Imaging Device Amplifier Gain Control for Dynamic Range
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Solution Overview
Problem
Existing imaging devices face challenges in achieving high-quality images with wide dynamic range and high readout speed, as the nonlinearity of amplifier circuits affects image quality when switching gain based on incident light.
Innovation Solution
The imaging device incorporates a pixel with a photoelectric converter, charge holding portion, and a readout circuit unit featuring an amplifier circuit, comparator, and switches, where the control unit manages the gain setting and switch states to optimize pixel signal output and maintain high readout speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gain of the amplifier circuit is switched for each pixel according to the amount of incident light, then the dynamic range is widened, but the readout speed decreases due to the time required for gain switching and signal settling
Solution Approach 1:
The patent applies preliminary action by determining the pixel signal level using a comparator before the amplifier gain is switched. The control unit predicts the appropriate gain based on the compared signal level, and the second switch is turned off in advance during charge transfer and settling periods. This preliminary determination allows the system to prepare for gain switching without waiting for the actual signal stabilization, thereby maintaining high readout speed while achieving wide dynamic range through adaptive gain selection.
2Reliability
If the gain of the amplifier circuit is switched based on incident light amount, then signal integrity is improved for varying light conditions, but luminance differences occur near the gain switching boundary
Solution Approach 1:
The patent implements feedback by using a comparator to continuously monitor the pixel signal level and provide this information to the control unit. The control unit uses this feedback to determine the appropriate gain setting and to identify pixels located near gain switching boundaries. Based on this feedback mechanism, the system can apply corrective measures to eliminate luminance differences at boundaries while maintaining accurate signal integrity across the full dynamic range through adaptive gain selection.
3Reliability
If the second switch is kept on during charge transfer to maintain signal continuity, then signal integrity is maintained, but the output unit becomes unstable during the transition period
Solution Approach 1:
The patent applies periodic action by controlling the second switch to be turned off during specific periods (charge transfer period and settling period) and turned on during the readout period. This periodic switching strategy ensures that the second switch is off when the first switch is on or during the settling period, preventing output instability. The switch is turned on again after settling to maintain signal continuity during normal operation, thus achieving both signal integrity and output stability through time-dependent control.
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 enables high-quality image acquisition without reducing readout speed by accurately determining pixel signal levels and adjusting amplifier gain, thereby correcting luminance differences and maintaining signal integrity across varying light conditions.
Implementation Method 1
a pixel including a photoelectric converter
Data Source
AI summary
The imaging device includes a pixel including a photoelectric converter, a first switch, a charge holding portion, and an output unit, an output line, a readout circuit unit connected to the output line, and a control unit. The readout circuit unit includes an amplifier circuit, a second switch between the output line and the amplifier circuit, and a comparator comparing the amplified pixel signal with a reference signal. The control unit performs outputting a pixel signal by transferring the charge in the photoelectric converter to the charge holding portion, determining a level of the pixel signal amplified by the amplifier circuit, and setting a gain of the amplifier circuit in accordance with a result of determination, and sets the second switch to off during the first switch is in on and until the output unit is settled after the first switch transitions from on to off.