Fujinon Corporation

Shuji Akiya

Arihiro Saita

Mototaka Kanaya

Etsuo Terayama

An optical filter has a multilayer thin film comprising first to i-th layers stacked in alternate layers of high and low refractive indices on a transparent substrate. Respective odd-numbered layers (high refractive index layers) and respective even-numbered layers (low refractive index layers) form repetitive sequences of layers each of which cyclically changes in optical thickness throughout the multilayer thin film. Each of k-th from-the-bottom alternate layers of high and low refractive indices has such an optical thicknesses as meet the following conditional expressions (1) and (2), concurrently:(/4)&#xd7;[1+sin{(1)&#xd7;.}&#xd7;.]&#x2003;&#x2003;(1)0 . . . &#x3c;1 &#x2003;&#x2003;(2)where

Optical filter

It is disclosed that a color separation optical system improves color reproducibility by obtaining a characteristic which approximates an ideal spectral characteristic in view of influence of polarization separation caused according to the magnitude of an incidence angle. In the color separation optical system, a curve representing a characteristic of a green-reflecting dichroic film DG has a shape along the characteristic curve representing an ideal spectral characteristic corresponding to green light. Further, the characteristic of the blue-reflecting dichroic film DB is associated with that of the green-reflecting dichroic film DG. A part, in which the transmittance of the blue-reflecting dichroic film DB changes from a low transmittance to a high transmittance, in the transmittance characteristic curve representing the characteristic of the blue-reflecting dichroic film DB is included in a predetermined wavelength region associated with the characteristic of the green-reflecting dichroic film DG.

Color separation optical system and image pickup apparatus

Two types of layers are simultaneously formed on a substrate and another substrate under the same layer forming condition, the heights of which are equal to a half height of an intended retardation compensation layer. Physical properties of the respective two types of layers formed on the substrates are identical to each other, and if deviations are produced in retardation distribution characteristics for azimuth angles of incident light, these deviations are commonly provided in the respective two types of layers. When one substrate is superposed with the other substrate and these superposed substrates are integrated with each other in order to make a single sheet of retardation compensation element, after one of these substrates is rotated by an angle of 90 degrees with respect to the other substrate, these substrates are stuck to each other by an adhesive agent.

Retardation compensation element and manufacturing method of the same

A curve representing a characteristic of a blue-light reflecting dichroic film DB and a curve representing a characteristic of a red-light reflecting dichroic film DR are configured to have shapes that track an ideal spectral characteristic of green. Accordingly, it is possible to obtain a characteristic approximated to the ideal spectral characteristic without using a trimming filter having a dichroic film in an exiting surface of a prism. Since it is not necessary to use the trimming filter having the dichroic film, it is possible to prevent ghost and flare from occurring due to the dichroic film of the trimming filter. Accordingly, it is possible to embody an imaging apparatus having the ideal spectral characteristic with ghost and flare being reduced.

Color-separation optical system and imaging apparatus

A cross dichroic prism for color decomposition includes a blue-reflecting dichroic film for reflecting a blue light component and a red-reflecting dichroic film for reflecting a red light component. Each dichroic film comprises lower and higher refractive index materials alternately laminated on a prism base. The cross dichroic prism satisfies 1.105&#x2266;N/N&#x2266;1.450 if N&#x2266;N, or 1.118&#x2266;N/N&#x2266;1.150 if N&#x3e;N, where Nis the refractive index of the prism base, Nis the refractive index of the higher refractive index material, and Nis the refractive index of the lower refractive index material.

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Saitama, Japan

Shuji Akiya