OPTICAL DEVICE HAVING ABSORPTION GRADATION AND SELECTIVE SPECTRAL FILTRATION AND LENS CONSTITUTION PROVIDED WITH THE OPTICAL DEVICE AND CAMERA

摘要

PROBLEM TO BE SOLVED: To provide an optical device where both functions of a spectral filter and an absorption gradation filter are combined in the same element by making a block consisting of transparent uniform filter material have the change of thickness fit to a specified absorption coefficient and specified absorption profile. SOLUTION: This optical device 6 arranged on the front side of the incident surface 10 of a semiconductor optical sensor 12 and attached in the optical path of a photographing lens constitution 8 adopts the form of the block consisting of the uniform transparent filter material. The filter material means material having substantially the same absorption coefficient with respect to all the wavelength of the spectrum of visible light transmitted through the material. This kind of material is called neutral filter material. In such a case, the appropriate absorption coefficient value is selected and the thickness of the block consisting of the filter material is changed as the function of a distance from the lens constitution 8 to an optical axis, whereby the specified gradation absorption profile is attained and the uniform light irradiation to an image plane by the lens constitution to which the block is attached is obtained.