Does a Interline Transfer CCD sensor have a dichroic prism or that is true only for a CCD 3chip 2/3 inch sensor?

[davide sorasio]

Hello everybody, I'm reading more about camera sensor and I've read that 3chip CCD sensors have a dichroich prism system that break the light in different color wavelenght etc etc. my big question is does a Interline Transfer CCD sensor (that I've read being a 1 chip sensor) have a dichroic prism or that is true only for a CCD 3chip 2/3 inch sensor?

Thanks so much in advance for the help

[Satsuki Murashige]

I don't know anything about an Interline Transfer CCD but if it's a single chip sensor then I can't imagine it would need a prism. The prism is used to break the incoming light from the lens into separate RGB light for each chip. So without a 3-chip sensor, there would be no point to having the prism.

[David Mullen ASC]

I think the interline transfer design for the CCD is a different issue from whether it is a single sensor with a color array filter like a Bayer pattern versus a 3-sensor system with a prism block. But a single sensor wouldn't use a prism block since there is no need to split the light up to multiple sensors.

[David Mullen ASC]

https://en.wikipedia.org/wiki/Charge-coupled_device

The CCD image sensors can be implemented in several different architectures. The most common are full-frame, frame-transfer, and interline. The distinguishing characteristic of each of these architectures is their approach to the problem of shuttering.

In a full-frame device, all of the image area is active, and there is no electronic shutter. A mechanical shutter must be added to this type of sensor or the image smears as the device is clocked or read out.

With a frame-transfer CCD, half of the silicon area is covered by an opaque mask (typically aluminum). The image can be quickly transferred from the image area to the opaque area or storage region with acceptable smear of a few percent. That image can then be read out slowly from the storage region while a new image is integrating or exposing in the active area. Frame-transfer devices typically do not require a mechanical shutter and were a common architecture for early solid-state broadcast cameras. The downside to the frame-transfer architecture is that it requires twice the silicon real estate of an equivalent full-frame device; hence, it costs roughly twice as much.

The interline architecture extends this concept one step further and masks every other column of the image sensor for storage. In this device, only one pixel shift has to occur to transfer from image area to storage area; thus, shutter times can be less than a microsecond and smear is essentially eliminated. The advantage is not free, however, as the imaging area is now covered by opaque strips dropping the fill factor to approximately 50 percent and the effective quantum efficiency by an equivalent amount. Modern designs have addressed this deleterious characteristic by adding microlenses on the surface of the device to direct light away from the opaque regions and on the active area. Microlenses can bring the fill factor back up to 90 percent or more depending on pixel size and the overall system's optical design.

[Tyler Purcell]

The problem with single CCD imagers is that they actually have less resolution per physical size then cameras with 3 imagers because the pixel shift technology. Single CCD imagers went away years ago because the Bayer pattern CMOS imagers have greater latitude and aren't loosing light through a beam splitter like the 3 chip CCD's. There are pro's of CCD's, one of which is the single pulse of data which prevents rolling shutter, but global shutter technology has cured those issues on CMOS imagers.