Sensor sizes

Started 5 months ago | Questions thread
Eamon Hickey
Veteran MemberPosts: 3,170
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the terminology was practical for engineers
In reply to crashpc, 5 months ago

crashpc wrote:

Wonder how can they create new piece of technology, use aged technology terminology which wasn´t right anyway, and still are allowed to sell it like that. I´d call it a crime.

There was nothing incorrect about the original system -- a 1-inch vidicon tube had an optical format of approx. 13 x 9mm. Both dimensions are important and correct -- one is the diameter of the tube, which you need to know in order to build a camera around it, and the other is the size of the light sensitive area, which you need to know in order to design a lens for it.

There's actually a fairly simple reason why the old vidicon tube terminology was applied to the new solid state sensors (CCDs, mostly) when they came along -- and it was for engineering, not marketing reasons.

Over the years, engineers had built hundreds of thousands of video camera systems (mostly for industrial applications) using those vidicon tubes, and all of them had optical assemblies in front of them that were designed specifically for the optical format of the vidicon tube.

Now it comes time to replace the 1-inch vidicon tube in your assembly line inspection system, let's say, with the newer, better CCD sensors. You don't want to rebuild your entire lens system if you don't have to, which means you need a CCD that is the same optical format as the 1-inch vidicon tube was.

So a 1-inch vidicon tube has an optical format of 13 x 9mm. As you're thumbing through your sensor catalog, you know to turn to the page that says "1-inch type" sensors to find CCDs with a 13 x 9mm area, which will be compatible with your pre-existing lens system.

This is why it happened. It made sense to the engineers who were using it back in the 1960s and 70s when vidicon tubes were being phased out in favor of CCDs. Obviously, it doesn't make a lot of sense now.

But neither does the imperial measurement system we use in the U.S. (inches, feet etc.), and yet it survives because tradition is a powerful force.

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