The wide angle optical system includes in order from a side of an object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and the catadioptric optical element has a first surface, a second surface, and a third surface, and the first surface has a first transmitting surface and a first reflecting surface, the second surface has a second transmitting surface and a second reflecting surface, and the third surface has a third transmitting surface, and the third transmitting surface is a side surface of a circular truncated cone, and the following conditional expressions (1), (2), and (3) are satisfied:

νp<νn  (1),

|φp|<|φn|  (2), and

90°−θk<α/2  (3).

An attachable image display device includes a light guiding prism that guides image light from a display element, and an eyepiece that emits the image light guided by the light guiding prism, wherein the light guiding prism includes an outer peripheral surface, and a reflection surface off which the image light is reflected to the eyepiece; and a portion of or the entirety of an intersection line of the outer peripheral surface and a plane including an optical axis of the image light before the image light is reflected off the reflection surface has a negative inclination angle to the optical axis in a direction downstream of the light path, and a tangential inclination angle of the portion of or the entirety of the intersection line becomes gradually larger from an upstream side to a downstream side of the light path.

Provided is light flux controlling member for controlling a distribution of light emitted from a plurality of light emitting elements disposed on a substrate, which includes a plurality of incidence units for allowing incidence of the light emitted from the plurality of light emitting elements, respectively; and an emission unit which emits the light incident on the plurality of incidence units while guiding the light, and which is disposed between the plurality of incidence units in a direction along the substrate. The light flux controlling member has a rectangular shape with rounded corners in plan view, and includes four corner portions and four side portions, and the inclination angle of the corner portions is different from the inclination angle of the side portions.

A light guide prism for guiding image light from a display device to an observer's eye and displaying a virtual image of the display device in the observer's field of view includes at least four sides disposed to surround an optical path of image light incident from one end, a reflecting surface configured to reflect the image light guided by the at least four sides, and an emission surface configured to emit the image light reflected at the reflecting surface towards the observer's eye. At least one groove in a V-shape is formed on each of the at least four sides. As a result, a light guide prism that reduces stray light and ghost light occurring due to reflection at inner surfaces and an image display apparatus using this light guide prism can be provided.

A light guide device that does not cause non-uniformity in image light and external light and does not cause ghosts, and a virtual image display apparatus provided with the light guide device. The light guide device includes a parallel light guide, an incident section, and an emission section. Here, the light guide device is set such that image light rays are reflected without reflecting from a boundary surface between the parallel light guide and the reflection unit and head for an observer. Thus, the image light rays only pass through half mirrors, which are positioned in positions where the image light rays are emitted from the reflection unit of the emission section or are positioned therearound. Accordingly, it is possible to prevent luminance non-uniformity or light reduction by reducing the number of times of the image light rays to be observed pass through the half mirrors.

A lighting lens for a biometric measurement device comprises a paraboloidal or ellipsoidal reflector with symmetry of revolution, and a dioptric surface that has two different refractive power values in two perpendicular directions, said two refractive power values being negative or zero. Such a lens can be produced in the form of a block of transparent material and be used in a biometric measurement device. In particular, it makes it possible to capture skin prints as an image with an exposure time that is short.

An optical module in the present disclosure includes a first image display panel including a first display part and a first coupling part, a second image display panel including a second display part and a second coupling part, a third image display panel including a third display part and a third coupling part, and a cross dichroic prism configured to synthesize first, second, and third image light. The cross dichroic prism has a cross axis at which a two of photosynthesis surfaces cross each other. The first, second, and third image display panel are respectively bonded to different surfaces of the cross dichroic prism in a state where a long side of each of the first, second, and third display part extends along the cross axis and where the first, second, and third coupling part are each positioned on an outer side of the cross dichroic prism.

A first light guide guides first light in a first light guiding path. The first light is of light irradiated from the light source to a sheet. A first detection unit receives reflected light from the sheet and outputs an image signal indicating an image of a surface of the sheet. A second light guide guides second light in a second light guiding path different from the first light guiding path. The second light is of the light irradiated from the light source and is different from the first light. A second detection unit receives the second light and output a detection signal corresponding to a light amount of the second light. A control unit controls a light emission amount of the light source based on the detection signal.

The invention provides an optical path adjusting unit and a display device. The optical path adjusting unit, for adjusting light rays from different directions to transmit in approximately the same direction, comprises a light converging part, a reflective part and a light scattering part. The light converging part and the light scattering part form a hollow space, and the reflective part is disposed within the hollow space and connected to the middle of the light converging part and the middle of the light scattering part to divide the hollow space into two parts. The light converging part is used to converge the light rays from different directions; the reflective part is used to reflect the converged light rays onto the light scattering part, and the light scattering part is used to transmit the light rays reflected thereon by the reflective part out in approximately the same direction.

An optical system includes a splitting optic configured to receive a light beam from a light source and form a set of light bands radiating from the optical system at predetermined angles relative to illuminate a scene. The optical system further includes a lens configured to project a field of view of the scene into a two-dimensional format. The optical system further includes an optical sensor arranged offset from the central axis of the lens to capture a segment of the field of view projected by the lens.