Photoelectric Conversion Apparatus Stabilizing Source Voltage Fluctuations
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Solution Overview
Problem
Existing photoelectric conversion apparatuses face noise issues due to capacitive coupling, particularly in the initial stages of operation and during large current flows, which affect the signal-to-noise ratio (S/N ratio) and detection precision in auto-focusing sensors.
Innovation Solution
The apparatus includes a sensor cell unit with a photodiode, a reset switch, and a select switch, where both switches are controlled to be conductive for a predetermined period to stabilize the source voltage fluctuations, enhancing the correlation between noise signals and reducing noise impact through capacitive coupling, thereby improving the S/N ratio and focus detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photoelectric conversion apparatus employs conventional switching control, then the device complexity is reduced, but noise is generated due to source voltage fluctuations affecting the photodiode potential through capacitive coupling
Solution Approach 1:
The invention applies preliminary action by setting both the reset switch and select switch to conductive states before the photodiode potential becomes sensitive to source voltage fluctuations. This preliminary switching configuration prevents noise generation by establishing a stable electrical path before signal accumulation begins, thereby improving the signal-to-noise ratio without requiring additional circuit components.
2Measurement precision
If the photodiode capacity is reduced to increase the number of focusing points, then the measurement precision of focus detection is improved, but noise impact increases due to reduced signal strength
Solution Approach 1:
By preliminarily configuring both switches to conductive states before signal accumulation, the invention stabilizes the electrical path and prevents source voltage fluctuations from coupling into the photodiode. This preliminary action maintains low noise levels even when photodiode capacity is reduced, thereby preserving signal-to-noise ratio while enabling higher measurement precision through increased focusing point density.
Solution Approach 2:
The invention implements feedback by continuously maintaining both switches in conductive states during the signal accumulation period. This feedback mechanism ensures that the electrical path remains stable and isolated from noise sources throughout the entire measurement process, compensating for the reduced signal strength from smaller photodiodes and maintaining high signal-to-noise ratio.
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 stabilizes potential fluctuations caused by parasitic capacitance, leading to improved S/N ratio and enhanced precision in focus detection, even in scenarios with reduced photodiode capacity.
Implementation Method 1
a sensor cell unit including a photoelectric conversion unit
Data Source
AI summary
Provided is a photoelectric conversion apparatus, including: a sensor cell unit including a photoelectric conversion unit, an amplification unit, a select switch, and a reset switch, the amplification unit including an input node and an output node; an output line; a signal processing unit; and a control unit. The output node is electrically connected to the signal processing unit via the select switch and via the output line in this order. The input node is electrically connected to the photoelectric conversion unit, and is electrically connected to the signal processing unit via the reset switch and via the output line in this order. The control unit controls the reset switch and the select switch to be both in a conductive state in a predetermined period.