Save and Share Current Circuitry for Time-of-Flight Pixel Drivers

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Solution Overview

Problem

Time-of-flight camera systems face challenges with rising and falling times of mixing signals, leading to pixel depth non-uniformity and increased power consumption due to higher pixel counts, which affect the quality of depth images.

Innovation Solution

The implementation of Save and Share current circuitry connected to the Mix driver, which saves charge during a charging or discharging phase and shares it with the pixel chip when needed, optimizing peak/average currents and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the number of pixels is increased, then the imaging quality is improved, but the load capacitance increases causing longer rising and falling times of mixing signals

Engineering Contradiction:
Improveimaging qualityVSAvoidrising and falling times
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The pixel array is divided into multiple blocks, with each block having its own Mix driver. This segmentation reduces the load capacitance on each driver, thereby decreasing the rising and falling times while maintaining high imaging quality through the combined output of multiple blocks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Capacitors are pre-charged during the integration period before the mixing signal needs to be output. This preliminary charging action ensures that when the mixing signal is needed, the capacitors can quickly discharge, reducing the rising and falling times without requiring higher peak currents.

Inventive Principle:
Principle #10Preliminary action

2Loss of time

If the size of the output driver stage is increased, then the rising and falling times are reduced, but the area and power consumption increase

Engineering Contradiction:
Improverising and falling timesVSAvoidpower consumption
Core Design Contradiction:
Loss of timeVSUse of energy by moving object

Solution Approach 1:

Capacitors are pre-charged during the integration period before the mixing signal needs to be output. This preliminary charging action ensures that when the mixing signal is needed, the capacitors can quickly discharge, reducing the rising and falling times without requiring higher peak currents from the driver stage.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent converts the accumulated charge during the integration period (which could be considered wasted energy) into a beneficial resource. This pre-accumulated charge is then used to rapidly charge or discharge the pixel capacitance, reducing the rising and falling times without increasing power consumption.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Loss of time

If the voltage supply values are increased, then the rising and falling times are reduced, but the area and reliability are compromised

Engineering Contradiction:
Improverising and falling timesVSAvoidsystem reliability
Core Design Contradiction:
Loss of timeVSReliability

Solution Approach 1:

Capacitors are pre-charged during the integration period before the mixing signal needs to be output. This preliminary charging action ensures that when the mixing signal is needed, the capacitors can quickly discharge, reducing the rising and falling times without requiring higher voltage supplies that would compromise reliability.

Inventive Principle:
Principle #10Preliminary action

4Speed

If the peak current is increased, then the charging/discharging speed is improved, but the cyclic error and calibration difficulty increase

Engineering Contradiction:
Improvecharging/discharging speedVSAvoiddepth image quality
Core Design Contradiction:
SpeedVSMeasurement precision

Solution Approach 1:

Capacitors are pre-charged during the integration period before the mixing signal needs to be output. This preliminary charging action provides the necessary charge reservoir to achieve fast charging/discharging speeds without requiring high peak currents, thereby avoiding cyclic errors and calibration difficulties.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentUS20240134014A1Electronic device, method and computer program
Publication Date: 2024.04.25 SONY SEMICON SOLUTIONS CORP
  • US20240134014A1 patent drawing
  • US20240134014A1 patent drawing
  • US20240134014A1 patent drawing

AI summary

An electronic device comprising circuitry, the circuitry comprising a mix driver (MVD) for providing a modulation In signal to pixels of a time of flight pixel chip (P500), and at least one Save and Share current circuitry (51, S2) connected to the mix driver (MVD), wherein the Save and Share circuitry (S1, S2) is configured to save charge provided by a power supply (VDD) in a capacitor (CS1, CS2) and to share the saved charge to the pixels of the time of flight pixel chip (P500). A logic chip (L500) comprises an input (l_in) and a buffer block (CLT500), where a modulation signal (GDA) is supplied to the input (1_in) and is delivered to the pixel chip (P500) via the buffer block (CLT500). Capacitors (CS1, CS2) help the mix driver (MVD) with the charging and discharging, respectively, of the pixel units in the pixel chip (P500). Frequencies used for the modulation signal (GDA) may be in the range of several tens of MHz to several hundreds of MHz. The buffer block (CLT500) comprises two inverting buffers (1501, 1502), and the Mix driver (MVD). The total average and peak to peak current consumption may be reduced, and the rising and falling slopes are also improved. The electronic device may for example be an image sensor, e.g. an image sensor of an indirect time of flight camera, iToF. An indirect time of flight camera may resolve distance by measuring a phase shift of an emitted light and a back scattered light.