Although the concept of this sensor is similar to the past reported one,11 this sensor has some features especially for long-range imaging in addition to high frame rate and simple sensor configuration. First, the receiver adopts the APD, of which the receiving sensitivity is about 10 times as high as the PD that was used by Moss et al.11 because of the avalanche gain. Additionally, the array configuration of the APD improves the responsiveness for the short pulse. If a single-element APD that has the large receiving area is used, the responsiveness for a short pulse is decreased by a large electrical capacitance of the large receiving area, as shown in Fig. 2(a). For the prevention of this issue, the proposed sensor adopts the array configuration with the high-aspect elements. This reduces the electrical capacitance and improves the responsiveness for the short pulse, as shown in Fig. 2(b). Further, the SSD improves the noise characteristic at the output of the add circuit. In many cases, a received light is focused at a point of the receiving area in the high-aspect APD array; only one element in the array receives the light, and the corresponding TIA outputs a signal of the received light. On the other hand, other elements do not receive the light and their corresponding TIAs output only noises. If the adder circuit adds all output signals from TIAs simply, the circuit adds both the signal of the received light and the noises from the other TIAs, as shown in Fig. 3(a). This causes the noise level to increase and the signal-to-noise ratio (SNR) to decrease. To prevent this issue, the SSDs are inserted between the TIAs and adder circuit. The SSD consists of a comparator and a switch. The comparator detects an input signal from the TIA by comparing with a previous determined threshold level. If the comparator detects the input signal, the switch is closed, and the input signal passes through the switch. The threshold level is usually set at slightly higher than the noise level. If the noises are input into the SSDs, the switches are still open, and the noises do not pass through the switches. Therefore, only the input signal is output from the SSDs, and the adder circuit adds only the signal as shown in Fig. 3(b). Therefore, the SSDs are able to keep from decreasing SNR, and consequently, contribute to long-range imaging.