KAI-4021 datasheet(32/56 Pages) ONSEMI

32 / 56 page

KAI-4021 Image Sensor

www.truesenseimaging.com

Revision 1.1 PS-0014 Pg 32

Summed Interlaced Scan

Figure 21: Summed Interlaced Scan Operation

In the summed interlaced scan read out mode, charge from two photodiodes is summed together inside the vertical

CCD. The clocking of the VCCD is such that one pixel occupies the space equivalent to two pixels in the progressive

scan mode. This allows the VCCD to hold twice as many electrons as in progressive scan mode. Now the maximum

useful signal is limited by the charge capacity of two photodiodes at 80,000 electrons. If only one field is read out of

the image sensor the apparent vertical resolution will be 1024 rows instead of the 2048 rows in progressive scan

(equivalent to binning). To recover the full resolution of the image sensor two fields, even and odd, are read out. In

the even field rows 0+1, 2+3, 4+5, … are summed together. In the odd field rows 1+2, 3+4, 5+6, … are summed

together.

The modulation transfer function (MTF) of the summed interlaced scan mode is less in the vertical direction than the

progressive scan. But the dynamic range is twice that of progressive scan. The vertical MTF is better than a simple

binning operation. In this mode the VCCD needs to be clocked for only 1037 rows to read out each field.

Figure 22: Summed Interlaced Scan Flow Chart

even field

odd field

Summed

Interlaced Even

Frame

Timing

Interlaced Line

Timing

Repeat for

1037 Lines

Summed

Interlaced Odd

Frame

Timing

Interlaced Line

Timing

Repeat for

1037 Lines

KAI-4021 Datasheet(PDF) 32 Page - ON Semiconductor