WO2007142100A1

WO2007142100A1 - Optical system manufacturing method

Info

Publication number: WO2007142100A1
Application number: PCT/JP2007/061016
Authority: WO
Inventors: Tomokazu Masubuchi; Masayuki Imaoka; Toshiya Takitani; Kohtaro Hayashi; Jun Ishihara; Yasuhiro Matsumoto; Yoshihiro Okumura
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2006-06-05
Filing date: 2007-05-30
Publication date: 2007-12-13
Also published as: CN101460295A; JPWO2007142100A1; KR20080113298A; KR101034431B1; CN101460295B; JP4111251B2

Abstract

A projection optical system (PS) manufacturing method evaluates an optical performance of an entire system from approximate planes of all the optical planes in the projection optical system (PS) and changes at least one of the approximate planes of all the optical planes (such as a reduction side lens plane (S(L2s)) of a second lens L2 of an initial article referred to as 'a change approximate plane') so as to obtain a change amount of tbe change approximate plane when optimal optical performance is obtained as the entire system. According to the change amount, a correction treatment amount for the cavity plane of a metal mold corresponding to the change approximate plane is obtained to perform correction treatment, thereby manufacturing a new cavity plane.

Description

Specification

Manufacturing method of optical system

Technical field

The present invention relates to a method for manufacturing an optical system mounted on an image projection apparatus (projector) or the like.

Background art

In recent years, optical elements molded with a resin such as plastic have been used in a processing optical system and a laser scanning optical system. This is because such an optical element made of resin is cheaper and lighter than an optical element made of glass, and is superior in mass productivity.

[0003] Further, a resin optical element is manufactured by a molding method such as injection molding or injection compression molding using a mold (mold member). Therefore, a resin optical element has an advantage that it can easily form a curved surface (optical surface) having an aspherical shape or a free-form surface shape, compared to a glass optical element.

However, when an optical element having an optical surface with a complicated shape such as an aspherical shape or a free-form surface is molded with a mold, surface defects occur due to non-uniform cooling and shrinkage on the optical surface. It's easy to do. For this reason, it is generally performed to measure a defective and difficult surface shape and correct the mold based on the measurement result (Patent Document 1).

[0005] Patent Document 2 is an example of the measurement of the surface shape. In the method of Patent Document 2, the optical surface is aspherically approximated using data obtained by three-dimensional measurement of the optical surface, and the polynomial approximated surface is incorporated into the optical system, so that the optical surface of the optical element is integrated. Performance (change in aberrations). Then, by evaluating the optical performance, the optical surface (optimum shape optical surface) required to exhibit the desired optical performance is found, and the mold is corrected so that it becomes the optimal shape optical surface. It may be processed.

Patent Document 1: JP-A-7-60857

Patent Document 2: JP 2004-361274 A

Disclosure of the invention Problems to be solved by the invention

[0006] However, the evaluation method of Patent Document 2 approximates an error between optical surface measurement data (three-dimensional measurement data) and predetermined design value data as a whole surface by a polynomial (error polynomial). Therefore, if there is a local undulation (undulation part) on the measured optical surface, using an approximate expression of higher order to properly represent the undulation part, other than the undulation (non-undulation part) High-order undulation will occur. On the other hand, if the low-order approximation formula is used to properly represent the non-waviness part, the waviness part cannot be represented properly.

[0007] Further, in the optical element molding method of Patent Document 1, the optical surface is corrected so that an error between the measurement data on the optical surface that appropriately corrects the waviness portion and the predetermined design value data is offset. The cavity surface of the mold corresponding to is corrected and processed, and the optical element is reshaped.

However, in this molding method, in the case of an optical system having a plurality of optical elements, it is necessary to correct the mold of each optical element with the aim of the design value shape. For this reason, at least the number of mold corrections is required by the number of optical surfaces of the optical element, and it takes a very long time to manufacture the optical system.

[0009] The present invention has been made in view of the above situation. An object of the present invention is to provide a method for manufacturing an optical system (more specifically, an optical system including a plurality of optical elements) in a short time and at a low cost while being efficient.

Means for solving the problem

The present invention is a method for manufacturing an optical system including a plurality of optical surfaces by molding using a mold member. In this method of manufacturing an optical system, an approximate surface of all the optical surfaces of the optical system including the optical surface formed by the initial molding is set, and an approximate surface of all the optical surfaces in the optical system is used. The first optical performance evaluation process for evaluating the optical performance and at least one of the approximate surfaces of all optical surfaces molded by the mold member is a change approximate surface, while the molded member of the approximate surfaces of all the optical surfaces is molded At least one surface that is

The amount of change calculation process to obtain the amount of change of the approximated surface when the optimum optical performance of the entire system is exhibited, and the amount of correction processing to the cavity surface of the mold member corresponding to the approximated surface of change based on the amount of change The first correction processing step to create a new cavity surface, and the first molding to mold the optical element using the correction mold member processed in the first correction processing step And a second molding step in which the optical element is molded using a mold member other than the correction mold member.

[0011] According to this manufacturing method, not all the cavity surfaces of all the mold members are corrected. In other words, a powerful manufacturing method can perform correction processing with a desired optical surface as a change approximate surface and priority given to the corresponding cavity surface. Therefore, the number of corrections of the mold member is relatively small, and the optical system is manufactured in a short time and at a low cost while being efficient.

[0012] In the first molding step, an approximate surface is set based on the measurement result of the surface shape of the optical surface corresponding to the new cavity surface in the optical element molded with the mold member having the new cavity surface. And a second correction processing step for correcting the new cavity surface so as to cancel out the shape error between the approximate surface of the optical surface corresponding to the new cavity surface and the new cavity surface, and a second correction processing step. And a step of molding an optical element using the correction mold member processed in step (b).

[0013] The second correction process is performed only on the already corrected cavity surface (new cavity surface). For this reason, the second correction processing is only a light burden compared to the burden of correcting all the cavity surfaces. In addition, the optical performance of the optical system falls within an allowable range if correction processing that cancels the shape error is performed with high accuracy. Then, the existence of this lightly burdened second correction process enables the optical system manufacturing method to easily manufacture an optical system that exhibits high optical performance.

Incidentally, in the step of setting the approximate surface, an approximate surface based on the measurement surface shape of the optical surface formed by the initial molding is set for the optical surface formed by the molding using the mold member. It is desirable.

In the step of setting the approximate surface, when the optical surface is a polished surface, it is preferable that design data of the optical surface is set as the approximate surface on the polished surface.

[0016] It is desirable that an approximate surface having the largest difference between the approximate surface of each optical surface in the optical system and the design data of the optical surface corresponding to each approximate surface is a change approximate surface.

[0017] Also, assuming that the approximate surface of the optical surface closest to the optical surface having the largest difference between the approximate surface of each optical surface in the optical system and the design data of the optical surface corresponding to each approximate surface is the change approximate surface. Desired Les.

[0018] In addition, it is desirable that the change approximation plane is at most two planes.

[0019] In addition, in the step of setting the approximate surface, a plane perpendicular to a predetermined reference axis on the optical surface of the optical element is divided into a plurality of spaces, and a plurality of spaces with these divided planes as the bottom are set. It is desirable that a space division setting step is included and an approximate expression having continuity at the boundary between spaces is used.

[0020] In this manufacturing method, it is desirable that the approximate expression is a function of at least a third order or higher. Note that continuity means that the second derivative of the approximate expression is continuous at the boundary between the divided spaces. An example of such an approximate expression is a spline function.

