Protective mask for an optical receiver

A lidar system comprising:

• a light source configured to emit pulses of light;
• a scanner configured to scan the emitted pulses of light across a field of regard of the lidar system;
• an optical receiver configured to detect incident light including a portion of one of the emitted pulses of light scattered by a target located a distance from the lidar system, the optical receiver comprising:
• an application-specific integrated circuit (ASIC);
• a light detector element with a top surface oriented toward the incident light, the top surface including a portion configured to receive the incident light and via which the incident light reaches an active area of the light detector element, the light detector element disposed on the ASIC;
• and
• a protective mask placed over the ASIC so as to (i) cover, from the incident light, at least a portion of the ASIC, and (ii) provide an aperture that defines an optical path for the incident light through the protective mask to the portion of the top surface of the light detector element, wherein the aperture in the protective mask comprises (i) an opening on a top surface of the protective mask oriented toward the incident light and (ii) an opening on a bottom surface of the protective mask oriented toward the light detector element, wherein the opening on the bottom surface is larger than the opening on the top surface, wherein a length, width, or diameter of the opening on the bottom surface is greater than a corresponding length, width, or diameter of the opening on the top surface, and wherein the length, width, or diameter of the opening on the bottom surface is between 100 micrometers and 1,000 micrometers, and the corresponding length, width, or diameter of the opening on the top surface is between 25 micrometers and 600 micrometers;
• and
• a processor configured to determine the distance to the target based on a round-trip time of the portion of the emitted pulse of light, the round-trip time corresponding to a time between when the portion of the emitted pulse of light is emitted by the light source and when the portion of the emitted pulse of light is detected by the optical receiver.

An optical receiver comprising:

• an application-specific integrated circuit (ASIC);
• a first light detector element with a top surface oriented toward a first beam of incident light, the top surface including a portion configured to receive the first beam of incident light and via which the first beam of incident light reaches a first active area of the first light detector element, the first light detector element disposed on the ASIC;
• a second light detector element having a second active area, the second light detector element configured to receive a second beam of incident light;
• a protective mask placed over the ASIC so as to:
• cover, from the first beam of incident light, at least a portion of the ASIC;
• provide a first aperture that defines an optical path for the first beam of incident light through the protective mask to the portion of the top surface of the first light detector element, wherein the first aperture in the protective mask comprises (i) an opening on a top surface of the protective mask oriented toward the first beam of incident light, and (ii) an opening on a bottom surface of the protective mask oriented toward the first light detector element, wherein the opening on the bottom surface is larger than the opening on the top surface;
• and
• provide a second aperture that defines a second optical path for the second beam of incident light through the protective mask to the second active area of the second light detector element.

An optical receiver comprising:

• an application-specific integrated circuit (ASIC);
• a light detector element with a top surface oriented toward incident light, the top surface including a portion configured to receive the incident light and via which the incident light reaches an active area of the light detector element, the light detector element disposed on the ASIC, wherein:
• the incident light includes a received pulse of light;
• the light detector element is configured to produce a pulse of electrical current corresponding to the received pulse of light;
• and
• the ASIC includes:
• an electronic amplifier configured to amplify the pulse of electrical current to produce a voltage pulse that corresponds to the pulse of electrical current;
• one or more comparators, wherein each comparator is coupled to the electronic amplifier and configured to produce an electrical-edge signal when the voltage pulse rises above or falls below a particular threshold voltage;
• and
• one or more time-to-digital converters (TDCs), wherein each TDC is coupled to one of the one or more comparators and is configured to produce a time value corresponding to a time when the electrical-edge signal was received by the TDC, wherein a time of receipt for the received pulse of light is determined based on one or more time values produced by one or more of the TDCs;
• and
• a protective mask placed over the ASIC so as to (i) cover, from the incident light, at least a portion of the ASIC, and (ii) provide an aperture that defines an optical path for the incident light through the protective mask to the portion of the top surface of the light detector element, wherein the aperture in the protective mask comprises (i) an opening on a top surface of the protective mask oriented toward the incident light and (ii) an opening on a bottom surface of the protective mask oriented toward the light detector element, wherein the opening on the bottom surface is larger than the opening on the top surface.