| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light beam having a desired divergence angle, and to sharply reduce energy consumption by providing a vertical cavity surface emission laser which emits a light beam, a data-transmitting element having a diverging device in the path, and a data-receiving element which is separated from the element and receives the transmitted light. SOLUTION: A light source 20 contains a vertical cavity surface emission laser(VCSEL) 22 for producing a photosignal in the shape of a laser beam 23, and a lid 28 is arranged on a lateral wall 27 surrounding the VCSEL22. The laser beam 23 proceeds through the lid 28, and passes a lens 30 (diverging device) supported by the lid 28. The lens 30 is a concave lens, and the angle of divergence is extended to forty-five degrees, and a light beam having the desired angle of divergence is obtained. When a visual angle of forty-five degrees is obtained using the VCSEL as a light source, about 48mA is required if an inclination efficiency is to be 0.4W/A. Sharp reduction in energy consumption, as compared to the conventional LED which needs a pulse of 250mA at a visual angle of thirty degrees. |