[0021] Further, the optical system preferably includes at least one lens and at least one mirror as elements molded by the mold member, and at least the lens surface is used as a change approximation surface. ,.

[0022] Further, it is desirable that at least one of the lenses and mirrors included in the optical system is formed by glass molding.

[0023] Further, it is desirable that the optical system includes a non-rotationally symmetric surface, and in the change amount calculating step, an approximate surface corresponding to the non-rotationally symmetric surface is a change approximate surface.

[0024] Further, the optical system includes at least one lens and at least one mirror as an element molded by the mold member, and at least one lens surface is a non-rotationally symmetric surface and changes. In the quantity calculation step, it is desirable that the non-rotationally symmetric surface be a change approximate surface.

[0025] Further, when the optical system includes at least one lens and at least one mirror as optical elements (particularly, at least one of the lenses and mirrors included in the optical system). If one lens is formed by glass molding), it is desirable to use at least one lens surface as the approximate surface.

The invention's effect

[0026] According to the method for manufacturing an optical system of the present invention, it is possible to preferentially perform a correction process on a cavity surface corresponding to an optical surface that easily affects optical performance. Therefore, the number of corrections of the mold member is relatively reduced, and the optical system is manufactured in a short time and at a low cost while being efficient. Brief Description of Drawings FIG. 1 is a flowchart showing the steps of a method for manufacturing a projection optical system.

FIG. 2 is a plan view showing a measurement state of a lens surface in a second lens.

FIG. 3 is a plan view showing a divided space on the lens surface.

[Figure 4] is a spot diagram of the projection optical system including only the initial product.

[Fig. 5] is a spot diagram of the projection optical system including the reshaped product.

[Fig. 6] is a spot diagram of a projection optical system that includes a glass optical element and a resin optical element, which are composed only of initial products (however, in the Z-axis direction on the screen surface). Half of the minus side).

[FIG. 7] is a spot diagram showing the positive half of the Z-axis direction on the screen surface, unlike FIG.

[Fig. 8] is a spot diagram of a projection optical system that includes a glass optical element and a resin optical element, of which a reconstructed product is included (however, the Z-axis on the screen surface) Half of the negative direction).

[Fig. 9] is a spot diagram showing the positive half of the Z-axis direction on the screen, unlike Fig. 8.

FIG. 10 is a block diagram of an image projection apparatus.

Explanation of symbols

PS Projection optical system (optical system)

Ml 1st mirror (optical element)

L1 1st lens (optical element)

M2 Second mirror (optical element)

L2 Second lens (optical element)

M3 3rd mirror (optical element)

M4 4th mirror (optical element)

FM flat mirror (optical element)

SCN screen

PDS image projector

F Optical element design value data f Initial cavity surface data in the mold

G Initial surface data for initial products

D New cavity surface data

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1]

An embodiment of the present invention will be described below with reference to the drawings.

[1. About image projection apparatus]

FIG. 10 shows a screen SCN, an illumination optical system (not shown), a light modulation element MD that modulates light from the illumination optical system, and light (image light) modulated by the powerful light modulation element MD. An image projection apparatus PDS including a projection optical system PS that leads to an SCN is shown. The image projector PDS is a rear projection type that projects light obliquely from the light modulation element MD (reduction side) toward the back of the screen SC N (enlargement side).

[0031] The projection optical system PS includes a first mirror (spherical mirror) Ml and a first lens (rotationally asymmetric free-form surface lens) Ll according to the light traveling order from the light modulation element MD to the screen SCN. , 2nd mirror (rotationally symmetric aspherical mirror) M2, 2nd lens (rotationally asymmetric free-form surface lens) L2, 3rd mirror (rotationally asymmetric free-form surface mirror) M3, 4th mirror (rotationally asymmetric free-form surface mirror) M4, And the flat mirror FM is arranged.

[0032] Note that a protective cover glass CG is disposed on the front surface of the light modulation element MD (emitted surface of the modulated light), and between the first mirror Ml and the first lens L1, there is no light. An optical aperture ST that blocks part of the light is placed. The plane mirror FM is a folding mirror that reflects and reflects the light from the fourth mirror M4 to the screen SCN.

[0033] [2. Production process of projection optical system]

Here, a method for manufacturing the projection optical system (optical system) PS will be described with reference to the flowchart of FIG. 1 (operations STEP1 to STEP22). Since the plane mirror FM is not a curved reflecting surface, it is assumed that another manufacturing method is used instead of resin molding which is advantageous for the subsequent curved surface production. In addition, the flat mirror FM is unlikely to have a significant effect on the optical performance, so the subsequent optical performance evaluation Etc., the plane mirror FM is not included in the projection optical system PS.

[0034] (STEP1: Optical design process of all optical elements)

First, six (8 surfaces) optical designs are performed according to the first mirror Ml, first lens Ll, second mirror M2, second lens L2, third mirror M3, and fourth mirror M4, which are optical elements. Is called.

[0035] Specifically, the reflecting surface S (M1) of the first mirror Ml that is the optical surface (S), the reduction side lens surface S (Lls) and the enlargement side lens surface S (Lle) of the first lens L1, Reflection surface S (M2) of the second mirror M2, reduction side lens surface S (L2s) and enlargement side lens surface S (L2e) of the second lens L2, reflection surface S (M3) of the third mirror M3, and second The reflection surface S (M4) of the 4-mirror M4 is expressed by a polynomial (the surface expressed in this way may be called the design optical surface).

However, such a design optical surface is set so that desirable optical performance can be exhibited as the entire projection optical system PS (entire system). The polynomial representing the design optical surface is “F”, and the polynomial F corresponding to each optical surface is listed below. And the design optical surface shown by the polynomial F may be called “design data”.

[0037] · Design optical surface corresponding to reflecting surface S (M1) of first mirror Ml: F [S (M1)]

• Design optical surface corresponding to the reduction lens surface S (Lls) of the first lens L1: F [S (Lls)] • Design optical surface corresponding to the magnification lens surface S (Lle) of the first lens L1: F [S (Lle)] • Design optical surface corresponding to reflecting surface S (M2) of second mirror M2: F [S (M2)] • Design corresponding to reduction side lens surface S (L2s) of second lens L2 Optical surface: F [S (L2s)] • Design optical surface corresponding to the magnification side lens surface S (L2e) of the second lens L2: F [S (L2e)] • Reflecting surface S (M3) of the third mirror M3 Design optical surface corresponding to: F [S (M3)] • Design optical surface corresponding to the reflective surface S (M4) of the fourth mirror M4: F [S (M4)]

[0038] As an example of the polynomial representing the design optical surface, the following equation (Equation 1) using local orthogonal coordinates (X, Y, Z) with the surface vertex of each design optical surface as the origin is given. It is done.

[Number 1]

X = CoH ² 1 {1 + VI-sCo ² H ² } + ∑ ΑΉ * + J _J G _jk Y ^j Z ^k

> jk where X: Displacement from the reference plane in the X direction at the position of height H (plane vertex reference) H: Height in the direction perpendicular to the X axis [H = (Y ² + Z ² )]

Co: Curvature at surface apex

ε: quadric surface parameter

Ai: i-th order aspheric coefficient

〇 ”: Surface coefficient of k-th free surface

It is.

