Optical: systems and elements – Lens – With support
Reexamination Certificate
1999-09-30
2001-02-06
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S811000, C353S122000, C349S058000
Reexamination Certificate
active
06185052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an optical component housing made of metal to hold optical components that constitute an optical system, and to a projection display device using the optical component housing.
2. Description of Related Art
Hitherto, a projection display device has been used which may consist of a light source, an optical unit for forming an optical unit by modulating a light beam emitted from the light source according to image information, and a projection lens for enlarging and projecting the modulated light beam onto a projection plane. The optical unit includes an illumination optical system for uniformizing the in-plane illumination distribution of a light beam emitted from the light source, a color separation optical system for separating the light beam from the illumination optical system into color beams of the primary colors, red, blue, and green, an optical modulation system for modulating the color beams according to image information, and a color synthesizing optical system for synthesizing the modulated color beams.
Optical components, such as dichroic mirrors for constituting the color separation optical system, and condenser lenses placed on the incident side of the optical modulation device, are usually housed in an optical component housing, called a “light guide”, because they need to be precisely placed on the optical axis extending from the light source to the projection lens. The adoption of an optical component housing made of metal, such as a magnesium alloy, as such an optical component housing has been examined. When the optical component housing made of metal is adopted in the projection display device, since the strength of the material is high, it is reduced in thickness, thereby reducing the weight of the device. Since a metal having high thermal conductivity is adopted as the material, it is possible to improve efficiency in cooling various optical components housed therein.
In addition to molding methods, such as casting and forging, thixomolding is known as a method of producing the above-described optical component housing made of metal, in which injection molding is performed using semi-molten metal consisting of coexisting solid and liquid phases, by agitating the semi-molten metal and thereby lowering the viscosity thereof.
According to this thixomolding method, since an injected material can be molded at a lower temperature than in casting, such as die casting, less shrinkage occurs due to solidification by cooling, and it is easy to ensure dimensional accuracy. Moreover, since the surface of a molded article is close, it is possible to simplify subsequent processes such as buffing.
SUMMARY OF THE INVENTION
The optical component housing may consist of, however, a box-shaped section for covering the bottom, side, and top portions of the optical components, so as to prevent the entry of dust and the like, and optical component positioning portions for precisely positioning the optical components. Since the optical component positioning portions must precisely place the optical components along the axis parallel to the light traveling direction, high dimensional accuracy is required. Therefore, in a case in which the optical component positioning portions are formed by thixomolding, problems arise in that molding is difficult and in that it is difficult to ensure accuracy, which substantially increases the production cost of the optical component housing.
An object of the present invention is to provide an easy-to-form structure, which allows dimensional accuracy to be high, for an optical component housing in which at least an optical component positioning portion is formed by thixomolding using metal material. Another object of the present invention is to provide a projection display device in which the production cost can be reduced by using an optical component housing having such a structure.
In order to achieve the above objects, an optical component housing of the present invention is an optical component housing formed by thixomolding using a metal material, and having an optical component positioning portion, the optical component positioning portion may include a first side plate and a second side plate that form a predetermined angle, a first support portion that supports one of a light incident surface and a light emitting surface of the optical component, and a second support portion that supports a peripheral edge portion of the optical component, the first support portion projecting on an inner side face of the first side plate so as to be in contact with the second side plate, and a portion of the second side plate in contact with the first support portion having a portion previously removed that is formed by inserting an insert in a mold used in the thixomolding.
A portion for positioning an optical component is generally shaped to be thin-walled and tall. Moreover, since the surface in contact with the optical component must be provided with a draft of 0°, the positioning portion clings to the mold and cannot be separated from the mold after molding. If demolding is forcibly performed, the optical component is deformed, or the thin-walled positioning portion is broken at the middle point thereof. Since the optical component positioning portion has a previously removed portion that is formed from an insert, and the previously removed portion is formed before an upper mold and a lower mold are opened, the positioning portion can be prevented from clinging to the mold. Accordingly, it is possible to form the optical component positioning portion with high precision. Therefore, it is possible to easily and precisely produce the optical component housing, to improve the quality of molding of the optical component housing, and to substantially reduce the production cost.
In the above, it is preferable that the above-described previously removed portion be formed of a recess formed in the other side plate. That is, since the previously removed portion is formed of a recess, even when an alloy slurry enters the clearance between the insert and the casting mold, and casting fins or the like are thereby produced in the portion of the second side plate in contact with the first support portion, the casting fins can be absorbed by the recess. Therefore, it is possible to simplify operations for removing the casting fins, and to thereby further reduce the production cost of the optical component housing.
Preferably, the planar shape of the recess is at least one of a substantially cross-shape, a substantially T-shape, a substantially L-shape, a substantially concave shape, and a substantially convex shape, or a combination thereof.
That is, since the insert in the previously removed portion is narrow and long and does not have a guide at the leading end, it is apt to be tilted due to the pressure of molten metal during molding, and furthermore, it is apt to be distorted due to the pressure of the molten metal. Therefore, the recess is formed in the above planar shape to provide resistance to tilting, and is engaged with a guide portion of the insert to limit the tilting. This also makes it possible to improve rigidity of the insert against distortion, and to improve and stabilize molding accuracy.
Furthermore, in the above-described optical component housing, a plate-like member may be attached to the optical component positioning portion. The plate-like member can be attached to the optical component positioning portion by, for example, welding, screwing, or riveting.
That is, since the optical component housing is constructed by attaching the plate-like member to the optical component positioning portion, it can be formed by molding a skeletal portion, which requires high dimensional accuracy, by thixomolding, and by subsequently attaching a plate-like member. Therefore, the structure of the mold in thixomolding is simplified, and it is easier to ensure dimensional accuracy. In addition, thixomolding can also be performed more rapidly and at lower cost by forging or the
Fujimori Motoyuki
Hirabayashi Tatsuto
Takei Atsuki
Epps Georgia
Oliff & Berridg,e PLC
Seiko Epson Corporation
Seyfari Saeed
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