.5 + 1. It is because it becomes = 9. Here, data is handled in a two-dimensional array. When the array in the Y-axis direction is represented by i, the X-axis direction is represented by j. If a sequence of coordinate values measured by XYZ is stored in a two-dimensional array according to the arrangement of measurement points, X (i, j), Y (i, j), and Z (i, j) These are arranged on the actual XY (ij) plane.

Next, with respect to the measurement data string i of each YZ section extracted by the data extraction unit 92, the coefficients a _j and b that minimize the square of the difference from the quadratic function of Zd = a * Y * Y + b * Y + c. The values _j and c _j are calculated by the calculation unit 94a of the deviation amount evaluation means 94, and stored in the memory 93 by the control unit 91 together with the value of the X coordinate position _Xj (step C5).

Next, for the measurement data string i of each YZ section extracted by the data extraction means 92, each coefficient ar _j , br that minimizes the square of the difference from the quadratic function of Z = ar * Y * Y + br * Y + cr The values of _j and cr _j are calculated by the calculation unit 94a and stored in the memory 93 by the control unit 91 together with the value of the X coordinate position _Xj (step C6). In the first and second embodiments, the positional deviation in the Y direction was evaluated, whereas in the third embodiment, the curvature R of the lens is evaluated. In order to emphasize this meaning, The coefficients ar _j , br _j , cr _j are obtained by using a suffix of r as a coefficient.

  Next, the controller 91 performs the sequence of (Step C4), (Step C5), and (Step C6) on the entire measurement surface 1a of the lens 1 (Step C7).

Next, an approximate radius R of the measurement surface 1a of the lens 1 in the predetermined cross section is obtained by the calculation unit 94a based on the measurement data of the predetermined cross section sequentially extracted by the data extraction unit 92. Specifically, by using the value of the coefficient ar _j at the calculated X coordinate position X _j , the approximate arc radius (approximate radius) R _i in the YZ section of the lens 1 is set as R _i = 1 / (2 The calculation unit 94a calculates from ar _j ) (step C8).

Next, the approximate radius R _i , the slope of a straight line approximated to each difference Zd in the cross section of the extracted measurement data of the predetermined cross section, or the approximate slope of coefficients such as a quadratic curve, and the cross section The calculation unit 94a obtains the product of the approximate radius R _i at. Specifically, using the value of the coefficient (approximate inclination) b _{j at} the calculated X coordinate position X _j and the calculated approximate arc radius R _j at the YZ cross section of the lens 1, A displacement amount of the optical axis position (a displacement amount of the center position of the lens 1) ΔY _j is calculated by the calculation unit 94a from ΔY _j = b _j * R _j (step C9).

Next, the controller 91 performs the sequence of (Step C8) and (Step C9) on the entire measurement surface 1a of the lens 1 with respect to the X coordinate position _Xj (Step C10).

Next, the product value is calculated by the calculation unit 94a as the displacement of the center position of the lens 1 in the cross section, so that the lens 1 position of the lens 1 is calculated based on the calculated displacement of the lens center position in the cross section. Evaluate characteristics. Specifically, a graph is displayed on the display device 95 by the control unit 91 with respect to the calculated X coordinate position X _j and optical axis position deviation amount ΔY _j , and based on the displayed graph, the characteristics of the lens 1, that is, The lens linearity in the scanning direction in the XY cross section is evaluated by the evaluation unit 94b of the deviation amount evaluation means 94 (step C11). As a calculation result, an output similar to that in the form shown in FIG. 4 is obtained.

  With the configuration according to the third embodiment, a difference between shape measurement data output from a conventional measuring machine such as a three-dimensional shape measuring machine and design shape data (design data) stored in the memory 93 or the like is obtained. By using the difference between the measurement data output from the measurement means 96 of the three-dimensional shape measuring machine 96 and the design data, without using a separate comparison calculation in the lens design formula in the subsequent calculation, and using the measurement data itself, Even when the approximate radius R in each cross section changes, the displacement of the optical axis position in each part of the lens 1 (in other words, the central position of the lens 1) according to the light passing through a part on the lens 1 simply. Displacement) can be calculated. Therefore, the characteristics of the lens can be evaluated based on the calculated displacement of the lens center position in the cross section.

(Fourth embodiment)
Linearity data (lens linearity data) of the optical axis position of the lens 1 obtained by the lens evaluation method of the second embodiment or the third embodiment, for example, the evaluated lens 1 When the approximate arc radii of the XZ cross section and the YZ cross section are close, or when the non-arc amount in the YZ cross section is small, (Step A2), (Step B2) or (Step) in the first to third embodiments. In the calculation step of C2), the calculated value of tilt A may not be calculated with sufficient accuracy. This is because not only the tilts (rotational positions) A and B around the X and Y axes but also the tilt C around the Z axis is calculated simultaneously by the calculation unit 94a, so that all the parameters to be calculated are uniform. This is considered to be calculated so that the error of the sum of squares is distributed.

  Therefore, in order to obtain the tilt A around the X axis with higher accuracy by the calculation unit 94a, a brief description will be given with reference to FIGS. 9A to 9C. The XZ cross-sectional shape of the lens 1 is effective for a bowl-shaped portion or a bowl-shaped portion that is inverted up and down.

Using the calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ , which are positional deviation amounts, obtained in (Step A2), (Step B2), or (Step C2) of the lens 1. The coordinate conversion of the measurement data is performed by the calculation unit 94a, and the coordinate position of the lens 1 is obtained by the calculation unit 94a in the evaluation procedure of the second embodiment or the fourth embodiment. As described above, this correction calculation is effective when the shape of the optical axis of the lens 1 in the XY cross section is deformed into a U shape. As described above, this is calculated by the arithmetic unit 94a so that the square of {(measurement data)-(design data)} is minimized with respect to all the axes of XYZABC. It is not required to minimize the sum of squares at A. Therefore, the correction value ΔA for the obtained tilt A is calculated by the calculation unit 94a.

  When the shape of the lens 1 in the XZ section is saddle-shaped as shown in FIG. 9C and is inclined with respect to the design shape by the correction value ΔA around the X axis, the optical axis of the lens 1 is viewed in the YZ section. 9C, the optical axis of the lens 1 is also distorted. Specifically, the maximum positional shift amount in the Y-axis direction is Ymax at the end of the X-axis effective area of the measurement surface 1a of the lens 1, and at this time, the sag amount (depth in the Z-axis direction) of the lens 1 is In the case of S, from FIG. 9C, the correction value ΔA is calculated by the calculation unit 94a at ΔA = Ymax / S based on geometric considerations.

  The calculation unit 94a adds the correction value (correction amount) ΔA to the calculated tilt A value, and the calculation unit 94a performs the calculation again from the sequence of (Step A2), (Step B2), or (Step C2). Thus, the more accurate linearity of the measurement surface 1a of the lens 1 can be evaluated by the evaluation unit 94b of the deviation amount evaluation means 94.

