JP2005292860A - Manufacturing method of diffractive lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a diffraction lens by calculating diffraction efficiencies for a plurality of wavelengths at a high speed. <P>SOLUTION: Diffraction efficiencies in a plurality of regions comprising at least one zone are calculated for a plurality of wavelengths sequentially and stored in a first storage means. Using the information on the diffraction efficiencies of the respective regions stored in the first storage means and the information of weights for the respective regions stored in a second storage means, the diffraction efficiency of the whole diffraction lens is calculated. On the basis of the calculation result, the performance of the diffraction lens is optimized, and thereafter the diffraction lens is manufactured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a diffractive lens, and in particular, to calculate the diffraction efficiency of a diffractive lens obtained by cutting with a diamond tool or a diffractive lens obtained by molding using a die cut with a diamond tool ( The present invention relates to a simulation) technique and an achromatic diffraction lens design technique.

  In recent years, many proposals have been made to increase the functionality of lenses such as achromatic lenses and bifocal lenses using diffractive lenses (for example, Patent Document 1 and Patent Document 2). Many of these diffractive lenses are so-called relief type diffractive lenses in which a periodic undulation is formed on the surface of a flat plate such as a lens or glass.

  There are two types of processing methods for relief type diffractive lenses. One is cutting with a diamond tool, and in this case, a serrated relief (undulation shape) can be processed. The other is a photolithography method, which approximates the serrated relief in a step shape, and is called a binary type.

  When using or designing a diffractive lens, diffraction efficiency is an important characteristic value.

  In the case of the binary type, the relationship between the number of masks used in the manufacturing process and the diffraction efficiency is generally known by Swanson et al. (Non-patent Document 1).

The diffraction efficiency of a periodic relief type diffraction grating whose pitch is sufficiently longer than the wavelength and whose phase change is about one wavelength is based on the cross-sectional shape of the material, and the phase lag of the transmitted wavefront from the refractive index of the material. Is obtained as a Fourier coefficient when the value is Fourier transformed (scalar diffraction theory) (for example, Non-Patent Document 2).
JP-A-8-171052 Japanese Patent Application No. 8-290080 G. J. Swanson and Wilfird B. Veldkamp, "Diffractive optical elements for use in infrared systems", Optical Engineering, Vol. 28, No. 6, (1989) M. C. Hutley, "Diffraction Grating", Academic Press, Chap. 2, 1982)

  FIG. 23A is a schematic view showing the processing of a diffraction lens mold using a diamond tool. A mold 1901 that rotates in the direction of the arrow is processed by a diamond tool 1902. The diamond tool has a sharp tip and is suitable for processing a diffraction lens or a mold for a diffraction lens.

  FIG. 23B is an enlarged view of the processing portion A of FIG. The tip 1903 of the diamond bit has an arc shape having a certain radius of curvature (nose radius) 1904. Here, even if the design shape is a sawtooth shape as indicated by a two-dotted line 1905, the hollow portion is processed into an arc shape 1906 having a radius substantially the same as the radius of curvature of the tip of the diamond bite. .

  FIG. 24 is a schematic cross-sectional view for explaining processing of a mold and a lens when a diffractive lens is formed on a flat plate for simplicity.

  When the design shape of the lens is FIG. 24A, the design shape of the mold for manufacturing this lens is as shown in FIG. However, when machining is performed using an arc-shaped diamond cutting tool 2001 having a predetermined radius of curvature, the corners that are concave in the cross section of the mold are rounded as shown in FIG. As a result, the molded lens has a relief shape as shown in FIG.

  FIG. 24 (e) is an enlarged cross-sectional view when the surface A part of the mold surface of FIG. 24 (c) after processing is finely observed. Depending on the feed speed of the cutting tool and the radius of curvature of the cutting tool, a cutting trace 2002 consisting of minute undulations remains. This cutting mark is also transferred to the lens surface.

  Since the diffraction efficiency of the diffractive lens is affected by the relief shape, the diffraction efficiency deviates from the design value when the shape deteriorates during the manufacturing process of the lens.

  In order to prevent the change in diffraction efficiency as described above, it is only necessary to use a cutting tool with a sharp tip, but at this time, the cutting distance necessary for processing becomes long, deterioration due to wear of the cutting tool becomes large, There are many technically difficult issues such as the fact that the bite itself tends to cause chipping and the like, and as a result, productivity is remarkably deteriorated.

  Here, as long as the relationship between the radius of curvature of the cutting tool tip and the diffraction efficiency of the obtained diffractive lens can be known, any tool can be selected in order to suppress the reduction in diffraction efficiency during the manufacturing process to an allowable range. This is useful in terms of production efficiency because it can be determined before cutting and it is not necessary to use a sharper cutting tool than necessary.

  In addition, if the diffraction efficiency can be calculated in consideration of the processing method when designing the diffractive lens, a lens that is easy to manufacture can be designed using the processing method as one of the lens design parameters. Therefore, there is a need for a method for simply calculating the finally obtained diffraction efficiency in consideration of the processing method during lens design.

  A typical example of the application of a diffractive lens is an achromatic lens. This corrects the chromatic aberration of the refractive lens with the chromatic aberration of the diffractive lens. As such lenses, JP-A-6-242373 and JP-A-8-171052 are known. The lenses disclosed in both of the above publications have a large number of ring zones of diffractive lenses, so that processing becomes difficult when the lens mold is processed by cutting using a diamond tool, etc. The diffraction efficiency is lowered due to the shape deterioration due to the curvature of the apex of. However, design considerations have not been made for these problems, and it has been difficult to ensure both diffraction efficiency and productivity.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for simply calculating the diffraction efficiency of a lens using a lens mold by cutting using a diamond tool.

  It is another object of the present invention to provide a diffractive integrated lens having excellent productivity in cutting using a diamond cutting tool and sufficiently satisfying an achromatic effect.

  In order to solve the above problems, the present invention has the following configuration.

  That is, the diffraction efficiency calculation device according to the first configuration of the present invention is a device that calculates the diffraction efficiency of a diffraction lens that is divided into a plurality of regions each including at least one annular zone. Information is extracted from first storage means for storing diffraction efficiency information, second storage means for storing weight information for the respective regions, and the first and second storage means, and the diffraction And a first calculating means for calculating the diffraction efficiency of the entire lens using the following formula (1).

j: Integer representing the order of the diffracted light E _j : Diffraction efficiency of the diffractive lens for the j-th order diffracted light M: Positive integer indicating the number of regions for calculating the diffraction efficiency (M> 1)
m: number of region η _mj : diffraction efficiency for j-th order diffracted light of m-th region
(Saved in the first storage means)
W _m : Weight ratio for the m-th area (stored in the second storage means)
The diffraction efficiency calculation method according to the first configuration of the present invention is a method for calculating the diffraction efficiency of a diffractive lens divided into a plurality of regions each including at least one annular zone. A first storage procedure for storing diffraction efficiency information; a second storage procedure for storing weight information for each region; and information stored by the first and second storage procedures. And a first calculation procedure for calculating the diffraction efficiency of the entire diffractive lens using the following equation (1).

j: Integer representing the order of the diffracted light E _j : Diffraction efficiency of the diffractive lens for the j-th order diffracted light M: Positive integer indicating the number of regions for calculating the diffraction efficiency (M> 1)
m: number of region η _mj : diffraction efficiency for j-th order diffracted light of m-th region
(Saved by the first storage procedure)
W _m : Weight ratio for the m-th area (saved by the second storage procedure)
The recording medium according to the first configuration of the present invention is a computer-readable recording medium that records a program for calculating the diffraction efficiency of a diffraction lens divided into a plurality of regions each including at least one annular zone. A first storage procedure for storing diffraction efficiency information in each region, a second storage procedure for storing weight information for each region, and the first and second storage procedures. The stored information is extracted, and a program for causing a computer to execute a first calculation procedure for calculating the diffraction efficiency of the entire diffractive lens using the following formula (1) is recorded.

j: Integer representing the order of the diffracted light E _j : Diffraction efficiency of the diffractive lens for the j-th order diffracted light M: Positive integer indicating the number of regions for calculating the diffraction efficiency (M> 1)
m: number of region η _mj : diffraction efficiency for j-th order diffracted light of m-th region
(Saved by the first storage procedure)
W _m : Weight ratio for the m-th area (saved by the second storage procedure)
According to each of the first configurations of the present invention, the diffraction lens is divided into a plurality of regions, and weighting is given to each region to obtain the overall diffraction efficiency. Even when the efficiency is different, the diffraction efficiency of the entire lens can be accurately and efficiently calculated. The calculation of the diffraction efficiency of the present invention is suitable to be performed using a computer.

