Orthicon

Orthicon is a class of early television camera tubes used in broadcast television, particularly the image orthicon and related variants produced in the mid-20th century. The term often refers to the Image Orthicon (IO) and its successors, which were widely used by RCA and other manufacturers from the 1950s into the 1970s. These tubes provided high sensitivity and relatively low image lag, making them standard in many studios and outside broadcasts before solid-state cameras became common.

Operating principle: Light entering the camera is focused onto a photosensitive photocathode. Electrons emitted by the photocathode are accelerated and directed to a target by an electron-optical system. The charge pattern formed on the target is scanned by a subsequent electron beam to generate a video signal. The design allowed a large image format and good performance under varying lighting conditions, which was advantageous for live television.

Variants and performance: The Orthicon family includes the Image Orthicon and higher-resolution versions such as the Super-Orthicon. These tubes were noted for high sensitivity, good dynamic range, and manageable image lag relative to earlier camera tubes. They were used in many studios and production environments during the height of tube-based television.

Decline and legacy: With the rapid adoption of solid-state pickup devices, including vidicon-based tubes and ultimately CCD and CMOS sensors, orthicon tubes phased out of mainstream use by the late 1970s to 1980s. Today, they are of historical interest, reflecting the evolution of image sensing technology in broadcast television.