Akihito Hirai

3D imaging LADAR with linear array devices: laser, detector and ROIC

This paper introduces the recent development of 3D imaging LADAR (LAser Detection And Ranging) in Mitsubishi Electric Corporation. The system consists of in-house-made key devices which are linear array: the laser, the detector and the ROIC (Read-Out Integrated Circuit). The laser transmitter is the high power and compact planar waveguide array laser at the wavelength of 1.5 micron. The detector array consists of the low excess noise Avalanche Photo Diode (APD) using the InAlAs multiplication layer. The analog ROIC array, which is fabricated in the SiGe- BiCMOS process, includes the Trans-Impedance Amplifiers (TIA), the peak intensity detectors, the Time-Of-Flight (TOF) detectors, and the multiplexers for read-out. This device has the feature in its detection ability for the small signal by optimizing the peak intensity detection circuit. By combining these devices with the one dimensional fast scanner, the real-time 3D range image can be obtained. After the explanations about the key devices, some 3D imaging results are demonstrated using the single element key devices. The imaging using the developed array devices is planned in the near future.

Development of long range, real-time, and high resolution 3D imaging ladar

In the previous study, we have introduced the concept of the real-time 3D imaging LADAR (LAser Detection And Ranging) using linear array receiver. In this paper, we demonstrate a long range, high resolution, and high speed 3D imaging using the developed system. The system consists of in-house-made key components. The linear array receiver consists of the previously reported APD array and the ROIC array assembled in one package. We newly developed the transmitting optics using pupil divide method which realizes a uniform illumination on a target. By combining these devices with the one dimensional fast scanner, we realized a 256 × 256 pixels range imaging with a on-line frame rate of more than 10 Hz at a distance of more than 1 km.

Recent development of 3D imaging laser sensor in Mitsubishi Electric Corporation

We have been developing 3-D imaging laser sensors for several years, because they can acquire the additional information of the scene, i.e. the range data. It enhances the potential to detect unwanted people and objects, the sensors can be utilized for applications such as safety control and security surveillance, and so forth. In this paper, we focus on two types of our sensors, which are high-frame-rate type and compact-type. To realize the high-frame-rate type system, we have developed two key devices: the linear array receiver which has 256 single InAlAs-APD detectors and the read-out IC (ROIC) array which is fabricated in SiGe-BiCMOS process, and they are connected electrically to each other. Each ROIC measures not only the intensity, but also the distance to the scene by high-speed analog signal processing. In addition, by scanning the mirror mechanically in perpendicular direction to the linear image receiver, we have realized the high speed operation, in which the frame rate is over 30 Hz and the number of pixels is 256 x 256. In the compact-type 3-D imaging laser sensor development, we have succeeded in downsizing the transmitter by scanning only the laser beam with a two-dimensional MEMS scanner. To obtain wide fieldof- view image, as well as the angle of the MEMS scanner, the receiving optical system and the large area receiver are needed. We have developed the large detecting area receiver that consists of 32 rectangular detectors, where the output signals of each detector are summed up. In this phase, our original circuit evaluates each signal level, removes the low-level signals, and sums them, in order to improve the signalto- noise ratio. In the following paper, we describe the system configurations and the recent experimental results of the two types of our 3-D imaging laser sensors.

Pulsed 3D laser sensor with scanless receiver

3D laser sensor is a real-time remote sensor which offers 3D images of scenes. In this paper, we demonstrate a new concept of the pulsed 3D laser sensor with 2D scanning of a transmitting beam and a scan-less receiver. The system achieves the fast and long-range 3D imaging with a relatively simple system configuration. We newly developed a highaspect APD array, a receiver IC, and a range and intensity detector. By combining these devices, we realized a 160 × 120 pixels range imaging with an on-line frame rate of 8 Hz at a distance of about 50 m.

Image rejection mixer using tunable poly phase filter with negative feedback control and reference resistor

A temperature, process and mismatch variation tolerant image rejection mixer using tunable poly phase filter is proposed. The ploy phase filter consist of variable resistors using MOSs and a negative feedback circuit which controls the resistance by comparing DC voltage of variable resistors with an IC external resistor. The proposed IRM is fabricated in 0.18µm SiGe-BiCMOS process. The IRM achieves more than 30dB of image rejection ratio from 1.3 GHz to 2.4 GHz IF band depending on an external reference resistance.

Demonstration on range imaging of 256×256 pixels and 30 frames per second using short wavelength infrared pulsed time-of-flight laser sensor with linear array receiver

Abstract. We demonstrated the range imaging with high resolution of 256×256  pixels and high frame rate of 30 frames per second (fps) using a short wavelength infrared pulsed time-of-flight laser sensor, which is suitable for long range imaging. We additionally demonstrated the long range imaging of more than 1 km and wide field of view imaging of 12  deg× 4  deg, 768×256  pixels, and 10 fps. For these demonstrations, we developed the linear array devices of the aluminum indium arsenide avalanche photodiode array and silicon germanium bipolar complementary metal oxide semiconductor read-out integrated circuit array. We also deployed the flattop beam illumination optics with the beam division and recombination method and realized efficient line shape illumination.

Range imaging pulsed laser sensor with two-dimensional scanning of transmitted beam and scanless receiver using high-aspect avalanche photodiode array for eye-safe wavelength

Abstract. We demonstrate a range imaging pulsed laser sensor with two-dimensional scanning of a transmitted beam and a scanless receiver using a high-aspect avalanche photodiode (APD) array for the eye-safe wavelength. The system achieves a high frame rate and long-range imaging with a relatively simple sensor configuration. We developed a high-aspect APD array for the wavelength of 1.5  μm, a receiver integrated circuit, and a range and intensity detector. By combining these devices, we realized 160×120  pixels range imaging with a frame rate of 8 Hz at a distance of about 50 m.

A 0.3-to-5.5 GHz Digital Frequency Discriminator IC with Time to Digital Converter

A 0.3 to 5.5 GHz range, 50ns-detection Digital Frequency Discriminator (DFD) using a Time to Digital Converter is presented. Wide frequency range and high accuracy are achieved by an averaging technique using all periods of the input signal and periodical number during the measurement time using TDC. The DFD, fabricated in 0.18-μm SiGe-BiCMOS, achieves measured absolute error below 0.39MHz and standard deviation below 1.53MHz-RMS during 50 ns detection time in the band from 0.3 GHz to 5.5 GHz.

Performance improvement of real-time 3D imaging ladar based on a modified array receiver

In the previous study, we have demonstrated the first development result of the 3D imaging LADAR (LAser Detection And Ranging) which can obtain the 3D data using linear array receiver. The system consists of in-house-made key components. The linear array receiver consists of the previously reported APD (Avalanche Photo Diode) array, the ROIC (Read Out Integrated Circuit) array assembled in one package, and the transmitting optics using pupil divide method which realizes a uniform illumination on a target. In this paper, we report the advanced 3D imaging LADAR with improved ROIC. The ROIC has the function to set the optimum threshold for pulse peak detection in each element and switch the measurement range width on a case by case basis. Moreover, the response of MUX in ROIC is improved. Installing this ROIC, we realized 256× 256 pixels range imaging with an on-line frame rate of more than 30 Hz. Then, we tried online object detection with the obtained 3D image using a simple detection algorithm. We demonstrated system has the potential to detect the object even in the scene with some clutters.