Exposure Control Unit for Accurate Subject Light Detection
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Solution Overview
Problem
Existing exposure control systems for cameras face challenges in accurately detecting the light quantity of a desired subject in scenes with both bright and dark elements, leading to difficulties in precise exposure control.
Innovation Solution
An exposure control unit comprising a photometer with multiple zones, a designator, calculators, and an exposure controller, which calculates differences in light values between target and neighboring zones to categorize areas as low- or high-luminous, allowing for accurate exposure control based on these classifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photometer is used to detect light quantity in divided photometric zones, then the area can be divided into multiple zones for detection, but it becomes difficult to accurately detect the light quantity of the desired subject when the scene has large quantity of light and the subject has small quantity of light
Solution Approach 1:
The photometric zones are further segmented into evaluation zones and non-evaluation zones based on luminance threshold comparisons. This segmentation allows the system to focus measurement efforts on zones containing the desired subject while excluding zones dominated by bright background elements, thereby improving subject light quantity detection accuracy.
Solution Approach 2:
Different evaluation criteria are applied to different photometric zones based on their local luminance characteristics. Zones with luminance values below the threshold are identified as potential subject zones and given higher evaluation priority, while zones above the threshold are treated as background. This local quality differentiation enables accurate subject detection in high-contrast scenes.
2Reliability
If exposure control is performed based on brightness measured by a photometer, then exposure can be controlled, but it is difficult to control exposure accurately when there is a scene with large quantity of light and a subject with small quantity of light
Solution Approach 1:
The system segments photometric zones into evaluation and non-evaluation categories based on luminance threshold comparisons. By excluding bright background zones from evaluation and focusing only on zones with luminance below the threshold, the system accurately measures subject light quantity and achieves reliable exposure control even in high-contrast scenes.
Solution Approach 2:
The invention extracts and isolates the subject region from the overall scene by identifying photometric zones with luminance values below the threshold. This extraction process separates the subject measurement from the interfering bright background, enabling accurate exposure control based solely on subject light quantity.
3Area of stationary object
If the photometer detects light from the entire area including both bright background and dark subject, then all areas are covered, but the desired subject's light quantity cannot be accurately detected
Solution Approach 1:
While maintaining comprehensive photometric coverage of the entire imaging area, the system segments zones into evaluation and non-evaluation categories. This segmentation allows the system to utilize data from all zones for coverage while selectively evaluating only those zones containing the desired subject, thereby achieving both full area coverage and accurate subject measurement.
Solution Approach 2:
The system applies different evaluation qualities to different zones based on their luminance characteristics. Zones below the luminance threshold are marked as subject-containing zones requiring accurate measurement, while zones above the threshold are marked as background zones to be excluded from subject evaluation. This local quality differentiation enables simultaneous full coverage and precise subject measurement.
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 precise exposure control by accurately estimating light quantities for both bright and dark subjects, improving image capture quality, especially under front or rear lighting conditions.
Implementation Method 1
The photometer comprises a plurality of photometric zones on a light-receiving surface. An optical image of an object to be imaged by the imaging apparatus is made incident on the light-receiving surface of the photometer. Each of the photometric zones detects a partial quantity of light incident on each photometric zone.
Data Source
AI summary
An exposure control unit comprising a photometer, a designator, a first calculator, a first counter, a selector, a second calculator, a categorizer, and an exposure controller is provided. The photometer comprises a plurality of photometric zones. The designator designates the photometric zones one by one as a target zone. The first calculator calculates a first difference. The first counter counts a first determination number. The selector selects the target zone of which the first determination number is greater than a second threshold. The second calculator calculates a categorization value. The categorizer categorizes a target zone into low- or high-luminous zones. The exposure controller controls an exposure of the imaging apparatus on the basis of the partial value of light for one of the low- and high-luminous zones.