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MT9V023 データシート(PDF) 25 Page - ON Semiconductor |
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MT9V023 データシート(HTML) 25 Page - ON Semiconductor |
25 / 43 page MT9V023 www.onsemi.com 25 The algorithm works as follows: Logical columns 755-790 in the pixel array provide 36 optically black pixel values. Of the 36 values, two smallest value and two largest values are discarded. The remaining 32 values are averaged by summing them and discarding the 5 LSB of the result. The 10-bit result is subtracted from each pixel value on the row in turn. In addition, a positive constant will be added (Reg0x71, bits 7:0). This constant should be set to the dark level targeted by the black level algorithm plus the noise expected on the measurements of the averaged values from dark columns; it is meant to prevent clipping from negative noise fluctuations. Pixel value + ADC value – dark column average ) R0x71[9 : 0] (eq. 21) Note that this algorithm does not work in color sensor. Automatic Gain Control and Automatic Exposure Control The integrated AEC/AGC unit is responsible for ensuring that optimal auto settings of exposure and (analog) gain are computed and updated every frame. AEC and AGC can be individually enabled or disabled by R0xAF. When AEC is disabled (R0xAF[0] = 0), the sensor uses the manual exposure value in coarse and fine shutter width registers. When AGC is disabled (R0xAF[1] = 0), the sensor uses the manual gain value in R0x35 or R0x36. See “Pixel Integration Control” and the MT9V023 Developer Guide, for more information. Figure 27. Controllable and Observable AEC/AGC Registers EXP. LPF (R0xA8) 1 0 1 0 EXP. SKIP (R0xA6) Coarse Shutter Width Total AEC ENABLE (R0xAF[0 or 8]) MAX. EXPOSURE (R0xBD) MIN EXPOSURE (R0xAC) AEC UNIT To exposure timing control AEC OUTPUT R0xBB R0xBA To analog gain control HISTOGRAM GENERATOR UNIT AGC UNIT GAIN LPF (R0xAB) GAIN SKIP (R0xA9) MANUAL GAIN A or B AGC ENABLE (R0xAF[1 or 9]) AGC OUTPUT MAX. GAIN (R0xAB) MIN GAIN DESIRED BIN (desired luminance) (R0xA5) 16 The exposure is measured in row-time by reading R0xBB. The exposure range is 1 to 2047. The gain is measured in gain-units by reading R0xBA. The gain range is 16 to 63 (unity gain = 16 gain-units; multiply by 1/16 to get the true gain). When AEC is enabled (R0xAF), the maximum auto exposure value is limited by R0xBD; minimum auto exposure is limited by AEC Minimum Exposure, R0xAC. NOTE: AEC does not support sub-row timing; calculated exposure values are rounded down to the nearest row-time. For smoother response, manual control is recommended for short exposure times. When AGC is enabled (R0xAF), the maximum auto gain value is limited by R0xAB; minimum auto gain is fixed to 16 gain-units. The exposure control measures current scene luminosity and desired output luminosity by accumulating a histogram of pixel values while reading out a frame. All pixels are used, whether in color or mono mode. The desired exposure and gain are then calculated from this for subsequent frame. When binning is enabled, tuning of the AEC may be required. The histogram pixel count register, R0xB0, may be adjusted to reflect reduced pixel count. Desired bin register, R0xA5, may be adjusted as required. Pixel Clock Speed The pixel clock speed is same as the master clock (SYSCLK) at 26.66 MHz by default. However, when column binning 2 or 4 (R0x0D or R0x0E, bit 2 or 3) is enabled, the pixel clock speed is reduced by half and one-fourth of the master clock speed respectively. See “Read |
同様の部品番号 - MT9V023_17 |
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同様の説明 - MT9V023_17 |
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