  The diffraction efficiency calculation apparatus according to the second configuration of the present invention is an apparatus that calculates the diffraction efficiency of a diffraction lens divided into a plurality of regions each including at least one annular zone for a plurality of wavelengths. A first storage means for storing diffraction efficiency information for a plurality of wavelengths in each region; a second storage means for storing weight information for each region; and a relief cross-section of the diffraction lens. Third storage means for storing shape information, fourth storage means for storing information on a plurality of wavelengths, and a fifth storage section for storing information on a plurality of refractive indexes of the material of the diffractive lens for the plurality of wavelengths. A storage unit; a fourth calculation unit that calculates a cross-sectional shape of the relief of the diffractive lens stored in the third storage unit; and each region for the plurality of wavelengths stored in the first storage unit. Second diffraction means for calculating the diffraction efficiency using the information extracted from the third, fourth and fifth storage means, and the second calculation means is repeated as many times as the number of wavelengths. Information is extracted from the first and second storage means, the third repeating means to be operated, the fourth repeating means for causing the third repeating means to operate repeatedly as many times as the number of the regions, And a first calculating means for calculating the diffraction efficiency of the entire diffractive lens using the following equation (5).

j: Integer representing the order of diffracted light l: Wavelength number E _jl : Diffraction efficiency of the diffractive lens at the l-th wavelength with respect to j-th order diffracted light M: Positive integer indicating the number of regions where diffraction efficiency is calculated (M> 1)
m: number of region W _m : weight ratio for m-th region η _mjl : diffraction efficiency for j-th order diffracted light of m-th region at l-th wavelength Further, the diffraction efficiency calculation method according to the second configuration of the present invention Is a method for calculating the diffraction efficiency of a diffractive lens divided into a plurality of regions each including at least one annular zone with respect to a plurality of wavelengths, wherein information on the diffraction efficiency for the plurality of wavelengths in each region is obtained. A first storage procedure for storing; a second storage procedure for storing information on the weights for the respective regions; a third storage procedure for storing information on the sectional shape of the relief of the diffractive lens; A fourth storage procedure for storing wavelength information, a fifth storage procedure for storing information on a plurality of refractive indexes of the material of the diffractive lens for the plurality of wavelengths, and a third storage procedure. Diffraction The fourth calculation procedure for calculating the cross-sectional shape of the relief of the lens, and the diffraction efficiency in each of the regions for the plurality of wavelengths stored in the first storage procedure are the third, fourth, and fifth. A second calculation procedure for extracting and calculating information stored by the storage procedure, a third repetition procedure for repeating the second calculation procedure the same number of times as the number of wavelengths, and the third repetition procedure. Is extracted the same number of times as the number of the regions, and information stored by the first and second storage procedures is extracted, and the diffraction efficiency of the entire diffractive lens is expressed by the following equation (5). And a first calculation procedure to be used for calculation.

j: Integer representing the order of diffracted light l: Wavelength number E _jl : Diffraction efficiency of the diffractive lens at the l-th wavelength with respect to j-th order diffracted light M: Positive integer indicating the number of regions where diffraction efficiency is calculated (M> 1)
m: area number W _m : weight ratio for m-th area η _mjl : diffraction efficiency for j-th order diffracted light of m-th area at l-th wavelength The recording medium according to the second configuration of the present invention is A computer-readable recording medium on which a program for calculating the diffraction efficiency of a diffraction lens divided into a plurality of regions each including at least one annular zone with respect to a plurality of wavelengths is recorded, A first storage procedure for storing diffraction efficiency information with respect to a wavelength; a second storage procedure for storing weight information for each of the regions; and a third storage procedure for storing information on the sectional shape of the relief of the diffraction lens. A fourth storage procedure for storing information on a plurality of wavelengths, and a fifth storage procedure for storing information on a plurality of refractive indexes of the material of the diffractive lens for the plurality of wavelengths, A fourth calculation procedure for calculating a sectional shape of the relief of the diffractive lens, which is stored in the third storage procedure, and each region for the plurality of wavelengths stored in the first storage procedure. A second calculation procedure for calculating the diffraction efficiency by extracting the information stored by the third, fourth, and fifth storage procedures, and the second calculation procedure are repeated the same number of times as the number of wavelengths. A third iterative procedure to perform, a fourth iterative procedure to repeat the third iterative procedure as many times as the number of areas, and the information stored by the first and second storage procedures, A program for causing a computer to execute a first calculation procedure for calculating the diffraction efficiency of the entire diffractive lens using the following formula (5) is recorded.

j: Integer representing the order of diffracted light l: Wavelength number E _jl : Diffraction efficiency of the diffractive lens at the l-th wavelength with respect to j-th order diffracted light M: Positive integer indicating the number of regions where diffraction efficiency is calculated (M> 1)
m: number of region W _m : weight ratio for m-th region η _mjl : diffraction efficiency for j-th order diffracted light of m-th region at l-th wavelength According to each of the second configurations of the present invention, a plurality of When it is necessary to calculate the diffraction efficiency with respect to the wavelength, it can be calculated at a high speed with a relatively small storage capacity.

  The lens shape measuring device of the present invention is a lens shape measuring device for measuring the surface shape of an object to be measured comprising a diffractive lens or a diffraction lens mold, and measures the surface shape of the object to be measured. A shape measuring means, an arithmetic device for removing any one of a spherical surface, an aspherical surface and a flat surface of the object to be measured from the measurement data obtained by the shape measuring means, and the macroscopic component are removed. And a diffraction efficiency calculation device for calculating the diffraction efficiency of the diffractive lens based on the measured data, wherein the diffraction efficiency calculation device is the diffraction efficiency calculation device according to the first configuration.

  The diffraction efficiency calculation method of the present invention is a method for calculating the diffraction efficiency of a diffractive lens by measuring the surface shape of the object to be measured comprising a diffractive lens or a diffractive lens mold, A shape measurement procedure for measuring a surface shape, a calculation procedure for removing any component of the macroscopic spherical surface, aspherical surface, and plane of the object to be measured from the measurement data obtained by the shape measurement procedure; A diffraction efficiency calculation procedure for calculating the diffraction efficiency of the diffractive lens based on the measurement data from which the target component has been removed, and using the diffraction efficiency calculation method according to the first configuration as the diffraction efficiency calculation procedure. Features.

  The recording medium of the present invention is a computer-readable recording medium that records a program for calculating the diffraction efficiency of a diffractive lens by measuring the surface shape of an object to be measured, which is a diffractive lens or a diffractive lens mold. From the shape measurement procedure for measuring the surface shape of the object to be measured and the measurement data obtained by the shape measurement procedure, the macroscopic spherical surface, aspherical surface, or plane component of the object to be measured is removed. And a computer program for causing the computer to execute a calculation procedure for calculating the diffraction efficiency of the diffraction lens based on the measurement data from which the macroscopic component has been removed is recorded. The program for executing the procedure is a program recorded on the recording medium according to the first configuration.

  According to each of these configurations, the diffraction efficiency of the diffractive lens can be obtained by measuring the relief shape of the actually obtained diffractive lens or diffractive lens molding die. It is possible to know how much the shape accuracy of the mold affects the diffraction efficiency, and to obtain an effective judgment material for quality control of the product such as determination of tolerance of shape accuracy and selection of defective products. In addition, by comparing the diffraction efficiency calculated from the actually obtained relief shape with the diffraction efficiency obtained from the design relief shape, the relationship between the various conditions in the manufacturing process of the diffractive lens and the diffraction efficiency of the obtained lens Can know. Therefore, by reflecting this relationship in the lens design, it is possible to accurately predict the diffraction efficiency of the finally obtained diffractive lens and to select the optimum manufacturing conditions.

  The lens design apparatus of the present invention is an apparatus for designing a diffractive lens, and includes input means for inputting lens design data, and optical performance and diffraction efficiency of the diffractive lens obtained based on the design data. And a calculating means for calculating the diffraction efficiency is the diffraction efficiency calculating apparatus according to the first configuration.

  The lens design method of the present invention is a method for designing a diffractive lens, and includes an input procedure for inputting lens design data, and optical performance and diffraction efficiency of the diffractive lens obtained based on the design data. A calculation procedure for calculating the diffraction efficiency based on the result of the calculation procedure, and an optimization procedure for optimizing the performance of the lens. It is a method.

  The storage medium of the present invention is a computer-readable recording medium in which a program for designing a diffractive lens is recorded, and a program for causing a computer to execute an evaluation function used for lens performance evaluation is recorded. The program includes a program recorded on the recording medium according to the first configuration.

  According to each of these configurations, the optical characteristics and diffraction efficiency of the finally obtained diffractive lens can be accurately predicted based on the design data, so that both the correction amount of chromatic aberration and the allowable amount of diffraction efficiency are constrained. It is possible to design a lens while taking this into consideration. Accordingly, it is possible to design a diffractive lens having good characteristics efficiently in a short time. In addition, the calculation of the diffraction efficiency of the obtained lens takes into account the relationship between various conditions of the manufacturing process (for example, the radius of curvature of the tip of the cutting tool, the feed speed of the tool, etc.) and the diffraction efficiency of the resulting lens. The optimum manufacturing conditions can be selected simultaneously with the design.

A refractive / diffraction integrated lens according to the present invention is a refractive / diffraction integrated lens formed by forming a diffractive lens composed of a plurality of concentric annular zones on at least one surface of a refractive lens. K defined by the following formula (6) is
0.1 ≦ k
It is characterized by satisfying.

f: Synthetic focal length of the refractive and diffractive integrated lens f _d : Focal length of the diffractive lens f _g : Focal length of the refractive lens ν _d : Partial dispersion coefficient ν _g in the wavelength range of use of the diffractive lens ν: The refractive lens According to the above configuration, a refractive diffraction integrated lens or a refractive diffraction integrated lens molding die can be manufactured with high productivity by cutting using a diamond bite.

The objective lens according to the present invention is a refractive and diffractive integrated light formed by forming a diffractive lens composed of concentric annular zones on at least one surface of a single lens composed of an entrance surface and an exit surface. An objective lens for an information recording / reproducing apparatus, wherein k defined by the following equation (6) is
0.2 ≦ k ≦ 0.6
It is characterized by satisfying.

f: Synthetic focal length of the refractive and diffractive integrated lens f _d : Focal length of the diffractive lens f _g : Focal length of the refractive lens ν _d : Partial dispersion coefficient ν _g in the wavelength range of use of the diffractive lens ν: The refractive lens According to the above configuration, when manufacturing an objective lens or a molding die for an objective lens by cutting using a diamond tool, both good chromatic aberration correction and lens productivity can be achieved. Can do. Therefore, the optical head device provided with the objective lens of the present invention has a small change in the focal length of the objective lens even when the wavelength of the light source changes, and can reduce stray light, so that a good signal output can be obtained. Further, since the objective lens having such characteristics can be constituted by a single lens, the optical head can be miniaturized.

The imaging lens according to the present invention is a refractive and diffraction integrated type formed by forming a diffractive lens composed of concentric annular zones on at least one surface of a single lens composed of an entrance surface and an exit surface. An imaging lens, and k defined by the following formula (6) is
0.3 ≦ k
It is characterized by satisfying.

f: Synthetic focal length of the refractive and diffractive integrated lens f _d : Focal length of the diffractive lens f _g : Focal length of the refractive lens ν _d : Partial dispersion coefficient ν _g in the wavelength range of use of the diffractive lens ν: The refractive lens According to the above configuration, the imaging lens or the imaging lens molding die can be manufactured with high productivity by cutting using a diamond bite. Furthermore, when 0.4 ≦ k ≦ 0.7 is satisfied, an imaging lens having excellent processability and good imaging performance can be obtained. Therefore, the image pickup apparatus including the image pickup lens of the present invention can obtain an image with less flare and excellent chromatic aberration.

