Mitsubishi Rayon Company, Limited

Masae Ono

Tomoyoshi Yamashita

Makoto Ookawa

A planar light source device has a primary light source (), a light guide () having a light incident surface () on which light emitted from the primary light source () is incident and a light emitting surface () for emitting light guided in the light guide, and a light deflector () opposed to the light emitting surface of the light guide. The light deflector () has a light input surface () to which light is inputted and a light output surface () which is disposed on the opposite side of the light input surface and outputs the inputted light. Elongated prisms each having two prism faces are arranged in parallel to each other on the light input surface (). At least one of the two prism faces is a non-single planar surface. The vertex split angle &#x3b1; of one of the prism faces is 2 to 25 degrees, and the vertex split angle &#x3b2; of the other prism face is 33 to 40 degrees. The difference (|&#x3b1;&#x2212;&#x3b2;|) between the vertex split angle &#x3b1; and the vertex split angle &#x3b2; is 8 to 35 degrees. As a result, the output light distribution is controlled and narrowed. Thus, a light source device having an improved ratio of utilization of the amount of light from the primary light source, a simplified structure, and an improved image definition is produced.

Light deflector and light source device

An optical deflector element has a light incoming surface () in which light enters and a light outgoing surface () located opposite the light incoming surface and from which light exits. In the light incoming surface () are arranged elongated prisms (A) in parallel to each other. Each of the elongated prisms (A) is formed by a top end flat face () located at the top end of the elongated prism and having an inclination angle (b) of 1 to 50 degrees, a first prism face () located at one side of the flat face, and a second prism face () at the other side. A light source device is formed by combining the optical deflector element, light guide and a primary light source. The light guide has a light incident face in which light emitted from the primary light source enters, and a light emitting face from which guided light exits. The combination above provides a light source device that does not have degradation in luminance and has excellent quality free from visual defects including a black stripe and a Moire pattern.

Optical deflector element and light source device

A planar light guide () having a light entrance end face () receiving light from a spot-like primary light source and a light exit face () outputting the entered light, wherein a plurality of lens arrays () are formed, at least a part of the light entrance end face, to extend from the light exit face toward the opposite face substantially in parallel with each other. The lens array () has an asymmetric cross-sectional shape defined by a combination of at least two different curves. When the light guide () is combined with a primary light source disposed oppositely to the light entrance end face () and a light deflecting element disposed oppositely to the-light exit face (), a high quality planar light source having a high uniformity and no variation in luminance is provided even when a relative small number of spot-like light sources are used as the primary light source.

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Kanagawa, Japan

Masae Ono