  Here, by obtaining the correction value ΔA in the state of FIG. 9A and converting the coordinates of the measurement data in this direction, the result of FIG. 9B can be obtained. That is, the lens linearity can be displayed with high accuracy by calculating the value of A obtained in the sequence of steps A2, B2, and C2 with higher accuracy.

  Hereinafter, a more detailed and highly accurate calculation procedure will be described with reference to FIG.

  Similar to the first embodiment, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement unit 89 of the three-dimensional shape measuring machine (step D1). Thereafter, the sequence of (Step D2), (Step D3), (Step D4), and (Step D5) is (Step A2), (Step A3), (Step A4), and (Steps) of the first embodiment. Each is the same as A5).

Next, the displacement state (change shape) of the center position of the lens 1 is approximated by the arithmetic unit 94 a on a plane perpendicular to the optical axis of the lens 1. For example, displacement of the center position in each cross section of the lens 1 in a plane perpendicular to the optical axis of the lens 1 is approximated in the perpendicular plane by the arithmetic unit 94a by a quadratic function, Based on the calculated second-order coefficient, the amount of displacement in the approximated vertical plane is calculated by the calculation unit 94a. Specifically, with respect to the measurement data string i of the XY section extracted by the data extraction unit 92, each of the squares of the difference from the quadratic function of Y = a _A * X * X + b _A * X + c _A is minimized. The values of the coefficients a _A , b _A , and c _A are calculated by the calculation unit 94a of the deviation amount evaluation means 94. By approximating with the function in this way, there is data on the amount of displacement at each center position or the amount of displacement caused by dust on the measurement surface 1a, and the X coordinate position X _i and the displacement amount Y _pi Even when an error is included in a part of the displacement amount, the calculation unit 94a calculates a positional deviation amount corresponding to the maximum positional deviation amount Ymax in the Y-axis direction without being affected by variations or dust on the measurement surface 1a. (Step D6).

Subsequently, the arithmetic unit 94a divides the displacement amount on the approximated vertical surface by the sag amount (the maximum depth of the lens 1 in the X-axis direction) which is a value in the depth direction of the lens 1, thereby The amount of positional deviation in the direction of rotation in the direction perpendicular to the cross section is obtained. Specifically, using the coefficient a _A calculated by the arithmetic unit 94a and assuming that the sag amount in the X-axis direction of the lens 1 (the maximum depth of the lens 1 in the X-axis direction) is S, the correction value ΔA ( Here, α is the rotation angle A of the difference of (XYZ coordinates of measurement data) − (XYZ coordinates of design data) about the X axis.
ΔA = a _A * Xmax * Xmax / S (where Xmax: lens evaluation area / 2) [where the lens evaluation area is an area where light actually enters the lens and acts as a lens. ]
As
A ₁ ′ = A ₁ + fb * ΔA
Is calculated by the calculation unit 94a (step D7).
(Here, fb is a coefficient depending on whether the lens is concave or convex, and takes a value of +1 or −1 for a concave or convex shape on the front or rear surface of the lens 1. ₁ was determined by a sequence of steps A2, B2, C2, the value of the calculated value _{a 1} is a position deviation amount.).

When the correction value ΔA is smaller than the predetermined value, the calculation value of the tilt A does not need to be corrected, so the calculation is terminated, and the data string of the X coordinate position X _i and the positional deviation amount Y _pi is used as the optical axis of the lens 1. The linearity is output to the evaluation unit 94b of the deviation amount evaluation means 94 (step D8). Here, the predetermined value is a value equal to or less than the calculation accuracy of A to be obtained, and this calculation is achieved by performing repeated operations. That is, for example, when a differential equation is solved by Newton's method or the like in a general numerical calculation, the solution H obtained repeatedly is substituted into the equation, and when the value is stable, the calculation is terminated assuming that the numerical value has been obtained. Yes. In this case, the calculation ends when the change ΔH of the solution H is equal to or less than a predetermined value. When the answer is in the order of 0.1, it is determined that the answer has been obtained if the change is 0.05. Utilizing this, in the case of this embodiment, the calculation is terminated when the temperature is stabilized to 0.1 minutes = 0.016 degrees or less.

When the correction value ΔA is equal to or greater than the predetermined value, (Step D9), (Step D10), and (Step D11) are performed in the same sequence as (Step D3), (Step D4), and (Step D5). Further, by performing (Step D12), which is the same sequence as (Step D6), and performing the sequence of (Step D7), the predetermined value calculated optimally for the tilt A around the X axis by the calculation unit 94a. The correction value ΔA is calculated by the calculation unit 94a, and the data string of the X coordinate position X _i and the positional deviation amount Y _pi is output to the evaluation unit 94b of the deviation amount evaluation means 94 as the optical axis linearity of the lens 1.

  FIG. 11 shows an example of optical axis linearity data after correcting the tilt A correction value ΔA. According to the evaluation procedure, the large U-shaped undulation is removed, and the small undulation due to processing that is originally intended to be evaluated can be evaluated by the evaluation unit 94b of the deviation amount evaluation means 94.

  With the configuration according to the fourth embodiment, the amount of tilt of the center position of the lens 1 in each cross section of the lens 1 is calculated by adding the tilt amount obtained using the measurement data of the entire measurement surface 1 a of the lens 1. By using the sag amount, the amount of positional deviation is obtained by the computing unit 94a, and correction is added by the computing unit 94a, so that the tilt amount of the lens 1 can be obtained by the computing unit 94a with high accuracy. Compared with the case where the tilt is calculated, the characteristics of the long lens 1, that is, the linearity of the scanning optical axis can be evaluated with higher accuracy by the evaluation unit 94b of the shift amount evaluation means 94.

  Furthermore, the displacement amount of the center position in each cross section of the lens 1 and the displacement are approximated by a quadratic function to the tilt amount obtained by the calculation unit 94a using the data of the entire measurement surface 1a of the lens 1. Using the approximate function, the displacement amount in the vertical plane and the sag amount are used to determine the displacement amount by the calculation unit 94a, and the correction is added by the calculation unit 94a to obtain the displacement amount at each center position. Even when there is data on the amount of positional deviation caused by variation or dust on the measurement surface, and the error is included in a part of the displacement, the tilt amount of the lens 1 can be obtained with high accuracy by the calculation unit 94a. The linearity of the scanning optical axis of the long lens can be evaluated with higher accuracy by the evaluation unit 94b of the deviation amount evaluation means 94, compared to the conventional case where the tilt is calculated only from the entire data.

(Fifth embodiment)
Hereinafter, the lens evaluation method according to the fifth embodiment of the present invention will be described with reference to FIG. Similarly to the first embodiment, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement unit 89 of the three-dimensional shape measuring machine capable of performing the lens evaluation method (step E1). .