  According to the diffraction efficiency calculation apparatus of the present invention, the diffraction lens is divided into a plurality of regions, and weighting is given to each region to obtain the overall diffraction efficiency. Therefore, the diffraction efficiency is different for each region. Even in this case, the diffraction efficiency of the entire lens can be calculated accurately and efficiently. The calculation of the diffraction efficiency of the present invention is suitable to be performed using a computer.

  Further, according to the lens shape measuring apparatus of the present invention, the diffraction efficiency of the diffractive lens can be obtained by measuring the relief shape of the actually obtained diffractive lens or diffractive lens molding die. Can determine how much the accuracy of the shape of the lens and lens mold influences the diffraction efficiency, and is an effective judgment material for quality control of products such as determining the tolerance of shape accuracy and selecting defective products Can be obtained. In addition, by comparing the diffraction efficiency calculated from the actually obtained relief shape with the diffraction efficiency obtained from the design relief shape, the relationship between the various conditions in the manufacturing process of the diffractive lens and the diffraction efficiency of the obtained lens Can know. Therefore, by reflecting this relationship in the lens design, it is possible to accurately predict the diffraction efficiency of the finally obtained diffractive lens and to select the optimum manufacturing conditions.

  Further, according to the lens design apparatus of the present invention, the optical characteristics and diffraction efficiency of the finally obtained diffractive lens can be accurately predicted based on the design data, so the correction amount of chromatic aberration and the allowable amount of diffraction efficiency. It is possible to design a lens while considering both of these constraints. Accordingly, it is possible to design a diffractive lens having good characteristics efficiently in a short time. Further, by considering the relationship between various conditions of the manufacturing process and the diffraction efficiency of the obtained lens in the calculation of the diffraction efficiency of the obtained lens, it is possible to simultaneously select the optimum manufacturing conditions simultaneously with the lens design.

  In addition, according to the refractive and diffraction integrated lens of the present invention, a refractive and diffraction integrated lens or a refractive and diffraction integrated lens molding die can be manufactured with high productivity by cutting using a diamond bite.

  In addition, according to the objective lens of the present invention, it is possible to achieve both good chromatic aberration correction and lens productivity when manufacturing an objective lens or a molding die for an objective lens by cutting using a diamond tool. Therefore, the optical head device provided with the objective lens of the present invention has a small change in the focal length of the objective lens even when the wavelength of the light source changes, and can reduce stray light, so that a good signal output can be obtained. Further, since the objective lens having such characteristics can be constituted by a single lens, the optical head can be miniaturized.

  Further, according to the imaging lens of the present invention, the imaging lens or the imaging lens molding die can be manufactured with high productivity by cutting using a diamond bite. Furthermore, when 0.4 ≦ k ≦ 0.7 is satisfied, an imaging lens having excellent processability and good imaging performance can be obtained. Therefore, the image pickup apparatus including the image pickup lens of the present invention can obtain an image with less flare and excellent chromatic aberration.

  Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

(First embodiment)
In the case of a diffractive lens manufactured by cutting, the degree of shape change due to the cutting tool varies depending on the ring zone. In an annular zone where the interval (pitch) of the annular zone is long, the influence of the shape deterioration due to the cutting tool is relatively small, whereas in an annular zone where the interval of the annular zone is short, the influence becomes serious.

  In general, in a diffractive lens, the annular zone at the center of the lens has a long pitch and becomes shorter toward the periphery.

  For this reason, the diffraction efficiency differs between the vicinity of the center of the lens and the vicinity of the periphery.

  In order to know the diffraction efficiency of the entire lens, it can be obtained by a weighted average of diffraction efficiency for each part of the lens.

(Example 1)
FIG. 1 shows an external view of a diffraction efficiency calculation apparatus according to the first embodiment of the present invention.

  Reference numeral 101 denotes a computer main body, 102 a display, 103 an FDD (flexible disk drive device), 104 a keyboard, 105 an HDD (hard disk drive device), and 106 a printer. Each device is connected to the computer main body 101 by a connection cable 107. An arithmetic unit and a local memory device are built in the computer main body 101.

  FIG. 2 shows the configuration of the apparatus described above. Input from the keyboard and data read by FDD are stored in the HDD device. Data necessary for the calculation is read from the HDD into the local memory, and a calculation necessary for the calculation unit is performed, and the result is stored in the HDD. The calculation result is output to a display or a printer.

  A computer program for calculating diffraction efficiency using a computer is recorded in the HDD, and the arithmetic unit reads the program from the HDD onto a local memory and executes the program. The program may be recorded on the flexible disk 108 or the optical disk 109 shown in FIG.

  Here, the “storage means” of the present invention is means for storing information, and information printed (output) by an information recording medium such as a flexible disk, hard disk, local memory, optical disk, or printer. It refers to recording media. The “storage procedure” refers to a process of storing information, and includes recording (saving) information on a flexible disk, hard disk, local memory, optical disk, etc., printing (output) by a printer, and the like.

  The “calculation means” of the present invention is a means for performing numerical calculation using information, and generally refers to an arithmetic unit of a computer. The “calculation procedure” refers to a process of performing numerical calculation using information.

  The “repeat means” of the present invention refers to repeatedly operating the arithmetic unit by a computer program, but the computer operator may send an instruction to the computer via means such as a keyboard to repeat the calculation operation. Further, the “repeating procedure” means repeating a predetermined procedure (processing).

  In the present invention, “retrieving information from storage means” refers to reading data from a flexible disk using an FDD, reading data from a hard disk using an HDD, and reading data from an optical disk using an optical disk drive. Reading data from a local memory, and inputting data printed out by a computer operator from a keyboard.

  The “recording medium on which the program is recorded” of the present invention refers to any medium for storing computer software, such as a flexible disk, a hard disk, an optical disk, or a print output by a printer.

  These means (procedures) may be devised as new means (procedures) due to the advancement of computer technology in the future. The newly devised apparatus and method also have the functions of each means of the present invention. Needless to say, if the same as (procedure), it is included in the present invention. In the present invention, each means (procedure) described above does not depend on a specific apparatus or method, but depends on the function of each means (procedure). For example, instead of a storage medium such as a flexible disk, an information terminal connected to a network via a network cable may be used, and data may be transmitted / received from the information terminal. This corresponds to the extraction of information from.

  Further, in the following description, in order to avoid duplicated explanation, explanation will be focused on “apparatus” having predetermined “means”, but these explanations are related to “method” having a predetermined “procedure” at the same time. It should be construed that the description relates to a computer-readable “recording medium” in which a program for causing a computer to execute a predetermined “procedure” is recorded.

When the diffraction efficiency of the m-th region when the diffraction element is divided into a plurality of regions is η _mj and the weighting factor for each region is W _m , the apparatus of the present embodiment has the following formula ( 1) is calculated.

Here, in order for the calculation of Expression (1) to be a weighted average of η _mj , W _m needs to satisfy the following Expression (7).

  However, the above formula (7) does not necessarily have to be satisfied when performing simple calculations.

  FIG. 3 shows an algorithm for calculating the above. In this example, the diffractive lens is divided into M areas.

  The storage means stores in advance the diffraction efficiency information of each region when the diffractive lens is divided into M regions, and the weight of each region.

  FIG. 4 is a conceptual diagram showing storage states of the diffraction efficiency information stored in the first storage unit and the weight ratio information stored in the second storage unit.

  FIG. 4A shows the configuration of the first storage means for storing diffraction efficiency information when the diffraction orders to be calculated are three orders of 0th order, −1st order, and 1st order. When there are three orders to be calculated, a two-dimensional data array composed of M × 3 elements is obtained. Such a data array may be configured on any storage means such as a main memory or a flexible disk of a computer as long as it is an apparatus capable of storing data and reading out necessary data.

  FIG. 4B shows the configuration of the second storage unit that similarly stores information on the weight of each region. This is M data strings. Similarly to the above, any storage device of the computer may be used.

  In the present invention, the storage means refers to a recording area inside or outside the computer main body for storing such data arrangement or data string or single data, and any storage area constituting the calculation device. You may comprise above. Hereinafter, description of which storage area is used for each storage means is avoided, and only memory is described.

In addition, regarding a data array, when the subscript is omitted, it indicates the entire array, and when it is described with a subscript, it indicates a single element therein. For example, in the case of FIG. 4, “η” indicates a storage area secured on a computing device made up of (M × 3) elements, and “η ₁₀ ” indicates one of the elements.

In FIG. 3, in the first step 2101, the diffraction order to be calculated is set. In the next step 2102, the value of the memory E _i is initialized to 0 and the area counter m is initialized to 1. In the next step 2103, the diffraction efficiency information η _mi of the i-th order diffracted light in the m-th region and the weight ratio W _m for the m-th region are read from the first and second storage means, respectively, and η _mi and W _m Add the product to E _i . In the next step 2104, it is checked whether or not the area counter m is equal to M in order to determine whether or not the calculation of all areas has been completed. If not m = M, there is an area that has not yet been added, so the process proceeds to step 2105, where the area counter m is incremented by 1, and step 2103 is performed. If m = M in 2104, the process proceeds to step 2106. Steps 2102 to 2015 correspond to the first calculation means of the present invention. In step 2106, it is determined whether to calculate another diffraction order. If it is necessary to calculate the diffraction efficiency of another order, the process proceeds to step 2107, the diffraction order to be calculated next is set to i, and the processing after step 2102 is performed again. If other order calculations are unnecessary, the calculation is terminated.

  By using the apparatus of the present embodiment, it becomes possible to efficiently and accurately calculate the diffraction efficiency of the entire lens of lenses having different diffraction efficiency for each region.

  In the present embodiment, the case of calculating a plurality of diffraction orders has been described as an example. However, in the case of calculating only a single order, in order to calculate a plurality of orders in the steps shown in FIG. The calculation can be performed by the algorithm prepared in step 2 omitting steps 2101, 2106, and 2107.

