1-2. CA2 CIRCUIT DESCRIPTION

1. Circuit Description

1-1. Scannning converter (Interlace converter)

This circuit uses the function of a 64-Mbit SDRAMs to convert the non-interlaced signal which is output from the CCD into an interlaced signal for the video monitor.

1-2. Camera signal processor

This comprises circuits such as the digial clamp circuit, white balance circuit, γcircuit, color signal generation circuit, matrix circuit and horizontal aperture circuit.

1. Digital clamp circuit

The optical black section of the CCD extracts 16-pixel averaged values from the subsequent data to make the black level of the CCD output data uniform for each line. The 16-pixel averaged value for each line is taken as the sum of the value for the previous line multiplied by the coefficient k and the value for the current line multiplied by the coefficient 1-k.

2. White balance circuit

This circuit controls the white balance by using the AWB judgement value computed by the CPU to control the gain for each R, G and B pixel based on the CCD data which has been read.

3. γ circuit

This circuit performs (gamma) correction in order to maintain a linear relationship between the light input to the camera and the light output from the picture screen.

4. Color generation circuit

This circuit converts the CCD data into RGB signals.

1-7. 8-bit D/A circuit (Audio)

This circuit converts the audio signals (analog signals) from the microphone to 8-bit digital signals.

1-8. 8-bit A/D circuit (Audio)

The audio signals which were converted to digial form by the 8-bit A/D circuit are temporarily to a sound buffer and then recorded in the SSFDC card. During playback, the 8-bit D/A circuit converts these signals into analog audio signals.

1-9. Sound buffer

Audio memory

1-10. LCD driver

The Y/C signals which are input to the LCD driver are converted to RGB signals, and the timing signal which is necessary for LCD monitor display and the RGB signals are then supplied to the LCD monitor.

1-11. LCD monitor

This is the image display device which displays the image signals supplied from the LCD driver.

1-12. UART

This circuit is used for transmitting serial data to a PC. The interface is RS-232C-compatible.

1-13. SSFDC control

This reads data from the SSFDC card and stores it in SDRAM, and writes out the image data stored in SDRAM. In addition, error correction is carried out when the data is read.

1-14. MJPEG compression

5. Matrix circuit

This circuit generates the Y signals, R-Y signals and B-Y signals from the RGB signals.

6. Horizontal aperture circuit

Still and continuous frame data is converted to JPEG format, and movie images are compressed and expanded in MJPEG format.

2. Outline of Operation

This circuit is used generate the aperture signal.

1-3. SDRAM controller

This circuit outputs address, RAS, CAS and AS data for controlling the SDRAM. It also refreshes the SDRAM.

1-4. PIO

The expansion parallel port can be used for functions such as stroboscope control and LCD driver control.

1-5. SIO (Serial control)

This is the interface for the 8-bit microprocessor.

1-6. TG, SG block

This is the timing generation circuit which generates the clocks (vertical transfer clock and electronic shutter clock) which drive the CCD.

When the shutter opens, the reset signals, TEST0, TEST1 and the serial signals (“take a picture” commands) from the 8-bit microprocessor are input and record operation starts. When the TG drives the CCD, picture data passes through the A/D and is then input to the ASIC as 10-bit data. This data then passes through the DCLP, AWB, shutter and γ circuit, after which it is input to the SDRAM. The AWB, shutter, γ , and AGC value are computed from this data, and two exposures are made to obtain the optimum picture. The data which has already been stored in the SDRAM is read by the CPU and color generation is carried out. Each pixel is interpolated from the surrounding data as being either R, G or B primary color data to produce R, G and B data. At this time, correction of the lens distortion which is a characteristic of wide-angle lenses is carried out. Aperture correction is carried out, and in case of still picture the data is then compressed by the JPEG method and in case of picture it is compressed by MJPEG method and is written to SSFDC card. When the data is to be output to an external device, it is read JPEG picture data from the SSFCD card and output to PC via the UART.

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