Analog-to-digital converters for LIDAR systems
Embodiments of the present disclosure propose analog-to-digital conversion (ADC) systems particularly suitable for Light Detection and Ranging (LIDAR) implementations. An exemplary proposed ADC system is configured to determine whether an absolute value of an analog value is greater than a threshold, and, upon positive determination, assign a predetermined digital value as a digital value corresponding to the analog value, without proceeding with the analog-to-digital conversion of the analog value. Because the ADC system only proceeds with the analog-to-digital conversion, using an ADC, when the input analog value is smaller than the threshold, and otherwise the input analog value is simply assigned some predefined digital value, design complexity and power consumption of the system may be significantly reduced, compared to conventional ADCs used in LIDAR applications.
1. A LIDAR system comprising:
a light source configured to emit pulses of light;
a light sensor configured to detect light comprising contributions of the pulses of light reflected from an object;
a sensor storage array configured to store a plurality of analog values indicative of the contributions of the pulses of light reflected from the object;
an analog-to-digital converter (ADC) system provided with a predetermined multi-bit digital value and configured to convert at least one analog value of the plurality of analog values to a multi-bit digital value by:
determining whether an absolute value of the at least one analog value is greater than a threshold,
upon positive determination, assigning the predetermined multi-bit digital value as the digital value corresponding to the at least one analog value without proceeding with an analog-to-digital conversion of the analog value to generate one or more bits of the digital value, and
upon negative determination, proceeding with the analog-to-digital conversion to convert the at least one analog value to the digital value; and
a processor configured to determine at least one of a distance to and a speed of the object based on the digital value.
2. The LIDAR system according to claim 1 , wherein:
the threshold is one threshold of a plurality of thresholds, and the predetermined value is one predetermined value of a plurality of predetermined values corresponding to the plurality of thresholds,
the determining comprises determining whether the absolute value of the analog value is greater than any of the plurality of thresholds, and
the assigning upon positive determination comprises assigning a predetermined digital value corresponding to a largest threshold of the plurality of thresholds which is smaller than the absolute value of the analog value.
3. The LIDAR system according to claim 1 , wherein the ADC system comprises a three-level flash ADC for implementing the analog-to-digital conversion.
4. The LIDAR system according to claim 1 , wherein the ADC system comprises an amplifier to amplify the analog value prior to the analog-to-digital conversion.
5. The LIDAR system according to claim 1 , wherein:
the ADC system comprises a successive approximation routine (SAR) converter for implementing the analog-to-digital conversion;
the SAR converter includes a plurality of sampling capacitors to sample the analog value in an acquire phase, and
one or more of the plurality of sampling capacitors are non-binary weighted with respect to remaining sampling capacitors of the plurality of sampling capacitors.
6. The LIDAR system according to claim 5 , wherein the one or more non-binary weighted sampling capacitors comprise one or more most significant bit (MSB) sampling capacitors.
7. The LIDAR system according to claim 5 , further comprising a bridge capacitor connected to the one or more non-binary weighted sampling capacitors.
8. The LIDAR system according to claim 1 , wherein the light source comprises a laser or a laser diode.
9. The LIDAR system according to claim 1 , wherein the light sensor comprises a charge coupled device.
10. The LIDAR system according to claim 1 , wherein the light source and the light sensor are configured to enable time-of-flight measurements.
11. A method for determining at least one of a distance to and a speed of an object based on an analog value indicative of one or more pulses of light reflected from the object, the method comprising:
determining whether an absolute value of the analog value is greater than a threshold;
upon negative determination, using an analog-to-digital converter (ADC) provided with a predetermined multi-bit digital value to convert the analog value to a multi-bit digital value and providing the converted multi-bit digital value as a digital value corresponding to the analog value;
upon positive determination, assigning the predetermined multi-bit digital value to the analog value without finishing an analog-to-digital conversion for at least one bit of the multi-bit digital value and providing the predetermined multi-bit digital value as the digital value corresponding to the analog value; and
determining the at least one of the distance to and the speed of the object based on the digital value corresponding to the analog value.
12. The method according to claim 11 , wherein using the ADC comprises sampling the analog value on a plurality of sampling capacitors of the ADC during an acquire phase and subsequently converting voltages on the plurality of sampling capacitors to the digital value during a conversion phase.
13. The method according to claim 11 , wherein:
the threshold is one threshold of a plurality of thresholds, and the predetermined value is one predetermined value of a plurality of predetermined values corresponding to the plurality of thresholds,
the determining comprises determining whether the absolute value of the analog value is greater than any of the plurality of thresholds, and
the assigning upon positive determination comprises assigning a predetermined digital value corresponding to a largest threshold of the plurality of thresholds which is smaller than the absolute value of the analog value.
14. The method according to claim 11 , further comprising amplifying the analog value prior to the analog-to-digital conversion.
15. The method according to claim 11 , further comprising using a successive approximation routine (SAR) converter for implementing the analog-to-digital conversion, wherein:
the SAR converter includes a plurality of sampling capacitors to sample the analog value in an acquire phase, and
one or more of the plurality of sampling capacitors are non-binary weighted with respect to remaining sampling capacitors of the plurality of sampling capacitors.
16. The method according to claim 15 , wherein the one or more non-binary weighted sampling capacitors comprise one or more most significant bit (MSB) sampling capacitors.
17. A system for determining at least one of a distance to and a speed of an object, the system comprising:
a sensor storage configured to store an analog value indicative of a contribution, as detected by a light sensor, of one or more pulses of light emitted by a light source and reflected from the object;
an analog-to-digital converter (ADC) system provided with a predetermined multi-bit digital value and configured to convert the analog value to a multi-bit digital value by:
determining whether an absolute value of the analog value is greater than a threshold,
upon negative determination, proceeding with an analog-to-digital conversion to convert the analog value to a multi-bit digital value, and
upon positive determination, assigning the predetermined digital value as a digital value corresponding to the analog value without performing the analog-to-digital conversion to determine at least one bit of the multi-bit digital value, and
and
a processor configured to determine the at least one of the distance to and the speed of the object based on the digital value.
18. A system for determining at least one of a distance to and a speed of an object based on an analog value indicative of one or more pulses of light reflected from the object, the system comprising:
an analog-to-digital converter (ADC); and
a processor configured to:
determine whether an absolute value of the analog value is greater than a threshold,
upon negative determination, use the ADC provided with a predetermined multi bit digital value to convert the analog value to a multi-bit digital value and provide the converted multi-bit digital value as a digital value corresponding to the analog value,
upon positive determination, assign the predetermined digital value to the analog value without performing an analog-to-digital conversion for at least one bit of the multi-bit digital value and provide the predetermined digital value as the digital value corresponding to the analog value, and
determine the at least one of the distance to and the speed of the object based on the digital value corresponding to the analog value.
19. The system according to claim 18 , further comprising a light sensor configured to detect light that includes a contribution of the one or more pulses of light reflected from the object, wherein the analog value is indicative of the contribution.
20. The system according to claim 18 , further comprising a light source configured to emit the one or more pulses of light to be reflected from the object.
21. The system according to claim 18 , further comprising a sensor storage configured to store the analog value.