The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

A light modulation apparatus 1A includes a first spatial light modulator, a pinhole member, and a second spatial light modulator. The first spatial light modulator has a phase modulation plane on which a kinoform for performing intensity modulation is displayed, and generates modulated light P2. The pinhole member has a light passing hole for letting a first-order light component of the modulated light P2 pass therethrough, and blocks a zeroth-order light component of the modulated light P2. The second spatial light modulator has a polarization modulation plane that controls the polarization state of the modulated light P2 incident on the polarization modulation plane through the light passing hole of the pinhole member, and generates modulated light P3.

A light modulation apparatus 1A includes a first spatial light modulator, a pinhole member, and a second spatial light modulator. The first spatial light modulator has a phase modulation plane on which a kinoform for performing intensity modulation is displayed, and generates modulated light P2. The pinhole member has a light passing hole for letting a first-order light component of the modulated light P2 pass therethrough, and blocks a zeroth-order light component of the modulated light P2. The second spatial light modulator has a polarization modulation plane that controls the polarization state of the modulated light P2 incident on the polarization modulation plane through the light passing hole of the pinhole member, and generates modulated light P3.

An acquisition, pointing, and tracking (ATP) apparatus for free space optical (FSO) communications systems incorporates a multi-element detector array positioned at a focal plane of an optical telescope. An optical communications element lies at the center of the detector array. In lieu of traditional beam steering, the apparatus performs pointing and tracking functions internally by first calculating a position of an optical maximum on the detector array, and then translating the detector array within the focal plane of the telescope such that the optical communications element lies at the optical maximum for transmitting and/or receiving optical communications signals.

An acquisition, pointing, and tracking (ATP) apparatus for free space optical (FSO) communications systems incorporates a multi-element detector array positioned at a focal plane of an optical telescope. An optical communications element lies at the center of the detector array. In lieu of traditional beam steering, the apparatus performs pointing and tracking functions internally by first calculating a position of an optical maximum on the detector array, and then translating the detector array within the focal plane of the telescope such that the optical communications element lies at the optical maximum for transmitting and/or receiving optical communications signals.

The projection optical system forms an intermediate image of an image displayed on an image display surface and forms a magnified image by projecting the intermediate image. The projection optical system consists of a first optical system and a second optical system, in order from the reduction side to the magnification side. The first optical system is telecentric on the magnification side, is a coaxial system having a common first optical axis and is non-telecentric on the reduction side. The second optical system is a coaxial system having a common second optical axis and is telecentric on the reduction side. The first optical axis and the second optical axis are parallel.

The projection optical system forms an intermediate image of an image displayed on an image display surface and forms a magnified image by projecting the intermediate image. The projection optical system consists of a first optical system and a second optical system, in order from the reduction side to the magnification side. The first optical system is telecentric on the magnification side, is a coaxial system having a common first optical axis and is non-telecentric on the reduction side. The second optical system is a coaxial system having a common second optical axis and is telecentric on the reduction side. The first optical axis and the second optical axis are parallel.

A fixed-focus projection lens module used for projecting an image beam provided by a light valve onto a screen is provided. The fixed-focus projection lens module includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a light-transmitting element arranged in sequence from a screen side to a display side along an optical axis. The fixed-focus projection lens module satisfies: 1<|OAL/BFL|<2.1, and OAL is a distance from the screen side surface of the first lens to the display side surface of the seventh lens on the optical axis, BFL is a distance from the screen side surface of the light-transmitting element to a display surface of the light valve on the optical axis.

A fixed-focus projection lens module used for projecting an image beam provided by a light valve onto a screen is provided. The fixed-focus projection lens module includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a light-transmitting element arranged in sequence from a screen side to a display side along an optical axis. The fixed-focus projection lens module satisfies: 1<|OAL/BFL|<2.1, and OAL is a distance from the screen side surface of the first lens to the display side surface of the seventh lens on the optical axis, BFL is a distance from the screen side surface of the light-transmitting element to a display surface of the light valve on the optical axis.

An optical imaging assembly is provided, having an optical axis; an object axis defined by an object being imaged; an aperture stop disposed on the optical axis; a light-transmissive sleeve enclosing the object axis, being disposed in object space defined by the object axis; and at least three refractive lens elements being arranged between the object and the aperture stop without any other intervening optical component, at least one of the elements having surfaces having at least one of cylindrical and acylindrical prescription, with an image plane, wherein the object being imaged lies within the sleeve.