[0039] Step 2: Mold Design Process for All Optical Elements>

Next, molds (first mold to eighth mold) corresponding to each optical element are designed. For that purpose, machining data (Numerical Control Data; NC data) corresponding to the design data of all optical surfaces is created. However, the processing tool is a diamond cutter with a rounded tip. Therefore, as the shape of the workpiece in the mold changes, the contact point of the diamond cutter tip with respect to the machined surface changes. Therefore, machining data is created by calculating the force point coordinates taking into account the shape of the machining tool.

[0040] It should be noted that the mold cavity surface (the mold surface for molding the optical surface) is subjected to nickel-containing phosphorous treatment. Therefore, the polished surface is processed with a diamond cutter, and the entire surface of the polished surface is uniformly polished to complete the cavity surface.

[0041] The cavity surface of each mold (first mold to eighth mold) can also be expressed using the polynomial "f". Therefore, the polynomial f corresponding to each cavity surface (T) is listed below. The cavity surface represented by the polynomial f may be referred to as “initial cavity surface data”.

[0042] · Cavity surface T (M1) of the first mold corresponding to the reflective surface S (M1) of the first mirror Ml

: F [S (Ml)]

• Cavity surface of the second mold corresponding to the reduction side lens surface S (Lls) of the first lens L1 T (Lls): f [S (Lls)]

• Cavity surface T (Lle) of the third mold corresponding to the enlargement side lens surface S (Lle) of the first lens L1: f [S (Lle)]

• Cavity surface of the 4th mold corresponding to the reflective surface S (M2) of the second mirror M2 T (M2): f [S (M2)] 'Cavity surface of the fifth mold corresponding to the reduction side lens surface S (L2s) of the second lens L2 T (L2s): f [S (L2s)]

'Cavity surface of the 6th mold corresponding to the enlargement side lens surface S (L2e) of the second lens L2 T (L2e): f [S (L2e)]

• Cavity surface of the 7th mold corresponding to the reflective surface S (M3) of the third mirror M3 T (M3): f [S (M3)]

• Cavity surface of the 8th mold corresponding to the reflective surface S (M4) of the 4th mirror M4 T (M4): f [S (M4)]

[0043] Ku STEP3: Initial molding process of all optical elements>

Then, all the optical elements are produced by injection molding the resin, which is the optical element material, using the first to eighth molds (note that the initial optical element is “initial” This molding, which may be referred to as “product”, may also be referred to as “initial molding”).

[0044] However, reproducible molding must be performed under molding conditions with little variation in surface accuracy of the molded optical surface. For that purpose, various molding conditions (parameters) such as the temperature at which the optical element material is melted (resin temperature), the mold temperature of the mold, and the injection speed when injecting the optical element material (injection pressure) are tested. Molding conditions with good reproducibility are set.

[0045] For example, the molding conditions of the second lens L2 are as follows. The second lens L2 produced under the following molding conditions has a thickness (core thickness) of 3.5 mm and a maximum effective area EA (see Fig. 2 and 3 below) having a diameter of 52 mm. .

• Resin temperature: 285 ° C

• Mold temperature: 135 ° C

• Injection speed: 15mmZs

• Injection pressure: 1050kgZcm ²

[0046] Ku STEP 4: Surface shape measurement process for all initial products>

Next, the shape measurement of the optical surface in all initial products is performed. The equipment for measuring the surface shape is not limited, but examples include ultra-high-precision three-dimensional measuring machine UA3P manufactured by Matsushita Electric Industrial Co., Ltd. and Form Talysurf manufactured by Rank Taylor Hobson. The

[0047] Fig. 2 shows the measurement state (however, Fig. 2 measures the reduction lens surface S (L2s) of the second lens L2). This figure 2 shows a local right-handed Cartesian coordinate system (X, Y, Z) with the surface vertex of the lens surface S (L2s) as the origin and the normal direction of the optical surface as the X axis (reference axis). It is illustrated on the basis of Specifically, a YZ plane (a plane formed by forces in the Y-axis direction and the Z-axis direction) is shown.

[0048] Then, such a measurement method performs line measurement along one direction (Z-axis direction) on the YZ plane. However, this measurement method uses line measurement at a pitch interval of 0.15 mm (measurement interval in the Z-axis direction). The measurement interval in the Y-axis direction is 1. Omm, and the measured point may be referred to as “measurement point MP”.

[0049] If the measurement point MP is not present around the light ray passage area (effective area EA) on the lens surface S (L2s), the accuracy of the approximate surface of the initial product, which will be described later, is reduced. For this reason, line measurement is performed in an area wider than the effective area EA (for example, a range 0.5 mm wider than the effective area EA in the Y-axis direction and the Z-axis direction).

[0050] Note that the raw data when measuring the optical surface includes the amount of shift of each of the X-axis, Υ-axis, and Ζ-axis in addition to the molding change amount, and the X-axis, Υ-axis, and ζ-axis. It includes setting errors when measuring the rotation around the axis. Therefore, the measurement data consisting of the measurement point MP is calculated in consideration of these setting errors.

[0051] Ku STEP5: Approximate surface setting process for all initial products>

Subsequently, the approximate surface of the optical surface in all initial products is set using the measurement data. However, for this approximate surface setting, as shown in Fig. 3, the YZ surface (plane perpendicular to the X axis) covering the effective area EA is equally divided into 25 (Y axis direction divided into 5 XZ axis directions 5) A plurality of spaces (spaces in which the thickness of the divided surface extends in the X-axis direction; divided spaces) with the divided YZ plane (divided surface DA) as the bottom [space division setting process

L

[0052] Then, the optical surface (initial surface) of the initial product is approximated by a polynomial that takes into account a plurality of powerful divided spaces. An example of a function suitable for such approximation is a spline function (B-spline function, etc.). Therefore, in the following, we will explain with spline functions I will do it. A spline function is defined as follows (however, it is a case of a quintic spline function).

The k-direction vector in the X direction when the interval is divided into n in any X direction is (χθ, χθ, χθ, χθ, χθ, χθ, 1, 2 3, 4-, (11-1), 11 11, 11 11 11 The basic function of the 8_spline defined in 11) is expressed by the following equation (Equation 2).

[Equation 2]

[0054] Similarly, the basis function of the B-spline defined when the knot vector in the Υ direction when divided into m in the Υ direction is (yOyOyOyOyOyOyly 2y3y4 '-' y (m_l), ymymymymym, ym) is The formula is as follows.

[Equation 3]

In such a case, the surface function f (x, y) of the fifth-order B—spline function is defined by the linear sum of the surface base (n + 5) X (m + 5) spline bases (Equation 4). Is done.

[Equation 4] f (x, y) =, ∑7 = 0 'AMx) bAy)

[0056] However, the k-th order B—spline basis function bik (x) is a function expressed by the following equation (Equation 5 · Equation 6):

[ ^Equation 5] ( ^χ = ^ι (χ> ≤z <, ₊₁ )

= 0 (otherwise)

[Equation 6] ^X i + k ^X i ^X i + k + l- ^X i + l bi, k (x) has a value only in the following equation (Equation 7), and is "0" otherwise.

[Equation 7]

i — < ^X i + k + \

[0057] Then, the spline function G corresponding to the optical surface of each optical element of the initial product is listed below. The approximate surface indicated by the spline function G may be referred to as “initial surface data”.

