In this paper we present a $2\times 192$ pixel SPAD-based sensor for LiDAR applications fabricate... more In this paper we present a $2\times 192$ pixel SPAD-based sensor for LiDAR applications fabricated in a $0.35\ \boldsymbol{\mu}\mathbf{m}$ standard CMOS process. Distance measurement is performed using the direct time-of-flight technique. For time acquisition a DLL-based pixel-parallel TDC with 312.5 ps resolution and a $1.28\ \boldsymbol{\mu}\mathbf{m}$ range is integrated. Employing four single SPADs in each pixel enables background light suppression by detecting temporal correlated photons. Moreover, by using adjustable correlation parameters the dynamic range is increased significantly allowing a constant range at varying target reflectivity.
2017 European Conference on Circuit Theory and Design (ECCTD), 2017
This communication addresses the range accuracy of SPAD-based time-of-flight (TOF) sensors that e... more This communication addresses the range accuracy of SPAD-based time-of-flight (TOF) sensors that employ laser pulse modulation. Two basic approaches are considered: indirect and direct TOF. We investigate confidence intervals and derive formulas for standard errors of the relative distance error for both approaches based on photon statistics.
Advances in laser diode technology enable the generation of eye-safe laser pulses with short puls... more Advances in laser diode technology enable the generation of eye-safe laser pulses with short pulse duration and high peak power. This opens up new opportunities for Light Detection and Ranging (LiDAR)-systems based on the direct time-of-flight (dTOF) principle because their range performance is mainly limited by the requirement of eye-safe laser pulse energy. Another limiting factor for dTOF LiDAR is the sensitivity to background noise. Shorter pulse width enables better parasitic light suppression inside the LiDAR system for improved performance in high background flux scenarios. With the improvements caused by using short laser pulses, new challenges emerge. Shorter pulse duration and limited achievable timing resolution of time discrimination circuits inside of dTOF detectors lead to histogram data distributions in which the laser originated time stamps can only fill few time bins. The time stamp histogram of the detected and clocked laser photons shows a sharp exponential declin...
Detektor zur Detektion elektromagnetischer Strahlung mit folgenden Merkmalen: einem ersten Halble... more Detektor zur Detektion elektromagnetischer Strahlung mit folgenden Merkmalen: einem ersten Halbleiterchip (12; 312) mit einem ersten Halbleitermaterial als Substratmaterial; einem zweiten Halbleiterchip (22; 322) mit einem zweiten Halbleitermaterial als Substratmaterial, das unterschiedlich vom ersten Halbleitermaterial ist, wobei der erste Halbleiterchip (12; 312) und das zweite Halbleiterchip (22; 322) mit gegenuberliegenden Hauptoberflachen (14, 24) zueinander angeordnet sind; einem ersten Array mit einer Mehrzahl von ersten Detektionsstrukturen (18; 318) innerhalb des ersten Halbleiterchips (12; 312), die als eine Lawinenphotodiodenstruktur oder eine Single-Photon-Avalanche-Photodiodenstruktur innerhalb des ersten Halbleiterchips ausgebildet sind; einem zweiten Array mit einer Mehrzahl von zweiten Detektionsstrukturen (28; 328) innerhalb des zweiten Halbleiterchips (22; 322), die jeweils mit den ersten Detektionsstrukturen (18; 318) uberlappend angeordnet sind, wobei jede Detekt...
A fast and reliable three dimensional monitoring of the environment is indispensable for robotics... more A fast and reliable three dimensional monitoring of the environment is indispensable for robotics, automation engineering or autonomous driving. For these applications LiDAR is a key sensor technology. Normally a light source in the near infrared range is used, which is invisible to human eyes. High ambient light compared to the laser source intensity is a major problem for these systems. Therefore, a measurement concept to reduce the impact of ambient light is necessary. In this paper we present a measurement concept in which the full distance range is scanned and the probability to detect events from far objects is improved. The general problem is that a photon of the background illumination can be detected instead of the reflected laser signal which stops the measurement. The concept allows us to detect the received laser pulse buried in the superimposed background light easier and improve the measurement quality. This is possible due to the delayed start of the measurement and t...
