A high-sensitivity pickup tube using HARP (high-gain avalanche rushing amorphous photoconductor) photoconductive film, which makes use of the avalanche multiplication phenomenon, has been studied for making a high-sensitivity television camera. The avalanche multiplication factor, i.e., sensitivity, was increased by thickening the film. A 35-µm-thick HARP film, which was more sensitive than the previous 25-µm-thick film with an avalanche multiplication factor of about 600, and a 2/3rd-inch pickup tube using the film were developed. Measurements on the pickup tube demonstrated that it had an avalanche multiplication factor of about 1000, low lag, and high resolution. Moreover, image defects caused by shooting of intense spot lights were investigated, and it was found that exposing the film to UV light before operation and controlling the temperature of the film during operation could suppress the defects.

We have developed an ultrahigh-sensitivity "New Super-HARP" handheld camera, which has a sensitivity that is about 100 times as great as that of a CCD camera. The sensitivity of TV cameras is determined by the performance of the imaging device. We developed the world's first imaging device that achieves high sensitivity and high picture quality by using the avalanche multiplication phenomenon in an amorphous selenium photoconductive target. This "Super-HARP" pickup tube, which has already been used in TV production, has a selenium target 8-µm thick. It is about 10 times as sensitive as CCDs. We have now developed a greatly improved version of the Super-HARP tube with a target 25-µm thick. This improved version, called the New Super-HARP pickup tube, is about 10 times as sensitive as the Super-HARP pickup tube. The New Super-HARP handheld camera equipped with the new tubes has a maximum sensitivity of 11 lx at F8. This camera is a powerful tool for reporting breaking news at night and other low-light conditions, the production of scientific programs, and numerous other applications.