A terahertz wave spectroscopic measurement device includes a light source that emits a terahertz wave and probe light having a wavelength different from that of the terahertz wave, an internal total reflection prism including an incidence surface of the terahertz wave, a placement surface on which a measurement target is placed, and an emission surface of the terahertz wave, the internal total reflection prism internally totally reflecting the terahertz wave incident from the incidence surface by means of the placement surface and emitting the terahertz wave from the emission surface, and a terahertz wave detection unit that indirectly detects the terahertz wave emitted from the emission surface using the probe light. The internal total reflection prism includes an avoidance portion on which incidence of the probe light on the measurement target on the placement surface is avoided.

A terahertz wave spectroscopic measurement device includes a light source that emits a terahertz wave and probe light having a wavelength different from that of the terahertz wave, an internal total reflection prism including an incidence surface of the terahertz wave, a placement surface on which a measurement target is placed, and an emission surface of the terahertz wave, the internal total reflection prism internally totally reflecting the terahertz wave incident from the incidence surface by means of the placement surface and emitting the terahertz wave from the emission surface, and a terahertz wave detection unit that indirectly detects the terahertz wave emitted from the emission surface using the probe light. The internal total reflection prism includes an avoidance portion on which incidence of the probe light on the measurement target on the placement surface is avoided.

An optical device and the prism module thereof are provided. The prism module includes a first prism, a second prism, a third prism and a fourth prism. The second prism is disposed beside the first prism. The second prism is attached to the third prism and the fourth prism. In operation, first visible light enters the first prism, is reflected plural times in the first prism, enters the second prism and then the fourth prism, is reflected at least one time in the fourth prism, returns to the second prism, is reflected at least one time in the second prism, enters the third prism and exits from the third prism. Also, second visible light enters the third prism, is reflected plural times in the third prism and exits from the third prism.

An optical device and the prism module thereof are provided. The prism module includes a first prism, a second prism, a third prism and a fourth prism. The second prism is disposed beside the first prism. The second prism is attached to the third prism and the fourth prism. In operation, first visible light enters the first prism, is reflected plural times in the first prism, enters the second prism and then the fourth prism, is reflected at least one time in the fourth prism, returns to the second prism, is reflected at least one time in the second prism, enters the third prism and exits from the third prism. Also, second visible light enters the third prism, is reflected plural times in the third prism and exits from the third prism.

A finder optical system is achieved in which object images can be more easily observed. A finder optical system includes an image-erecting member, which erects an object image formed by an objective optical system, provided on an optical path from the object side toward an eyepiece side, wherein the image-erecting member is formed as a penta roof prism provided with a first reflection surface and a second reflection surface, which define a roof reflection surface that reflects an incident light bundle emanated from the object, and the first reflection surface and the second reflection surface are configured as total-reflection surfaces that totally reflect the light bundle including the object image.

A head-up display system includes a projector adapted to project an image, a primary reflector, and an exit pupil replicator, the primary reflector adapted to reflect an image projected by the projector to the exit pupil replicator, and the exit pupil replicator adapted to split the projected image into a two-dimensional array of identical projected images having equal intensity.

A head-up display system includes a projector adapted to project an image, a primary reflector, and an exit pupil replicator, the primary reflector adapted to reflect an image projected by the projector to the exit pupil replicator, and the exit pupil replicator adapted to split the projected image into a two-dimensional array of identical projected images having equal intensity.

Disclosed is a head-up display device for a vehicle including at least one light source, a liquid crystal display, and at least one polarization converter disposed between the light source and the liquid crystal display and configured to convert unpolarized light generated by the light source into single linearly polarized light and to provide the single linearly polarized light to the liquid crystal display.

Described examples include an optical device, having a light source with a light source output and a light integrator having a light integrator input and a light integrator output, the light integrator input optically coupled to the light source output, and the light integrator configured to provide divergent light at the light integrator output responsive to the light at the light source output. The optical device also has projection optics with an optics input and an optics output, the projection optics configured to project output light at the optics output responsive to modulated light at the optics input, in which a focal point of the optics input matches a divergence of the modulated light and a spatial light modulator optically coupled between the light integrator output and the optics input, the spatial light modulator configured to provide the modulated light responsive to the divergent light.

Described examples include an optical device, having a light source with a light source output and a light integrator having a light integrator input and a light integrator output, the light integrator input optically coupled to the light source output, and the light integrator configured to provide divergent light at the light integrator output responsive to the light at the light source output. The optical device also has projection optics with an optics input and an optics output, the projection optics configured to project output light at the optics output responsive to modulated light at the optics input, in which a focal point of the optics input matches a divergence of the modulated light and a spatial light modulator optically coupled between the light integrator output and the optics input, the spatial light modulator configured to provide the modulated light responsive to the divergent light.