Patent ID: 7418109

Claim:
An acoustic-electrical converter comprising: a diaphragm comprising an integral structure of a light reflective part ( 1 a ) at a central area thereof, suspension part ( 1 c, 1 d ) surrounding the light reflective part, and margin part ( 1 f ) surrounding the suspension part and fixed to a frame ( 2 or 9 ); and a light emitting element ( 3 ) and a light receiving element ( 4 ) disposed at positions opposed to the light reflective part so that a displacement of said diaphragm is detected by receiving light emitted from said light emitting element and then reflected from the light reflective part at said light receiving element; wherein a first slit is formed from a first outer periphery point of the suspension part to a first inner point near the light reflective part, wherein a second slit is formed from a second outer periphery point of the suspension part, which is apart from said first outer periphery point by a predetermined width, to a second inner point near the light reflective part so that an area of the suspension part between said first and second slits constitutes a first cantilever suspension ( 1 c ) which supports the light reflective part with connecting the light reflective part to the margin part ( 1 f ), wherein a third slit is formed from a third outer periphery point of the suspension part to a third inner point near the light reflective part, wherein a fourth slit is formed from a fourth outer periphery point of the suspension part, which is apart from said third outer periphery point by a predetermined width, to a fourth inner point near the light reflective part so that an area of the suspension part between said third and fourth slits constitutes a second cantilever suspension ( 1 c ) which supports the light reflective part with connecting the light reflective part to the margin part ( 1 f ), wherein an outer slit is formed between the second and third outer periphery points along the outer periphery of said suspension part and an area of the suspension part between the second and third slits constitutes a pressure receiving surface ( 1 d ) which is connected to the light reflective part 1 a through a portion between the second and third inner points but free of the margin part ( 1 f ).