[0058] 'Approximate surface corresponding to reflective surface S (M1) of first mirror Ml of initial product

: G [S (M1)]

• Approximate surface corresponding to the reduction lens surface S (Lls) of the first lens L1 of the initial product: G [S (Lls)]

• Approximate surface corresponding to the magnification side lens surface S (Lle) of the first lens L1 of the initial product: G [S (Lle)]

• Approximate surface corresponding to the reflective surface S (M2) of the second mirror M2 of the initial product

: G [S (M2)]

• Approximate surface corresponding to the reduction lens surface S (L2s) of the second lens L2 of the initial product: G [S (L2s)]

• Approximate surface corresponding to the enlargement side lens surface S (L2e) of the initial second lens L2: G [S (L2e)]

'Approximate surface corresponding to the reflective surface S (M3) of the initial third mirror M3

: G [S (M3)]

'Approximate surface corresponding to the reflective surface S (M4) of the initial fourth mirror M4

: G [S (M4)]

[0059] Note that a spline function indicating an approximate surface corresponding to the magnification side lens surface S (L2e) of the second lens L2. Table 1 and Table 2 list the approximate surface coefficients of the number G [S (L2e)] as an example.

《Knot vector coefficient》

[table 1]

《Coefficient of function basis of surface》

[Table 2]

The In

Magnification side lens surface S (L2e) of the second lens L2

STEP6: Optical performance evaluation process for the entire system consisting of initial products>

And initial surface data (G [S (M1)], G [S (Lls)], G [S (Lle)], G [S (M2)], G [S (L2s)], G [S ( L2e)], G [S (M3)], G [S (M4)]), the optical simulation device evaluates the optical performance of the projection optical system PS. [Optical performance evaluation of the initial product type optical system] Valuation process (first optical performance evaluation process)]. Therefore, the initial surface data corresponding to all optical surfaces is input to the optical simulation software in the optical simulation device. It has become so.

[0063] Various optical simulation apparatuses exist in the past, and are not particularly limited. Also, the optical performance evaluation items are not particularly limited. For example, various aberration evaluations, magnification evaluations, MTF (Modulation Transfer Function) evaluations, or spot diagram evaluations.

[0064] FIG. 4 shows a spot diagram as an example of optical performance evaluation. The spot diagram in Fig. 4 is a spot diagram calculated from the initial plane data. Over the 25 evaluation points on the screen plane SCN, the spot diagrams for 3 wavelengths (460, 546, 620nm) are superimposed. Shows the imaging characteristics (scale is expressed as ± lmm). The coordinates (Υ, Ζ) in the figure are the local coordinates (Y, Z; mm) of the screen surface SCN indicating the projected position of the spot centroid at each evaluation point. Also, since the projection optical system PS is an optical system that is plane-symmetric with respect to the XY plane of the screen surface, the spot diagram shows only the negative half of the Z axis direction on the screen surface SCN, and the remaining half is omitted. is doing.

<Step 7: Judgment Process of Optical Performance Evaluation Result of Projection Optical System Consisting of Initial Product> Here, determination of optical performance evaluation result, that is, optical performance of projection optical system PS composed of initial product is within an allowable range It is determined whether or not. The subsequent steps are determined based on the determination result.

[0066] For example, when the optical performance of the projection optical system PS, which is the initial product strength, is within the allowable range, the powerful projection optical system PS has sufficiently satisfactory optical performance. Therefore, the die does not have to be corrected. Therefore, the manufacturing power S of the projection optical system PS has been completed (STEP 7 → STEP 20).

[0067] On the other hand, when the optical performance of the projection optical system PS, which is the initial product strength, is outside the allowable range, the projection optical system PS has an optical performance that cannot be fully satisfied. Therefore, the mold must be corrected. Therefore, the process for obtaining new mold surface data (referred to as “new cavity surface data”) for the mold and performing re-molding with the corrected mold according to the new cavity surface data. I will explain.

[0068] Step 8: Correction amount calculation process for specific optical surface>

Normally, the initial surface data and design data for each optical element are different. There are many. However, it is not necessary to correct the mold of all optical elements. Projection optical system PS that can achieve sufficient optical performance by newly setting the mold shape of the optical surface (specific optical surface) of a specific optical element PS Can be produced.

Specifically, initial surface data other than the specific optical surface is fixed, the specific optical surface is changed, and the projection optical system PS is redesigned. However, the specific optical surface may be any surface, and it is desirable that the surface having the largest deviation between the initial surface data and the design data (maximum shape error surface) is the specific optical surface. This is because the initial surface data of the remaining optical surfaces other than the specific optical surface has little deviation from the design data, and as a result of redesigning the specific optical surface, there is little deviation from the design performance of the projection optical system PS. It is.

Note that the specific optical surface may be a surface closest to the maximum shape error surface. There are cases where it is not desired to correct the mold shape, for example, when the maximum shape error surface is a flat surface. In such a case, the specific optical surface may be the surface closest to the maximum shape error surface. This is because the state of the light incident on the surface closest to the maximum shape error surface is close to the state of the light incident on the maximum shape error surface. It is.

[0071] Hereinafter, the specific optical surface is the reduction side lens surface S (L2s) of the second lens L2, and the fifth mold cavity surface T (L2s) corresponding to the reduction side lens surface S (L2s) of the second lens L2 is used. A case where L2s) is corrected will be described as an example. The correction processing to the cavity surface T (L2 s) corresponding to the specific optical surface that is strong may be referred to as “first correction processing”.

[0072] First, the new cavity surface data of the cavity surface T (L2s) subjected to the first correction processing is defined as "D" and defined as follows.

D = f [S (L2s)] + H

However,

f [S (L2s)]: Initial cavity surface data of cavity surface T (L2s)

H: Function indicating the correction amount for the existing cavity surface T (L2s) (for example,

, Spline function)

It is.

[0073] Then, the coefficients included in the function H (which will be described below as an example of the spline function H) Is determined, the new cavity surface data D will be determined. Therefore, the optical performance evaluation is performed using the initial surface data of the reduction side lens surface S (L2s) of the second lens L2 in consideration of the spline function H, that is, “G [S (L2s)] + H”.

[0074] Specifically, initial surface data (G [S (M1)], G [S (Lls)], G [S (Lle)], G [S (M2)], G [S (L2s) ] + HG [S (L2e)], G [S (M3)], G [S (M4)]), the optical simulation device evaluates the optical performance of the projection optical system PS. This optical performance evaluation may be referred to as “search optical performance evaluation”, and the result of this search optical performance evaluation may be referred to as “search result”).

[0075] In detail, the retrieval optical performance evaluation is based on design data (F [S (M1)], F [S (Lls)], F [S (Lle)], F [S (M2) in the projection optical system PS. ], F [S (L2s)], F [S (L2e)], F [S (M3)], F [S (M4)] The shape is changed to optimize. The optimization here does not mean finding the best value by searching for a so-called local minimum. Then, the result of the optimization (search result) should have the desired performance. When the optimum result is realized by such a search optical performance evaluation, the spline function H is determined.

[0076] Therefore, the initial surface data G [S (L2s)] of the reduction side lens surface S (L2s) of the second lens L2 is changed (that is, G [S (L2s)] + H. The amount of change in the initial surface data G [S (L2s)] of the reduction-side lens surface S (L2s) of the second lens L2 when the optimum performance as the projection optical system PS is exhibited (that is, It can be said that the spline function H) is obtained [change calculation process]. Note that optimization may be performed using a correction amount as a variable instead of directly changing the initial plane data G [S (L2s)] to obtain a change amount as a difference.

