公开(公告)号：US5994844A

公开(公告)日：1999-11-30

申请号：US989923

申请日：1997-12-12

申请人： James J. Crawford ,  Kevin J. Crawford

发明人： James J. Crawford ,  Kevin J. Crawford

IPC分类号： G03B15/02 ,  H05B39/04 ,  G01J1/32

CPC分类号： H05B39/042 ,  G03B15/02 ,  Y02B20/14

摘要： A video lighthead mountable to a video camera and having a dimmer control that varies the intensity of the light output from the lighthead using pulse width modulation techniques. A photo sensor measures the intensity of light reflected from a subject in front of the lighthead. The intensity of light output from the lighthead is adjusted by control circuitry in response to changes in measured reflected light intensity to maintain a constant level of illumination. The adjustment is carried out by modifying the duty cycle of a pulse width modulation circuit. The duty cycle adjustment of the pulse width modulation is also used to compensate for supply voltage variations in order to maintain constant light output.

摘要翻译： 一种可安装到摄像机的视频光头，并具有使用脉冲宽度调制技术改变从光头的输出强度的调光控制。 光传感器测量从光头前面的被摄体反射的光的强度。 响应于测量的反射光强度的变化，由光控制器输出的光的强度由控制电路进行调节，以保持恒定的照明水平。 通过修改脉宽调制电路的占空比进行调整。 脉冲宽度调制的占空比调整也用于补偿电源电压变化，以保持恒定的光输出。