Next, using the measurement data point sequence and the design formula of the lens 1, the positional deviation amount of each position and the positional deviation of each tilt in the XYZ position in the XYZ coordinate system and in the respective ABC directions of rotation about the XYZ axes. The amount is calculated by the calculation unit 94 a of the deviation amount evaluation means 94. Specifically, the calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , and C ₁ that are positional deviation amounts are converted into the deviation amounts by the sequence of (Step E2) corresponding to the sequence of (Step A2). The calculation unit 94a of the evaluation means 94 calculates (Step E2).

  Next, the measurement data of a predetermined cross section of the lens 1 is sequentially extracted by the data extraction means 92 at a predetermined pitch. Specifically, XYZ measurement data point sequences of the YZ cross section of the lens 1 are sequentially extracted by the data extraction unit 92 at a pitch of 0.5 mm in the X-axis direction (step E3).

Next, of the positional deviation amount, each position on the entire surface of the measurement surface 1a of the lens 1 other than the position and the tilt deviation amount in a total of three directions including two parallel movement directions and a tilt in the plane of the predetermined cross section. Is calculated by the calculation unit 94a using the positional deviation amount and the positional deviation amount of each tilt, and the radius parameter Ry in the predetermined section of the design formula of the lens 1 is calculated. The optimum radius parameter Rybf is set so that the difference between the value of the radius parameter Ry and the measurement data point sequence extracted from the predetermined section is the minimum at the position displacement calculation amount in the predetermined section. It is obtained by the arithmetic unit 94a. Specifically, with respect to the measurement data of each YZ section extracted by the data extraction unit 92, out of the displacement amount, the two parallel movement directions in the YZ direction within the plane of the YZ section and the tilt A around the X axis. In addition to the total amount of misalignment in the three directions, the measurement data using the misalignment amount of each position and the misalignment amounts X ₁ , B ₁ , C ₁ of each tilt on the entire measurement surface 1a of the lens 1 The displacement amounts Y _i , Z _i , A _{i in the} three directions in which the sum of squares of the difference in design shape data is minimized (in order to distinguish from the previously calculated values Y ₁ , Z ₁ , A ₁ , Y _pi , Z _pi and A _pi ) and an optimum radius Rybf _j that minimizes the sum of squares of the difference between the measurement data and the design shape data for the radius parameter Ry included in the design formula of the lens 1 is calculated by the calculation unit 94a. , X coordinate position X _j , radius parameter Ry _j It memorize | stores in the memory 93 sequentially according to each cross section (step E4).

  Next, the optimal radius parameter Rybf of each cross section of the entire surface of the measurement surface 1a of the lens 1 is obtained by the calculation unit 94a. Specifically, the controller 91 performs the sequence of (Step E3) and (Step E4) on the entire measurement surface 1a of the lens 1 (Step E5).

Next, using the difference between the arc radius R _j obtained from the design formula of the lens 1 and the radius parameter Ry _j , the radius R deviation amount ΔR _j in the focal direction of the lens 1 is expressed as follows _: ΔR _j = Rybf _j −R _j Is calculated by the calculation unit 94a. (Step E6).

  Next, the controller 91 performs the sequence of (Step E6) on the entire measurement surface 1a of the lens 1 (Step E7).

Next, the characteristics of the lens 1 are evaluated based on the optimum radius parameter Rybf (specifically, the radius deviation amount ΔR) of each of the obtained cross sections. That is, the control unit 91 displays a graph of the radius shift amount ΔR proportional to the position shift amount from the lens focus position (focal position of the lens 1) on the display device 95 by the control unit 91 with respect to the X coordinate position X _j and the radius R shift amount ΔR _j. Then, based on the displayed graph, the characteristic of the lens 1, that is, the focus position shift amount is evaluated by the evaluation unit 94b of the shift amount evaluation means 94 (step E8).

  With the configuration according to the fifth embodiment, the predetermined measurement value is compared with the shape measurement data of the measurement surface 1a of the lens 1 in the vicinity thereof according to the light passing through a part on the lens 1 to thereby determine the predetermined value. By obtaining the optimum radius Rybf in each cross section, the focus position of the lens 1 at each part of the lens 1 can be calculated.

(Sixth embodiment)
In the case of the evaluation by the lens evaluation method according to the fifth embodiment, the radius parameter Ry serving as a base for calculating the optimum radius Rybf needs to be expressed by the design formula of the lens 1. With the evolution of technology, diversification of lens shape expressions has progressed, and the shape in the YZ section can be expressed by a combination of series, etc., and the design parameter of the lens 1 may not have a radius parameter Ry. In some cases, the approximate arc radius R, which is a reference for evaluating the quantity, cannot be obtained.

  A lens evaluation method according to the sixth embodiment of the present invention will be described below with reference to FIG. Similarly to the first embodiment, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement unit 89 of the three-dimensional shape measuring machine capable of performing the lens evaluation method (step F1). .

Next, using the measurement data point sequence and the design formula of the lens 1, the positional deviation amount of each position and the positional deviation of each tilt in the XYZ position in the XYZ coordinate system and in the respective ABC directions of rotation about the XYZ axes. The amount is calculated by the calculation unit 94a of the deviation amount evaluation means 94 that evaluates the design deviation of the lens 1 and the coordinate deviation amount of the measurement data point sequence. Specifically, the calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , and C ₁ that are positional deviation amounts are converted into the deviation amounts by the sequence of (Step F2), which corresponds to the sequence of (Step B2). The calculation unit 94a of the evaluation means 94 calculates (Step F2).

Next, based on the positional deviation amount of each position and the positional deviation amount of each tilt, each calculation unit 94a obtains each difference Zd between each measurement data point sequence and the design formula of the lens 1. Specifically, with respect to the measurement data coordinate-converted by the calculation unit 94a using the positional deviation amounts X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C _1, at the same point in the XY coordinates {( The Z value Zd _i of (measurement data)-(design data)} is sequentially calculated by the calculation unit 94a, and is stored in the memory 93 as the X coordinate position X _i , the position shift amount Y _pi , and the position shift amount Zd _i (step F3). ).

Next, the measurement data of the predetermined cross section of the lens 1 and the difference Zd are sequentially extracted by the data extraction means 92 at a predetermined pitch. Specifically, an XYZ measurement data point sequence of the YZ cross section of the lens 1 is represented by a data sequence (Y _i , Zd _i ) (Y _i , Zd _i ) (provided that the pitch is 0.5 mm in the X axis direction and the X axis direction). i = 1 to 9 and j is 9 points of measurement data 1 to 9 and is calculated using these 9 points.) is sequentially extracted by the data extraction means 92 (F4). Note that the maximum value of i is 9 in the measurement example in FIG. 6, an area of ± 2 mm in the Y direction is measured at a pitch of 0.5 mm, and the number of scanning lines is 4 / 0.5 + 1. It is because it becomes = 9. Here, data is handled in a two-dimensional array. When the array in the Y-axis direction is represented by i, the X-axis direction is represented by j. If a sequence of coordinate values measured by XYZ is stored in a two-dimensional array according to the arrangement of measurement points, X (i, j), Y (i, j), and Z (i, j) These are arranged on the actual XY (ij) plane.

