Optical: systems and elements – Lens – With field curvature shaping
Reexamination Certificate
1999-11-16
2001-02-13
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With field curvature shaping
C353S069000
Reexamination Certificate
active
06188523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection lens unit for a projector for enlarging and projecting an image on a screen, and more particularly, to a improved projection lens unit for a projector which can improve aberration characteristics and which can reduce the space occupied by lenses.
2. Description of the Related Art
In general, a projector includes a lamp for generating and irradiating light using halogen or xenon, a transmission or reflection type display device for generating an image by selectively transmitting or reflecting the light irradiated from the lamp, and a projection lens unit for enlarging an image and projecting the same on a screen. A liquid crystal display (LCD) or a micro-mirror device is be employed as the display device.
The projection lens unit must be designed in consideration of optical performance such as vertical and horizontal angle of view, aberration and the like, or space occupied by the lenses in the projector.
Taking this into consideration, the present applicant previously proposed a projection lens unit which is filed on Jan. 24, 1996 in Korean patent application No. 1858 (invented by Dong-ha Kim in the title of Wide View-Angle Liquid Crystal Projection Lens System).
The proposed projection lens unit includes a prism for switching the angle of an optical axis to arrange the optical axis to be bent by 90° or greater, thereby reducing the space occupied in the projector and achieving a wide angle of view.
However, since the respective lens groups have circular shapes, there is a limit in reducing the space occupied thereby.
Also, in “Reflection Type Projecting Apparatus” proposed by the present applicant, U.S. Ser. No. 09/057,585 filed on Apr. 9, 1998, invented by Soon-chul Choi, light is made to be incident or reflected slantingly into or from a ferroelectric liquid crystal device (FLCD) using a critical angle prism to convert the traveling path of the light. Accordingly, in the case where a conventional projection lens unit which is widely known is employed, the light reflected from the FLCD travels slantingly with respect to the optical axis of the projection lens unit, thereby causing deterioration in contrast and aberration characteristics of an image formed on a screen.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide an improved projection lens unit for a projector which can reduce a space occupied by an optical system by using only substantially half region of a lens group and can change the traveling path of light incident slantingly with respect to the optical axis of incident light.
Accordingly, to achieve the above objective, there is provided a projection lens unit for a projector employed to a projector having a light source and a display device disposed slantingly with respect to an optical axis of light irradiated from the Is light source, for enlarging and projecting the light incident slantingly with respect to the optical axis via the display device, the projection lens unit including: a first lens group having a positive power to focus incident light and arranged such that the central axis thereof is tilted with respect to the optical axis of the incident light to allow the light incident from the display device to be transmitted slantingly toward either side of the optical axis; and a second lens group having a negative power to diverge and enlarge a focused image, arranged such that the optical axis thereof is coaxially disposed with the optical axis of the first lens group and the second lens group having at least one aspherical lens for correcting a distortional aberration, the second lens group for diverging and transmitting the light having passed through the first lens group slantingly in view of the optical axis, the first and second lens groups sequentially disposed from the display device side.
According to another aspect of the present invention, there is provided a projection lens unit for a projector employed to a projector having a light source and a display device disposed slantingly with respect to an optical axis of light irradiated from the light source, for enlarging and projecting the light incident slantingly with respect to the optical axis via the display device, the projection lens unit including: a first lens group having a positive power to focus incident light and arranged such that the central axis thereof is tilted with respect to the optical axis of the incident light to allow the light incident from the display device to be transmitted slantingly toward either side of the optical axis; and a second lens group having a negative power to diverge and enlarge a focused image, arranged such that the optical axis thereof is off-axis from the optical axis of the first lens group slantingly with respect to the light transmitted through the first lens group, the first and second lens groups sequentially disposed from the display device side.
REFERENCES:
patent: 5475534 (1995-12-01), Okajima et al.
patent: 5709445 (1998-01-01), Takamoto
patent: 5820240 (1998-10-01), Ohzawa
patent: 5986806 (1999-11-01), Sugawara
Epps Georgia
Samsung Electronics Co,. Ltd.
Schwartz Jordan M.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Projection lens unit for projector does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Projection lens unit for projector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projection lens unit for projector will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2605359