Abstract: A projection television system (10) is provided which has a CRT (16) and a projection lens system (13) for forming an image on a screen (14). The projection lens system (13) is characterized by a diffractive optical surface (DOS) which provides color correction for the lens system. The diffractive optical surface (DOS) can be formed as part of a diffractive optical element (DOE) or as part of an existing lens element of the lens system. The diffractive optical surface (DOS) is located between the object side (S2) of the lens' first lens unit (U1) and the image side (S11) of the lens' third lens unit (U3). The distance between the diffractive optical surface (DOS) and the lens' aperture stop (AS) is less than 0.1·f0, where f0 is the focal length of the projection lens (13).

Abstract: Projection lens systems for use in CRT projection televisions are provided. The lens systems include a negative lens unit (U4) which is associated with the CRT during use of the lens system and four lens elements (L1, L2, L3, CR) on the image side of the negative lens unit (U4). Three of those lens elements (L1, L2, L3) are arranged as follows from the long conjugate to the short conjugate of the lens system: a first lens element (L1) which has a weak optical power and at least one aspherical surface; a second lens element (L2) which has a positive focal length and provides most of the optical power of the lens system; and a third lens element (L3) which has a positive focal length and at least one aspherical surface. The last lens element of the system is a corrector lens element (CR) which is located adjacent to the second lens element (L2) and has a weak optical power, at least one aspherical surface, and is substantially flat.

Abstract: Optical systems for use with reflective LCDs (8,9,32,34,36) are provided. The systems include a polarization beam splitter (5) which can be composed of polarization beam splitting cubes (26) having sheet polarizers (30) and/or half wave plates (28) at their mating surfaces. By orienting the half wave plates (28) so that they convert S polarization to P polarization and P polarization to S polarization, the polarization beam splitter (5) can provide a high contrast ratio at a viewing screen between light from the “on” and “off” pixels of the reflective LCDs (8,9,32,34,36).

Abstract: A prism (13) for use in a projection system which employs a digital light panel (35) is provided. The prism includes first (19) and second (21) spaced part surfaces which are oriented such that: (a) light from a light source (33) will pass through the spaced apart surfaces to the digital light panel; (b) light from “on” pixels will undergo total internal reflection at the second surface (21) and be directed into the acceptance angle of a projection lens (39); and (c) light from “off” pixels which reflects from the second surface will be directed away from the lens' acceptance angle.

Abstract: Six-component projection lens systems (13) for use in CRT projection televisions (10) are provided. To provide an improved overall modulation transfer function across the field of view of the lens, the system's first lens element (L1) has an object side surface (S2) which has a best fit spherical surface which is convex to the CRT (16). To provide partial axial color correction, the system's second lens element (L2) is made of a high dispersion material, such as styrene.

Abstract: A zoom projection lens for use with LCD or DMD panels is provided. The lens has two units U1 and U2, which are moved relative to one another for zooming. It also has a corrector unit (CR) at a fixed distance from the LCD or DMD panel (PP). The corrector unit, which may be a color correcting doublet, is at the object (panel) end of the lens and has a weak power. This unit allows for a high level of distortion and lateral color correction, without unduly increasing the complexity or cost of the lens.

Abstract: Projection lens for use with pixelized panels are provided which consist of a first lens unit which has a negative power and a second lens unit which has a positive power. The V-values and Q-values of the lens elements of the first and second lens units are selected so that the projection lenses can simultaneously have: (1) a high level of lateral color correction, including correction of secondary lateral color; (2) low distortion; (3) a large field of view in the direction of the image (screen); (4) a telecentric entrance pupil; and (5) a relatively long back focal length.

Abstract: A zoom projection lens for use with pixelized panels is provided. The projection lens has a negative/positive (retrofocus) form, with the positive lens unit (U2) having two positive subunits (U2S1, U2S2). The image (screen) side subunit (U2S1) serves as focus corrector for the lens, i.e., after zooming, this subunit is moved to adjust the focus of the lens. Compared to moving the negative unit (U1), this approach achieves better aberration correction and involves moving less mass through smaller distances.

Abstract: A projection lens for use with LCD or DMD panels is provided. The lens has three lens units, the first unit having a weak power, at least one aspheric surface, a high dispersion negative lens element, and a low dispersion positive lens element, the second lens unit having a positive power, and the third lens unit having a negative power and an overall meniscus shape. The projection lens satisfies the following relationships:0.3>D.sub.23 /f.sub.0 >0.1,.vertline.f.sub.1 .vertline./f.sub.0 >1.3, andBFL/f.sub.0 >0.3where (i) f.sub.0 is the effective focal length of the combination of the first, second, and third lens units; (ii) f.sub.1 is the effective focal length of the first lens unit; (iii) D.sub.23 is the distance between the second and third lens units; and (iv) BFL is the back focal length of the combination of the first, second, and third lens units for an object located at infinity along the long conjugate side of the projection lens.