  Next, the approximate radius R of the measurement surface of the lens 1 at the predetermined cross section is obtained by the calculation unit 94a from the measurement data of the predetermined cross section sequentially extracted by the data extracting means 92. Next, the calculation unit 94a approximates the approximate radius R and each difference Zd in the cross section of the extracted measurement data of the predetermined cross section with a quadratic or higher function. Next, the second-order coefficient is obtained by the calculation unit 94a.

  This will be specifically described below.

First, with respect to the measurement data string i of each YZ section extracted by the data extraction means 92, each coefficient a _j , which minimizes the square of the difference from the quadratic function of Zd = a * Y * Y + b * Y + c. The values of b _j and c _j are calculated by the calculation unit 94a and stored in the memory 93 together with the value of the X coordinate position X _j (step F5).

  Next, the controller 91 performs the sequence of (Step F4) and (Step F5) on the entire measurement surface 1a of the lens 1 (Step F6).

Next, using the arc radius R _j in the YZ cross section at the X coordinate position X _j and the coefficient a _j , the radius R deviation amount ΔR _j in the focal direction of the lens 1 is expressed as ΔR _j = 2 * a _It is calculated by the calculation unit 94a by the calculation formula of _j * (R _j * R _j ) (step F7).

  Here, the content of the calculation formula will be briefly described with reference to FIG.

  When the measured spherical lens shape of the lens 1 is processed by shifting from the design radius R by the positional shift amount Δh at the position y, the calculation unit 94a calculates the radial shift amount ΔR by the following procedure.

In FIG. 14, when the sag amount at the y position of the lens is h, when y = 2 mm and R is 50 mm or more, the similarity of the triangle in the left diagram of FIG.
h / y≈y / (2 * R) ... [1]
(Δh + h) / y≈y / 2 / (R + ΔR) [2]
From the formula [1]-[2], Δh / y = y / (2 * R) −y / 2 / (R + ΔR)
Δh / y≈y / 2 * ΔR / (R * R)
If this is transformed,
Δh / (y * y) = 1/2 * ΔR / (R * R)
Than,
ΔR = 2 * Δh * (R * R) / (y * y) [3]
Here, when the positional deviation amount Δh from the spherical surface of the lens 1 (lens surface in FIG. 14) is expressed by a quadratic expression, Δh = a * y * y, the expression [3] is
ΔR = 2 * a * (R * R) [4]
Using the quadratic coefficient a of the quadratic function and the radius R, the positional deviation amount can be calculated by the calculation unit 94a. That is, a value that is twice the product of the coefficient and the square of the approximate radius R of the measurement surface of the lens 1 in the cross section is obtained by the calculation unit 94a.

Next, the controller 91 performs the sequence of (Step F7) on the entire measurement surface 1a of the lens 1 for each X coordinate position _Xj (Step F8).

Next, the calculation unit 94a calculates the above-described value as the arc radius deviation amount in the cross section, thereby evaluating the characteristics of the lens 1 based on the arc radius deviation amount in the cross section. Specifically, a graph is displayed on the display device 95 by the control unit 91 with respect to the calculated X coordinate position X _j and radius R deviation amount ΔR _j , and based on the displayed graph, characteristics of the lens 1, that is, XY The focus shift amount in the scanning direction in the cross section is evaluated by the evaluation unit 94b of the shift amount evaluation means 94 (step F9).

  With the configuration according to the sixth embodiment, the lens 1 is designed in the subsequent calculation using the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine. Passing a part on the lens 1 simply by using the difference between the measurement data and the design data output from the measurement means 89 of the three-dimensional shape measuring machine and the measurement data itself, without separately performing a comparison calculation using a formula. The amount of focus position shift of the lens 1 at each part of the lens 1 can be calculated according to the light to be emitted.

In the sixth embodiment, the positional deviation amounts Y _pi and Zd _i data are approximated by a quadratic function. However, a quadratic function may be used by approximating by a function of third order or higher. The effect of can be obtained.

(Seventh embodiment)
Furthermore, a lens evaluation method according to a seventh embodiment of the present invention will be described with reference to FIG. Similar to the first embodiment, an XYZ measurement data point sequence on the measurement surface 1a of the lens 1 is acquired by the measurement unit 89 of the three-dimensional shape measuring machine capable of performing the lens evaluation method (step G1). .

Next, using the measurement data point sequence and the design formula of the lens 1, the positional deviation amount of each position and the positional deviation of each tilt in the XYZ position in the XYZ coordinate system and in the respective ABC directions of rotation about the XYZ axes. The amount is calculated by the calculation unit 94a of the deviation amount evaluation means 94 that evaluates the design deviation of the lens 1 and the coordinate deviation amount of the measurement data point sequence. Specifically, using the measurement data point sequence and the design formula of the lens 1, the arithmetic unit 94a obtains the sum of squares of the differences between the points of the measurement data point sequence with respect to the design formula at the same point in the XY coordinates. The XYZ horizontal movement of the measurement data is executed by the calculation unit 94a of the deviation amount evaluation means 94, and the rotation directions A, B, and C around the X, Y, and Z axes are rotated by the calculation unit 94a. Calculated values X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ , which are positional deviation amounts that minimize the sum, are calculated by the arithmetic unit 94a (step G2).

Next, based on the positional deviation amount of each position and the positional deviation amount of each tilt, each calculation unit 94a obtains each difference Zd between each measurement data point sequence and the design formula of the lens 1. Specifically, with respect to the measurement data coordinate-converted by the arithmetic unit 94a using the positional deviation amounts X ₁ , Y ₁ , Z ₁ , A ₁ , B ₁ , C ₁ (measurement at the same point in the XY coordinates) The Z value Zd _i of (data)-(design data) is sequentially calculated by the calculation unit 94a and stored in the memory 93 as the X coordinate position X _i , the positional deviation amount Y _pi , and the positional deviation amount Zd _i (step G3).

Next, the measurement data of the predetermined cross section of the lens 1 and the difference Zd are sequentially extracted by the data extraction means 92 at a predetermined pitch. Specifically, an XYZ measurement data point sequence of the YZ cross section of the lens 1 is converted into a data sequence (Y _i , Zd _i ), (Y _i , Z _i ) (where i = 1 to 9 and j is 9 points of measurement data 1 to 9 and is calculated using these 9 points) is sequentially extracted by the data extraction means 92 ( Step G4). Note that the maximum value of i is 9 in the measurement example in FIG. 6, an area of ± 2 mm in the Y direction is measured at a pitch of 0.5 mm, and the number of scanning lines is 4 / 0.5 + 1. It is because it becomes = 9. Here, data is handled in a two-dimensional array. When the array in the Y-axis direction is represented by i, the X-axis direction is represented by j. If a sequence of coordinate values measured by XYZ is stored in a two-dimensional array according to the arrangement of measurement points, X (i, j), Y (i, j), and Z (i, j) These are arranged on the actual XY (ij) plane.