We present a 1×80 pixel line sensor for direct time-of-flight measurement based on single-photon ... more We present a 1×80 pixel line sensor for direct time-of-flight measurement based on single-photon avalanche diodes fabricated in a high-voltage 0.35 pm CMOS process. An in-pixel time-to-digital-converter with a resolution of 312.5 ps determines the arrival time of the first-photon for each emitted laser pulse from a flash illumination source for all pixels in parallel. Distance determination is performed by collecting the time stamps over multiple pulses in a histogram and applying proper software algorithms. Ambient light suppression is achieved by detection of photon coincidences from four single SPADs in each pixel. By adjusting the time and depth of the coincidence detection a good result in varying ambient conditions is achieved.
The semiconductor structure (10) a semiconductor layer (12) of a first conductivity type, a photo... more The semiconductor structure (10) a semiconductor layer (12) of a first conductivity type, a photosensitive zone (14) which is formed so that photo-generated charges can be collected in a first potential well (19); formed in a semiconductor layer (12) region (18) of the second conductivity type for temporarily storing the photo-generated charges in a second potential well; a transfer gate (20) between the region (18) of the second conductivity type and the photosensitive zone (14) for defining a potential barrier (23) between the first and the second potential well in a non-transfer phase, and lifting of the potential barrier (23) between the first and second potential well in a transfer phase; and a readout structure to read out the temporarily stored photo-generated charges, which includes a JFET (22), whose gate is constituted by the region (18) of the second conductivity type, said JFET (22), one at the area (18) of the second conductivity type adjacent the channel region (40) of...
We present a novel silicon photomultiplier based on a shallow junction obtained within a standard... more We present a novel silicon photomultiplier based on a shallow junction obtained within a standard 0.35 <inline-formula> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> complementary metal oxide semiconductor process. The sensitive structure is equipped with a dedicated optical window as well as an optimized antireflective coating. The device exhibits performances comparable to custom-based commercial technologies: an unprecedented photon detection efficiency of 43% at 420 nm, a breakdown voltage temperature dependence of (27.9 ± 0.9) mV/K, a dark count rate of 480 kHz/mm<sup>2</sup>, a gain of <inline-formula> <tex-math notation="LaTeX">${3\times 10^{6}}$ </tex-math></inline-formula>, and a single photon time resolution of (78 ± 2) ps (FWHM). The process proposed in this letter can be applied to new generation single photon sensors with on-chip integrated intelligent electronics.
We present a SPAD-based LiDAR sensor fabricated in an automotive certified 0.35 µm CMOS process. ... more We present a SPAD-based LiDAR sensor fabricated in an automotive certified 0.35 µm CMOS process. Since reliable sensor operation in high ambient light environment is a crucial factor in automotive applications, four SPADs are implemented in each pixel to suppress ambient light by the detection of photon coincidences. By pixel individual adjustment of the coincidence parameters to the present ambient light condition, an almost constant measurement performance is achieved for a wide range of different target reflectance and ambient illumination levels. This technique allows the acquisition of high dynamic range scenes in a single laser shot. For measurement and demonstration purpose a LiDAR camera with the developed sensor has been built.
ABSTRACT We report on the design and characterization of a smart pixel for long-distance ranging,... more ABSTRACT We report on the design and characterization of a smart pixel for long-distance ranging, comprising a high performances Single-Photon detector and sub-nanosecond Time-to-Digital Conversion (TDC), in 0.35 μm CMOS technology.
