page_title: Video camera tube
section_title: Image orthicon
hierarchical_section_title: Video camera tube / Image orthicon
context_page_description: Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images prior to the introduction of charge-coupled device image sensors in the 1980s. Several different types of tubes were in use from the early 1930s to the 1980s.
  In these tubes, the cathode ray was scanned across an image of the scene to be broadcast. The resultant current was dependent on the brightness of the image on the target. The size of the striking ray was tiny compared to the size of the target, allowing 483 horizontal scan lines per image in the NTSC format, or 576 lines in PAL.
context_section_description: The image orthicon (sometimes abbreviated IO), was common in American broadcasting from 1946 until 1968. A combination of the image dissector and the orthicon technologies, it replaced the iconoscope in the United States, which required a great deal of light to work adequately.
  The image orthicon tube was developed at RCA by Albert Rose, Paul K. Weimer, and Harold B. Law. It represented a considerable advance in the television field, and after further development work, RCA created original models between 1939 and 1940. The National Defense Research Committee entered into a contract with RCA where the NDRC paid for its further development. Upon RCA's development of the more sensitive image orthicon tube in 1943, RCA entered into a production contract with the U.S. Navy, the first tubes being delivered in January 1944. RCA began production of image orthicons for civilian use in the second quarter of 1946.
  While the iconoscope and the intermediate orthicon used capacitance between a multitude of small but discrete light sensitive collectors and an isolated signal plate for reading video information, the image orthicon employed direct charge readings from a continuous electronically charged collector. The resultant signal was immune to most extraneous signal crosstalk from other parts of the target, and could yield extremely detailed images. For instance, image orthicon cameras were still being used by NASA for capturing Apollo/Saturn rockets nearing orbit, although the television networks had phased the cameras out. Only they could provide sufficient detail.
  An image orthicon camera can take television pictures by candlelight because of the more ordered light-sensitive area and the presence of an electron multiplier at the base of the tube, which operated as a high-efficiency amplifier. It also has a logarithmic light sensitivity curve similar to the human eye. However, it tends to flare in bright light, causing a dark halo to be seen around the object; this anomaly was referred to as blooming in the broadcast industry when image orthicon tubes were in operation. Image orthicons were used extensively in the early color television cameras, where the increased sensitivity of the tube was essential to overcome the very inefficient optical system of the camera.
  The image orthocon tube was at one point colloquially referred to as an Immy. Harry Lubcke, the then-President of the Academy of Television Arts & Sciences, decided to have their award named after this nickname. Since the statuette was female, it was feminized into Emmy.
caption: A 1960s-era RCA Radiotron Image Orthicon TV Camera Tube
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