Illumination apparatus for microscope

1. A transmission illumination apparatus for a microscope comprising:

an optically transparent sample mount plate on which a sample is mountable;

a surface light source that projects substantially uniform illumination light toward the sample mount plate; and

at least one light orientation member that restricts diffusion of the illumination light in relation to at least one direction, wherein the light orientation member is interposed between the sample mount plate and the surface light source, and

wherein a length D of a shortest side of a light emission portion of the surface light source, a distance L from a sample mount surface of the sample mount plate to a light emission surface of the surface light source, and a maximum angle (a half angle) A of the illumination light that falls on the sample satisfy the following expressions:

L<0.7D

A< 0.9 tan −1 ( D/ 2 L ).

2. The transmission illumination apparatus for a microscope according to claim 1 , wherein the light orientation member comprises a louver film that comprises an optically transparent parallel-plate type transparent resin and a plurality of optically opaque micro louvers arranged in the transparent resin at equal intervals.

3. The transmission illumination apparatus for a microscope according to claim 2 , wherein the micro louvers of the louver film are perpendicular to parallel planes of the transparent resin.

4. The transmission illumination apparatus for a microscope according to claim 3 , wherein the microscope is a binocular stereoscopic microscope, and the light orientation member restricts diffusion of the illumination light in a direction vertical to a plane containing two optical axes of the binocular stereoscopic microscope.