Rolling Shutter Depth Sensor Phase Shift
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Solution Overview
Problem
Existing depth information acquisition methods face challenges in achieving high precision due to limitations in the rolling shutter scheme, particularly in the extraction of depth information from image signals with varying exposure times and phase shifts of illumination light.
Innovation Solution
A method and apparatus that modulate illumination light with a phase shift of 90° at the start exposure time of the center row of a pixel array region in a rolling shutter scheme, allowing for staggered exposure times across rows and calculating depth information from image signals acquired over multiple frames, thereby maximizing signal amplitude and reducing precision errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rolling shutter scheme is used for depth information acquisition, then device complexity is reduced and ease of operation is improved, but measurement precision of depth information deteriorates due to varying exposure times and phase shifts across rows
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the phase of the illumination light signal for different row regions. Specifically, the phase is shifted by 90 degrees for the intermediate region (center rows) while maintaining the original phase for the first and second regions (top and bottom rows). This parameter change compensates for the varying exposure times inherent in the rolling shutter scheme, ensuring that all rows achieve optimal signal amplitude and depth precision without requiring a global shutter mechanism.
2Measurement precision
If phase shifting is applied to the intermediate region only, then depth precision in the center region is improved, but device complexity increases due to region-specific phase control
Solution Approach 1:
The patent implements local quality by applying different phase shift parameters to different spatial regions of the pixel array. The intermediate region (center rows) receives a 90-degree phase shift, while the first and second regions (top and bottom rows) maintain the original phase. This localized approach optimizes depth precision specifically where it is most needed (the intermediate region that experiences the most significant exposure time variations) without unnecessarily complicating the control of the entire device.
3Productivity
If staggered exposure times are used across rows, then productivity is improved by continuous data acquisition, but measurement precision deteriorates due to varying exposure durations affecting signal amplitude
Solution Approach 1:
The patent employs periodic action by modulating the illumination light with a periodic signal and applying periodic phase shifts (0 degrees for first region, 90 degrees for intermediate region, 0 degrees for second region) synchronized with the rolling shutter exposure sequence. This periodic phase modulation ensures that despite the staggered and varying exposure times across different rows, each row receives illumination at the optimal phase point, maintaining consistent signal amplitude and depth precision across the entire array while preserving continuous data acquisition capability.
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
This approach enhances the precision of depth information extraction by maximizing signal amplitude in the intermediate region of the pixel array, reducing errors, and achieving performance comparable to global shutter schemes while operating in a rolling shutter mode.
Implementation Method 1
emitting illumination light, of which an amount has been modulated by a modulation signal, towards a subject
Implementation Method 2
a light source configured to emit illumination light
Implementation Method 3
A pixel of the depth sensor includes a photoelectric conversion element. The photoelectric conversion element generates photocharges depending on an amount of light returning
Implementation Method 4
A difference between a projection time point of light and a detection time point thereof is referred to as time of flight (TOF). A distance to an object may be calculated using TOF
Data Source
AI summary
An apparatus and a method for acquiring depth information are disclosed. To acquire depth information, illumination light of which an amount of light has been modulated by a modulation signal is emitted towards a subject, and an image is captured using an image sensor. An image signal is sequentially acquired from a plurality of rows while shifting a phase of the illumination light at a start exposure time of a row belonging to an intermediate region of a pixel array region of the image sensor. Depth information is calculated from image signals acquired during a plurality of frames while shifting a phase of the modulation signal.