Abstract: A light controlling apparatus comprises a GH cell and a polarizing plate. The polarizing plate is attached to an iris blade, and movable inside/outside the effective optical path of the light incident to the GH cell. The iris blades are driven by a motor not shown in the drawing to overlap each other, and at the time, the polarizing plate is moved inside the effective optical path to cover the aperture. If the brightness of an object increases more, the GH cell absorbs the light to control the light. Because the polarizing plate is movable outside the effective optical path of the light, the light is not absorbed by the polarizing plate, and the maximum transmittance of the light controlling apparatus is increased, therefore the contrast ratio is increased and the light quantity is maintained uniform.

Abstract: An optical unit which comprises a pair of substrates 1, 1', which are provided with electrodes of specific configuration 4a, 4b, 4a', 4b', facing each other with the electrodes inside, a substance 7 placed between said paired substrates, said substance being capable of controlling the amount of transmitted light in response to a specific voltage applied to said electrodes, and light shielding films 2, 2' to confine the area to be shielded, said light shielding films being formed on the same side of the substrates 1, 1' that on which the electrodes 4a, 4b, 4a', 4b' are formed.

Abstract: A small-sized diaphragm device for an image pickup lens system having an electrochromic element the light transmitting properties of which are changed on application of an electrical voltage. The diaphragm device also includes a first set of plural concentrically arranged transparent electrodes, a second set of plural concentrically arranged transparent electrodes and third electrodes formed on the outermost peripheries of these sets of transparent electrodes for acting as counter-electrodes for the transparent electrodes. The diaphragm device has a sufficient light transmittance when in the transparent state, while having high light interrupting properties when in the light interrupting state.

Abstract: An image pickup optical system having an image pickup lens system having in turn a plurality of lenses arranged in multiple stages for forming an image of an object on an image plane of an image pickup device is disclosed. The image pickup optical system includes a double refraction plate arranged downstream of the image pickup lens system, a diaphragm unit, as a first optical unit, for determining the F-number of the image pickup lens system by a diaphragm aperture, and a second optical unit. When the F-number is equal to a pre-set value Fd or less, the second optical unit operates in conjunction with the double refraction plate for lowering the modulation transfer function (MTF) by the aberration due to an aspherical surface for a range of the spatial frequency not less than the cut-off frequency r.sub.c. Sufficient spurious signal suppressive effects may be obtained even if the optical low-pass filter is constituted by a sole double refraction plate, such as a quartz plate.

Abstract: A video camera in which an iris in an optical system is composed of a plurality of diaphragms, and at least two of the plurality of diaphragms are respectively provided with a light amount limiting filter such that the light amount limiting filters attached on the at least two diaphragms completely surround a transparent portion when the iris is half closed, to thereby provide satisfactory characteristics of the optical system when the iris is half closed.

Abstract: An optical low-pass filter for use in the optical system of a color video camera has first and second periodic structures on the same or opposed major surfaces of a transparent substrate and which are dimensioned and arranged in respect to each other to provide a modulation transfer function, in at least the horizontal scanning direction of the camera, which is higher than a predetermined value for frequencies in a range lower than a cut-off spatial frequency and which is low over a range of frequencies extending from the cut-off spatial frequency to substantially more than twice said cut-off spatial frequency.