Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2002-06-18
2004-10-26
Von Buhur, Maria N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C425S137000
Reexamination Certificate
active
06810303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an injection mold, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method, a molded component, and an optical system therewith, and specifically relates to an injection mold of precision components such as a plastic lens, a production method thereof, a production system thereof, a designing apparatus and a designing computer program thereof, an injection method using the injection mold, a molded component produced by the injection mold, and an optical system that is equipped with an optical component that includes the molded component.
2. Description of the Related Art
Optical components, such as a lens, are often made of resin, such as plastics, due to a low cost and lightweight. Most of the optical components are produced by an injection molding, and the like. A method of the injection molding uses an injection mold that has a cavity in a shape according to a product to be produced. A surface of the molding part is processed such that the cavity can be formed based on the shape of the product (design shape).
Then, melted and pressurized resin is injected to the cavity of the mold using an injection molding machine, and the like. After the resin is cooled, solidified resin is separated from the mold, and the product of the shape according to the surface shape of the molding part is obtained.
As for the resin for the injection molding, thermal plastics, such as amorphous polyolefin resin and acrylic resin (PMMA), are often used in the case of production of optical components. The resin is heated to 200 degrees C. or higher to be melted, and is injected to the injection mold while it is melted. For this reason, the molded product is subject to contraction when the injected resin solidifies, and further cooled to room temperature. Dimensions of the product tend to be smaller than the dimensions of the mold cavity. Then, in order to compensate the contraction, the contraction is estimated in advance by approximating the contraction by an inverse of isotropic deformation ratio (contraction ratio), and is applied to design of the cavity, i.e., the surface of the molding part.
The optical components are widely applied to a laser beam printer, a digital reproducing machine (copying machine) and the like, in view of economical prices. Recently, a demand for a high quality image has been increasing, which requires a high precision of the optical components used in an optical scanning system that greatly influences the image quality, while keeping the low costs. Therefore, a demand for a high precision and a low cost plastic optical component is increasing.
A product molded by the injection molding contains an uneven internal stress due to an unevenness of a cooling speed, an unevenness of resin temperature, and an asymmetry of the shape of the product. The internal stress causes an uneven deformation (strain). Further, a production error of the molding part cannot be disregarded. For these reasons, an actual deformation of the products is caused not only by a proportional contraction, but also by other periodical deformations that contain various frequency components. Therefore, it has been difficult to produce a high precision molded component that satisfies required properties (such as optical properties) by designing the cavity and the surface in precaution of only the isotropic contraction. This indicates that a process and a production method that consider various deformations occurring in the molded component are desired, such that a molded component that realizes designed properties is produced.
In order to control dimensions and a sphere of the molded component within predetermined tolerances, a practice has been that the shape of the molded component is measured to obtain shape data, the shape data is compared with designed dimensions, errors are determined, and the surface of the molding part is processed to correct the errors.
For convenience of computer processing, a polynomial (a shape regression) is widely used to approximate an amount of compensation from the shape data, because processing and production of the molded part are often performed by a processing apparatus managed and controlled by a computer. This approximation process not only interpolates values at an unmeasured point, but also extracts a low frequency component (a long wavelength component), that is, it has a low pass filter effect.
However, sometimes, designed properties were not obtained even after correcting the errors based on the long wavelength component contained in the shape data. Then, studies were made about shorter wavelength components (undulations).
For example, Japanese Laid-Open Patent Application No. 2000-263391 (hereinafter referred to as the first public knowledge) reveals a method in which a wavelength of a representative undulation component of a molded component is obtained, and removed. This method does not use a process of acquiring data from a polynomial, such as the shape regression, but performs a frequency analysis, such as the Fourier analysis, and extracts the undulation component.
Further, Japanese Laid-Open Patent Application No. 2001-62871 (hereinafter referred to as the second public knowledge) reveals a method of acquiring a compensation amount by a shape formula (a polynomial or a shape regression) that expresses a simulated figure considering a contraction ratio, and by extracting an undulation component.
Furthermore, Japanese Patent Publication No. 2898197 (hereinafter referred to as the third public knowledge) reveals a molding method that offsets shape errors, based on an approximation formula of a polynomial. In applying the approximation formula, an optically functional area of an optical component produced under stable molding conditions is divided into a plurality of areas. Then, the formula is applied to each of the areas, and continuity is provided to each boundary of the areas.
The first public knowledge is capable of identifying a wavelength of a governing undulation component, however, it is not capable of separating the undulation component from the shape of the molded component, and it is not capable of extracting sufficient information regarding an amplitude of the undulation component. For this reason, the first public knowledge cannot be applied to a method that provides a compensation amount varying from point to point in a corrective process. The first public knowledge uses elasticity and viscosity of a processing tool in order to remove the undulation component. However, in the case of processing a surface with varying curvatures, a concordance of a processing tool with an object of the process is a prerequisite. That is, the elasticity of the processing tool has to be low, which causes an insufficient removal of the undulation component. The second public knowledge considers a comparatively short wavelength component that is not included in a conventional shape regression, however, there is a possibility that a compensation amount contains an unnecessary high frequency component that is irrelevant to properties (such as optical properties) that are to be enhanced. This causes a process to become unstable and inefficient, depending on response characteristics of a processing apparatus. Further, this method applies a uniform contraction ratio regardless of wavelength, and for this reason, accuracy at an important wavelength tends to be low.
In
FIG. 31
, an example is presented, where the molded component is a scanning lens of a polygon scanner optical system of a laser beam printer. The polygon scanner optical system shown in
FIG. 31
includes a semiconductor laser S
1
as a light source, a collimator lens S
2
, a polygon mirror S
3
, a scanning lens S
4
, and a photo conductor S
5
. A light flux emitted from the semiconductor laser S
1
passes through the collimator lens S
2
, and irradiates the polygon mirror S
3
. The light flux is deflected by rotation of the poly
Endoh Hiroyuki
Iseki Toshiyuki
Kaneko Yutaka
Sagae Eiri
Shimbo Kohei
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh Company LTD
Von Buhur Maria N.
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