[0077] Tables 3 and 4 show coefficients in the spline function H determined thereafter. When the force and coefficient are determined, the correction machining amount to be applied to the cavity surface T (L2s) of the fifth die is also determined according to the coefficient.

[0078] << Knot Vector Coefficient >>

[Table 3]

mi

《Deer Deer》 [6 00]

lOT90 / .OOZdf / X3d 8 ΟΟΐ ひ動 OAV Spline function H

[0080] Ku STEP9: Mold Correction Process for Specific Optical Surfaces>

Then, the cavity surface T (L2s) of the fifth mold is subjected to the first correction processing according to the determined correction processing amount [first correction processing step]. Therefore, it can be said that this first correction process is a correction process for realizing the cavity surface T (L2s) corresponding to the new cavity surface data D.

[0081] Ku STEP 10: Molding process with corrected mold>

Next, a new second lens L2 is molded (re-molded) with the fifth mold subjected to the first correction processing. The second lens L2 reshaped in this way may be referred to as a “reshaped product”.

[0082] (STEP 11: Surface shape measurement process of remolded product)

Subsequently, as in STEP 4, the reduction-side lens surface S (L2s) of the new second lens L2 is measured with the apparatus for measuring the surface shape. Note that force and measurement data may be referred to as “re-molded product measurement data”.

[0083] Ku STEP12: Approximate Surface Setting Process of Reformed Product>

Further, as in STEP 5, using the reshaped product measurement data, an approximate surface (approximate surface of the specific optical surface) of the reduction-side lens surface S (L2s) in the second lens L2 of the reshaped product is set. The approximate surface of the lens surface S (L2s) set in this way may be referred to as “reformed product surface data” (G ′ [S (L2s)]).

[STEP 13: Optical Performance Evaluation Process of Projection Optical System Including Remolded Product>

The initial plane data (G [S (M1)], G [S (Lls)], G [S (Lle)], G [S (M2)], G [S (L2e)], G [S ( M3)], G [S (M4)]) and the reshaped part surface data (G '[S (L2s)]) Perform performance evaluation [Optical performance evaluation process of remolded product-containing optical system].

That is, a projection including the first mirror Ml, the first lens Ll, the second mirror M2, the third mirror M3, the fourth mirror M4, which is the initial product, and the second lens L2, which is a reshaped product. The optical performance of the optical system PS will be evaluated. The result of the powerful optical performance evaluation is the spot diagram shown in Fig. 5 (Fig. 5 is expressed in the same way as Fig. 4).

[0086] (STEP 14: Judgment Step of Optical Performance Evaluation Result of Projection Optical System)

Then, it is determined whether or not the result of the optical performance evaluation of the projection optical system PS including the reshaped product (spot diagram, etc. in FIG. 5) is within the allowable range. If the optical performance of the projection optical system PS including the reshaped product is within an allowable range, the projection optical system PS has sufficiently satisfactory optical performance. Therefore, manufacturing may be completed (STEP14 → STEP20).

[0087] (STEP 15: Addition to new cavity surface data, machining process)

However, if the optical performance of the projection optical system PS including the reshaped product is out of the allowable range, the projection optical system PS having such a power will have optical performance that cannot be sufficiently satisfied. This The situation where only insufficient optical performance can be achieved is due to the fact that the cavity surface T (L2s) of the 5th mold after the 1st correction processing is processed according to the new cavity surface data D. Or due to non-uniform cooling on the optical surface, shrinkage during cooling of the optical element, and inadequate molding conditions.

[0088] Therefore, correction processing (follow-up processing) is performed to offset the shape error between the new cavity surface data D and the reshaped product surface data G '[S (L2s)] determined in STEP 12. 2 correction machining process].

[0089] (STEP 16: Molding process after die and post-molding)

Then, the second lens L2 is molded again (increase molding) with the fifth die that has been provided with the cavity surface T (L2s) that has been driven in. Note that the second lens L2 that has been cast in this way may be referred to as “tracking, including the product”.

[0090] (STEP 17: tracking, process of measuring the shape of the surface of the included product)

Subsequently, as in STEP 4, the reduction-side lens surface S (L2s) of the second lens L2, which is a driven-in product, is measured with a device that measures the surface shape. Such measurement data may be referred to as “follow-up product measurement data”.

[0091] (STEP18: Approximate surface setting process for tracking and inclusions)

Further, as in STEP 5, the approximate surface of the reduction side lens surface S (L2s) in the second lens L2 of the driven-in product is set using the driven-up product measurement data. The approximate surface of the set lens surface S (L2s) may be referred to as “driven surface data” (G ′ ′ [S (L2s)]).

[0092] Ku STEP 19: Optical Performance Evaluation Process of Projection Optical System Including Drive-in Product>

The initial plane data (G [S (M1)], G [S (Lls)], G [S (Lle)], G [S (M2)], G [S (L2e)], G [S ( M3)], G [S (M4)]) and the driven surface data (G '' [S (L2s)]) Performs performance evaluation [Optical performance evaluation process for driven-in type optical system]. That is, the projection optical system PS including the first mirror Ml, the first lens Ll, the second mirror M2, the third mirror M3, and the fourth mirror M4, which are initial products, and the second lens L2, which is a driven product, is provided. Optical performance evaluation will be conducted.

[0093] Ku STEP14: Judgment process of optical performance evaluation result of projection optical system> Then, from the result of the optical performance evaluation of the projection optical system including the driven product, it is determined whether or not the optical performance is within the allowable range (STEP 19 → STEP 14). If the optical performance of the projection optical system PS including the driven-in product is within an allowable range, the projection optical system PS has sufficiently satisfactory optical performance. Therefore, even if the production is completed (STEP19 → STEP14 → STEP20).

[0094] However, when the optical performance of the projection optical system PS including the driven-in product is out of the allowable range, the projection optical system PS having such a force has optical performance that cannot be sufficiently satisfied. Therefore, the follow-up process is performed again (re-start process; multiple times STEP14 → STEP15).

[0095] Further, the surface shape of the second lens L2 (re-push-in product) molded with the fifth die after the re-push-up processing is measured, and an approximate surface is set based on the measurement data, and the optical performance is measured. Evaluation is performed (STEP 16 to STEP 19). Then, based on the results of the force and optical performance evaluation (from the results of optical performance evaluation of the re-entry product-containing optical system), the optical performance of the projection optical system PS including the re-entry product is within the allowable range. For example, the manufacturing may be completed (STEP 19 → STEP 14).

[0096] However, if the optical performance of the projection optical system PS including the re-pushing product is out of the allowable range, the cavity surface T (L2s) of the fifth mold may be pushed again. That is, the follow-up processing and the like are continued until the optical performance as the projection optical system PS is within the allowable range at STE P14 (STEP 19 → YES at STEP 14) (STEP 15 to STEP 19 are repeated).

Note that a mold capable of forming an optical element having an optical performance within the allowable range as the projection optical system PS in STEP 14 is referred to as a correction mold (correction mold member).

[0098] Ku STEP 20-22: Completion of optical system>

Finally, the optical system uses the optical element produced by molding using the correction mold (first molding process; STEP20), and the correction mold and mold (molds other than the correction mold). Completed by assembling the optical elements produced by the former molding (2nd molding process; STEP21)

EP22).

