US 6,685,342 B2Granted

Prism structure for flash illumination devices

AssigneeOlympus Optical Co., Ltd.

InventorHiroshi Terada

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Abstract

A prism unit has transmitting/totally-reflecting surfaces which cross each other, formed using at least one prism. Light emanating from a light source falls on the prism unit. The light is transmitted or totally reflected from the surfaces according to an angle of incidence at which the light falls on the prism unit. Transmitted light is radiated forwards, while totally-reflected light is directed laterally. A reflecting member is located laterally in order to cover the prism unit, whereby light totally reflected laterally by the prism unit is reflected forwards. In order to constitute the transmitting/totally—reflecting surfaces, a first air layer and a second air layer are formed in the prism unit so to have a substantially uniform width and oppose each other with a plane, which contains a glowing member of the light source and extends forwards, between them.

Claims13

Dependent claims

An illumination device comprising:

a first prism adapted to be located in front of a flash tube, and having a first transmitting/totally-reflecting surface adapted to be opposed substantially entirely to a longitudinal direction of said flash tube so that light diverging from said flash tube at an angle smaller than a predetermined angle relative to a center axis of radiation in said illumination device which lies in the longitudinal direction of said flash tube will be transmitted and radiated forwards, and so that light diverging from said flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in said illumination device will be totally reflected and laterally directed;
a second prism also adapted to be located in front of said flash tube, and having a second transmitting/totally-reflecting surface adapted to be opposed substantially entirely to the longitudinal direction of said flash tube so that light diverging from said flash tube at an angle smaller than the predetermined angle relative to the center axis of radiation in said illumination device that lies in the longitudinal direction of said flash tube will be transmitted and radiated forwards, and so that light diverging from said flash tube at an angle larger than the predetermined angle relative to the center axis of radiation in said illumination device will be totally reflected and laterally directed;
a reflecting member, formed to cover at least part of a periphery of said optical prism, for reflecting light that passes the periphery of said optical prism;
a housing prism having:
(i) an incidence surface on which light transmitted or totally reflected from said transmitting/totally-reflecting surface finally falls, and (ii) an emitting surface that radiates incident light on said incidence surface forwards, said emitting surface being exposed as a housing member;
and
a prism unit forming means for use in placing said first transmitting/totally-reflecting surface of said first prism and said second transmitting/totally-reflecting surface of said second prism on said incidence surface of said housing prism with a gap of a substantially uniform width between them.

4 more elements

An illumination device comprising:

a prism unit adapted to be located in front of a cylindrically long flash tube, and having:
(i) an incidence surface on which light diverging from said flash tube falls, (ii) a transmitting/totally-reflecting surface that transmits or totally reflects light, which has passed through said incidence surface, according to an angle of incidence of the light, and that is adapted to be opposed substantially entirely to a longitudinal direction of said flash tube so that transmitted light will be radiated forwards and totally-reflected light will be directed laterally, and (iii) an emitting surface that finally radiates light, which is transmitted or totally reflected from said transmitting/totally-reflecting surface, forwards;
and
a reflecting member for reflecting light, which is totally reflected laterally by said transmitting/totally-reflecting surface, forwards toward said emitting surface;
wherein said incidence surface and said emitting surface of said prism unit are substantially parallel to the longitudinal direction of said flash tube;
wherein said transmitting/totally-reflecting surface of said prism unit comprises a first transmitting/totally-reflecting surface and a second transmitting/totally-reflecting surface that are substantially symmetrical to each other in the longitudinal direction of said flash tube with respect to a center axis of radiation in said illumination device, and wherein said first transmitting/totally-reflecting surface and second transmitting/totally-reflecting surface cross each other near the center axis of radiation;
and
wherein:
said first transmitting/totally-reflecting surface comprises a first air layer having a substantially uniform width, and
said second transmitting/totally-reflecting surface comprises a second air layer having a substantially uniform width,
said second air layer is formed to be symmetrical to said first air layer in the longitudinal direction of said flash tube with respect to the center axis of radiation in said illumination device, and
said first air layer and said second air layer cross each other near the center axis of radiation.

9 more elements

Dependencies are inferred from the claim text.