Abstract: A visual display apparatus, for example, a head-mounted display apparatus, which enables an image to be observed at a wide field angle and high resolution. The apparatus includes a pair of two-dimensional display devices (4 and 5) disposed with their display surfaces facing each other, and two half-mirrors (6 and 7) which are paired with the display devices (4 and 5) and combined to each other in the shape of a V. The apparatus further includes a concave mirror (8) having a center axis coincident with the center axis of the half-mirrors (6 and 7) combined in a V shape. The two-dimensional display devices (4 and 5) are adapted to display images (11 and 10) each including an overlap region (9) and having an area wider than one half of the image for observation. The images (11 and 10) are combined together into one continuous image by the two half-mirrors (6 and 7) combined in a V shape.

Abstract: An optical system which is usable as either an ocular optical system or an imaging optical system, and which is satisfactorily corrected for both field curvature and comatic aberration for a field angle of up to about 120.degree. and for a pupil diameter of up to about 15 millimeters. The optical system includes a partial optical system (10) having a flat semitransparent surface (1) which is closer to a pupil plane (E), and a concave semitransparent surface (2) which is closer to an image plane (I). A refracting optical element (4) is disposed at the pupil plane (E) or image plane (I) side of the partial optical system (10) with an air spacing provided therebetween. Alternatively, the refracting optical element (4) may be cemented to the partial optical system (10). The refracting optical element (4) has a focal length f.sub.a which satisfies the condition of f.sub.a >0.

Abstract: A concentric optical system usable as either an imaging optical system or an ocular optical system, which enables a clear image to be obtained at a field angle of up to about 90.degree. and with a pupil diameter of up to about 10 millimeters with substantially no chromatic aberration. The concentric optical system includes a first optical component having a first semitransparent reflecting surface (2), and a second optical component having a second semitransparent reflecting surface (3). The first and second semitransparent reflecting surfaces (2 and 3) have respective centers of curvature disposed at approximately the same position (1). The first and second optical components are different in dispersion from each other.

Abstract: The invention relates to a reduction projection lens system of high resolution which enables chromatic aberration to be corrected, and can be improved in terms of transmittance by making the total thickness of the vitreous material forming said lens system. This reduction projection lens system includes refractive and diffractive optical elements and uses as the light source a spectral light source having a center wavelength of up to 300 nm and a wavelength spectral bandwidth of .+-.0.5 pm to .+-.200 pm such as an ArF or KrF excimer laser. The refractive optical element includes at least one aspheric surface, and the refractive and diffractive optical elements are made of the same vitreous material, e.g., SiO.sub.2. conditions, 0.02<.vertline.d/D.vertline.<0.17 and 0.01<.vertline.h/H.vertline.<0.