Abstract: A method of ranging using a time-of-flight (ToF) ranging system includes: receiving, by a processor, a histogram generated by a ToF imager of the ToF ranging system, where the ToF imager is configured to transmit a light pulse for ranging purpose; finding a rising edge of a pulse region in the histogram, where the pulse region corresponds to a reflected light pulse from a target; fine-tuning a location of the rising edge by performing a fitting process between the rising edge and a pre-stored high-solution rising edge; and calculating an estimate of a distance of the target by adding a pre-determined offset to a distance of the rising edge after fine-tuning the location of the rising edge.

Abstract: According to an embodiment, a time-of-flight sensor system includes a light emitter, a detector array, and a histogram processing circuit. The histogram processing circuit processes time-of-flight measurement data using sequential bin-by-bin histogram processing. This approach enables efficient processing with minimal memory requirements, suitable for low-power applications. The circuit applies on-the-fly operations during processing, including crosstalk removal and peak detection. A correlator circuit within the system uses multiply-accumulate (MAC) circuits to calculate ambient light contribution, perform main correlation, and compute crosstalk contribution in a bin-serial manner. Additionally, a phase/bin computation circuit applies filter coefficients to preprocessed histogram data and detects positive zero crossings to calculate the median phase.

Abstract: A differential correlator filter includes: a pre-pulse region, where first filter coefficients in the pre-pulse region have negative values; and a pulse region including: a rising edge region adjacent to the pre-pulse region, where second filter coefficients in the rising edge region have positive values; an accumulation region adjacent to the rising edge region, where third filter coefficients of the accumulation region have positive values; and a falling edge region adjacent to the accumulation region, where fourth filter coefficients of the falling edge region have positive values, where the accumulation region is between the rising edge region and the falling edge region. The differential correlator filter further includes a post-pulse region adjacent to the pulse region, where the pulse region is between the pre-pulse region and the post-pulse region, where fifth filter coefficients of the post-pulse region have negative values.

Abstract: A method of processing a histogram generated by a time-of-flight (ToF) imager includes: filtering the histogram using a zero-crossing filter (ZCF) to generate a ZCF output signal; finding zero-crossing points in the ZCF output signal, where the zero-crossing points define one or more pulse regions in the ZCF output signal; computing, for each pulse region of the one or more pulse regions, a weighted sum of the pulse region; finding, in each pulse region, a maximum peak; classifying the maximum peak in each pulse region as a first type of peak or a second type of peak based on the weighted sum of the pulse region; and generating a list of ZCF targets from the maximum peaks classified as the first type of peaks.

Abstract: A single-pass method for identifying peaks in a time of flight histogram, the single-pass method including conducting an ordered comparison of each bin with an adaptive threshold until finding a bin that exceeds the adaptive threshold; enabling peak tracking in response to finding the bin that exceeds the adaptive threshold; in response to enabling peak tracking, continuing the ordered comparison of each bin with the adaptive threshold until finding a bin that falls below the adaptive threshold; and in response to finding the bin that falls below the adaptive threshold, marking a peak location between the bin exceeding the adaptive threshold and the bin that falls below the adaptive threshold.

Abstract: A method of operating a time-of-flight (ToF) ranging system includes: receiving a histogram that includes a cross-talk signal generated by reflected light pulses from a cover glass of the ToF ranging system; finding, in a first region of the histogram, a first rising edge having a gradient that is larger than a threshold or is a maximum gradient in the first region, where the first rising edge is in a first histogram bin having a first value; determining a second value of a second histogram bin in the first region, where the first histogram bin precedes the second histogram bin by a pre-determined distance; estimating a ratio between the first region of the histogram and a pre-stored light pulse shape based on the first value and the second value; scaling the pre-stored light pulse shape with the estimated ratio; and subtracting the scaled pre-stored light pulse shape from the histogram.

Abstract: A differential correlator filter includes: a pre-pulse region, where first filter coefficients in the pre-pulse region have negative values; and a pulse region including: a rising edge region adjacent to the pre-pulse region, where second filter coefficients in the rising edge region have positive values; an accumulation region adjacent to the rising edge region, where third filter coefficients of the accumulation region have positive values; and a falling edge region adjacent to the accumulation region, where fourth filter coefficients of the falling edge region have positive values, where the accumulation region is between the rising edge region and the falling edge region. The differential correlator filter further includes a post-pulse region adjacent to the pulse region, where the pulse region is between the pre-pulse region and the post-pulse region, where fifth filter coefficients of the post-pulse region have negative values.