LiDAR is a key sensor technology for future driving. For autonomous vehicles a fast and reliable ... more LiDAR is a key sensor technology for future driving. For autonomous vehicles a fast and reliable three dimensional monitoring of the environment is essential for managing a wide variety of common traffic situations. Since these kinds of systems use typically light in the near infrared range, ambient light of the sun is a serious problem due to its high intensity compared to the laser source. Therefore, reducing the influence of ambient light on the distance measurement is very important. In this paper we present a 2 × 192 pixel SPAD-based direct time-of-flight line sensor for flash LiDAR applications with high ambient light rejection integrated in standard CMOS technology. Two commercially available 905 nm laser diodes emitting short pulses are employed for scene illumination. For time measurement an in-pixel timeto- digital-converter with a resolution of 312.5 ps and full range of 1.28 μs has been implemented. Each pixel uses four vertically arranged single SPADs for background lig...
Optical distance meter (400) that has the following characteristics: a pulsed radiation source (1... more Optical distance meter (400) that has the following characteristics: a pulsed radiation source (110) configured to transmit, in a period of temporarily continuous pulses of radiation, a radiation pulse (110a) with a pulse duration (tp) shorter than the period of radiation pulses, and not to transmit radiation pulses during a dark period temporarily continuous; a detection device (420) for detecting different amounts of radiation in two detection periods that overlap in the period of radiation pulses to capture reflections of the radiation pulse on the surface of an object and a background radiation and / or, in two detection periods that overlap in the dark period, capture a background radiation; and an evaluation device (470) which, based on the amounts of radiation detected, calculates a signal that depends on a distance of the optical distance meter from an object (105).
Pixel structure (400) for optical distance measurement with the following characteristics: a semi... more Pixel structure (400) for optical distance measurement with the following characteristics: a semiconductor substrate (302); a photoactive region (402) which is integrated on the substrate (302); a reference potential terminal (410) for a reference potential; a plurality of at least three Auswertekapazitaten (408; FDn) are arranged from an edge of the photoactive region around the photoactive region around in the form of floating diffusion regions that are spaced laterally; a plurality of at least four transfer gates (404; TXn) in the form of MOS capacitors that are formed at different peripheral regions of the photoactive region (402) to transport the charge carriers generated from the photoactive region (402), wherein at least three the plurality of transfer gates are formed in order to transport the charge carriers generated from the photoactive region (402) to a respective evaluating capacity; and a control circuit (406).
In this paper we present a $2\times 192$ pixel SPAD-based sensor for LiDAR applications fabricate... more In this paper we present a $2\times 192$ pixel SPAD-based sensor for LiDAR applications fabricated in a $0.35\ \boldsymbol{\mu}\mathbf{m}$ standard CMOS process. Distance measurement is performed using the direct time-of-flight technique. For time acquisition a DLL-based pixel-parallel TDC with 312.5 ps resolution and a $1.28\ \boldsymbol{\mu}\mathbf{m}$ range is integrated. Employing four single SPADs in each pixel enables background light suppression by detecting temporal correlated photons. Moreover, by using adjustable correlation parameters the dynamic range is increased significantly allowing a constant range at varying target reflectivity.
2017 European Conference on Circuit Theory and Design (ECCTD), 2017
This communication addresses the range accuracy of SPAD-based time-of-flight (TOF) sensors that e... more This communication addresses the range accuracy of SPAD-based time-of-flight (TOF) sensors that employ laser pulse modulation. Two basic approaches are considered: indirect and direct TOF. We investigate confidence intervals and derive formulas for standard errors of the relative distance error for both approaches based on photon statistics.
Advances in laser diode technology enable the generation of eye-safe laser pulses with short puls... more Advances in laser diode technology enable the generation of eye-safe laser pulses with short pulse duration and high peak power. This opens up new opportunities for Light Detection and Ranging (LiDAR)-systems based on the direct time-of-flight (dTOF) principle because their range performance is mainly limited by the requirement of eye-safe laser pulse energy. Another limiting factor for dTOF LiDAR is the sensitivity to background noise. Shorter pulse width enables better parasitic light suppression inside the LiDAR system for improved performance in high background flux scenarios. With the improvements caused by using short laser pulses, new challenges emerge. Shorter pulse duration and limited achievable timing resolution of time discrimination circuits inside of dTOF detectors lead to histogram data distributions in which the laser originated time stamps can only fill few time bins. The time stamp histogram of the detected and clocked laser photons shows a sharp exponential declin...
