Image Sensor Gradation Conversion for Lower-Bandwidth Output
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Solution Overview
Problem
Current imaging apparatuses face challenges in transmitting high-bit-depth digital image signals efficiently, leading to increased costs and manufacturing difficulties due to the need for wider transmission bandwidths and more pins, as well as complex compression and expansion processes.
Innovation Solution
An image sensor with a pixel unit, A/D converter, gradation converter, and selector that performs gradation conversion based on human visual sensation characteristics and display apparatus gradation characteristics, reducing the bit width of digital image signals through selective gradation conversion, allowing for efficient transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the transmitting frequency is raised or the number of transmission pins is increased to transmit multibit digital image signals, then the transmission bandwidth is improved, but the manufacturing cost and difficulty increase
Solution Approach 1:
The patent applies parameter changes by converting the digital image signal from a multibit format to a reduced-bit format through gradation conversion. This changes the bit depth parameter from 10 bits or more to a lower number of bits, thereby reducing the transmission bandwidth requirement without increasing manufacturing complexity. The gradation conversion unit performs nonlinear transformation of the digital signal based on human visual characteristics, achieving efficient compression that allows standard transmission infrastructure to handle high-resolution images.
2Quantity of substance
If compression processes are applied to reduce data transmission amount, then the transmission bandwidth requirement is reduced, but the circuit scale and manufacturing cost increase
Solution Approach 1:
The patent uses parameter changes through gradation conversion that transforms the bit depth parameter from multibit to reduced-bit format. This nonlinear transformation based on human visual characteristics achieves significant data reduction without requiring complex compression algorithms. The conversion unit implements efficient bit-depth reduction that maintains image quality within perceptual thresholds while dramatically reducing the data transmission amount.
Solution Approach 2:
The patent employs a simple, cost-effective gradation conversion approach that sacrifices some digital precision in exchange for dramatically reduced transmission requirements. By converting to a lower bit depth format that is sufficient for human visual perception, the system uses a simpler, more economical transmission scheme without requiring expensive high-bandwidth infrastructure or complex compression hardware.
3Quantity of substance
If the bit width of digital image signals is reduced through gradation conversion, then the transmission bandwidth is reduced, but the image quality may deteriorate
Solution Approach 1:
The patent applies parameter changes through nonlinear gradation conversion that transforms the digital signal based on human visual characteristics. This conversion changes the distribution of quantization levels to match human perception thresholds, allocating more precision where the human eye is most sensitive and less precision where it is less sensitive. This maintains perceived image quality while reducing the actual bit depth and transmission bandwidth requirements.
Solution Approach 2:
The gradation conversion implements local quality adaptation by applying different conversion characteristics to different luminance ranges. The conversion unit adjusts the transformation function based on local luminance levels, preserving fine gradation in shadow and highlight regions where human vision is most sensitive while using coarser quantization in mid-tone regions. This localized approach maintains overall image quality while achieving efficient compression.
Data Source
AI summary
There is provided an image sensor comprising: a pixel unit having a plurality of pixels; an A/D converter which converts an image signal from the pixel into a digital image signal; a gradation converter which performs a gradation conversion to the digital image signal; and a selector which selects gradation converting characteristics of the gradation conversion to the digital image signal performed by the gradation converter.