Endoscope Image Sensor Charge Amplification for Fluorescence
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Solution Overview
Problem
Current image pick-up devices for endoscopes face challenges in achieving optimal brightness and signal-to-noise ratio, especially in auto-fluorescent observation where weak fluorescent light requires high sensitivity and controlled amplification to distinguish between normal tissue and tumors.
Innovation Solution
An endoscope apparatus with an image pick-up device that includes a Charge Multiplying Device (CMD) and an amplifying circuit, along with a light-amount control system, adjusts the amplification rate and light exposure to maintain desired image brightness by comparing signal amplitudes with target values, using a rotating filter wheel and motorized filters to control illumination and amplification dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amplification rate is increased to improve sensitivity for weak fluorescent light, then the signal-to-noise ratio deteriorates due to reading noises
Solution Approach 1:
The patent applies preliminary action by performing charge amplification within the CCD before the reading operation. The CMD (Charge Multiplying Device) amplifies the accumulated charges during the transfer period, so that when the charges are read out, they already have enhanced signal strength. This preliminary amplification ensures that the signal-to-noise ratio is improved because the amplification occurs before the reading noise is introduced, effectively making the signal stronger relative to the subsequent reading noise.
2Reliability
If the amplification rate is increased to improve sensitivity, then electromagnetic discharge increases causing safety issues
Solution Approach 1:
The patent performs the amplification action preliminarily within the safe operating conditions of the CCD's CMD during the charge transfer phase, before the system would need to operate at higher amplification rates that could cause electromagnetic discharge. By completing the necessary amplification within the sensor's safe operating parameters, the system achieves high sensitivity without exceeding the voltage and current thresholds that would trigger harmful electromagnetic discharge.
3Illumination intensity
If the amplitude of the image signal is increased to improve brightness, then the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies preliminary action by amplifying the charge signals within the CCD before they are converted to voltage signals and subjected to subsequent amplification stages. This early amplification in the charge domain, while the signals are still in the form of accumulated electrons, improves the signal-to-noise ratio because it occurs before the introduction of reading noises and other disturbances that would affect later amplification stages.
4Device complexity
If the amplification is performed outside the CCD, then the reading noise influence increases, but the device complexity is reduced
Solution Approach 1:
The patent merges the amplification function directly into the CCD structure by integrating the CMD (Charge Multiplying Device) within the charge transfer channels. This combination allows the CCD to perform internal amplification of the accumulated charges before they are read out, thereby reducing the influence of reading noises. The merging of the amplification function with the image sensor eliminates the need for separate external amplification stages while improving the 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 solution enables high-sensitivity image capture with improved signal-to-noise ratio, allowing for clear differentiation between normal and tumor tissues, while ensuring electrical safety and preventing unnecessary electromagnetic discharge.
Implementation Method 1
The CCD comprises a CMD (Charge Multiplying Device) arranged therein which can increase the charges by using the ionization
Implementation Method 2
the auto-fluorescent spectrums outputted from the living-body tissue are varied between the normal mucous membrane and the tumor upon hitting the ultraviolet to blue excitation light to the living-body tissue
Data Source
AI summary
An image pick-up apparatus includes an image pick-up device which picks-up an image of a subject and outputs an image signal, a first-amplitude changing portion which varies an amplitude of the image signal outputted form the image pick-up device, a second-amplitude changing portion which varies the amplitude of the image signal to be outputted, a comparing portion which compares the amplitude of the image signal with a value of a target amplitude, and a control portion which controls the first- and second-amplitude changing portions based on the comparison result of the comparing portion and changes the amplitude of the image signal so that it is approximate to the target amplitude so that an observed image of the subject displayed on display means has a desired brightness.