[0099] [3. Summary] In the manufacturing method described above, an optical element material is molded with a mold (mold member) to manufacture each optical element (initial product) in the projection optical system PS having a plurality of optical elements. In addition, the approximate surface (initial surface data) of each optical surface is set by defining an approximate expression based on the measurement result of the surface shape of the optical surface in each optical element.

[0100] Moreover, such a manufacturing method evaluates the optical performance of the entire system from the approximate surface of all the optical surfaces in the projection optical system PS, and further, at least one of the approximate surfaces of the entire optical surface {for example, The secondary lens L2's reduction-side lens surface S (L2s); referred to as the “change approximation surface”} is changed to provide the change approximation surface when optimal optical performance is achieved for the entire system. (The approximate surface that is not changed is called the non-changeable approximate surface). Then, based on the amount of change, a correction processing amount for the cavity surface of the mold corresponding to the change approximate surface is obtained and corrected to produce a new cavity surface.

[0101] This manufacturing method does not correct all the cavity surfaces in all dies. For example, a powerful manufacturing method can perform correction processing by giving priority to the cavity surface corresponding to the maximum shape error surface. Therefore, the number of mold corrections is relatively small, and the projection optical system PS is manufactured in a short time and at a low cost while being efficient.

[0102] Further, in this manufacturing method, the die is corrected based on the optical performance evaluation as the projection optical system PS. In other words, the optical surface having the same data as the optical surface design data F is not subjected to correction processing in order to mold the optical surface. The cavity surface corresponding to the surface {for example, the cavity surface T (L2s) of the fifth mold} is corrected and processed.

[0103] Therefore, it is assumed that there is a shape error (an error with design data F) on a specific optical surface {for example, the reduction-side lens surface S (L2s)} of the initial second lens L2). However, there is no problem if a specific optical surface has a surface shape that exhibits optimum optical performance as the projection optical system PS. For this reason, it can be said that the manufacturing method is difficult to be affected by the shape error of each optical surface in the projection optical system PS. This is because, when a cavity surface is corrected to form an optical surface having the same data as the optical surface design data F, all the cavity surfaces must be accurate so that the optical performance of the projection optical system PS can be optimized. This is because it must be corrected. [0104] However, there is a case where the first correction processing (first correction addition; production of a new cavity surface) on the cavity surface corresponding to a specific optical surface is not performed with high accuracy. In such a case, projection optics including an optical element molded with a mold having a new cavity surface (for example, the second lens L2 as a remolded product) and an optical element molded with an existing mold (initial product). The optical performance of the system PS is out of the acceptable range.

[0105] Therefore, in this manufacturing method, in an optical element molded with a mold having a new cavity surface (for example, the second lens L2 which is a remolded product), an optical surface corresponding to the new cavity surface is formed. An approximate surface is set by determining an approximate expression based on the measurement result of the surface shape. In addition, this manufacturing method uses a shape error between the approximate surface of the optical surface corresponding to the new cavity surface and the new cavity surface (for example, the reshaped product surface data G '[S (L2s)] and the new cavity surface. The new cavity surface is corrected so as to offset the error with surface data D).

[0106] Force / Curve correction processing [Second correction processing] is performed to eliminate the shape error, but it is performed only on the already corrected cavity surface (new cavity surface). is there. For this reason, this second correction processing is only a light burden compared to the burden of correcting all the cavity surfaces.

[0107] However, the second correction processing to the cavity surface corresponding to the specific optical surface (second correction processing) force If performed accurately, it is formed with a mold having a cavity surface that has been corrected multiple times. The optical performance of the projection optical system PS including the formed optical element (for example, the second lens L2 as a follow-up product) and the optical element (initial product) molded with an existing mold is within an allowable range. Then, the existence of this lightly-burden second correction process makes it possible to manufacture the projection optical system PS that easily exhibits high optical performance by the powerful manufacturing method.

Note that the manufacturing method described above is particularly effective for a manufacturing method of a reflection optical system including a plurality of eccentric surfaces, particularly an optical system including a free-form surface. Normally, an error during molding tends to generate an asymmetric error (for example, a false component) with respect to a design value. Therefore, if a non-rotationally symmetric surface (especially a free-form surface) that is not a rotationally symmetric surface is a change approximation surface, it is easy to correct the forming error. The eccentric surface means a surface that does not have a rotationally symmetric axis, or a surface in which the symmetric axis is greatly deviated from the center of the effective surface even if it is included.

[0109] By the way, in the optical performance evaluation, the optical surface of the optical element in the projection optical system PS is approximated. Surfaces (initial surface data, remolded surface data, driven surface data, etc.) are used. Specifically, the optical performance is evaluated by a ray tracing simulation using power obtained from the surface shape of the approximate surface. Therefore, how to set the approximate surface becomes important.

[0110] For example, when local waviness (waviness part) exists on the measured optical surface, if an approximation formula of a higher order is used to appropriately represent the waviness part, a place other than waviness ( High-order undulation will occur in the non-undulation area. On the other hand, if a low-order approximation is used to properly represent the non-swelled part, the swelled part cannot be represented properly.

[0111] Therefore, an approximate surface (initial surface data, reshaped surface data, driven surface data, etc.) of the optical surface can be expressed by a function that can efficiently express the waviness portion of the optical surface, for example, a spline function. It is desirable that As an example, a plane (YZ plane; see FIG. 3) perpendicular to a predetermined reference axis (for example, the X axis) on the optical surface of the optical element is divided into a plurality of parts, and these divided planes are used as bottoms. A plurality of spaces (divided spaces) are set, and a spline function having continuity at the boundary between the divided spaces can be mentioned.

[0112] However, it is desirable that the order of a powerful spline function or the like is at least 3 or more (in the above description, a 5th-order spline function is listed and explained). With such a third-order or higher-order spline function, it is possible to set an approximate surface corresponding to each divided space using the measurement point MP in the divided space. In particular, when using at least a third-order function (for example, a spline function), the second derivative of the approximate expression is continuous at the boundary between the divided spaces, and there is a step on the approximate surface at the boundary of the divided space. This does not occur, and continuity occurs in the power of the approximate surface, enabling ray tracing simulation.

[0113] Preferably, the order of the spline function or the like is 4-8. This is because the local undulation that has a large effect on the optical performance of the projector field is expressed by a 4th to 8th order function. In addition, by creating an approximate surface with a 4th to 8th order function, it is possible to express local waviness shapes that greatly affect optical performance, and to remove higher order waviness portions that are less likely to affect optical performance, It can be said that it also functions as a filter function.

[0114] [Embodiment 2]

It should be noted that the present invention is not limited to the above-described embodiment and does not depart from the spirit of the present invention. Various modifications are possible.

[0115] For example, the optical performance attributed to the reduction side lens surface S (L2s) and the enlargement side lens surface S (L2e) in the second lens L2 is represented by the shape of the reduction side lens surface S (L2s) of the second lens L2. Although there are examples of correction due to changes, this is not limited to this. For example, the optical performance caused by the enlargement-side lens surface S (L2e) of the second lens L2 is changed to the shape change of the reduction-side lens surface S (L2s) of the second lens L2 or the reflection surface S (M3) of the third mirror. You may correct by.