(Example 2)
In the first embodiment, it is assumed that the diffraction efficiency of each region is known in advance and is stored in the memory before the calculation is started. However, in practice, the diffraction efficiency of each region is often unknown. In such a case, the shape and refractive index of the diffractive lens are measured, and the diffraction efficiency of each region is obtained using the data, and the diffraction efficiency of the entire lens is calculated based on that. FIG. 5 shows a calculation algorithm in this case.

  In the memories as the third, fourth, fifth and second storage means, the sectional shape data of the relief of the diffractive lens, the wavelength of the light source, the refractive index of the lens material with respect to the wavelength, and each ring zone, respectively. It is assumed that each piece of weight information is stored in advance.

  In step 301, the number of lens ring zones is obtained and stored in the memory M based on the relief shape data stored in the memory as the third storage means. Also, the memory m, which is a ring zone counter, is initialized to 1.

  In step 302, the relief shape information of the mth annular zone is extracted from the third storage means, and the wavelength and refractive index information are extracted from the fourth and fifth storage means, respectively, and the diffraction efficiency of the mth annular zone is extracted. And the result is stored in the corresponding area of the memory η which is the first storage means. This step 302 is the second calculation means of the present invention.

  In step 303, it is checked whether step 302 has been performed for all the annular zones. If m = M does not hold, there is a ring zone that has not yet been calculated. At this time, the routine proceeds to step 304, where m is incremented by one and step 302 is performed again. These steps 303 and 304 are the first repeating means. Further, when m = M is established, it indicates that the step 302 has been executed for all the annular zones. At this time, all of the memories η as the first storage means are included in the memory η. The diffraction efficiency of the annular zone is preserved.

  Step 305 is a step for obtaining the diffraction efficiency of the entire lens. When all steps from step 301 to step 304 are executed, the diffraction efficiencies of all the annular zones are stored in the memory η which is the first storage means. The second storage means stores weight information as known information in advance. Therefore, the diffraction efficiency of the entire lens can be calculated by executing the algorithm already described in the first embodiment in step 305.

  As described above, the diffraction efficiency of the entire lens can be calculated if the relief shape and refractive index are known even if the diffraction efficiency information of the individual annular zone is unknown by using the apparatus of this embodiment. It is possible to obtain useful information.

Example 3
In the second embodiment, an example of an algorithm in the case where one annular zone of the diffractive lens is divided into one region is shown. The pitch of the annular zone of the diffractive lens is wide at the center of the lens and becomes narrower toward the periphery. Here, in the periphery of the lens, the pitch between adjacent annular zones may be substantially the same. In such a case, the diffraction efficiency of such an annular zone can be regarded as substantially the same. Therefore, if a plurality of annular zones that can be regarded as having substantially the same diffraction efficiency are handled as one region, it is possible to reduce the storage capacity required for the memory η and the memory W, and further, the calculation amount can be reduced. Can be calculated.

Example 4
Several methods are known for calculating the diffraction efficiency based on the fine relief shape of the diffraction element. In the case of a diffractive lens, sufficiently satisfactory accuracy can be obtained by scalar diffraction theory using Fourier transform. A detailed calculation algorithm at this time is shown in FIG.

  In step 401, the sectional shape data of the relief of the annular zone to be calculated is set in the data array D secured on the computing device for work. At this time, if the number of elements in the data array is set to a power of 2, FFT (Fast Fourier Transform) can be used in the Fourier transform, and the calculation process can be speeded up. Specifically, about 4096 are good.

  Subsequently, in step 402, the wavelength λ and the refractive index N are read from the memories which are the third and fourth storage units, respectively, and the complex amplitude of the transmitted light is obtained by using these, and from the same number of elements as the data array D. Is stored in the complex array P secured on the computer.

  In the next step 403, FFT of the complex array P is performed. The Fourier coefficient is stored in the complex array P by the processing of this step.

  In step 404, each element of the complex array P is multiplied by a complex conjugate to obtain a real number. Next, each element is normalized so that the sum of all elements of the complex array P is 1. As a result, the diffraction efficiency corresponding to each order is stored in the complex array P.

  In step 405, the required order diffraction efficiency information is read from the complex array P and stored in the memory η as the first storage means.

(Second Embodiment)
In the embodiments described so far, it is assumed that a suitable value is previously stored in the storage unit for the weighting ratio for each region when the diffractive lens is divided into a plurality of regions. However, if these can be calculated based on the intensity distribution of the light source and the diameter of the annular zone of the diffractive lens, the labor required for data input can be saved.

  The weight ratio may be a value obtained by dividing the amount of light incident on each region of the diffractive lens by the amount of light incident on the entire lens.

  When it can be assumed that the light incident on the diffractive lens has a uniform intensity distribution, use the value obtained by dividing the area of each region by the effective diameter of the lens as the weight factor. Is possible.

(Example 5)
The calculation of the weight ratio when the area information of each region is stored in the memory (sixth storage means) will be described.

The region (effective region) through which the light beam of the diffractive lens is transmitted is divided into M regions, and the area of the _mth region is Sm. First, read the area of each region is stored in the sixth storing means to sum it and calculating the area S _t of the effective region. That is, the following formula (8) is calculated.

  Subsequently, the following formula (9) is calculated from m = 1 to m = M in order.

  The third calculation means of the present invention calculates the weight of each annular zone by the above calculation.

The obtained weight ratio W _m for each annular zone is stored in a memory which is a second storage means for storing information on the weight ratio. The weight obtained in this way satisfies the following formula (7).

  Therefore, the product-sum operation of this weight factor and the diffraction efficiency of each region becomes a weighted average obtained by weighting the diffraction efficiency of each region by the area of the corresponding region.

(Example 6)
When the diffractive lens is composed of concentric annular zones, the weight ratio can be calculated from the information on the radius of the annular zone instead of the information on the area of each annular zone.

Here, it is assumed that the annular zones are counted in order from the center of the lens, and the total number of annular zones is M. That is, the annular zone at the center of the lens is the first annular zone and the outermost annular zone is the Mth zone. When the radius of the m-th zone is represented by R _m , the radius R _M of the outermost zone is the effective radius of the lens. _Assuming that R _m is stored in the data array that is the seventh storage means, this R _m is sequentially read out, and the following expression (3) and expression are given to each element of the weight array W that is the second storage means. Save the calculation result of (4).

R _m : Radius of the m-th annular zone counted from the lens center W _m : Weight ratio of the m-th annular zone M: Number of annular zones m: Number when the annular zones are counted in order from the lens center A weight factor W _m proportional to the area of each ring zone is obtained. Further, the weight obtained in this way satisfies the following formula (7).

  Therefore, the product-sum operation of this weight factor and the diffraction efficiency of each region becomes a weighted average obtained by weighting the diffraction efficiency of each region by the area of the corresponding region.

(Example 7)
When a laser light source or the like is used, it is known that the intensity distribution of the emitted light is not uniform but a Gaussian distribution. In the case of a semiconductor laser or the like, the emitted light beam has an elliptical shape.

  FIG. 7A schematically illustrates the state of light emitted from the semiconductor laser. In the semiconductor laser light source 601, the emitted light beam is an ellipse, and the intensity distribution of the emitted light beam is different between the short axis direction (x axis) 602 and the long axis direction (y axis) 603 of the ellipse. The biaxial intensity distribution is, for example, as shown in FIG. When such a light source is used, it is not preferable to use a weight ratio proportional to the area of the annular zone because the calculation result is greatly deviated from the actual result.

Therefore, as shown in FIG. 7B, when the intensity of the light beam at the center of the beam is normalized as 1, the intensity (ratio to the vertex) at the effective diameter 604 of the lens in the cross section along the x axis and the y axis is obtained. _{Let Ix} and Iy. In the case where the incident light intensity is as shown in FIG. 7B, if there is information of I _x and I _y , the incident light to each annular zone is more realistic than the weight ratio proportional to the area of the annular zone. The weight ratio proportional to the strength can be calculated.

  FIG. 8 shows a specific algorithm.

It is assumed that the incident light intensity information I _x and I _y is stored in advance in a memory which is an eighth storage unit.

  In step 501, assuming that the incident light has an intensity distribution as shown in FIG. 7B, the total amount of light incident on the lens is calculated, and the calculation result is stored in another memory.

  In the next step 502, the annular zone counter m is initialized to 1.

In step 503, the amount of light incident on the mth annular zone is determined using the information on the radius of each annular zone and the information on the intensity distribution of the incident light beam stored in the seventh storage means described in the sixth embodiment. calculate. In the subsequent step 504, the amount of light incident on the m-th annular zone obtained in step 503 is divided by the total amount of light stored in the memory, and the quotient is set as the weight W _m of the m-th annular zone in the second storage means. Is stored in the weight array W. Steps 503 and 504 are the third calculation means of the present invention.

  In step 505, it is confirmed whether or not steps 503 and 504 have been executed for all the annular zones. If m = M does not hold, the process proceeds to step 506, where m is incremented by one and steps 503 and 503 are performed. 504 is executed again. If m = M, it means that 503 and 504 have been executed for all the annular zones. At this time, W is in a state in which the weight ratio information of all the annular zones is stored.

According to this algorithm, it is possible to obtain a weight ratio approximately proportional to the light intensity of the light beam incident on each annular zone. Further, the weight ratio W _m obtained by this calculation satisfies the following formula (7).

  Therefore, the product-sum operation of the weighting factor and the diffraction efficiency of each region is a weighted average obtained by weighting the diffraction efficiency of each region with the light intensity incident on the corresponding region.

  Therefore, according to the present embodiment, it is possible to calculate the diffraction efficiency in consideration of the intensity distribution of the incident light to the lens.

(Third embodiment)
In the diffraction efficiency calculation apparatus of the embodiment described so far, the relief shape is assumed to be known. However, it is possible to calculate the relief shape after processing based on the design relief shape if you know the design relief shape data at the stage of designing the lens and the information about the tool bit for cutting or the feed speed of the bite. is there. That is, based on this information, it is possible to calculate the diffraction efficiency of the lens finally obtained by taking into account the change in the relief shape of the designed lens due to manufacturing.

