Image Sensor Readout Circuit With Alternating Bit Inversion

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Solution Overview

Problem

In solid-state imaging devices, the current consumption varies significantly with bit width, leading to noise and a drop in image quality, especially in large-format image sensors where sequential readout of identical pixel data causes substantial current changes, affecting other circuits and image quality.

Innovation Solution

A solid-state imaging device configuration that includes a latch circuit, a driver circuit, a sense amplifier, and a selector circuit to output pixel data in either normal or inverted form, reducing bit changes and fluctuations in current consumption during data transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If pixel data is read out sequentially using conventional latch driver circuits, then data transfer speed is improved, but current consumption varies significantly causing noise and image quality degradation

Engineering Contradiction:

Improvedata transfer speedVSAvoidcurrent fluctuation noise

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent applies inversion by outputting pixel data in inverted form alternately in odd and even columns. This causes successive data bits to change more frequently, increasing current consumption variations. However, this is intentionally done to counterbalance noise patterns and reduce overall noise impact on image quality, demonstrating the use of inversion to transform a harmful effect into a beneficial one.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If the bit width of pixel data is increased for large-format image sensors, then image quality is improved, but current consumption increases significantly

Engineering Contradiction:

Improveimage qualityVSAvoidcurrent consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent changes the parameter of data output form (normal vs. inverted) based on column position (odd vs. even). This parameter change causes successive pixel data to transition more frequently, which increases current consumption variations. However, this controlled variation helps manage the overall current consumption profile when handling large bit-width data from large-format sensors, allowing high-resolution imaging while managing power usage.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If identical pixel data is read out sequentially, then data transfer efficiency is improved, but current consumption remains constant causing noise

Engineering Contradiction:

Improvedata transfer efficiencyVSAvoidnoise from constant current

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent implements periodic action by alternating the output form (normal/inverted) between odd and even columns. This periodic switching ensures that even when identical pixel data is read out sequentially, the data transitions occur regularly. This periodic variation in current consumption prevents the noise issues associated with constant current, while maintaining efficient data transfer throughput.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11265502B2Solid-state imaging device

Publication Date: 2022.03.01 NUVOTON TECH CORP JAPAN

AI summary

A solid-state imaging device includes: a latch circuit that holds a digital signal of pixel data, the digital signal having 1 bit; a driver circuit that outputs the digital signal held in the latch circuit to a read bit line pair; a sense amplifier connected to the read bit line pair; and a selector circuit that selects whether the digital signal output from the sense amplifier is to be output in normal form or in inverted form.