[0116] In short, if the mold is corrected and processed so that the shape of at least one of the optical surfaces included in the projection optical system PS is optimal, the optical performance as the projection optical system PS is optimal. Yo! However, if the image height of light passing through an optical surface that affects the optical performance and a shape change in the optical surface through which light having approximately the same image height passes, the optical performance is effectively improved. Therefore, for example, it can be said that it is desirable to correct the optical performance caused by the enlargement side lens surface S (L2e) of the second lens L2 by the shape change of the reduction side lens surface S (L2s) of the second lens L2.

[0117] Further, when setting a divided space (in the case of a space dividing step), the relationship between the number of divided spaces and the number of measurement points in the divided spaces becomes important. For example, if the number of measurement data MP is relatively large even though the number of divided spaces is relatively small, the shape error is almost the same as expressing the error polynomial of the entire surface. Then, local waviness is not expressed on the approximate surface.

[0118] On the other hand, for example, when the number of measurement data MP is relatively small although the number of divided spaces is relatively large, the local undulation of the optical surface is approximated, but the direction perpendicular to the measurement direction The number of measurement data MP (in Fig. 3, measurement data MP in the Y-axis direction perpendicular to the Z-axis direction) decreases in the divided space. As a result, the approximate accuracy of the direction of the measurement data MP that has been reduced (the Y-axis direction in Fig. 3) decreases.

[0119] In view of the above, it is considered desirable if the number of divided spaces is relatively large and the number of points of the measurement data MP is relatively large. However, in such a case, it takes a very long time to measure the surface shape, resulting in the temperature drift of the measuring instrument due to changes in environmental temperature and humidity, and the change in the optical surface of the initial product over time. Decreases. In addition, since the number of measurement data MP is relatively large, the measurement efficiency also decreases. [0120] Therefore, it is possible to improve the measurement efficiency while ensuring the approximation accuracy of the local undulation of the optical surface and the approximation accuracy of the optical surface due to the reduction of the measurement point MP in the divided space. Thus, the number of division spaces and the number of measurement points in the division space are desirable. One example is the measurement method shown in Fig. 3, in which there are 25 division spaces and five lines are measured for each division space.

[0121] When creating an approximate surface, the accuracy of approximation increases as the number of measurement lines in each divided space increases. However, for example, if the approximate surface is created with a fifth-order function that affects the optical performance of the projector field, in order to create an approximate surface with high accuracy, 5 lines are normally used for each divided space. Although it is desirable, an approximate surface can be created accurately if there are at least three lines.

[0122] Also, in Fig. 3, the line measurement is performed along the Z-axis direction. The line measurement may be performed along the Y-axis direction. In addition, line measurement (matrix-like measurement) along both the Y-axis direction and the Z-axis direction may be performed. However, the measurement efficiency of the matrix-like measurement is reduced, but if it is a line measurement in one direction (Y-axis direction or Z-axis direction), the measurement efficiency is improved compared to the matrix-type measurement.

[0123] The polynomial representing the design data F and the initial cavity surface data F is not particularly limited, but may be a spline function.

[0124] Not all optical elements may be molded articles. For example, the first mirror Ml that is a spherical surface may be a polished product. Further, glass molding may be used instead of resin molding. Further, it is not necessary to obtain approximate surfaces for all optical elements and perform optical performance evaluation using the approximate surfaces of all optical elements. For example, when the first mirror Ml is a glass polished product, a shape almost as designed is obtained, so design data may be used as the approximate surface of the first mirror Ml.

[0125] [Embodiment 3]

Embodiment 3 will be described. Note that members having the same functions as those used in Embodiments 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

[0126] Examples of materials for optical elements such as mirrors and lenses include various materials (glass, resin, etc.). However, the temperature required for molding the glass optical element is higher than the temperature required for molding the resin optical element, and thus the glass optical element (particularly the outer shape The molding accuracy of a glass optical element having a relatively large size tends to be lower than that of a resin optical element. For this reason, glass optical elements are not easily formed into the surface shape as designed.

[0127] In general, when the effective luminous flux width of the light reaching the surfaces of the optical elements (for example, the mirror surface and the lens surface) is substantially the same, the error amount of the surface shape of each surface is the same. The optical performance degradation caused by the surface shape error of the mirror surface is larger than the optical performance degradation caused by the surface shape error of the lens surface (that is, the mirror surface is more sensitive than the lens surface in terms of sensitivity to optical performance). Is also high). For this reason, in the projection optical system PS in which glass optical elements and resin optical elements are mixed, if the glass optical element is a mirror, an error in the surface shape of the mirror is likely to occur, and the projection optical system PS The optical performance is greatly affected.

[0128] As an example of such optical performance, the spot diagrams of Figs.

These spot diagrams show the projection optics including the first mirror Ml and the second mirror M2 made of glass, and the first lens Ll, the second lens L2, the third mirror M3, and the fourth mirror M4 made of resin. Calculated from initial surface data of system PS. However, the deterioration of the optical performance shown in these spot diagrams is due to the fact that the reflecting surface S (M2) of the second mirror M2 is not formed into a desired surface shape.

[0129] The spot diagrams in these figures show the imaging characteristics by overlapping spot diagrams of three wavelengths (460nm, 546nm, 620nm) at 45 evaluation points on the screen surface SCN ( The scale is expressed in ± lmm). Fig. 6 shows only the positive half of the Z-axis direction on the screen surface SCN, and Fig. 7 shows the other half, the negative side of the Z-axis direction. The coordinates (Y, Z) in the figure are the same conventions apply as 4 and 5 (Incidentally, "e_ ^n" in the figure is a "10- ^n").

[0130] In order to prevent optical performance deterioration as shown in FIGS. 6 and 7, the manufacturing method described above may be used. That is, an optical element material (glass or resin) is molded with a mold to manufacture each optical element (initial product) in the projection optical system PS having a plurality of optical elements, and each manufactured optical element The approximate surface (initial surface data) of each optical surface is set by determining an approximate expression based on the measurement result of the surface shape of the optical surface in.

[0131] Further, the optical performance of the entire system is evaluated from the approximate surface of all the optical surfaces, and By changing at least one of the approximate surfaces (change approximate surface), the change amount of the change approximate surface when the optimum optical performance of the entire system is exhibited is obtained, and the change is based on the strong change amount. It is only necessary to calculate the amount of correction for the cavity surface of the mold corresponding to the approximate surface and perform the first correction process to create a new cavity surface.

[0132] However, in the projection optical system PS including the mirror and the lens, at least one lens surface is used as the change approximation surface. After the first correction process is performed based on the amount of change H in the initial surface data, if re-molding is performed with the new cavity surface data D as the target value, the new cavity surface data D and re-molding are performed. If a shape error occurs with the surface data G ', the optical performance deteriorates. However, since the lens surface is less sensitive than the mirror surface (mirror reflection surface), the change approximate surface is the lens surface, and the effect on the optical performance is reduced.

[0133] Thus, in the projection optical system PS, the reduction-side lens surface S (Lls) of the first lens L1 and the reduction-side lens surface S (L2s) of the second lens L2 are used as the change approximate surfaces, and initial surface data ( The amount of change of G [S (Lls)], G [S (L2s)]) was obtained. Furthermore, based on the amount of change, the amount of correction for the mold cavity surface corresponding to the change approximate surface {the second mold cavity surface T (Lls), the fifth mold cavity surface T (L2s)} The first correction process was performed to create a new cavity surface.