  In the following embodiments, a case where a diffractive lens is molded using a diffractive lens mold cut by a cutting tool will be described as an example. However, the present invention is not limited to such a case, and can be similarly applied to a case where a diffraction lens is directly cut with a cutting tool without using a mold.

(Example 8)
FIG. 9 shows a calculation algorithm of the diffraction efficiency calculation apparatus according to the third embodiment of the present invention.

  First, input the data necessary for the calculation. That is, the design shape of the relief of the diffractive lens, the tip radius of the cutting tool used for cutting the mold, the wavelength of the light source used for the lens, and the refractive index of the lens material are input in order, respectively. , 10th, 4th and 5th storage means are stored in the memory.

  In step 701, the number of annular zones of the diffractive lens is stored in the memory M, and the annular zone counter m is initialized to 1.

  Step 702 is a step of obtaining a relief shape after processing based on information on the shape of the design relief, and saving it in a relief shape storage memory as a third storage means.

  First, information about the design relief shape of the m-th annular zone and the nose radius information t at the tip of the machining tool are extracted from the memory serving as the ninth and tenth storage means.

  FIG. 10 illustrates the process in step 702. In FIG. 10A, reference numeral 801 denotes a design shape of a serrated relief. Here, when a lens is manufactured by press molding or injection molding using a mold, the shape obtained by rounding the apex that becomes concave in the mold (the apex that becomes convex in the lens) with the nose radius t of the bite is processed. Relief shape. That is, in the case of the relief 801, the vertex 802 may be rounded with the radius t. Therefore, by inscribing an arc 803 having a radius t to 801, a processed relief shape 804 shown in FIG. 10B is obtained. This 804 is stored in a memory for storing the relief shape, which is the third storage means. In the case where a lens is manufactured by cutting a lens material with a cutting tool, a concave portion in the relief of the lens may be rounded with a radius t. This step 702 is the fourth computing means of the present invention.

  Step 703 is a step of calculating the diffraction efficiency of the annular zone. In this step, for example, as described in the second embodiment, information on the relief shape, wavelength, and refractive index is respectively extracted from the memory that is the third, fourth, and fifth storage means, and the diffraction efficiency is calculated. The calculation result is stored in the memory η which is the first storage means.

  Step 704 checks whether m = M. If m = M does not hold, the process proceeds to step 705, m is incremented by 1, and steps 702 and 703 are repeated again. Steps 704 and 705 serve as both the first and second repeating means. When m = M is established in 704, it means that the steps 702 and 703 have been executed for all the annular zones, and in that case, the memory η as the first storage means has each annular zone. The diffraction efficiency information is stored.

  Step 706 is a step for obtaining the weight ratio W for each annular zone. Since the specific calculation contents of this step have already been described in the fifth, sixth, or seventh embodiment, a description thereof will be omitted. Information on the weight ratio of each zone obtained in step 706 is stored in the memory W as the second storage means.

  Step 707 is a step for obtaining the diffraction efficiency of the entire lens. The specific calculation contents are the same as those in the first embodiment, and a description thereof is omitted here.

  As described above, the diffraction efficiency can be calculated based on the lens design data and the processing tool information by using the apparatus of this embodiment.

  For reference, FIG. 11 shows an example of a relief shape after processing calculated by the apparatus of this embodiment. 2301 and 2306 are relief design shapes having pitches of 25 μm and 127 μm, respectively, and a depth of 1.292 μm (the scales in the vertical direction and the horizontal direction in FIG. 11 do not match). This depth D exactly satisfies the following formula (10) when the refractive index n of the material is 1.5262 and the wavelength λ of the light source is 680 nm.

  Therefore, the design reliefs 2301 and 2306 in FIG. 11 have a relief shape in which the diffraction efficiency of the first-order diffracted light is 100% when the surface reflection is ignored. When such a design relief mold is processed with a tool having a nose radius of 10 μm, the calculated relief shapes are 2302 and 2307, respectively. Also, the relief shape calculation results obtained when machining with a tool having a nose radius of 30 μm are 2304 and 2309, respectively. Two-dot chain lines 2303, 2305, 2308, and 2310 indicate the design relief shapes 2301 or 2306 of the respective annular zones. Further, the results of calculating the diffraction efficiency of the first-order diffracted light of these annular zones by the method using FFT are 100% for the design reliefs 2301 and 2306, 94.3% for the relief 2302, and 90.0% for the relief 2304. Relief 2307 is 73.5%, and relief 2309 is 54.5%.

Example 9
Depending on the feed speed of the cutting tool, cutting marks may remain on the relief after processing. Since the relief shape after processing has a periodic undulation due to the cutting trace, diffracted light is generated by the undulation. As a result, the diffraction efficiency of the actually used order of the lens is lowered. Therefore, if a simulation is performed in consideration of the cutting trace, the relationship between the processing tool feed speed and the obtained lens diffraction efficiency can be known. This can be useful data for studying the lens manufacturing process.

  In order to perform this calculation, it is possible to use the algorithm shown in FIG. 12 as the fourth calculation means shown as step 702 in the description of the eighth embodiment. FIG. 13 is a diagram for explaining this algorithm.

  In FIG. 13A, the relief design shape is a sawtooth shape indicated by a solid line 901, the nose radius of the machining tool is t, and the machining tool feed amount per rotation of the die to be cut is s. In addition, it is assumed that these pieces of information are stored in advance in the ninth, tenth, and eleventh storage units of the calculation device in advance.

  In FIG. 12, in step 1001, the design relief shape is read from the memory which is the ninth storage means, and stored in a data array temporarily reserved in the memory of the computer for work.

In the next step 1002, using the value of the memory S which is the eleventh storage means, the contact at the tip of the byte is obtained on the relief, and this is temporarily saved in the memory of the computer for use as a work. Save to array P. Specifically, in FIG. 13A, a line 902 in which the spacing in the relief pitch direction (horizontal axis direction in FIG. 13) is parallel to the feed speed s is drawn, and the intersection point P ₁ between the line 902 and the design relief 901 is drawn. , P ₂ , P ₃ ,..., P _G−1 , P _G are obtained, and the coordinates are stored in the memory. Here, it is assumed that there are G intersections.

  In the next step 1003, the counter g is initialized to 1.

In step 1004, determining the arc C _g of radius t in contact with the design relief in P _g.

In step 1005, it is checked whether or not the arc obtained in 1004 intersects the design relief shape. If intersects (e.g., if the arc C _G in FIG. 13) proceeds to step 1007. If not, the process proceeds to step 1006.

  In step 1006, the arc shape obtained above is stored in the shape storage array, and the process proceeds to step 1007.

  In step 1007, it is confirmed whether or not step 1004 has been performed for all intersection points P. If g = G is not satisfied, the process proceeds to 1008, where g is incremented by 1, and the next calculation is performed. When g = G, the calculation is complete.

  Thus, the shape data 903 after processing taking into consideration the cutting feed rate shown in FIG. 13B is stored in the shape storage array. This data is stored in a memory which is a third storage means.

(Fourth embodiment)
In the case of a lens used over a wide wavelength range such as a photographic lens, it is necessary to calculate the diffraction efficiency at a plurality of wavelengths. In this case, the calculation processing of the embodiment described so far may be repeated for the necessary wavelengths, but the calculation amount increases in proportion to the number of wavelengths to be calculated.

  Here, since the step of obtaining the relief shape after processing from the design relief shape is a step of obtaining an equation of an arc inscribed in the design relief as shown in, for example, Example 8, and obtaining the envelope thereof, There is a lot of calculation. Since the calculation for calculating the relief shape after processing is the same regardless of the calculation of diffraction efficiency for any wavelength, the relief shape should be calculated and stored once, and the result used for calculating the diffraction efficiency for all wavelengths. Thus, the amount of calculation can be reduced and the processing speed can be increased as compared with the case where the calculation methods described in the embodiments so far are repeated by the number of wavelengths. The same can be said for the calculation of the weight ratio.

  Furthermore, when the relief shape after processing a certain annular zone is obtained from the design relief shape, the diffraction efficiencies at all wavelengths calculated using the relief shape after processing are calculated in order, and are calculated in the storage means. It is only necessary to store the diffraction efficiency and then calculate the relief shape after processing the next annular zone. The calculation of such a procedure is to first calculate the relief shapes after processing of all the annular zones, save them in the storage means, and then sequentially read out the stored relief shapes after processing. Compared with the case of sequentially calculating the diffraction efficiency at the wavelength to be processed, the relief shape data after processing has a large capacity, so that there is an advantage that the required storage capacity can be reduced and the time required for reading the data can be reduced.

(Example 10)
FIG. 14 is an explanatory diagram of an algorithm of the diffraction efficiency calculation apparatus according to the fourth embodiment.

  In advance, in the memories which are the ninth, tenth, fourth, fifth and seventh storage means, respectively, the information on the design shape of the relief of the lens, the information on the processing tool, the plurality of wavelength information, It is assumed that information on the refractive index corresponding to a plurality of wavelengths and information on the radius of the annular zone of the diffractive lens are stored.

  Step 1101 is an initialization step for starting the calculation. A memory which is the first, second and third storage means is secured on the calculation device, the number of lens ring zones is M, and the wavelength to be calculated. Is initialized to L and the memory m is initialized to 1.

  Step 1102 extracts the relief design shape and bite nose radius information from the ninth and tenth memories, calculates the relief shape after processing the annular zone, and stores it in the memory as the third storage means. . Detailed calculation contents of this step correspond to step 702 of the eighth embodiment. This step 1102 corresponds to the fourth calculation means of the present invention.

  In step 1103, the wavelength counter is initialized to 1. In the subsequent step 1104, the processed relief shape, the wavelength corresponding to the 1st wavelength, and the refractive index information of the material for the lth wavelength are extracted from the memory as the third, fourth and fifth storage means. Then, the diffraction efficiency is calculated and stored in the memory which is the first information storage means. This step 1104 is the second calculation means.

