Hitachi, Ltd.

Masaaki Iwanaga

Atsushi Maruyama

Kazutaka Naka

Hiroyuki Urata

Masanori Ogino

Fumio Inoue

Kiyoshi Yamamoto

Masahiro Eto

In a video signal processing device, an input video signal VO representing a test pattern having two gradations of black and white is converted to 8-bit data by an A/D converterin synchronism with sampling clocks generated in a write-in control circuit, and then stored in a memory. An MPUreads out picture element data in an effective area of the video signal stored in the memory, and calculates the difference AT between the average value of white-level picture element data whose values are larger than a predetermined value and the average value of black-level picture element data whose values are smaller than a predetermined value, and the total variance VT between the variance of the white-level picture element data and the variance of the black-level picture element data. The MPUcontrols the phase of the sampling clocks generated in the write-in control circuitso that the AT is maximum and the VT is minimum. With this operation, the sampling phase can be automatically adjusted to the optimum value when the video signal is converted to digital data.

Video signal processing device for automatically adjusting phase of sampling clocks

In a video signal processing device, an input video signal VO representing a test pattern having two gradations of black and white is converted to 8-bit data by an A/D converter 4 in synchronism with sampling clocks generated in a write-in control circuit 5, and then stored in a memory 6. An MPU 9 reads out picture element data in an effective area of the video signal stored in the memory 6, and calculates the difference AT between the average value of white-level picture element data whose values are larger than a predetermined value and the average value of black-level picture element data whose values are smaller than a predetermined value, and the total variance VT between the variance of the white-level picture element data and the variance of the black-level picture element data. The MPU 9 controls the phase of the sampling clocks generated in the write-in control circuit 5 so that the AT is maximum and the VT is minimum. With this operation, the sampling phase can be automatically adjusted to the optimum value when the video signal is converted to digital data.

Video signal processing device for automatically adjusting phase of

In order to enable sampling of high definition still video signals in addition to common video signals, a function is added for sampling video signals with every other plurality of picture elements as an interval to an image processing apparatus without using a sampling circuit which requires high speed operations. The invention is also intended to change over between two circuits that is, a circuit for using a picture element clock regenerated by a PLL circuit as a sampling clock for analog to digital converters and a circuit for using a clock obtained by dividing the picture element clock as a sampling clock for the analog to digital converters to sample video signals with every other plurality of picture elements as an interval. Thus, it is possible to carry out sampling of high definition video signals with high frequencies in addition to common video signals without necessity of raising the operating speed of the sampling circuit.

Image processing apparatus with change over of clock signals

Growing community of inventors

Yokohama, Japan

Masaaki Iwanaga