Next, with respect to the measurement data string i of each YZ section extracted by the data extraction unit 92, the coefficients a _j and b _j that minimize the square of the difference from the quadratic function of Zd = a * Y * Y + b * Y + c. , C _j are calculated by the calculation unit 94a and stored in the memory 93 together with the value of the X coordinate position X _j (step G5).

Next, for the measurement data string i of each YZ section extracted by the data extraction means 92, each coefficient ar _j , br that minimizes the square of the difference from the quadratic function of Z = ar * Y * Y + br * Y + cr The values of _j and cr _j are calculated by the calculation unit 94a and stored in the memory 93 together with the value of the X coordinate position _Xj (step G6).

  Next, the control unit 91 performs the sequence of these (Step G4), (Step G5), and (Step G6) on the entire measurement surface 1a of the lens 1 (Step C7).

Next, using the value of the coefficient ar _j at the position of the calculated X coordinate position X _j , the approximate arc radius R _i in the YZ section of the lens 1 is expressed as R _i = 1 / (2 · ar _j ). Is calculated by the calculation unit 94a (step G8).

Next, using the value of the coefficient b _j at the calculated X coordinate position X _j and the calculated approximate arc radius R _j at the YZ section of the lens 1, the amount of deviation of the optical axis position within the XY section ΔY _j is calculated by the calculation unit 94a from the equation _: ΔY _j = b _j * R _j (step G9).

Next, by using the arc radius R _j in the YZ cross section at the X coordinate position X _j and the a _j , the deviation amount ΔR _j of the radius R in the focal direction of the lens 1 is expressed as ΔR _j = 2 * a _{j * (R j * R j} ) wherein in is calculated by the calculating section 94a of the (step G10).

Next, the control unit 91 performs the sequence of (Step G8), (Step G9), and (Step G10) on the entire measurement surface 1a of the lens 1 for each X coordinate position _Xj (Step G11).

Next, a graph is displayed on the display device 95 by the control unit 91 with respect to the calculated X coordinate position X _j and optical axis position deviation amount ΔY _j , and based on the displayed graph, the characteristics of the lens 1, that is, within the XY cross section The lens linearity in the scanning direction is evaluated by the evaluation unit 94b of the deviation amount evaluation means 94 (step G12). Further, a graph is displayed on the display device 95 by the control unit 91 with respect to the calculated X coordinate position X _j and radius R deviation amount ΔR _j , and based on the displayed graph, characteristics of the lens 1, that is, in the XY cross section. The focus shift amount in the scanning direction is evaluated by the evaluation unit 94b of the shift amount evaluation means 94 (step G13).

  Next, an output in the form shown in FIG. 16 is obtained as the calculation result.

  With the configuration according to the seventh embodiment, the lens 1 is designed in the subsequent calculation using the difference between the shape measurement data and the design shape data output from a conventional measuring machine such as a three-dimensional shape measuring machine. Using the difference between the measurement data and the design data output from the measurement means 89 of the three-dimensional shape measuring machine and the measurement data itself, the approximate radius R in each cross section can be obtained without performing a separate comparison calculation using a formula. Even in the case of changing, it is possible to easily calculate the linear positional deviation amount and the focus positional deviation amount of the lens 1 in each part of the lens 1 according to the light passing through a part on the lens 1.

(Eighth embodiment)
FIGS. 17A and 17B are a lens holding jig 30 and a cover held by the lens holding jig 30 used when carrying out the lens evaluation method according to the eighth embodiment of the present invention. It is a block diagram of the lens 1 without a part and the lens 1 with an edge part. The lens holding jig 30 has a rectangular through hole 30a in the center of the rectangular plate so that the front surface of the lens 1 and the lens holding jig 30 holding the lens 1 can be reversed so that the back surface of the lens 1 can be measured. In addition, the support legs 30b are vertically provided at three locations so that the lens holding jig 30 can be stably held even when the lens holding jig 30 is reversed.

  In addition, in the vicinity of the end portion of the through-hole 30a, holding portions 31a and 31b are provided to hold the side surfaces of both end portions in the longitudinal direction of the lens 1, and one holding portion 31a is fixed to the lens holding jig 30. The other holding portion 31 b is attached to the lens holding jig 30 so that the position of the other holding portion 31 b can be adjusted in the longitudinal direction of the lens 1.

  Further, at four locations on both sides in the width direction of the through-hole 30a, there are provided a pair of opposed clamp portions 30c and 30c that can clamp the lens 1 by screw feed, and for the lens 1 without the edge portion, Two positions on the side surface along the longitudinal direction of the lens 1 can be clamped.

  Further, the lens holding jig 30 can measure the coordinates of the lens holding jig 30 from the front side of the lens 1 of the lens holding jig 30 and from the back side of the lens 1 by inverting the lens holding jig 30. 17A, there is a lens holding jig 31 having three balls BA, BB, BC fitted and fixed in a fitting hole penetrating vertically in the upper surface of FIG. 17A, and the measurement described above from the front side and the back side of the lens 1, respectively. Can be performed by the measuring means 89.

  In order to evaluate a lens using the lens holding jig 30, the following is performed.

  First, the surface of the lens 1 and the spherical surfaces of the three spheres BA, BB, and BC are measured by the probe 3 of the measuring means 89 from the surface side of the lens holding jig 30.

  Next, the lens holding jig 30 is turned upside down, and the back surface of the lens 1 and the surfaces of the three balls BA, BB, and BC are inserted into the through hole 30a from the back side of the lens holding jig 30. Measured according to 3.

  Next, the coordinate axis of the surface of the lens 1 is calculated by the calculation unit 94a with reference to the centers of the three spheres BA, BB, and BC.

  Next, the coordinate axis of the back surface of the lens 1 is calculated by the calculation unit 94a with the center of the three spheres BA, BB, and BC as a reference.

  Next, the measurement data of the front and back surfaces of the lens 1 is synthesized by the calculation unit 94a using the three spheres BA, BB, and BC as a reference, and the characteristics of the lens 1 on the back surface with respect to the front surface of the lens 1 or with respect to the back surface of the lens 1 are obtained. Evaluation is performed by the evaluation unit 94b.

  On the other hand, in FIG. 17B, when the lens 1 having the edge portion 1 b is supported by the lens holding jig 30, holding portions 31 a and 31 b that hold both end portions of the lens 1 in the longitudinal direction are provided. The holding portion 31a on one side (the right side in FIG. 17B) has one sphere 31c from the top and bottom, and supports the front and back surfaces of the edge portion 1b of the lens 1 with the spherical surface of each one sphere 31c. . In the other holding portion 31b (left side in FIG. 17B), the lower surface has two spheres 31d, the spherical surfaces of the two spheres 31d support the back surface of the edge portion 1b of the lens 1, and the upper surface has one sphere 31e. The surface of the edge portion 1b of the lens 1 is supported by the spherical surface of one sphere 31e. Even with the lens 1 having the edge portion 1b, the lens can be evaluated by the same method as described above.

