Endoscope Illumination Control for Rolling Shutter Exposure Uniformity
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Solution Overview
Problem
Endoscope apparatuses using CMOS image sensors face exposure unevenness issues due to pulsed illumination timing, leading to image quality deterioration, particularly when the intensity of illuminating light is not consistently controlled during video reading and all-line simultaneous exposure periods.
Innovation Solution
An endoscope apparatus and video processor that switch between two illumination modes: a first mode where light is applied in both exposure and reading periods, and a second mode where light is only applied in the exposure period, adjusting the drive signal to ensure simultaneous exposure of all lines and balancing light amounts between periods to maintain image brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pulsed illumination is provided during video reading period, then illuminating light amount can be reduced, but exposure unevenness occurs depending on timing of light emission
Solution Approach 1:
The illumination control is segmented into two distinct periods: all-line simultaneous exposure period where PWM control is applied, and video reading period where intensity-constant control is applied. This segmentation allows different control strategies to be used at different times, achieving both energy reduction and exposure uniformity.
Solution Approach 2:
The illumination control dynamically switches between PWM control mode and intensity-constant control mode based on the operational period. During all-line simultaneous exposure, PWM control dynamically adjusts light emission; during video reading, intensity-constant control maintains stable illumination, creating a dynamic adaptation to different operational requirements.
2Use of energy by moving object
If intensity-constant control is stopped in video reading period to further decrease illuminating light amount, then light consumption is reduced, but brightness of endoscopic image may be insufficient
Solution Approach 1:
The patent applies partial action by using intensity-constant control only during the video reading period when needed for image capture, rather than continuously. This partial application of constant intensity control balances energy reduction with maintaining sufficient image brightness when required.
Solution Approach 2:
The control strategy changes parameters based on operational phase: during all-line simultaneous exposure, PWM control varies the illumination parameters to reduce overall light amount; during video reading, intensity-constant control adjusts parameters to ensure sufficient brightness for image capture, achieving adaptive parameter optimization.
3Stability of the object's composition
If current level control is adjusted to make light amount continuous before and after transition, then illuminating light amount changes smoothly, but control complexity increases
Solution Approach 1:
The control system uses feedback mechanisms to monitor light amount during transitions between control modes. By detecting the actual illumination levels and adjusting control parameters accordingly, the system ensures continuous light amount changes while maintaining relatively simple control logic through automated feedback adjustment.
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 reduces luminance unevenness and maintains proper image brightness by adjusting the light emission based on the drive signal's current value, effectively addressing exposure unevenness and image quality issues.
Implementation Method 1
a light-emitting section configured to emit light for illuminating a subject; a drive section configured to generate a drive signal for causing the light to be emitted from the light-emitting section, the drive section enabling an amount of the light emitted by the light-emitting section to be changed according to a current value of the drive signal
Implementation Method 2
a rolling shutter-type image pickup device including a plurality of lines that receive reflected light from the subject to which the light is applied
Data Source
AI summary
An endoscope apparatus includes: a light-emitting element; a rolling shutter-type image pickup device allowing an exposure period in which the plurality of lines are simultaneously exposed and a reading period in which image pickup signals of the respective lines are sequentially read to be alternately switched to each other; and a control section. The control section controls an intensity of the light emitted by the light-emitting element. The control section can perform switching between a first illumination mode in which the light is applied from the light-emitting element in the exposure period and the reading period and a second illumination mode in which the light is applied from the light-emitting element only in the exposure period, and if the intensity of the light is controlled so as to have a predetermined value, performs control to switch one of the first mode and the second mode to the other.