Indirect ToF Pixel Layout for Uniform Depth Image Rows
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Solution Overview
Problem
Display variation in depth images occurs in the vertical direction due to differences in voltage drop magnitude for each row of pixels in distance measuring devices using indirect time of flight methods.
Innovation Solution
Incorporating light-shielded pixels with a light-shielding film on both ends of the row direction, which act as zero reset signals for AD conversion circuits, ensuring consistent voltage levels across rows and inhibiting display variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple rows of pixels are used to increase the depth image resolution, then the measurement precision is improved, but display variation in the vertical direction occurs due to different voltage drops for each row
Solution Approach 1:
The patent changes the operational parameters of pixels in different rows by applying different reset levels. Specifically, pixels in rows other than the reference row are reset to a level corresponding to a predetermined light amount, while the reference row pixels maintain normal operation. This parameter differentiation compensates for the voltage drop variations across rows, ensuring that depth image signals from all rows have consistent baseline levels and eliminating vertical display variation.
2Device complexity
If AD conversion is performed for each row to reduce processing complexity, then the device complexity is reduced, but voltage drop differences between rows cause display variation
Solution Approach 1:
The patent implements a parameter change strategy where the reset level parameter is differentiated by row. A reference row is selected to maintain normal reset operation, while other rows are reset to a predetermined light amount level. This simple parameter modification approach maintains the existing AD conversion architecture without adding complex processing circuits, yet effectively compensates for voltage drop variations and ensures display consistency across all rows.
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 configuration effectively inhibits variations in AD conversion results between rows, thereby reducing display variations in depth images, including those caused by vertical shading, streaking, and power supply rejection ratio (PSRR).
Implementation Method 1
a plurality of light-shielded pixels provided in the column direction on at least one of two end sides in the row direction with respect to a region provided with the plurality of valid pixels, each of the plurality of light-shielded pixels being covered with a light-shielding film
Data Source
AI summary
A distance measuring device (500) including a plurality of pixels (11a, 12a) provided in a row direction and a column direction, a plurality of AD conversion circuits (6, 7) provided in the row direction, each of the plurality of AD conversion circuits performing AD conversion on pixel signals of a corresponding column, and a signal processing section (92) that generates a depth image signal based on conversion results of the plurality of AD conversion circuits, wherein the plurality of pixels (11a, 12a) include a plurality of valid pixels (11a) provided in the row direction and the column direction to correspond to the depth image signal, each of the valid pixels including a plurality of charge transfer sections (TA, TB) that extract pixel signals corresponding to a light amount of incident light in different periods, and a plurality of light-shielded pixels (12a) provided in the column direction on at least one of two end sides in the row direction with respect to a region provided with the plurality of valid pixels (11a), each of the plurality of light-shielded pixels being covered with a light-shielding film (M).