Biometric sensors for wearable devices have a dilemma between the small physical size to fit within the small device and the large sensing area to obtain enough information for reliable recognition. A swipe-type fingerprint sensor is a good candidate that satisfies both of small size and large sensing area. This paper proposes a compact swipe-type fingerprint sensor using a fixed-displacement shuttering scheme to avoid the swiping-speed dependent image distortion. The shutter for a line image sensor is adaptively controlled by the displacement measure unit, which are consist of two lines of pixel array, Soft-XOR circuits and digital control circuits. The displacement of a finger is detected by calculating the pattern matching of two line images, which are separated for fixed distance. The proposed system utilizes optical pixels for high-speed image capturing. The prototype sensor chip was fabricated with $0.25~\mu \text{m}$ standard CMOS process. The sensor chip occupies only 4mm $\times 0.9$ mm and provides 625 dpi up to 25cm/s of swiping speed. Experimental results obtained from the sensor demonstrate that the proposed shuttering method reduced minutiae distribution by factor of 3 over the conventional fixed-time interval shuttering.

中文翻译：

---

一种采用固定位移快门方案的刷卡式指纹传感器

用于可穿戴设备的生物识别传感器在适合小型设备的小物理尺寸和大传感区域之间存在两难境地，以获得足够的信息以进行可靠识别。刷卡式指纹传感器是一个很好的候选者，它同时满足小尺寸和大感应区域的要求。本文提出了一种使用固定位移快门方案的紧凑型滑动式指纹传感器，以避免与滑动速度相关的图像失真。线图像传感器的快门由位移测量单元自适应控制，该单元由两行像素阵列、软异或电路和数字控制电路组成。手指的位移是通过计算两个固定距离的线图像的模式匹配来检测的。所提出的系统利用光学像素进行高速图像捕获。原型传感器芯片是用 $0.25~\mu \text{m}$ 标准CMOS工艺。传感器芯片仅占4mm $\times 0.9$ 毫米并提供 625 dpi 高达 25 厘米/秒的滑动速度。从传感器获得的实验结果表明，与传统的固定时间间隔快门相比，所提出的快门方法将细节分布减少了 3 倍。