Image Sensor A/D Conversion With Selectable Reference Voltage Slopes

Solution Overview

Problem

Existing analog-to-digital (A/D) conversion methods in image sensors face challenges in suppressing errors, particularly in achieving high gradation precision while reducing conversion time without increasing circuit area and power consumption.

Innovation Solution

A signal processing device and method that includes a selection unit to choose a reference voltage based on a comparison of an analog signal with a determination voltage, a switching unit to supply the selected reference voltage, and a measurement unit to determine the timing of the comparison result, allowing for adaptive gradation precision and reduced errors in A/D conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If two A/D conversion circuits are connected to the same pixel output signal with two reference voltages having different slopes, then gradation precision is increased and conversion time is reduced, but circuit area and power consumption double

Engineering Contradiction:

Improvegradation precisionVSAvoidcircuit area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent applies dynamics by making the reference voltage slope selectable and changeable based on signal magnitude. A selection unit chooses between first and second reference voltages with different slopes according to the determined magnitude of the pixel output signal, allowing the system to adaptively switch between high precision (smaller slope) and fast conversion (larger slope) modes, thereby achieving high gradation precision without permanently doubling the circuit area.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of reference voltage slope dynamically. By providing two reference voltages with different slopes and selecting appropriate one based on signal magnitude, the system optimizes the balance between conversion precision and speed without requiring both circuits to be active simultaneously, thus avoiding the doubling of circuit area and power consumption.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If two A/D conversion circuits are connected to the same pixel output signal with two reference voltages having different slopes, then gradation precision is increased and conversion time is reduced, but power consumption doubles

Engineering Contradiction:

Improvegradation precisionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies dynamics by making the reference voltage slope selectable and changeable based on signal magnitude. A selection unit chooses between first and second reference voltages with different slopes according to the determined magnitude of the pixel output signal, allowing the system to adaptively switch between high precision (smaller slope) and fast conversion (larger slope) modes, thereby achieving high gradation precision without permanently doubling the circuit area.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of reference voltage slope dynamically. By providing two reference voltages with different slopes and selecting appropriate one based on signal magnitude, the system optimizes the balance between conversion precision and speed without requiring both circuits to be active simultaneously, thus avoiding the doubling of circuit area and power consumption.

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If one A/D conversion circuit is used with a determination unit to select reference voltages, then circuit area and power consumption are reduced, but it is difficult to sufficiently suppress errors in A/D conversion

Engineering Contradiction:

Improvecircuit areaVSAvoidA/D conversion accuracy

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent applies dynamics by making the reference voltage slope selectable and changeable based on signal magnitude. A selection unit chooses between first and second reference voltages with different slopes according to the determined magnitude of the pixel output signal, allowing the system to adaptively switch between high precision (smaller slope) and fast conversion (larger slope) modes, thereby achieving high gradation precision without permanently doubling the circuit area.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback by having a determination unit first determine the magnitude of the pixel output signal, then using this information to select the appropriate reference voltage slope. This feedback mechanism ensures that the most suitable reference voltage is chosen based on the actual signal characteristics, thereby suppressing A/D conversion errors while using only one A/D conversion circuit.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2856651B1Signal processing device and method, imaging element, and imaging device

Publication Date: 2022.06.29 SONY GROUP CORP

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AI summary

A signal processing device and signal processing method are described herein. By way of example, the signal processing method includes a selection unit configured to select, based on a first comparison of an analog signal with a determination voltage, a selected reference voltage to be compared with the analog signal, the selected reference voltage being selected from a plurality of reference voltages. The plurality of reference voltages include at least a first reference voltage and a second reference voltage.