An optical system and a projection device are provided. The optical system includes a display unit, a first lens group, a second lens group, and a reflector in sequence along a transmission direction of light; both the first lens group and the second lens group have positive focal powers; the optical system satisfies the following relationship: 0.01≤|φ.sub.100|≤0.02 and 0.005≤|.sub.φ200|≤0.015; φ.sub.100 represents a focal power of the first lens group, and φ.sub.200 represents a focal power of the second lens group.

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.

A large filed achromatic lens is disclosed, including a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element arranged sequentially along the propagation direction of an incident ray. The first lens element is a meniscus lens element including a first curved surface and a second curved surface; the second lens element is a meniscus lens element, including a third curved surface and a fourth curved surface; the third lens element is a biconvex lens element, including a fifth curved surface and a sixth curved surface; the fourth lens element is a biconvex lens element, including a seventh curved surface and an eighth curved surface; the fifth lens element is a biconcave lens element including a ninth curved surface and a tenth curved surface; and the sixth lens element is a plane lens element adapted to play a role in protecting other lens elements. The first to the fifth lens elements are arranged around a same axis sequentially along the propagation direction of an incident ray. The first to the tenth curved surfaces are arranged sequentially along the propagation direction of the incident ray. The above large filed achromatic lens can be used as a fine photoetching lens for laser marking, or other fine processing lenses.

A large filed achromatic lens is disclosed, including a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, and a sixth lens element arranged sequentially along the propagation direction of an incident ray. The first lens element is a meniscus lens element including a first curved surface and a second curved surface; the second lens element is a meniscus lens element, including a third curved surface and a fourth curved surface; the third lens element is a biconvex lens element, including a fifth curved surface and a sixth curved surface; the fourth lens element is a biconvex lens element, including a seventh curved surface and an eighth curved surface; the fifth lens element is a biconcave lens element including a ninth curved surface and a tenth curved surface; and the sixth lens element is a plane lens element adapted to play a role in protecting other lens elements. The first to the fifth lens elements are arranged around a same axis sequentially along the propagation direction of an incident ray. The first to the tenth curved surfaces are arranged sequentially along the propagation direction of the incident ray. The above large filed achromatic lens can be used as a fine photoetching lens for laser marking, or other fine processing lenses.

This disclosure is directed to an inner focus macrolens. The inner focus macrolens can include sequentially from an object side, a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power and a fourth lens unit having a positive refractive power, wherein the first lens unit comprises a negative lens as the closest powered lens to the object side and a positive lens, the second lens unit comprises an object side negative lens as the closest powered lens to the object side and a positive lens, the third lens unit comprises a negative lens, and the fourth lens unit comprises a positive lens.

This disclosure is directed to an inner focus macrolens. The inner focus macrolens can include sequentially from an object side, a first lens unit, an aperture stop, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power and a fourth lens unit having a positive refractive power, wherein the first lens unit comprises a negative lens as the closest powered lens to the object side and a positive lens, the second lens unit comprises an object side negative lens as the closest powered lens to the object side and a positive lens, the third lens unit comprises a negative lens, and the fourth lens unit comprises a positive lens.

The optical system according to the present invention consists of a first lens unit with positive refractive power disposed closest to an object side, a middle group including at least two lens units, and a final lens unit with negative refractive power disposed closest to an image side in which intervals between adjacent lens units are changed during focusing. The middle group includes a first focus lens unit configured to move during focusing, and a second focus lens unit disposed on the image side of the first focus lens unit and configured to move during focusing. An aperture stop is disposed between two lenses included in the middle group. Here, a focal length of the optical system, a focal length of the final lens unit, and a focal length of a second focus lens unit are appropriately determined.

An imaging optical system of the present invention includes first and second optical elements arranged in order from an object side and an aperture stop. Each of the first and second optical elements includes an aspherical surface which is rotationally asymmetric with respect to an optical axis. A curvature of the aspherical surface in a first cross section including the optical axis changes from the optical axis in a first direction perpendicular to the first cross section. A total length of the imaging optical system, a distance between the aspherical surface closest to the object side and the aperture stop, and Abbe numbers of the first and second optical elements are appropriately set.

Provided is imaging optical system, including: a first lens array including a plurality of lens rows each having a plurality of lenses arrayed in main array direction, the plurality of lens rows arranged in sub-array direction; and a second lens array including a plurality of lens rows each having a plurality of lenses arrayed in main array direction, the plurality of lens rows being arranged in sub-array direction. The imaging optical system forms an erect image of object in main array cross section, and forms an inverted image of object in sub-array cross section. At least one of first and second lens arrays includes at least one of a scattering and light-shielding portions arranged between adjacent lens rows. D/Rs≦0.2 is satisfied, where D represents length of at least one of scattering and light-shielding portions in sub-array direction, and Rs represents an effective diameter of imaging optical system in sub-array direction.

An objective for a microscope includes, in order from an object side, a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power. When NA represents a numerical aperture of the objective, FN represents a field number of the objective, β represents a magnification of the objective, ε represents an Airy disk diameter on an axis to a d-line of the objective, φ.sub.max represents a maximum value of an effective diameter of a lens included in the objective, and h.sub.exp represents a radius of an exit pupil of the objective, the objective satisfies the following conditional expressions:
0.8≦NA≦1.5  (1)
1000≦FN/|β|/ε≦10000  (2)
1.7≦φ.sub.max/2/h.sub.exp/NA≦4  (3).