CMOS image sensor chip OV5017 and its applications (1)

1 CMOS image sensor for general characteristics

Currently, the CCD (charge coupled device) is the main practical solid-state image sensors, it has read low noise, wide dynamic range, high response sensitivity.

But the CCD technology difficult and mainstream CMOS technology integration on the same chip. In this way, such as timing, driven zoom, automatic exposure control, analog-digital conversion and signal processing, and other support to the circuit will not be able to do with the pixel array, with the same chip CCD-based image sensors to achieve single-chip integration, thus has the volume and power consumption and higher.

CMOS image sensor is close to developing faster type image sensor, as a result of the same CMOS technology, so you can use the pixel array and peripheral support circuit integrated on the same chip.

Indeed, the CMOS image sensor is a more complete image system (Camera on Chip), which usually include: an image sensor core, single-clock and all the temporal logic, programmable function and ADC. The basic structure is shown in Figure 1.

　　

　　

Compared with CCD, CMOS image sensors to the entire image system integration in a chip, has the following advantages:

(1) small size, light weight, low power consumption;

(2) programming convenient, easy-to-control;

(3) the average cost is low.

2 OV5017 performance and features

2.1 OV5017 basic performance

OV5017 is United States OmniVision CMOS development company and white image sensor chip, the chip will CMOS optical sensing core and peripheral support integrated circuit, with programmable control and video mode/features such as the number of mixed output, the output of the video is black and white images, and CCIR standards compatible.

OV5017 chip's basic argument is:

(1) image size, pixel size 11 4.2mm×3.2mm μ μ m x 11 m;

(2) of the signal to noise ratio SNR > 42dB;

(3) frame rate 50, minimum illuminance for 0.5lux @ f1.4;

(4) the frame rate of 50, peak power is less than 100mW.

OV5017 output analog video signals, the format is progressive scan.

OV5017 internal embedded a 8bit of A/D, so you can sync output 8-bit digital video stream D [7 .. 0]. In the output digital video stream at the same time, also provides the pixel clock PCLK, horizontal reference signal HREF, vertical synchronization signal VSYNC, easy to read an image an external circuit.

OV5017 pixel array of 384 × 288, divided into 16 x 16 blocks, each block size is 24 x 18 in the entire image of the local window, the image in the output window.

2.2 OV5017 programming features

OV5017 has a wealth of programming control function, the image frame rate and exposure time, gain control, Gamma correction, image window can be passed on-chip internal registers are set to read-write, digital video stream output must also read through the registers can be achieved.

Chip has 11 8-bit registers, passed on the address line of A [3 ..0] setting to select the register, read and write data line [7 ..0] to read or set the register.

To register to read (or write), should make the movie selected CSB and OEB output enable (or the WEB).

　　

　　

Address, register for video 10xx data ports, it is read-only, and reads it is selected, the chip to the video stream output data.

Address register no. 0000 as status register, it is read-only, reflect the State of some chips.

Address register no. 0001 to frame control register, it is write-only, is used to control the frame and the rows of the synchronization signal.

Address register no. 0010 for exposure control registers, it is read-write, you can select the automatic exposure, you can also choose a manual exposure.

Exposure control in 1 frame to 1/100 frames.

Address register no. 0011 to gain control register, it is read-write, when the manual exposure, gain control between 0-18dB.

Address no. 0100 registers for frame rate control register, it is read-write, frame rate control in 50 ~ 0.5fps.

Address, register for miscellaneous 0101 control registers, it is read-write, is responsible for setting Gamma correction, image, images, backlight compensation, image sharpening, etc.

Address no. 0110 0111 registers for and window control register, they are all read-write, is responsible for setting the level of the window size, horizontal position, vertical position of the vertical size, in order to determine the image of a window.

Address number 1111 1110 and register reserved for testing.

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