  A more specific lens evaluation method using the lens holding jig 30 having such a configuration will be described below with reference to FIG.

  First, the lens 1 is held by the lens holding jig 30 that supports the lens 1 provided with three spheres BA, BB, and BC that can be measured from both the front and back sides that specify the reference position (step H1).

  Next, the shape coordinate data on the XY cross section is measured by the measuring means 89 on the measurement surface 1a of the lens 1 by the method shown in the first embodiment, and the shape data of the XYZ measurement data point sequence is acquired (step H2). ).

  Next, with respect to the vertices of the three spheres BA, BB, and BC, the position of the vertex on the XY axis is measured by the measuring means 89, and the precise position of the vertex is calculated by the calculation unit 94a (step H3).

  Next, the calculation unit 94a calculates the center positions of the spheres BA, BB, BC from the radii of the spheres BA, BB, BC measured in advance and the measured values (step H4).

  Next, the control unit 91 repeats the sequence of (Step H3) and (Step H4) to measure the three reference spheres BA, BB, and BC (Step H5).

  Next, the lens holding jig 30 is inverted, and the sequence of (Step H2), (Step H3), (Step H4), and (Step H5) is repeated by the control unit 91 (Step H6).

Next, the measurement data of the entire surface of the lens 1 on the surface side of the lens holding jig 30 and the design formula are compared by the calculation unit 94a, and the lens surface coordinates of the lens surface coordinates that minimize the least square sum of the surface shape differences are compared. The coordinate axis of the center position and direction (X _f , Y _f , Z _f , A _f , B _f , C _f ) is calculated by the arithmetic unit 94a (where the suffix f is a character representing the surface of the lens 1) ( Step H7).

  Next, on the surface side of the lens holding jig 30, the linearity of the surface that is the measurement surface 1a of the lens 1 and the amount of focus deviation are evaluated by the evaluation unit 94b by the evaluation method according to any one of the first to seventh embodiments. (Step H8).

Next, a plane on the surface side of the lens holding jig 30 that is the same surface as the surface of the lens 1 and passes through the center of the three balls BA, BB, BC, and two balls BA of the three balls BA, BB, BC , BB is defined as the X-axis direction, and the coordinate position of the center position and the direction (X _1j , Y _1j , Z _1j , A _1j , B _1j , C _1j ) of the lens holding jig 30 is calculated by the calculation unit 94a. (However, the suffix 1 here is a character representing the surface of the lens 1) (step H9).

Next, from the lens surface coordinates and the coordinate axes of the lens holding jig 30 obtained from the three balls BA, BB, BC, the lens surface coordinates (X _1s , Y _1s , Z _1s , (A _1s , B _1s , C _1s ) is calculated by the calculation unit 94a, and the coordinates of the evaluation data of the linearity of the surface of the lens 1 and the focus deviation amount on the surface side of the lens holding jig 30 are calculated using these coordinates. (However, the suffix 1 here is a letter representing the surface of the lens 1, and X _1s , Y _1s , Z _1s , A _1s , B _1s , C _1s are the three balls BA, BB, BC This is a coordinate system from the surface side defined by a plane passing through the center.) (Step H10).

Next, the measurement data of the entire back surface of the lens 1 on the back surface side of the lens holding jig 30 and the design formula are compared by the arithmetic unit 94a, and the lens back surface coordinate of the minimum square sum of the surface shape differences is minimized. The coordinate axis of the center position and direction (X _b , Y _b , Z _b , A _b , B _b , C _b ) is calculated by the arithmetic unit 94a (where suffix b is a character representing the back surface of the lens 1) ( Step H11).

  Next, on the back surface side of the lens holding jig 30, the linearity and defocus amount of the back surface, which is the measurement surface 1 a of the lens 1, are the same as those on the front surface in the evaluation method according to any of the first to seventh embodiments. Evaluation is performed by the evaluation unit 94b (step H12).

Next, a plane passing through the center of the three balls BA, BB, BC on the back surface side of the lens holding jig 30 and the same surface as the back surface of the lens 1, and two balls BA of the three balls BA, BB, BC. , BB is the vector in the X-axis direction, and the coordinate position of the center position and direction of the lens holding jig 30 (X _2j , Y _2j , Z _2j , A _2j , B _2j , C _2j ) is calculated (however, Here, the suffix 2 is a character representing the back surface of the lens 1) (step H13).

Next, the coordinates (X _2s , Y _2s , Z _2s , X _2s , Y _2s , Z _2s ) of the lens back surface based on the coordinates of the lens holding jig 30 are obtained from the lens back surface coordinates and the coordinate axes of the lens holding jig 30 obtained from the three balls BA, BB, BC. A _2s , B _2s , C _2s ) are calculated, and the coordinates of the evaluation data of the linearity and defocus amount of the back surface of the lens 1 on the back surface side of the lens holding jig 30 are converted by the calculation unit 94a. (However, the suffix 2 here is a character representing the back surface of the lens 1, and X _2s , Y _2s , Z _2s , A _2s , B _2s , C _2s are planes passing through the centers of the three balls BA, BB, BC. (Step H14).

  Next, from the data calculated above, the evaluation data of the surface linearity and defocus amount of the lens 1 on the front surface side of the lens holding jig 30 is converted into coordinates based on the back surface of the lens holding jig 30 by the calculation unit 94a. Conversion and display on the display device 95, and calculation unit for calculating linearity and defocus amount between the measurement surfaces (both front and back surfaces) 1a of the upper and lower (front and back) lenses 1 with reference to the back surface of the lens holding jig 30 It calculates by 94a (step H15). Here, the data on the surface of the lens 1 is evaluated based on the back surface, but the upper and lower standards may be reversed and the back surface of the lens 1 may be evaluated based on the surface reference.

  Next, examples of evaluation results obtained by the above evaluation method are shown in FIGS. 19A to 19D. The bold curve in FIG. 19B indicates the linearity of the lens 1 on the front surface with respect to the back surface, and the dashed-dotted curve in FIG. 19C indicates the linearity of the lens 1 on the back surface. In FIG. 19D, the thick line curve indicates the linearity of the front lens 1, the alternate long and short dash line curve indicates the linearity of the rear surface lens 1, and the dotted curve indicates the difference in linearity between the front surface and the back surface.

  With the configuration according to the eighth embodiment, the linearity and focus position of the lens 1 on the front surface can be evaluated on the back surface or on the back surface. Furthermore, since the lower side of the end face of the lens 1 is supported by the spherical surfaces of the three spheres 31c and 31d and the upper side is supported by the spherical surfaces of the two spheres 31c and 31e, the lens 1 is stably held and evaluated without distortion. Can do.

  In actual measurement, in order to avoid deformation of the measurement object and the jig due to a temperature change at the time of measurement, only the measurement may be performed first, and then the calculation process may be performed. For example, in the eighth embodiment, the surface of the lens and the surfaces of the three spheres are measured, the coordinate axis of the surface of the lens is calculated, and the back surface of the lens and the surfaces of the three spheres are measured. The coordinate axis of the back surface of the lens may be calculated, and the data of the front and back surfaces of the lens may be synthesized and evaluated.

