Department of Semiconductor Science, Dongguk University-Seoul, Seoul 04620, Korea.
Sensors (Basel). 2018 Feb 24;18(2):669. doi: 10.3390/s18020669.
This paper presents a single-bit CMOS image sensor (CIS) that uses a data processing technique with an edge detection block for simple iris segmentation. In order to recognize the iris image, the image sensor conventionally captures high-resolution image data in digital code, extracts the iris data, and then compares it with a reference image through a recognition algorithm. However, in this case, the frame rate decreases by the time required for digital signal conversion of multi-bit digital data through the analog-to-digital converter (ADC) in the CIS. In order to reduce the overall processing time as well as the power consumption, we propose a data processing technique with an exclusive OR (XOR) logic gate to obtain single-bit and edge detection image data instead of multi-bit image data through the ADC. In addition, we propose a logarithmic counter to efficiently measure single-bit image data that can be applied to the iris recognition algorithm. The effective area of the proposed single-bit image sensor (174 × 144 pixel) is 2.84 mm² with a 0.18 μm 1-poly 4-metal CMOS image sensor process. The power consumption of the proposed single-bit CIS is 2.8 mW with a 3.3 V of supply voltage and 520 frame/s of the maximum frame rates. The error rate of the ADC is 0.24 least significant bit (LSB) on an 8-bit ADC basis at a 50 MHz sampling frequency.
本文提出了一种使用具有边缘检测模块的数据处理技术的单比特 CMOS 图像传感器 (CIS)，用于简单的虹膜分割。为了识别虹膜图像，图像传感器传统上以数字代码捕获高分辨率图像数据，提取虹膜数据，然后通过识别算法将其与参考图像进行比较。然而，在这种情况下，通过 CIS 中的模数转换器 (ADC) 对多位数字数据进行数字信号转换所需的时间会降低帧率。为了减少整体处理时间和功耗，我们提出了一种具有异或 (XOR) 逻辑门的数据处理技术，通过 ADC 获得单比特和边缘检测图像数据，而不是多比特图像数据。此外，我们提出了一种对数计数器，以有效地测量可应用于虹膜识别算法的单比特图像数据。所提出的单比特图像传感器 (174×144 像素) 的有效面积为 2.84mm²，采用 0.18μm 1 多 4 金属 CMOS 图像传感器工艺。在 3.3V 电源电压和 520 帧/秒的最大帧率下，所提出的单比特 CIS 的功耗为 2.8mW。在 50MHz 采样频率下，基于 8 位 ADC 的 ADC 误差率为 0.24 个最低有效位 (LSB)。
