Solid-State Image Pick-Up Device Parallel AD Conversion
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Solution Overview
Problem
In solid-state image pick-up devices, the conventional configuration with a column amplifier unit in front of the analog-digital conversion unit limits the reduction of analog-digital conversion time due to remaining count and settling times, necessitating a method to shorten the overall pixel signal reading time including analog-digital conversion.
Innovation Solution
A solid-state image pick-up device configuration featuring a pixel array unit, an amplifier unit, a sample and hold unit with at least three capacitors, and an analog-digital conversion unit, where the sample and hold unit temporarily holds pixel signals, allowing parallel settling and analog-digital conversion, thereby reducing the effective analog-digital conversion time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a column amplifier unit with AGC function is disposed in front of the analog-digital conversion unit, then the resolution of the analog-digital conversion unit can be lowered and count time can be shortened, but the remaining settling time and count time still limit the reduction of one AD time
Solution Approach 1:
The sample and hold unit performs preliminary action by holding the pixel signal at a specific moment, allowing the analog-digital conversion to start immediately without waiting for the column amplifier to complete settling. This separates the settling process from the conversion timing, enabling parallel operation and reducing total AD time.
Solution Approach 2:
The sample and hold unit acts as an intermediary between the column amplifier and the analog-digital conversion unit. It buffers the pixel signal, allowing the conversion unit to read from the held signal while the amplifier processes subsequent signals, thus decoupling the timing constraints of the two units.
2Ease of operation
If the column amplifier unit adjusts pixel signal levels before analog-digital conversion, then signal level adjustment is achieved, but the output voltage needs to continuously keep constant values during conversion causing subsequent pixels to wait
Solution Approach 1:
The sample and hold unit captures and holds the pixel signal at a specific moment before analog-digital conversion begins. This preliminary action freezes the signal value, allowing the conversion process to proceed independently without requiring the column amplifier to maintain constant output voltage, thus eliminating the waiting period for subsequent pixels.
Solution Approach 2:
The sample and hold unit serves as an intermediary that decouples the column amplifier from the analog-digital conversion unit. It takes the amplified signal, holds it at a specific voltage level, and provides this held signal to the conversion unit, allowing the amplifier to immediately process the next pixel signal while conversion occurs in parallel.
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 shortens the substantial pixel signal reading time by performing settling and analog-digital conversion in parallel, improving frame rate and reducing power consumption.
Implementation Method 1
a pixel array unit obtained by disposing a plurality of unit pixels, each of which includes a photoelectric conversion unit
Implementation Method 2
the sample and hold unit includes at least three capacitors that hold pixel signals
Data Source
AI summary
A solid-state image pick-up device of the present disclosure includes a pixel array unit obtained by disposing a plurality of unit pixels, each of which includes a photoelectric conversion unit, in a matrix form, an amplifier unit that adjusts a level of a pixel signal output from a unit pixel through a vertical signal line provided to correspond to column arrangement of the pixel array unit, a sample and hold unit that samples and holds a pixel signal passing through the amplifier unit, and an analog-digital conversion unit that converts the pixel signal output from the sample and hold unit into a digital signal. Further, the sample and hold unit includes at least three capacitors that hold pixel signals and performs fetching of a pixel signal to one capacitor and outputting of an image signal fetched to another capacitor in advance to the analog-digital conversion unit in parallel.