  It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.

  According to the lens evaluation method of the present invention, the linearity in the scanning direction of the light and the focus position of the long lens can be evaluated with high accuracy. Conventionally, the evaluation can be performed only when the lens is completed as an embedded device. Can be evaluated at a single lens stage without making it into a device, and the lens evaluation process can be greatly streamlined, and it can be applied to high-precision and high-functionality printing equipment such as laser beam printers using this lens. it can.

The perspective view of the lens measurement by the three-dimensional shape measuring machine in the 1st Embodiment of this invention The figure which shows the scanning path | route on the upper surface of a measurement object in the lens measurement by the three-dimensional shape measuring machine in the 1st Embodiment of this invention. The block diagram which shows the relationship between the measurement means and control calculating part of the three-dimensional shape measuring machine in the 1st Embodiment of this invention The figure which shows the XYZ measurement data example in the three-dimensional shape measuring machine in the 1st Embodiment of this invention The flowchart which shows the evaluation procedure of the lens evaluation method in the 1st Embodiment of this invention. The graph which shows the calculation result example (example of linearity evaluation) of the deviation | shift of the linearity calculated | required by the lens evaluation method in the 1st Embodiment of this invention The flowchart which shows the evaluation procedure of the lens evaluation method in the 2nd Embodiment of this invention. The figure which shows the example of {(measurement data)-(design shape data)} in the three-dimensional shape measuring machine in the 2nd Embodiment of this invention. The figure for demonstrating briefly the content of the calculation formula of the lens evaluation method in the 2nd Embodiment of this invention. The figure for demonstrating briefly the content of the calculation formula of the lens evaluation method in the 2nd Embodiment of this invention. The flowchart which shows the evaluation procedure of the lens evaluation method in the 3rd Embodiment of this invention. In the lens evaluation method in the 4th Embodiment of this invention, it is explanatory drawing for demonstrating the alignment of the tilt A axis | shaft from surface data when calculating | requiring the tilt A around an X-axis with higher precision, a) is a perspective view of the lens, (b) is a plan view of the lens, and (c) is a right side view of the lens. In the lens evaluation method in the 4th Embodiment of this invention, it is explanatory drawing for demonstrating the alignment of the tilt A axis from linearity when calculating | requiring the tilt A around an X-axis with higher precision, a) is a perspective view of the lens, (b) is a plan view of the lens, and (c) is a right side view of the lens. Explanatory drawing for demonstrating calculating | requiring the tilt A around an X-axis more accurately in the lens evaluation method in the 4th Embodiment of this invention. The flowchart which shows the evaluation procedure of the lens evaluation method in the 4th Embodiment of this invention. The figure which shows the data example of an optical axis linearity after correct | amending the correction value (DELTA) A of the tilt A in the lens evaluation method in the 4th Embodiment of this invention. The flowchart which shows the evaluation procedure of the lens evaluation method in the 5th Embodiment of this invention. The flowchart which shows the evaluation procedure of the lens evaluation method in the 6th Embodiment of this invention. Explanatory drawing for demonstrating the content of a calculation formula simply in the lens evaluation method in the 6th Embodiment of this invention. The flowchart which shows the evaluation procedure of the lens evaluation method in the 5th Embodiment of this invention. The graph which shows the example of a calculation result calculated | required by the lens evaluation method in the 7th Embodiment of this invention (example of simultaneous evaluation of linearity and focus shift | offset | difference) The top view of the state which is a lens holding jig used when enforcing the lens evaluation method concerning the 8th Embodiment of this invention, and is supporting the lens without an edge part 17 is a lens holding jig used when carrying out the lens evaluation method according to the eighth embodiment of the present invention, in a state in which a lens with an edge portion is supported; Partial cross-sectional side view when fractured along the edge (when the support legs at both ends are obliquely penetrated toward the end of the through hole and broken along the through hole) The flowchart which shows the evaluation procedure of the lens evaluation method in the 8th Embodiment of this invention. Explanatory drawing for demonstrating the example of an evaluation result in the lens evaluation method in the 8th Embodiment of this invention. The graph which shows the linearity of the surface of a lens in the example of an evaluation result in the lens evaluation method in the 8th Embodiment of this invention The graph which shows the linearity of the back surface of a lens in the example of an evaluation result in the lens evaluation method in the 8th Embodiment of this invention. The graph which shows the linearity of the surface on the back surface reference | standard in the example of an evaluation result in the lens evaluation method in the 8th Embodiment of this invention Illustration of conventional lens evaluation method

Explanation of symbols

1 Lens 1a Lens surface (measurement surface)
DESCRIPTION OF SYMBOLS 1b Lens edge part 2 Laser measuring optical unit 3 Probe 4 Moving body 5 X stage 6 Y stage 7 Surface plate 30 Lens holding jig 30a Through hole 30b Support leg 30c Clamp part BA, BB, BC Sphere 31a, 31b Lens holding part 31c , 31d, 31e Sphere 89 Measuring means 90 Control operation part 91 Control part 92 Data extraction means 93 Memory 94 Deviation amount evaluation means 94a Operation part 94b Evaluation part 95 Display device

Claims (12)