  In step 1105, it is determined whether l = L. If l = L, it means that step 1104 has been executed for all wavelengths, and the process proceeds to the next 1107. If l = L does not hold, it means that there is a wavelength that has not been calculated yet, so the process proceeds to step 1106, where l is incremented by 1, and step 1104 is executed again. Steps 1105 and 1106 correspond to a third repeating unit.

  In step 1107, it is determined whether m = M. If m = M, it means that steps 1102, 1103, 1104 have been executed for all the annular zones. If m = M does not hold, it means that there is an annular zone that has not been calculated yet, so the process proceeds to step 1108, where m is increased by 1, and steps 1102, 1103, and 1104 are executed again. Steps 1107 and 1108 are the fourth repeating means.

  In step 1109, the information on the radius of the zonal zone is extracted from the memory which is the seventh storage means, the weight is calculated, and is stored in the memory which is the second storage means for storing the weight. The calculation content of this step may be the same as the content already described in the sixth embodiment. Note that the information on the weighting ratio stored in the second storage means is calculated by the method of Example 5 or Example 7 of the second embodiment, not by the method of Example 6 calculated from the radius of the annular zone. Also good.

  In step 1110, the wavelength counter l is initialized to 1. In the next step 1111, the diffraction efficiency information for each annular zone and the information on the weight of the annular zone for the l-th wavelength are extracted from the first and second storage means, and the entire lens for the l-th wavelength is extracted. Calculate the refractive index. In step 1112, it is determined whether l = L. If l = L, it means that step 1111 has been executed for all wavelengths, and the calculation is terminated. If l = L does not hold, it means that there is a wavelength that has not been calculated yet, so the procedure proceeds to step 1113, where l is increased by 1, and step 1111 is executed again. By these steps 1110, 1111, 1112, and 1113, the following formula (5) is executed.

j: integer representing the order of the diffracted light l: wavelength number E _jl : diffraction efficiency of the diffractive lens at the l-th wavelength with respect to the j-th order diffracted light M: positive indicating the number of areas of the object for calculating the diffraction efficiency Integer (M> 1)
m: Number of the area of the object to be calculated W _m : Weight ratio for the mth area η _mjl : Diffraction efficiency for the jth order diffracted light of the mth area at the _lth wavelength The steps 1110, 1111, 1112, 1113 are the first 1 computing means.

  When the calculation algorithm shown in this embodiment is used, it is possible to perform multi-wavelength calculations at a high speed with a relatively small storage capacity. Therefore, when designing a lens for use in a wide wavelength range such as a camera lens, the calculation time can be shortened, which is particularly useful.

(Fifth embodiment)
The shape of the manufactured diffractive lens or lens molding die can be measured using an ultra-precision shape evaluation device such as a surface roughness meter. In manufacturing a diffractive lens, knowing how much the accuracy of the shape of the lens or lens molding die affects the diffraction efficiency is important for product quality control, such as determining tolerances and selecting defective products.

(Example 11)
FIG. 15 is a configuration diagram of a lens shape measuring apparatus according to the fifth embodiment.

  The test lens 1201 is disposed on the stage 1202. The stage 1202 is moved in the horizontal direction by the stage controller 1203. The stylus 1204 is controlled to move in the vertical direction by the stylus control device 1205 so as to contact the lens.

  The stage control device 1203 and the stylus control device 1205 transfer the stage coordinate Y and the stylus coordinate Z to the arithmetic unit 1206. A data string composed of a set of stage coordinates Y and stylus coordinates Z corresponding thereto is lens shape information. A hard disk drive (HDD) 1207 stores a program for calculating diffraction efficiency using a computer, and an arithmetic unit 1206 reads the program to control the apparatus and obtain data. Data necessary for calculating the diffraction efficiency is input from the keyboard 1208. A display 1209 displays a calculation result, measured shape information, and the like.

  FIG. 16 shows a software algorithm for calculating the diffraction efficiency using the computer of this embodiment.

  Step 1301 is a step of inputting data. Data for shape measurement such as the measurement range and the number of sampling points of the measurement lens to be measured, and data necessary for diffraction efficiency such as the refractive index and wavelength of the glass material are input.

  Step 1302 is a step of measuring the shape. While moving the stage 1202 in the horizontal direction using the stage controller 1203, the coordinate data of the stage at that time and the coordinate data of the stylus from the stylus controller 1205 are calculated by the computer. The data is stored in the measurement data array U secured in advance in the memory area.

  Here, a solid line 2201 in FIG. 17A is an example of data obtained when a refractive / diffraction integrated lens is measured using a surface roughness meter. The vertical axis 2202 coincides with the optical axis of the lens to be measured, and the vertical axis direction corresponds to the sag amount of the lens. The horizontal axis 2203 corresponds to the direction from the lens center to the outer periphery (radial direction) of the lens.

  In the next step 1303, it is determined whether the measurement data is a mold or a lens. If the measurement data is a lens, the process proceeds to step 1305. If the measurement data is mold measurement data, the process proceeds to step 1304. In step 1304, the data is inverted to create lens shape data, and the measurement is performed. Save to data array U.

  In step 1305, the measured shape data is fitted to an aspherical surface, a spherical surface, or a plane using a least square method or the like. In the subsequent step 1306, the shape of the aspherical surface, spherical surface or plane obtained in step 1305 is removed from the measurement data array U and stored in the relief shape array L.

  FIG. 17 is a diagram for explaining the processes 1305 and 1306. In calculating the diffraction efficiency of a diffractive lens, the microscopic undulation shape of the lens surface is important. However, when a diffractive lens is measured using a shape measuring device such as a surface roughness meter, the measurement is performed in a state where a microscopic undulation shape is superimposed on a macroscopic curved surface shape as indicated by a solid line 2201. The Therefore, it is necessary to remove the macroscopic curved surface shape data of the lens from the measurement data. A broken line 2204 in FIG. 17A is a plot of the aspheric polynomial obtained in step 1305. A relief shape 2205 shown in FIG. 17B is a result of removing the macroscopic shape data 2204 from the measurement data 2201 in step 1306. The relief shape 2205 is stored in the shape array L.

  In step 1307, the annular zone counter m is initialized to 1, and in step 1308, the diffraction efficiency of the m-th annular zone is calculated and stored in the memory which is the first storage means. In step 1309, it is confirmed whether calculation has been completed for all the annular zones. If there is an annular zone that has not yet been calculated, m is incremented by one in step 1310 and step 1308 is repeated. If it is confirmed in step 1309 that the calculation has been completed for all the annular zones, the process proceeds to step 1311 where the weighting factor for each annular zone is calculated and the memory serving as the second storage means. Save to. In step 1312, information on the diffraction efficiency for each annular zone and the weighting factor for each annular zone is extracted from the memory serving as the first and second storage means, and the diffraction efficiency of the entire lens is obtained. The calculation of the diffraction efficiency of the entire lens in steps 1307 to 1312 can be calculated using the diffraction efficiency calculation apparatus of the present invention described in the first embodiment or the second embodiment.

  In this embodiment, the stylus type shape measuring device has been described. However, this is another shape measuring device such as an optical non-contact shape measuring device or a shape measuring device using atomic force. Needless to say, it works the same way.

  If the shape measuring apparatus described in the present embodiment is used as described above, the diffraction efficiency can be easily calculated from the measured shape of the diffraction lens or the diffraction lens mold.

(Sixth embodiment)
FIG. 18 is an explanatory diagram of a lens design algorithm in consideration of diffraction efficiency according to the sixth embodiment.

  First, the target specification of the lens is determined (step 1401), and then the initial parameters of the lens are input (step 1402). Subsequently, the optical performance is calculated by tracing the ray with respect to the input lens parameter (step 1403), and it is confirmed whether the performance satisfies the target specification (step 1404). If the performance is satisfactory, the process proceeds to step 1406; otherwise, the lens parameters are modified in step 1405, and step 1403 for evaluating the optical performance is repeated.

  In step 1406, the diffraction efficiency considering the processing is calculated. This calculation can be performed using the diffraction efficiency calculation apparatus described in the third embodiment of the present invention.

  It is examined whether the diffraction efficiency obtained by the calculation in Step 1407 satisfies the system design conditions. If the diffraction efficiency is satisfied, the design is completed (Step 1408). If the diffraction efficiency is unsatisfactory, The parameters of the diffractive lens are corrected (step 1405), and the process returns to step 1403 of the optical performance calculation.

  Correcting the parameters so as to improve the diffraction efficiency corrects the lens data in the direction of widening the pitch of the diffractive lens. At this time, it is effective to improve the diffraction efficiency especially when the narrow pitch portion of the outer peripheral portion of the lens is widened. At this time, it is necessary to correct the aberration caused by the correction of the pitch of the diffractive lens by correcting the aspherical coefficient of the refractive lens.

  Even if the power of the entire diffractive lens is reduced, the pitch of the diffractive lens can be increased as a result, which is effective in improving the diffraction efficiency. In this case, the chromatic aberration correction amount decreases when chromatic aberration correction is performed by a diffraction lens, but by designing using this method, both the correction amount of chromatic aberration and the allowable amount of diffraction efficiency can be achieved. It is possible to design a lens in consideration of the constraint conditions.

  If the method for calculating the diffraction efficiency of the present invention is incorporated in the lens design software, it is possible to obtain a more optimal design solution while simplifying the above-described steps. More specifically, as one of the merit functions (evaluation functions) of lens design, diffraction efficiency taking into account processing may be used. This can be easily realized simply by incorporating the program for calculating the diffraction efficiency of the present invention into the lens design software. In this way, the designer can request diffraction efficiency as an evaluation function in the same way as the aberration condition, and obtain a design solution that minimizes the evaluation function using a well-known optimization technique such as the DLS method. It becomes possible.

  As described above, as described in the present embodiment, if the diffraction efficiency can be known in consideration of processing at the time of lens design, it is effective when designing an optical system in which restrictions on the diffraction efficiency are severe.

(Seventh embodiment)
Here, a lens designed using the lens design apparatus of the sixth embodiment will be described.

