JVC GR-DVX90 Description of Progressive Scan CCD, EN23, Regular shooting of moving images

EN23

Description of Progressive Scan CCD

Progressive Scan is a special image sensing method which, unlike conventional interlace scanning, is able to pick up all the lines of picture information in one Scan. Since the Progressive Scan CCD is capable of outputting 50 full Frames* per second — twice the amount of conventional systems — it is able to deliver a high quality picture even when its output signal is converted to a format that can be viewed on a TV screen.

*A PAL TV screen image is composed of 25 Frames per second. 1 Frame is made up of 2 Fields.

1 Frame

Scan A Scan B

1. Regular shooting of moving images

Records 25 odd and 25 even image Fields, for a total of 50 per second. Since there is a time lag between an odd and even Field, when they are combined to make 1 Frame the part of the image that is moving appears as image jitter.

However, during normal playback, the moving picture looks smooth and natural.

2. Progressive mode shooting of moving images (Progressive Mode Recording
pg. 22)

Scan A is recorded, divided into an odd- and even-number Field, and then Scan B is skipped. Scans C and D are handled in the same way as Scans A and B, as illustrated below, thereby recording 25 Frames per second.

Since each recorded odd- and even-number Field originates from the same Scan there is no time lag between them, and so when they are combined into a Frame and a still image is displayed on a TV or PC monitor the picture does not look jittery. However, when moving images are played back, the picture can look unnatural.

Scan A		Scan B	Scan C		Scan D
		Skip			Skip
Odd-number	Even-number		Odd-number	Even-number
Field	Field		Field	Field	25 Frames per second