From the available CMOS camera with a CIF resolution (Common Intermediate Format 352x288) the C3088 camera module with OV6620 OmniVision sensor has been chosen. Selected parameters of OV6620 sensor are shown in the table below.
|Parameter||Value or Description|
|2||Pixel Size||9.0x8.2 µm|
|3||Array of color filters||Bayer filter|
|4||Dynamic Range||>72 dB|
|5||S/N Ratio||>48 dB|
|6||FPN (Level of Fixed Pattern Noise)
|7||Max Frame/Sec||60 fps|
Acceptable voltage range on inputs (High state)
The C3088 camera is equipped with the OV6620 image sensor which has 80 registers. In these registers data are stored corresponding to the parameters of the camera. For the user only 52 (8-bit) registers are available. By changing individual bits in these registers, we can adjust the various parameters of the camera. Setting the camera registers is done by SCCB interface. Among the entire group of registers we can identify the registers responsible for:
- the parameters of the synchronization signals (VSYNC, HREF and PCLK)
- image output format (RGB, YUV, 8 or 16 bit data mode)
- output resolution (CIF - 352x288, QCIF - 176x144)
- settings of automatic control systems (AEC, AGC, AWB)
- settings of parameters such as brightness, contrast, sharpness and saturation
PCLK frequency can be calculated using the following formula:
Active state (polarization) of individual synchronization signals (VSYNC, HREF, PCLK) can be set in the appropriate registers as shown in the table below.
|Sync signal||The Camera register responsible for the polarization|
The default camera resolution is 352x288 (CIF). By setting the bit COMC=1 we change the resolution to 176x144 (QCIF). The advantage of this camera is easily adjustable parameters such as brightness, contrast, sharpness and saturation. The following table shows the addresses of registers controlling these parameters, together with range of adjustment.
|Default value||Range of adjustment|
|Sharpness||0x7||0xC6||Bits[7:4] threshold settings (0÷80 mV)
Bits[3:0] - regulation
Fig. 1. Timing for different values of the registry COML