Digital Motion Picture Camera Dynamic Range Expansion
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Solution Overview
Problem
Digital motion picture cameras face limitations in dynamic range due to the linear characteristic of integrating sensors, which restricts their use in applications requiring high dynamic range, such as cinema, where moving objects cause positional displacement of highlights when images with different exposure times are combined.
Innovation Solution
Combining images taken with different exposure times by aligning their time centers, allowing for the expansion of dynamic range without positional displacement of moving objects, using integrating sensor elements and a mechanical shutter, and optionally applying motion blur correction offline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If images with different exposure times are combined to expand dynamic range, then the dynamic range is improved, but moving objects cause positional displacement of highlights
Solution Approach 1:
The patent applies preliminary action by capturing a sequence of images with different exposure times (short, medium, long) in rapid succession before the object moves significantly. This ensures that the positional displacement between images remains minimal, allowing for accurate alignment and combination of highlights from different exposure images without requiring complex motion correction
2Ease of operation
If integrating sensors are used, then the output signal is proportional to exposure time and brightness, but the dynamic range is limited
Solution Approach 1:
The patent segments the dynamic range capture into multiple images with different exposure times. Each image captures a specific portion of the brightness range, and these segmented images are then combined to form a complete high dynamic range image, overcoming the limited dynamic range of individual integrating sensor exposures
3Reliability
If non-integrating sensors are used, then the dynamic range is large due to logarithmic characteristic, but the output signal depends on instantaneous brightness requiring constant lighting
Solution Approach 1:
The patent uses preliminary action by capturing multiple images in rapid succession with different exposure times before the lighting conditions change significantly. This allows the system to capture accurate brightness information across different exposure levels even when lighting is not perfectly constant, and the images can be aligned and combined to produce a high dynamic range result
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
The solution achieves a dynamic range comparable to or exceeding that of film cameras, enabling reliable high-quality image capture without complex movement estimation, and allows for the use of mechanical shutters like rotating mirror shutters.
Implementation Method 1
an optoelectronic sensor device having a plurality of sensor elements for the generation of received signals in dependence on the exposure time
Data Source
AI summary
A digital motion picture camera for the taking of motion pictures includes an optoelectronic sensor device having a plurality of sensor elements for the generation of received signals in dependence on the exposure time, a digitizing device for the digitizing of the received signals and an electronic control device for the control of the exposure time and the reading out of the received signals and for the evaluation of these received signals. A plurality of images taken with different exposure times are combined with one another by means of the control device, with the time centers of the images to be combined with one another between a respective start of recording and a respective end of recording coinciding at least substantially.