| 摘要 |
PURPOSE:To observe electronic parts always with proper illuminance by compensating the sensitivity changes of a photoelectric receiving element caused by wavelength changes or temperature changes. CONSTITUTION:Light emitted from light emitting element 3 is reflected downwards by a half mirror 4, furthermore reflected by a board 7, and strikes a camera 1. Besides, a part of the light passes through the half mirror 4 and strikes a light receiving element 5. And the photoelectric output of the light emitting element 3 is controlled, feeding the output of the light receiving element 5 back to a drive controlling means 10 through the medium of a feedback means 14. On this occasion, the light emitting elements 3, light receiving element 5, and feedback means 14 have their respective temperature characteristics and wavelength characteristics, the sensitivity of the light receiving element 5 varies with the rise of temperature, and consequently the control of the light emitting diode 3 is subject to the bad influence of it. To prevent this, a filter 6 having a characteristic reverse to the overall sensitivity change is provided between the light emitting elements 3 and light receiving element 5. This makes it possible to control the photoelectric output of the light emitting element 3 with the drive controlling means 10 correctly as instructed, and the board 7 and electronic parts 8 are observed under specified illuminance. |