Detektor zur Detektion elektromagnetischer Strahlung mit folgenden Merkmalen: einem ersten Halble... more Detektor zur Detektion elektromagnetischer Strahlung mit folgenden Merkmalen: einem ersten Halbleiterchip (12; 312) mit einem ersten Halbleitermaterial als Substratmaterial; einem zweiten Halbleiterchip (22; 322) mit einem zweiten Halbleitermaterial als Substratmaterial, das unterschiedlich vom ersten Halbleitermaterial ist, wobei der erste Halbleiterchip (12; 312) und das zweite Halbleiterchip (22; 322) mit gegenuberliegenden Hauptoberflachen (14, 24) zueinander angeordnet sind; einem ersten Array mit einer Mehrzahl von ersten Detektionsstrukturen (18; 318) innerhalb des ersten Halbleiterchips (12; 312), die als eine Lawinenphotodiodenstruktur oder eine Single-Photon-Avalanche-Photodiodenstruktur innerhalb des ersten Halbleiterchips ausgebildet sind; einem zweiten Array mit einer Mehrzahl von zweiten Detektionsstrukturen (28; 328) innerhalb des zweiten Halbleiterchips (22; 322), die jeweils mit den ersten Detektionsstrukturen (18; 318) uberlappend angeordnet sind, wobei jede Detekt...
A fast and reliable three dimensional monitoring of the environment is indispensable for robotics... more A fast and reliable three dimensional monitoring of the environment is indispensable for robotics, automation engineering or autonomous driving. For these applications LiDAR is a key sensor technology. Normally a light source in the near infrared range is used, which is invisible to human eyes. High ambient light compared to the laser source intensity is a major problem for these systems. Therefore, a measurement concept to reduce the impact of ambient light is necessary. In this paper we present a measurement concept in which the full distance range is scanned and the probability to detect events from far objects is improved. The general problem is that a photon of the background illumination can be detected instead of the reflected laser signal which stops the measurement. The concept allows us to detect the received laser pulse buried in the superimposed background light easier and improve the measurement quality. This is possible due to the delayed start of the measurement and t...
We present a 1×80 pixel line sensor for direct time-of-flight measurement based on single-photon ... more We present a 1×80 pixel line sensor for direct time-of-flight measurement based on single-photon avalanche diodes fabricated in a high-voltage 0.35 pm CMOS process. An in-pixel time-to-digital-converter with a resolution of 312.5 ps determines the arrival time of the first-photon for each emitted laser pulse from a flash illumination source for all pixels in parallel. Distance determination is performed by collecting the time stamps over multiple pulses in a histogram and applying proper software algorithms. Ambient light suppression is achieved by detection of photon coincidences from four single SPADs in each pixel. By adjusting the time and depth of the coincidence detection a good result in varying ambient conditions is achieved.
The semiconductor structure (10) a semiconductor layer (12) of a first conductivity type, a photo... more The semiconductor structure (10) a semiconductor layer (12) of a first conductivity type, a photosensitive zone (14) which is formed so that photo-generated charges can be collected in a first potential well (19); formed in a semiconductor layer (12) region (18) of the second conductivity type for temporarily storing the photo-generated charges in a second potential well; a transfer gate (20) between the region (18) of the second conductivity type and the photosensitive zone (14) for defining a potential barrier (23) between the first and the second potential well in a non-transfer phase, and lifting of the potential barrier (23) between the first and second potential well in a transfer phase; and a readout structure to read out the temporarily stored photo-generated charges, which includes a JFET (22), whose gate is constituted by the region (18) of the second conductivity type, said JFET (22), one at the area (18) of the second conductivity type adjacent the channel region (40) of...