(I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in each ABC direction of the rotation direction around each XYZ axis,
(Iii) measurement data of a cross section of the lens obtained by sequentially extracting measurement data of a cross section of the lens parallel to the optical axis passing through the lens by a data extraction unit at a measurement pitch;
Of the amount of positional deviation of (ii) above, the amount of positional deviation in the total three directions of the two directions of translation and tilt in the plane of the cross section of the lens, except for the amount of positional deviation in the total three directions, Using the amount of positional deviation at each position and the amount of positional deviation at each tilt, the arithmetic unit calculates the amount of positional deviation in the three directions,
Based on the calculation result of the displacement amount in the three directions, the translation amount and tilt of each cross section over the entire measurement surface of the lens are obtained by the calculation unit, and the obtained parallel movement amount of each cross section A method for evaluating a lens, wherein the characteristic of the lens is evaluated based on a tilt. (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in the direction of each tilt ABC in the rotation direction around each XYZ axis,
(Iii) Based on the amount of each displacement, each difference between the measurement data point sequence and the lens design formula is obtained by a calculation unit;
The measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the difference are approximated to each difference in the cross section of the measurement data of the cross section of the lens, which is sequentially extracted by the data extraction means at the measurement pitch. A product of an approximate inclination of a coefficient of a straight line or a quadratic curve or the like and an approximate radius of the measurement surface of the lens in the cross section is obtained by the calculation unit,
By calculating the product value as the displacement of the center position of the lens in the cross section by the calculation unit, the characteristics of the lens are evaluated based on the calculated displacement of the center position of the lens in the cross section. A method for evaluating a lens, comprising: (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
The measurement of the lens at the cross section of the lens by the measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch. The approximate radius of the surface is obtained by the calculation unit,
This approximate radius, the slope of a straight line approximated to each difference in the cross section of the extracted cross section of the lens, or the approximate slope of a coefficient such as a quadratic curve, and the approximate radius in the cross section Is obtained by the arithmetic unit,
By calculating the product value as a displacement of the center position of the lens in the cross section by the calculation unit, the characteristics of the lens are evaluated based on the calculated displacement of the lens center position in the cross section. A lens evaluation method characterized by the above.   The lens evaluation method according to claim 2, wherein the calculation method of the approximate radius is a second-order least square method.   The displacement shape of the center position of the lens is approximated by the arithmetic unit in a plane perpendicular to the optical axis of the lens, and the displacement amount in the approximated perpendicular plane is a sag amount that is a value in the depth direction of the lens. 5. The lens evaluation method according to claim 1, wherein a position shift amount in a rotation direction in a perpendicular direction of the cross section is obtained by dividing by the calculation unit.   The displacement of the center position of each cross section of the lens in the plane perpendicular to the optical axis of the lens is approximated in the perpendicular plane by the arithmetic unit using a quadratic function, and the calculated quadratic coefficient is used. The amount of displacement in the approximated vertical plane is calculated by the calculation unit, and the calculation amount is divided by the calculation unit by the sag amount that is a value in the depth direction of the lens, whereby the perpendicular of the cross section is obtained. The lens evaluation method according to claim 1, wherein a positional deviation amount in a rotational direction of the direction is obtained. (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the positional deviation amount of each position and the positional deviation amount of each tilt in each ABC direction of the rotation direction around each XYZ axis,
(Iii) measurement data of a cross section of the lens obtained by sequentially extracting measurement data of a cross section of the lens parallel to the optical axis passing through the lens by a data extraction unit at a measurement pitch;
And (ii) out of the positional deviation amount of the lens, except for the position and the tilt deviation amount in a total of three directions of two directions of translation and tilt in the plane of the cross section of the lens. Using the amount of positional deviation at each position and the amount of positional deviation of each tilt, the calculation unit calculates the position in three directions and the amount of tilt deviation.
Further, the radius parameter in the lens cross section of the lens design formula is a value of the displacement calculation amount in the lens cross section, and the measurement data points extracted in the radius parameter value and the lens cross section The optimal radius parameter of each cross section obtained by the arithmetic unit and the optimal radius parameter of each cross section over the entire measurement surface of the lens is obtained by the arithmetic unit so that the difference from the column is minimized. A method for evaluating a lens, comprising evaluating a characteristic of the lens based on a parameter. (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And calculating each difference between each measurement data point sequence and the design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions in the rotational directions around the XYZ axes. ,
Data extraction means for sequentially extracting the measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the difference at a measurement pitch, and each difference in the cross section of the measurement data of the extracted cross section of the lens Approximate the function with a quadratic or higher order function, obtain this quadratic coefficient, and use the arithmetic unit to calculate a value that is twice the product of this coefficient and the square of the approximate radius of the measurement surface of the lens in the cross section. The characteristic of the lens is evaluated based on the calculated arc radius deviation amount in the cross section by calculating and calculating the value as an arc radius deviation amount in the cross section by the calculation unit. Lens evaluation method. (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
The measurement data of the cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch. The square of the difference from a quadratic function The value of the coefficient that minimizes is calculated by the calculation unit,
A value that is twice the product of the coefficient and the square of the approximate radius of the measurement surface of the lens in the cross section is obtained by the calculation unit,
A lens evaluation method characterized in that the characteristic of the lens is evaluated based on the arc radius deviation amount in the cross section by calculating this value as the arc radius deviation amount in the cross section by the calculation unit. (I) an XYZ measurement data point sequence on the measurement surface of the lens obtained by measurement means for measuring shape coordinate data in the XYZ directions on the measurement surface of the lens;
(Ii) XYZ position in the XYZ coordinate system obtained by the shift amount evaluation means for evaluating the coordinate shift amount of the lens design formula and the measurement data point sequence using the measurement data point sequence and the lens design formula And the difference between each measurement data point sequence and the lens design formula based on the positional deviation amount of each position and the positional deviation amount of each tilt in the respective ABC directions of the rotation directions around the XYZ axes. By the department,
For the measurement data of the YZ cross section of the lens parallel to the optical axis passing through the lens and the measurement data of the YZ cross section of the lens obtained by sequentially extracting the difference by the data extraction means at the measurement pitch, a quadratic function relating to each difference The value of the coefficient that minimizes the square of the difference from is calculated by the calculation unit,
For the measurement data of the YZ cross section of the lens sequentially extracted by the data extraction means, the calculation unit calculates the value of the coefficient that minimizes the square of the difference from the quadratic function with respect to the Z coordinate,
Using the value of the coefficient calculated later, an approximate arc radius in the YZ section of the lens is calculated by the calculation unit according to the formula: approximate arc radius = 1 / (2 × coefficient),
Using the previously calculated coefficient value and the calculated approximate arc radius in the YZ section of the lens, the deviation amount of the optical axis position in the XY section is calculated using the previously calculated coefficient and the approximate arc. Calculated by the calculation unit from the equation of the product with the radius,
The calculation unit obtains a value that is twice the product of the previously calculated coefficient and the square of the approximate radius of the measurement surface of the lens in the YZ section,
A lens evaluation method characterized in that the characteristic of the lens is evaluated based on the arc radius deviation amount in the cross section by calculating this value as the arc radius deviation amount in the cross section by the calculation unit. (I) The surface of the lens held by the lens holding jig can be measured from the front surface side of the lens holding jig, and the lens holding jig is inverted so that the lens holding jig is reversed from the back side of the lens holding jig. Using the lens holding jig having three spheres configured to measure the back surface and fixed to the lens holding jig, the surface of the lens and the three spheres from the front side of the lens holding jig. Measure the surface of
Next, the lens holding jig is turned upside down, and the back side of the lens and the surfaces of the three spheres are measured from the back side of the lens holding jig,
Next, the coordinate axis of the surface of the lens is calculated by a calculation unit with reference to the centers of the three spheres,
Next, the coordinate axis of the back surface of the lens is calculated by the calculation unit with reference to the center of the three spheres,
Next, the data of the front and back surfaces of the lens is synthesized based on the three spheres, and the characteristics of the lens on the front surface with respect to the front surface of the lens or on the front surface with respect to the back surface of the lens are evaluated. The lens evaluation method according to any one of 1 to 9.   In the lens holding jig, one holding part of the two holding parts for holding the lens of the lens holding jig supports the front and back surfaces of the end of the lens with one spherical surface from the vertical direction, 11. The measurement is performed in a state where the other holding portion supports the lower surface of the end portion of the lens with two spherical surfaces and supports the upper surface of the end portion of the lens with one spherical surface. The lens evaluation method described in 1.

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