Abstract: A method of operating a time-of-flight (ToF) ranging system includes: transmitting, by an emitter, a light signal toward one or more targets; receiving, by a ToF sensor, the light signal reflected by the one or more targets; generating a histogram based on the received light signal; estimating gradients of histogram bins of the histogram by computing differences between adjacent histogram bins; identifying one or more pulse regions in the histogram; finding, in a pulse region, a rising edge having a gradient that is larger than a pre-determined threshold or is a maximum gradient in the pulse region, where the rising edge is a leftmost rising edge in the pulse region having the gradient; fine-tuning a location of the rising edge; and computing an estimate of a distance of a target in the pulse region by adding a pre-determined offset to a distance of the rising edge.

Abstract: A method of ranging using a time-of-flight (ToF) ranging system includes: receiving, by a processor, a histogram generated by a ToF imager of the ToF ranging system, where the ToF imager is configured to transmit a light pulse for ranging purpose; finding a rising edge of a pulse region in the histogram, where the pulse region corresponds to a reflected light pulse from a target; fine-tuning a location of the rising edge by performing a fitting process between the rising edge and a pre-stored high-solution rising edge; and calculating an estimate of a distance of the target by adding a pre-determined offset to a distance of the rising edge after fine-tuning the location of the rising edge.

Abstract: A method of determining a distance of a closest target using a time-of-flight (ToF) ranging system includes: receiving, by a processor, a histogram generated by a ToF imager of the ToF ranging system, where the ToF imager is configured to transmit a light pulse for ranging purpose; finding a first rising edge in the histogram that corresponds to a rising edge of a reflected light pulse from the closest target; and calculating a first estimate of the distance of the closest target by adding a pre-determined offset to a distance of the first rising edge.

Abstract: A method of processing a histogram generated by a time-of-flight (ToF) imager includes: filtering the histogram using a zero-crossing filter (ZCF) to generate a ZCF output signal; finding zero-crossing points in the ZCF output signal, where the zero-crossing points define one or more pulse regions in the ZCF output signal; computing, for each pulse region of the one or more pulse regions, a weighted sum of the pulse region; finding, in each pulse region, a maximum peak; classifying the maximum peak in each pulse region as a first type of peak or a second type of peak based on the weighted sum of the pulse region; and generating a list of ZCF targets from the maximum peaks classified as the first type of peaks.

Abstract: A differential correlator filter includes: a pre-pulse region, where first filter coefficients in the pre-pulse region have negative values; and a pulse region including: a rising edge region adjacent to the pre-pulse region, where second filter coefficients in the rising edge region have positive values; an accumulation region adjacent to the rising edge region, where third filter coefficients of the accumulation region have positive values; and a falling edge region adjacent to the accumulation region, where fourth filter coefficients of the falling edge region have positive values, where the accumulation region is between the rising edge region and the falling edge region. The differential correlator filter further includes a post-pulse region adjacent to the pulse region, where the pulse region is between the pre-pulse region and the post-pulse region, where fifth filter coefficients of the post-pulse region have negative values.

Abstract: A method includes emitting a pattern of transmitted light into a three-dimensional environment from an optical transmitter and receiving reflected light from the pattern of transmitted light at an optical receiver. The method includes identifying light-sensitive pixels of that are stimulated by from the pattern of reflected light and generating an up-sampled matrix with subsections that correspond to light-sensitive pixels. The method includes sparsely populating subsections of the up-sampled matrix with a pattern of non-zero entries and imaging the three-dimensional environment.

Abstract: A method includes emitting a pattern of transmitted light into a three-dimensional environment from an optical transmitter and receiving reflected light from the pattern of transmitted light at an optical receiver. The method includes identifying light-sensitive pixels of that are stimulated by from the pattern of reflected light and generating an up-sampled matrix with subsections that correspond to light-sensitive pixels.