Abstract: A projection lens system for projecting an image from a cathode ray tube (CRT) onto a screen is provided. The spherochromatic aberration of the system is reduced through the use of a first lens element which has (i) a positive power on axis and at least one aspheric surface which causes the positive power to become negative in the vicinity of the lens element's clear aperture, and (ii) a high dispersion. The first lens element is preferably composed of styrene.

Abstract: Zoom projection lens systems are provided which have 1) an entrance pupil which remains at a substantially fixed position as zooming takes place, and 2) a operative aperture stop, distinct from the system's physical aperture stop, which moves through lens surfaces as zooming takes place. The fixed entrance pupil allows for efficient coupling to a light source throughout the magnification range of the system. Methods which can be used to design and produce zoom lens systems of this type and which employ a pseudo-aperture stop are also disclosed.

Abstract: A projection lens system for projecting an image from a cathode ray tube (CRT) onto a screen is provided which includes in order from the image end: a first lens unit (U1), a second positive lens unit (U2) which may include a color correcting doublet, a corrector lens unit (CR), and a third negative lens unit (U3) which is associated with the CRT during use. The first lens unit preferably has a hybrid construction and includes: a first lens element (L1) composed of glass and having spherical surfaces, a second lens element (L2) composed of plastic and having at least one aspherical surface, and a third lens element (L3) also composed of plastic and having at least one aspherical surface. L1 has substantially more optical power than either L2 or L3, e.g., .vertline.f.sub.L2 .vertline./f.sub.L1 and .vertline.f.sub.L3 .vertline./f.sub.L1 are each above 1.3. In this way, the lens system is easily fabricated and is relatively insensitive to changes in temperature of the lens elements.

Abstract: Projection lens systems for use in projection televisions are provided. The lens systems include a strong positive element which provides a majority of the power of the lens, a strong negative unit which provides most of the correction for the field curvature of the lens system, and four weak meniscus aspherical elements, two on each side of the positive element. By means of this arrangement, the lens system achieves a semi-field of view of approximately 40.degree. at a f-number of about 1.0 or less. The lens systems are used to minimize the size of projection television sets since their semi-field of view of approximately 40.degree. substantially matches the maximum numerical aperture of about 0.65 of projection screens used in such sets.

Abstract: A wide angle lens system of the retrofocus type is provided which includes two lens units. The first lens unit is of negative power and includes a combination of a positive element having a high dispersion and a negative element having a low dispersion for correction of lateral color. The second lens unit is of positive power and includes a combination of a positive element having a low dispersion and a negative element having a high dispersion for correction of longitudinal color. The lens units satisfy the relationship that the magnitude of f.sub.1 is less than about 1.15 times f.sub.2 and preferably satisfy the relationship that the magnitude of f.sub.1 is less than f.sub.0. The first and second lens units each preferably include an aspheric surface. Applications of the lens system include rear projection television systems wherein a single lens is used to project light from three LCD light valves onto a viewing screen.

Abstract: A lens system is provided which includes two lens units. The first lens unit includes two meniscus lenses whose concave surfaces face each other and the second lens unit has a positive power. The system can be configured to have a wide field of view and/or to be telecentric. In its basic form, a well-corrected lens having a relatively large aperture and field of view is achieved through the use of only three lens elements.

Abstract: Disclosed is an improved color projection TV lens system which provides reduced chromatic aberration and improved chromaticity. These improvements are achieved by incorporating a light absorbing material into at least one lens in the system wherein the lens has a substantially uniform thickness.

Abstract: A partially color corrected projection lens having three groups comprising from the image end a first group serving to correct aberrations, a second group supplying essentially all of the positive power of the lens and a third negative group where the second group comprises two positive elements with a negative element therebetween.

Abstract: A wide angle projection lens which comprises from the image end a first lens unit of negative power having at least one aspheric surface, a second positive lens unit comprising at least two elements and a third negative element having an aspheric concave to the image, where the first lens unit provides negative power to the overall lens and serves as an aberration corrector including some field curvature.

Abstract: A projection lens for a cathode ray tube consisting from the image end of a first lens unit including an element of overall meniscus shape and of positive power at the optical axis, a second lens unit which includes of a biconvex element and supplies the majority of the positive optical power of the lens, the biconvex element being of glass and having spheric surfaces, a third lens unit adjacent the cathode ray tube having a strongly concave image side surface and serving as a field flattener, and a corrector lens unit having at least one aspheric surface, the corrector unit being axially spaced from the second lens unit a distance such that the axial marginal rays from the second lens unit, as traced from the long cojugate intersect the image side surface of the corrector unit at a height from the optical axis that is less than the clear aperture of said corrector lens unit. The corrector lens unit is shaped to correct for off-axis aberrations above the intersection.

Abstract: A projection lens in which a lens unit which may comprise one or two elements is closely coupled at the object end of the lens to a cathode ray tube. At the image end is a lens unit of overall weak optical power which comprises from the image end a first positive element followed by a closely spaced negative element of substantially higher dispersion. Intermediate the object side lens unit and the image side lens unit is a lens unit of substantial optical power supplying substantially all of the positive optical power of the lens. Closely spaced to this power lens unit on the object side is a negative lens element of high dispersion. This negative lens element may be considered to be part of the power lens unit.