SPAD Distance Measurement With Preliminary Bias Control

Solution Overview

Problem

Distance measuring devices using single-photon avalanche diodes (SPADs) face accuracy issues due to temperature-dependent breakdown voltage fluctuations and sensitivity changes, particularly when surrounding brightness suddenly changes, as in automated driving applications.

Innovation Solution

A distance measuring device with a light receiving unit and bias control unit that adjusts bias voltage before and during distance measuring processing, using separate light receiving elements for measurement and bias control, and a system that includes a light emitting unit for accurate distance measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the number of light emitting elements is increased for middle/short-distance measurement, then measurement coverage is improved, but the temperature of the SPAD chip increases causing breakdown voltage fluctuations

Engineering Contradiction:

Improvemeasurement coverage areaVSAvoidSPAD chip temperature

Core Design Contradiction:

Area of stationary objectVSTemperature

Solution Approach 1:

The bias control unit performs preliminary bias voltage adjustment before distance measurement processing starts. When the surrounding brightness changes suddenly, the system controls the bias voltage in advance during a first period before the second period (distance measurement processing), preventing temperature-induced voltage fluctuations from affecting measurement accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system monitors the surrounding brightness and adjusts the bias voltage based on the detected changes. The bias control unit receives feedback about brightness changes and dynamically controls the bias voltage to compensate for temperature effects on the SPAD breakdown voltage, maintaining stable cathode voltage despite temperature variations.

Inventive Principle:

Principle #23Feedback

2Reliability

If the surrounding brightness changes suddenly, then the number of reactive SPADs changes, but this causes breakdown voltage fluctuations and reduces measurement accuracy

Engineering Contradiction:

Improvedetection sensitivity stabilityVSAvoiddistance measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The bias control unit performs preliminary bias voltage adjustment before distance measurement processing starts. When the surrounding brightness changes suddenly, the system controls the bias voltage in advance during a first period before the second period (distance measurement processing), preventing temperature-induced voltage fluctuations from affecting measurement accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the bias voltage parameter in response to brightness changes. By adjusting the bias voltage during the first period before distance measurement, the system compensates for temperature-induced breakdown voltage fluctuations, maintaining stable cathode voltage and consistent detection sensitivity despite changes in the number of reactive SPADs.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If bias voltage is controlled only during distance measurement processing, then power consumption is reduced, but accuracy is lost during mode switching

Engineering Contradiction:

Improvepower consumptionVSAvoiddistance measurement accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The bias control unit performs preliminary bias voltage adjustment before distance measurement processing starts. When the surrounding brightness changes suddenly, the system controls the bias voltage in advance during a first period before the second period (distance measurement processing), preventing temperature-induced voltage fluctuations from affecting measurement accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements periodic bias control with distinct phases: a first period for bias voltage control before distance measurement, and a second period for actual distance measurement processing. This periodic approach ensures accuracy is maintained during mode switching while power consumption is optimized during stable operation.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Ensures accurate distance measurement by stabilizing bias voltage levels, maintaining measurement accuracy despite sudden changes in surrounding brightness.

Implementation Method 1

a single-photon avalanche diode (SPAD) is often used to receive a reflected light pulse signal from an object. The SPAD has a detection capability of being able to detect one photon.

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Implementation Method 2

a light receiving chip in which a plurality of SPADs is aligned in a two-dimensional direction is used

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS20250327909A1Distance measuring device and distance measuring system

Publication Date: 2025.10.23 SONY SEMICON SOLUTIONS CORP

AI summary

To perform accurate distance measurement from the distance measuring start point even when the surrounding brightness changes suddenly. A distance measuring device includes: a light receiving unit that receives a reflected light pulse signal reflected by an object; a distance measuring unit that performs distance measuring processing on the basis of an output signal of the light receiving unit; and a bias control unit that controls a bias voltage of the light receiving unit before the distance measuring unit starts the distance measuring processing.