We present a novel silicon photomultiplier based on a shallow junction obtained within a standard... more We present a novel silicon photomultiplier based on a shallow junction obtained within a standard 0.35 <inline-formula> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> complementary metal oxide semiconductor process. The sensitive structure is equipped with a dedicated optical window as well as an optimized antireflective coating. The device exhibits performances comparable to custom-based commercial technologies: an unprecedented photon detection efficiency of 43% at 420 nm, a breakdown voltage temperature dependence of (27.9 ± 0.9) mV/K, a dark count rate of 480 kHz/mm<sup>2</sup>, a gain of <inline-formula> <tex-math notation="LaTeX">${3\times 10^{6}}$ </tex-math></inline-formula>, and a single photon time resolution of (78 ± 2) ps (FWHM). The process proposed in this letter can be applied to new generation single photon sensors with on-chip integrated intelligent electronics.
We present a SPAD-based LiDAR sensor fabricated in an automotive certified 0.35 µm CMOS process. ... more We present a SPAD-based LiDAR sensor fabricated in an automotive certified 0.35 µm CMOS process. Since reliable sensor operation in high ambient light environment is a crucial factor in automotive applications, four SPADs are implemented in each pixel to suppress ambient light by the detection of photon coincidences. By pixel individual adjustment of the coincidence parameters to the present ambient light condition, an almost constant measurement performance is achieved for a wide range of different target reflectance and ambient illumination levels. This technique allows the acquisition of high dynamic range scenes in a single laser shot. For measurement and demonstration purpose a LiDAR camera with the developed sensor has been built.
ABSTRACT We report on the design and characterization of a smart pixel for long-distance ranging,... more ABSTRACT We report on the design and characterization of a smart pixel for long-distance ranging, comprising a high performances Single-Photon detector and sub-nanosecond Time-to-Digital Conversion (TDC), in 0.35 μm CMOS technology.
LiDAR is a key sensor technology for future driving. For autonomous vehicles a fast and reliable ... more LiDAR is a key sensor technology for future driving. For autonomous vehicles a fast and reliable three dimensional monitoring of the environment is essential for managing a wide variety of common traffic situations. Since these kinds of systems use typically light in the near infrared range, ambient light of the sun is a serious problem due to its high intensity compared to the laser source. Therefore, reducing the influence of ambient light on the distance measurement is very important. In this paper we present a 2 × 192 pixel SPAD-based direct time-of-flight line sensor for flash LiDAR applications with high ambient light rejection integrated in standard CMOS technology. Two commercially available 905 nm laser diodes emitting short pulses are employed for scene illumination. For time measurement an in-pixel timeto- digital-converter with a resolution of 312.5 ps and full range of 1.28 μs has been implemented. Each pixel uses four vertically arranged single SPADs for background lig...
Optical distance meter (400) that has the following characteristics: a pulsed radiation source (1... more Optical distance meter (400) that has the following characteristics: a pulsed radiation source (110) configured to transmit, in a period of temporarily continuous pulses of radiation, a radiation pulse (110a) with a pulse duration (tp) shorter than the period of radiation pulses, and not to transmit radiation pulses during a dark period temporarily continuous; a detection device (420) for detecting different amounts of radiation in two detection periods that overlap in the period of radiation pulses to capture reflections of the radiation pulse on the surface of an object and a background radiation and / or, in two detection periods that overlap in the dark period, capture a background radiation; and an evaluation device (470) which, based on the amounts of radiation detected, calculates a signal that depends on a distance of the optical distance meter from an object (105).
Pixel structure (400) for optical distance measurement with the following characteristics: a semi... more Pixel structure (400) for optical distance measurement with the following characteristics: a semiconductor substrate (302); a photoactive region (402) which is integrated on the substrate (302); a reference potential terminal (410) for a reference potential; a plurality of at least three Auswertekapazitaten (408; FDn) are arranged from an edge of the photoactive region around the photoactive region around in the form of floating diffusion regions that are spaced laterally; a plurality of at least four transfer gates (404; TXn) in the form of MOS capacitors that are formed at different peripheral regions of the photoactive region (402) to transport the charge carriers generated from the photoactive region (402), wherein at least three the plurality of transfer gates are formed in order to transport the charge carriers generated from the photoactive region (402) to a respective evaluating capacity; and a control circuit (406).
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Papers by Werner Brockherde