This paper presents a novel optical proximity sensor behind a display panel based on silicon nanowires. Since silicon nanowires have high photoresponsivity, they can sense the distance even when placed under the display, without using a large current for driver operation. In addition, the dark leakage current generated by silicon nanowires can be removed through the read-out integrated circuit (ROIC) in the proposed optical proximity sensor. The ROIC has a resistive-feedback transimpedance amplifier (TIA) to provide a constant voltage to silicon nanowires and to convert the photocurrent of the silicon nanowires. The auto-zeroing technique reduces the ROIC’s offset and 1/f noise. The bias sampling is applied to a 12-bit single-slope analog-digital converter to reduce noise generated in the bias circuit of the ramp generator. The digital back-end cancels the offset due to dark leakage current through the correlated double sampling technique. The proximity sensor is fabricated in a 0.18 μm0.18~\mu \text{m} CMOS process and the ROIC occupies an area of 0.18 mm2. It draws an average current of 139.4 μA139.4~\mu \text{A} from a 3 V supply, and 60.2 μA60.2~\mu \text{A} from a 1.8 V supply when the conversion time is set to 50 ms, and the current of the vertical cavity surface emitting laser (VCSEL) driver is set to 12 mA. The proximity sensor is tested under a display panel with a light transmission of 6 %. It has an input-referred root mean square noise of 323 pA. The VCSEL driving current can be varied to 7 mA, 10 mA, and 12 mA, and the optical proximity sensor can detect an object that is closer than 40 mm in all three cases.

中文翻译：

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采用硅纳米线的屏下光学接近传感器


本文提出了一种基于硅纳米线的显示面板后面的新型光学接近传感器。由于硅纳米线具有高光响应性，即使放置在显示器下方也可以感应距离，而无需使用大电流进行驱动操作。此外，硅纳米线产生的暗漏电流可以通过所提出的光学接近传感器中的读出集成电路（ROIC）消除。 ROIC具有电阻反馈跨阻放大器（TIA），为硅纳米线提供恒定电压并转换硅纳米线的光电流。自动调零技术可降低ROIC 的偏移和1/f 噪声。偏置采样应用于12位单斜率模数转换器，以减少斜坡发生器偏置电路中产生的噪声。数字后端通过相关双采样技术消除暗漏电流造成的偏移。接近传感器采用 0.18 μm0.18~\mu \text{m} CMOS 工艺制造，ROIC 面积为 0.18 mm2。当转换时间设置为 50 时，它从 3 V 电源汲取的平均电流为 139.4 μA139.4~\mu \text{A}，从 1.8 V 电源汲取的平均电流为 60.2 μA60.2~\mu \text{A} ms，垂直腔表面发射激光器（VCSEL）驱动器的电流设置为12 mA。接近传感器在透光率为 6% 的显示面板下进行测试。它的输入参考均方根噪声为 323 pA。 VCSEL 驱动电流可以变化为 7 mA、10 mA 和 12 mA，光学接近传感器在这三种情况下都可以检测到距离小于 40 mm 的物体。