  In the present embodiment, a design of an achromatic lens that corrects chromatic aberration of a refractive lens with a diffraction lens will be described as an example. At the time of designing the lens, correcting the lens design data so as to improve the diffraction efficiency means correcting the pitch so as to widen the pitch of the diffractive lens. There are two ways of correcting the pitch as shown below.

  One is to increase the focal length of the diffractive lens. By doing so, the pitch can be expanded as a whole, and the diffraction efficiency is improved. When the focal length of the diffractive lens is increased under the constraint that the total focal length of the entire lens is constant, the refractive lens needs to be shortened accordingly, and as a result, the chromatic aberration correction condition can be satisfied. Therefore, the lens has optical characteristics such that chromatic aberration is insufficiently corrected.

  The other is to increase the pitch at the periphery of the lens. This is effective in preventing this because the diffraction efficiency is remarkably lowered at a fine pitch in the peripheral portion. In this case, the chromatic aberration of the light beam transmitted near the center of the lens is corrected, but the lens characteristic is such that the chromatic aberration is insufficiently corrected for the light beam passing through the periphery of the lens.

  A lens that combines the above two concepts can also be designed. In other words, the focal length of the diffractive lens is set to be slightly longer than the achromatic condition, and the pitch around the lens is slightly expanded from the normal pitch. When designed in this way, the overall amount of undercorrection of chromatic aberration and the amount of undercorrection of chromatic aberration with respect to the light beam transmitted through the periphery of the lens can be smaller than in the case of independently improving the diffraction efficiency. The deterioration of characteristics can be reduced.

  As described above, the chromatic aberration correction lens designed by using the lens design apparatus of the sixth embodiment seems to be insufficiently corrected for chromatic aberration, but when it is manufactured by cutting using a diamond tool, A lens with little decrease in diffraction efficiency due to manufacture can be obtained.

(Eighth embodiment)
Here, a refractive-diffraction integrated lens according to the eighth embodiment will be described. The integrated refractive and diffractive lens is a lens formed by forming a diffractive lens composed of a plurality of concentric annular zones on at least one surface of a refractive lens.

The design center wavelength of the lens is λ ₁ , and the wavelengths before and after that are λ ₂ and λ ₃ . When the refractive index of the lens material at each wavelength is n ₁ , n _2, and n ₃ , the partial dispersion coefficient ν _g in the used wavelength range of the refractive lens and the partial dispersion coefficient ν _d in the used wavelength range of the diffractive lens are as follows: It defines like Formula (11) and Formula (12).

When the focal length of the refractive lens is f _g , the focal length of the diffractive lens is f _d , and the combined focal length is f, the following formula (13)

When the focal length is selected so as to satisfy the above, chromatic aberration is removed at each wavelength of λ ₁ , λ ₂ , and λ ₃ .

  Here, in the design of a general optical apparatus, there is some tolerance for chromatic aberration, and it is often sufficient to reduce to about half of the chromatic aberration of a glass lens or a resin lens alone. In this case, the above equation (13) can be rewritten as the following equation (14).

  Here, k is a coefficient indicating how much the chromatic aberration of the glass (or resin) lens itself is removed, and when k = 0, the chromatic aberration is 0, and when k = 1, diffraction is performed. This is the case when no lens is used.

here,
0.1 ≦ k ≦ 0.9
Is a condition for correcting chromatic aberration while ensuring good diffraction efficiency. If k exceeds the lower limit, the lens has a large number of ring zones, and the pitch of the ring zones becomes narrow. In order to obtain efficiency, it is necessary to use a sharp bite, and productivity is deteriorated. If the upper limit is exceeded, chromatic aberration cannot be corrected satisfactorily, and the effect of integrating the diffractive lens becomes insufficient.

Also,
0.2 ≦ k ≦ 0.8
Is more preferable.

(Ninth embodiment)
FIG. 19 shows a schematic shape and an optical path of an objective lens used in the optical information recording / reproducing apparatus according to the ninth embodiment.

  Reference numeral 1501 denotes an objective lens for the optical information recording / reproducing apparatus of the present invention, which is a refractive / diffraction integrated lens provided with a diffractive lens 1502 on the incident surface side of the refractive lens. Reference numeral 1503 denotes a protective resin for the information recording medium, and 1504 denotes an incident light beam.

  In the optical information recording / reproducing apparatus, since the transmission wavelength of the light source laser changes when the output is changed, it is desirable that the objective lens has a small focal length change due to the wavelength change. The lens shown in this embodiment has a configuration in which the refractive lens and the diffractive lens have positive refractive powers, and the chromatic aberration of the refractive lens is corrected by the diffractive lens.

Here, since the wavelength variation of the semiconductor laser light source for the optical information recording / reproducing apparatus is about several nanometers, it is only necessary to consider achromaticity in the range of the design wavelength ± 10 nm. That is, partial dispersion may be calculated as λ ₂ = λ ₁ -10 nm and λ ₃ = λ ₁ +10 nm.

  Here, when the numerical aperture (NA) of the lens is N, the minimum pitch p of the diffractive lens can be roughly expressed by the following formula (15).

  Here, the optical information recording / reproducing apparatus has a light source wavelength λ of about 650 nm to 800 nm and an NA of about 0.45 to 0.65.

In general, when a lens mold is cut using a cutting tool, it is preferable that the nose radius at the tip of the cutting tool is about 10 μm. A bit smaller than that can improve the diffraction efficiency, but is not preferable because the productivity becomes worse. Here, for the above coefficient k,
0.2 ≦ k ≦ 0.6
Is a range of k suitable for an objective lens of an optical information recording / reproducing apparatus. When k is lower than the lower limit, the minimum pitch p is shortened when a lens or a lens mold is processed using a cutting tool having a nose radius of about 10 μm, leading to a decrease in diffraction efficiency. Further, when k exceeds the upper limit of the above formula, the effect of correcting chromatic aberration is reduced, and the merit of integrating the diffraction lens cannot be fully exhibited.

Also,
0.3 ≦ k ≦ 0.55
Is a condition for satisfactorily ensuring diffraction efficiency in the case of a high NA lens having an NA of 0.5 or more. Since the minimum pitch becomes fine when NA is high, the lower limit of k needs to be increased, and since the high NA lens has a short focal depth, the upper limit needs to be about 0.55.

(Example 12)
An example in which a lens for an optical head is designed by a combined system of a refractive lens and a diffractive lens (refractive diffraction integrated lens) when the focal length of the entire optical system is 3 mm is shown.

  Table 1 shows the refractive index for each wavelength of the lens material used in the design.

At this time, ν _g and ν _d are ν _g = 830.01735 and ν _d = −34.

  Tables 2 to 4 show the design results when the coefficient k is changed in three ways under the condition of the composite focal length f = 3.0 mm. In the table, the diffraction efficiency is the result of calculating the diffraction efficiency when processing using a tool having a nose radius of 10 μm using the diffraction efficiency calculation apparatus of the present invention.

  From the above, the diffraction efficiency can be improved by setting 0.3 ≦ k.

  Subsequently, similar design results when the combined focal length is 5 mm are shown in Tables 5 to 7 below.

  Subsequently, a case where the focal length is 3 mm and another material is used will be described.

  Table 8 shows the refractive index for each wavelength of the lens material used in the design.

At this time, ν _g and ν _d are ν _g = 881.50345 and ν _d = −34.0. Tables 9 to 11 show the design results.

  From the design examples shown in the above table, the diffraction efficiency can be improved by keeping k in a certain range regardless of the material and focal length.

In the present embodiment, m-th ring zone radius r _m of the diffractive lens was calculated by the following equation (16).

  Other methods for calculating the zonal radius are known, such as a method using a virtual high refractive index. The purpose of the present application is that a refraction / diffraction achromatic lens having excellent processability can be designed without impairing diffraction efficiency by selecting the focal length of the refraction lens and the diffraction lens so that k falls within a certain range. It goes without saying that the same effect can be obtained even when the zone radius is designed using the method.

  In this embodiment, the lens for the optical head is used. However, if the light source has an optical system having the same wavelength fluctuation as that of the semiconductor laser, the lens is designed within the scope of the present invention so that the diffraction efficiency and chromatic aberration can be corrected. Needless to say, a balance can be realized.

  In this embodiment, the diffractive lens is provided on the incident surface side of the lens. However, it goes without saying that the same effect can be obtained when the diffractive lens is provided on the exit surface side of the lens.

(Tenth embodiment)
Next, the configuration of an optical head according to the tenth embodiment of the invention will be described with reference to the drawings.

  FIG. 20 is a configuration diagram of the optical head of the present embodiment.

  The divergent light beam 1602 from the semiconductor laser light source 1601 becomes a substantially parallel light beam 1604 by the collimator lens 1603, passes through the beam splitter 1605, and is condensed on the disk 1607 by the objective lens 1606 for the optical information recording / reproducing apparatus of the present invention. The reflected light from the disk 1607 becomes a substantially parallel light beam by the objective lens 1606 for the optical information recording / reproducing apparatus of the present invention, is reflected by the beam splitter 1605, and is condensed on the light receiving element 1609 by the detection optical system 1608.

  Here, since the output of the semiconductor laser light source 1601 changes between information recording and reproduction, the wavelength slightly changes. Since the objective lens described in the ninth embodiment is used as the objective lens 1606, a change in the focal length of the objective lens due to chromatic aberration is small. In addition, since the diffraction efficiency of the diffractive lens is good, stray light can be reduced, so that a good signal output can be obtained.

(Eleventh embodiment)
Subsequently, an imaging lens according to an eleventh embodiment of the present invention will be described with reference to the drawings.

  FIG. 21 is a configuration diagram of the imaging lens of the present invention. Reference numeral 1701 denotes an imaging lens according to the present invention, which is an integrated refractive and diffractive lens provided with a diffractive lens 1702 composed of a plurality of concentric annular zones on the incident surface side of the refractive lens. Incident light 1703 is focused on an image plane 1704 by a lens.

  In this lens, both the refractive lens and the diffractive lens have a positive refractive power, and the chromatic aberration of the refractive lens is corrected using the diffractive lens.