[0134] Then, after reshaping the new first lens L1 and the second lens L2 with the second mold and the fifth mold subjected to the first correction processing, the reduction of the new first lens L1 The surface shape of the side lens surface S (Lls) and the reduction lens surface S (L2s) of the second lens L 2 is measured, and the data of the approximate surface of these surface shapes (reformed product surface data; G ' [S (Lls)], G '[S (L2s)]) were obtained.

[0135] Figures 8 and 9 show the reshaped part surface data (G '[S (Lls)], G' [S (L2s)]) and the initial surface data (G [S (M1)], G [ S (Lle)], G [S (M2)], G [S (L2e)], G [S (M3)], G [S (M4)]) 8 and 9 are expressed in the same manner as in FIGS. 6 and 7.

[0136] That is, these spot diagrams are the initial mirrors M1, M2, M3, and M4, and the first lens L1 and the reshaped product. The optical performance evaluation of the projection optical system PS including the second lens L2 is shown. And this These optical performance evaluation results could be judged to be within an acceptable range.

[0137] In particular, the second mirror M2 in the projection optical system PS is a glass-made rotationally symmetric aspherical mirror. Usually, when trying to form a rotationally symmetric aspherical mirror by glass molding, it is difficult to form a rotationally symmetric mirror surface due to a relatively low molding accuracy. That is, an error in the asymmetric surface shape is likely to occur on the mirror surface (from the viewpoint of such an asymmetric surface shape error, FIGS. 6 to 9 show the positive side and the negative side in the Z-axis direction on the screen surface SCN. )

[0138] However, it is difficult to perform free-form correction on the cavity surface of the mold corresponding to the mirror surface. This is because the correction processing for the cavity surface of the glass mold for high temperature is difficult compared to the correction process for the cavity surface of the resin mold.

[0139] Then, the optical performance deterioration due to the surface shape error on the reflecting surface S (M2) of the second mirror M2 is reduced. The fourth mold (glass molding mold) corresponding to the second mirror M2 has a cavity surface. Cavity surfaces {T (Lls), T of the second and fifth molds (resin molds) corresponding to the first lens L1 and the second lens L2 made of resin, which are not compensated for T (M2) It can be said that it is easy to correct with (L2s)}.

[0140] In addition, the correction of the free-form surface shape to the cavity surfaces {T (Lls), T (L2s)} of the second and fifth molds is easy, so the reflection of the second mirror M2 It is easy to correct (cancel) the error of the asymmetric surface shape generated on the surface S (M2).

[0141] From the above, in the projection optical system PS including at least one mirror and at least one lens, from the viewpoint of sensitivity to optical performance, at least one lens surface is a change approximate surface. It's good. In particular, the surface shape error of a glass-molded mirror, more specifically, the optical performance degradation caused by the surface shape error that occurs on the reflection surface (mirror surface), which is a rotationally symmetric aspheric surface, makes the lens surface a change approximate surface. In this case, it can be said that it is easily corrected.

[0142] However, the present invention is not limited to this, and the surface shape error of the lens surface of the glass molded lens, more specifically, the optical performance deterioration caused by the surface shape error generated on the lens surface which is a rotationally symmetric aspheric surface is not limited. When the surface (preferably the lens surface of a resin lens) is a change approximate surface, it can be said that it is easily corrected. Because the lens surface is less sensitive than the mirror surface Therefore, even if a shape error occurs in the remolded product, the influence on the optical performance is small. Finally, it goes without saying that embodiments obtained by appropriately combining the techniques disclosed above are also included in the technical scope of the present invention.

Claims

The scope of the claims

[1] A method for manufacturing an optical system including a plurality of optical surfaces by molding using a mold member.

Setting an approximate surface of all the optical surfaces of the optical system including the optical surface formed by initial molding;

A first optical performance evaluation step for evaluating the optical performance of the entire system from the approximate surface of the entire optical surface in the optical system;

Of the approximate surfaces of all the optical surfaces, at least one surface molded by the mold member is used as a change approximate surface, and among the approximate surfaces of all the optical surfaces, at least one surface molded by the mold member is used as the change approximate surface. A change amount calculating step for obtaining a change amount of the change approximate surface when the optimal optical performance as the entire system is exhibited,

Based on the change amount, a first correction processing step for obtaining a correction processing amount on the cavity surface of the mold member corresponding to the change approximate surface and performing correction processing to produce a new cavity surface; and the first correction processing step A first molding step of molding an optical element using the correction mold member processed in step 1;

A second molding step of molding an optical element using a mold member other than the correction mold member, and a method for producing an optical system.

[2] The first molding step is

A step of setting an approximate surface based on the measurement result of the surface shape of the optical surface corresponding to the new cavity surface; and an optical element molded with the mold member having the new cavity surface.

A second correction processing step for correcting and processing the new cavity surface so as to cancel out the shape error between the approximate surface of the optical surface corresponding to the new cavity surface and the new cavity surface;

Forming an optical element using the correction mold member covered in the second correction processing step;

The method for producing an optical system according to claim 1, comprising:

[3] In the step of setting the approximate surface,

The optical surface formed by molding using the mold member is shaped by initial molding. 2. The method of manufacturing an optical system according to claim 1, wherein an approximate surface based on a measurement surface shape of the formed optical surface is set.

[4] In the step of setting the approximate surface,

2. The method of manufacturing an optical system according to claim 1, wherein when the optical surface is a polished surface, design data of the optical surface is set as an approximate surface on the polished surface.

[5] The optical system according to claim 1, wherein the approximate surface having the largest difference between the approximate surface of each optical surface in the optical system and the design data of the optical surface corresponding to each approximate surface is the change approximate surface. Method.

[6] The approximate surface of the optical surface closest to the optical surface having the largest difference between the approximate surface of each optical surface in the optical system and the design data of the optical surface corresponding to each approximate surface is defined as the change approximate surface. A method for producing the optical system described in 1.

7. The method for manufacturing an optical system according to claim 1, wherein the change approximate surface is at most two surfaces.

[8] In the step of setting the approximate surface,

A plane perpendicular to a predetermined reference axis on the optical surface of the optical element is divided into a plurality of parts.

2. The optical system according to claim 1, further comprising a space division setting step for setting a plurality of spaces with the divided planes as a bottom, and using an approximate expression having continuity at a boundary between the spaces. Manufacturing method.

9. The method of manufacturing an optical system according to claim 8, wherein the approximate expression is a function of at least a third order or higher.

10. The optical system manufacturing method according to claim 9, wherein the continuity is that the second derivative of the approximate expression is continuous at a boundary between the spaces.

[11] The method for producing an optical system according to any one of [8] to [10], wherein the approximate expression is a spline function.

[12] The optical system includes at least one lens and at least one mirror as an element molded by the mold member,

2. The method of manufacturing an optical system according to claim 1, wherein at least a lens surface is used as the change approximate surface.

13. The method of manufacturing an optical system according to claim 12, wherein at least one of the lens and the mirror included in the optical system is formed by force glass molding.

[14] The optical system includes a non-rotationally symmetric surface,

2. The optical system manufacturing method according to claim 1, wherein, in the change amount calculation step, an approximate surface corresponding to the non-rotationally symmetric surface is a change approximate surface.

[15] The optical system includes at least one lens and at least one mirror as an element molded by the mold member,

15. The method of manufacturing an optical system according to claim 14, wherein at least a lens surface is used as the change approximate surface.

16. The method of manufacturing an optical system according to claim 15, wherein at least one of the lens and the mirror included in the optical system is formed by force glass molding.