Varifocal optical element
AssigneeCanon Kabushiki Kaisha
InventorsTakeshi Baba, Kazuhiko Matsuoka, Masayuki Usui, Kazuo Minoura, Atsushi Someya, Masayuki Suzuki
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Abstract
An optical element whose focal length is variable comprises a medium whose refractive index is variable by temperature, a heating device for imparting heat to the medium to cause an index gradient resulting from a temperature distribution to be created in the medium, and a device for controlling the amount of heat imparted to the medium by the heating device to vary the shape of the index gradient formed in the medium.
Claims9
An optical element having a variable focal length, comprising:
- a medium the refractive index of which varies with temperature, said medium passing an incident light beam therethrough;
- a plurality of independently controllable heating means for imparting heat to said medium to create a single continuous index gradient due to a temperature distribution resulting in said medium as a consequence of heat being imparted thereto, wherein said plurality of independently controllable heating means comprise an annular heater and a central heater provided at the center of said annual heater, wherein the heating of said annular heater and said central heater is capable of being selectively controlled by control means to thereby produce concave and convex lens functions of the index gradient formed in said medium, and wherein said plurality of independently controllable heating means is disposed in a plane crossing the light beam;
- and
- control means for independently controlling the amount of heat being imparted to said medium by each of said plurality of heating means to vary the shape of the index gradient formed in said medium.
An optical element the focal length of which is variable, said element comprising:
- a medium the refractive index of which varies with temperature, said medium defining a light beam incident plane and passing a light beam therethrough;
- a plurality of heating means for respectively imparting heat to different portions of said medium to form a plurality of index gradients in said medium, said plurality of heating means being disposed in a plane crossing the light beam;
- means for controlling the amount of heat imparted by said plurality of heating means;
- and
- means for selectively illuminating areas of said light beam incident plane excluding at least those areas in which said plurality of heating means lie.
An optical device comprising:
- a light source;
- a light receiving surface for receiving a light beam from said light source;
- spot forming means for forming a beam spot on said light receiving surface by use of a light beam from said light source;
- scanning means for relatively scanning the beam spot formed by said spot forming means on said light receiving surface;
- a medium the refractive index of which varies with temperature, said medium being disposed at a position where the light beam from said light source enters between said light source and said light receiving surface;
- heating means for applying heat to said medium in order to generate a refractive index distribution accompanied with a temperature distribution in said medium;
- and
- controlling means for controlling said heating means so as to vary a diameter of said beam spot, scanned on said light receiving surface, by varying said refractive index distribution in said medium.
Dependencies are inferred from the claim text.