In the case of an imaging lens, the wavelength range to be used is wide, and it is necessary to consider not only the diffraction efficiency of the reference wavelength λ ₁ but also the diffraction efficiency of λ ₂ and λ ₃ . When the diffraction efficiency is lowered at a wavelength other than the reference wavelength, the image obtained by the lens becomes an image containing flare, which is not preferable.

  In the imaging lens of the present invention, the coefficient k preferably satisfies the following relationship.

0.3 ≦ k
If k exceeds the lower limit of the above equation, it is necessary to process with a very sharp tool to obtain satisfactory diffraction efficiency, which impairs the productivity of the lens.

Moreover,
0.4 ≦ k ≦ 0.7
Is preferably satisfied. The lower limit of this expression is a condition for obtaining satisfactory diffraction efficiency in a bright lens having an F number of about 1.5, and the upper limit is a condition for reducing the residual chromatic aberration to half that of a refractive lens alone.

(Example 13)
Here, three design examples in which the value of k is changed for a lens having a combined focal length of 5 mm and an F number of 1.55 for the diffractive lens and the refractive lens will be compared.

λ ₁ , λ ₂ , and λ ₃ are d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) in consideration of using the visible light region.

  Table 12 shows the reference wavelength used in the design and the refractive index of the lens material at that wavelength.

  Tables 13, 15, and 14 are designs for k = 0, 0.4, and 0.7, respectively. In the table, the diffraction efficiency is the diffraction efficiency when processed using a tool having a nose radius of 10 μm. It is the result calculated using the diffraction efficiency calculation apparatus of invention.

  When k = 0, the number of annular zones is large and the minimum pitch is small. As a result, even if processing is performed using a tool having a nose radius of 10 μm, the diffraction efficiency cannot be secured satisfactorily.

  On the other hand, when designed with k = 0.4, good diffraction efficiency can be ensured even when a tool with a nose radius of 10 μm is used, and productivity is good. It can be seen that further improvement is obtained when k = 0.7.

In the present embodiment, m-th ring zone radius r _m of the diffractive lens, was calculated using the following equation (16).

  Other methods for calculating the zonal radius are known, such as a method using a virtual high refractive index. The purpose of the present application is that a refraction / diffraction achromatic lens having excellent processability can be designed without impairing diffraction efficiency by selecting the focal length of the refraction lens and the diffraction lens so that k falls within a certain range. It goes without saying that the same effect can be obtained even when the zone radius is designed using the method.

In this embodiment, d-line, F-line, and C-line are used as λ ₁ , λ ₂ , and λ ₃ , respectively, but this takes into account the spectral distribution of the subject and the sensitivity characteristics of the image sensor. May be changed. Even when the wavelength is changed, it goes without saying that a design solution that takes into account both diffraction efficiency and chromatic aberration correction can be obtained by designing with the method shown in the present invention.

  In this embodiment, the diffractive lens is provided on the incident surface side of the lens. However, it goes without saying that the same effect can be obtained when the diffractive lens is provided on the exit surface side of the lens.

(Twelfth embodiment)
Next, an imaging device according to a twelfth embodiment of the present invention will be described with reference to the drawings.

  The imaging apparatus shown in FIG. 22 is configured using an imaging lens 1801, a CCD device 1802, and a signal processing circuit 1803 of the present invention.

  The refraction / diffraction integrated lens 1801 forms an image of a subject on the CCD device 1802. The CCD device 1802 converts the optical image into an electrical signal. The electrical signal output from the CCD 1802 is processed into image data by the signal processing circuit 1803.

  Here, the lens according to the eleventh embodiment of the present invention is used as the refractive-diffraction integrated lens. Therefore, even if chromatic aberration is removed with a single lens integrated with a diffractive lens, the diffraction efficiency is good and an image output with little flare can be obtained.

1 is an external view of a diffraction efficiency calculation apparatus according to a first embodiment of the present invention. The block block diagram of the diffraction efficiency calculation apparatus which concerns on the 1st Embodiment of this invention Explanatory drawing of the algorithm of the diffraction efficiency calculation apparatus which concerns on the 1st Embodiment of this invention. Explanatory drawing of the data arrangement | sequence of the diffraction efficiency calculation apparatus which concerns on the 1st Embodiment of this invention. Explanatory drawing of the calculation algorithm of the diffraction efficiency calculation apparatus which concerns on the 1st Embodiment of this invention Explanatory drawing of algorithm of calculation method of diffraction efficiency using FFT Illustration of light intensity distribution of semiconductor laser Explanatory drawing of the calculation algorithm of the diffraction efficiency calculation apparatus which concerns on the 2nd Embodiment of this invention Explanatory drawing of the algorithm of the diffraction efficiency calculation apparatus which concerns on the 3rd Embodiment of this invention. Explanatory drawing of calculation of the relief shape after the process in the 3rd Embodiment of this invention. The figure which showed the example which calculated the relief shape after a process from the design relief shape in the diffraction efficiency calculation apparatus which concerns on the 3rd Embodiment of this invention. Explanatory diagram of the algorithm to calculate the relief shape after processing taking into account the feed rate of the tool Explanatory drawing of the process of calculating the relief shape after processing taking into account the feed rate of the tool Explanatory drawing of the calculation algorithm of the diffraction efficiency calculation apparatus which concerns on the 4th Embodiment of this invention. The block diagram of the lens shape measuring device which concerns on 5th Embodiment Explanatory drawing of the algorithm of the lens shape measuring apparatus which concerns on 5th Embodiment Explanatory drawing of data processing to remove macroscopic curved surface shape from shape measurement data Explanatory drawing of the algorithm of the lens design which considered the diffraction efficiency based on 6th Embodiment The figure which shows schematic shape and optical path of the objective lens of the optical information recording / reproducing apparatus concerning 9th Embodiment Configuration of an optical head according to the tenth embodiment The figure which shows the lens for imaging which concerns on 11th Embodiment Configuration of an imaging apparatus according to a twelfth embodiment Schematic diagram of die cutting using diamond tool Schematic diagram of mold processing using diamond tool and lens molded using it

Explanation of symbols

101 Computer Main Body 102 Display 103 FDD (Flexible Disk Drive Device)
104 Keyboard 105 HDD (Hard Disk Drive Device)
106 Printer 107 Connection cable 108 Flexible disk 109 Optical disk 601 Semiconductor laser 602 x-axis 603 y-axis 604 Effective diameter of lens 801 Design relief shape 802 Apex of design relief 803 Arc having the same radius as the nose radius of the cutting tool 804 Calculated Relief shape after machining 901 Design shape of relief 902 Straight line drawn in parallel at the same interval as the feed speed s of the cutting tool 903 Calculation result of relief shape after cutting 1201 Test lens 1202 Stage 1203 Stage controller 1204 Stylus 1205 Stylus control device 1206 Arithmetic device 1207 Hard disk drive device (HDD)
DESCRIPTION OF SYMBOLS 1208 Keyboard 1209 Display 1501 Objective lens for optical information recording / reproducing apparatus 1502 Diffraction lens 1503 Protective resin for information recording medium 1504 Incident light beam 1601 Laser light source 1602 Diverging light beam 1603 Collimating lens 1604 Substantially parallel light beam 1605 Beam splitter 1606 For optical information recording / reproducing apparatus Objective lens 1607 disc 1608 detection optical system 1609 light receiving element 1701 imaging lens 1702 diffractive lens 1703 incident light 1704 image plane 1801 imaging lens 1802 CCD device 1803 signal processing circuit 1901 mold 1902 diamond tool 1903 diamond tool tip 1904 nose Radius 1905 Design shape 1906 Shape after processing 2001 Diamond bit 2002 Cutting mark The data 2202 vertical axis obtained by 201 shape measurement (sag amount of the lens)
2203 Horizontal axis (lens diameter)
2204 Aspherical surface obtained by least square method 2205 Relief shape obtained by removing aspherical surface from measurement data 2301 Designed relief shape 2302 Relief shape processed with 10 μm byte 2303 Designed relief shape 2304 Relief shape processed with 30 μm bite 2305 Design Relief shape 2306 Design relief shape 2307 Relief shape machined with 10 μm bite 2308 Design relief shape 2309 Relief shape machined with 30 μm bite 2310 Design relief shape

Claims (1)

A method of manufacturing a diffractive lens, each of which is divided into a plurality of regions including at least one annular zone,
An input procedure for inputting design data of a diffractive lens to be manufactured;
A calculation procedure for calculating the optical performance and diffraction efficiency of the diffractive lens obtained based on the design data;
An optimization procedure for optimizing the performance of the diffractive lens based on the result of the calculation procedure;
A manufacturing procedure for manufacturing the diffractive lens obtained by the optimization procedure,
The calculation procedure is as follows:
A first storage procedure for storing diffraction efficiency information for a plurality of wavelengths in each region;
A second storage procedure for storing weight information for each of the areas;
A third storage procedure for storing information on the cross-sectional shape of the relief of the diffractive lens;
A fourth storage procedure for storing information of a plurality of wavelengths;
A fifth storage procedure for storing information on a plurality of refractive indexes of the material of the diffractive lens for the plurality of wavelengths;
A fourth calculation procedure for calculating a cross-sectional shape of the relief of the diffractive lens, which is stored in the third storage procedure;
Calculating the diffraction efficiency in each region for the plurality of wavelengths stored in the first storage procedure by extracting the information stored in the third, fourth, and fifth storage procedures and calculating the second Calculation procedure and
A third iterative procedure for repeating the second computation procedure as many times as the number of wavelengths;
A fourth iterative procedure in which the third iterative procedure is repeated as many times as the number of regions;
A first calculation procedure for extracting the information stored by the first and second storage procedures and calculating the diffraction efficiency of the entire diffractive lens using the following equation (5): A method for manufacturing a diffractive lens.

j: Integer representing the order of diffracted light l: Wavelength number E _jl : Diffraction efficiency of the diffractive lens at the l-th wavelength with respect to j-th order diffracted light M: Positive integer indicating the number of regions where diffraction efficiency is calculated (M> 1)
m: number of region W _m : weight ratio for m-th region η _mjl : diffraction efficiency for j-th order diffracted light of m-th region at l-th wavelength

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