Patent Application
20180213220
The invention is designed to solve problems in camera evaluation, namely the selection of camera equipment based on tests under conditions that are different to the conditions under which the cameras will be used. This is a significant problem, particularly in law enforcement, security and medical imaging.
The invetion comprises an apparatus that enables the testing and comparison of moving or still images from multiple cameras, the cameras recording identical two and three dimensional moving reference test targets. Cameras to be tested and compared are placed on a support mechanism that enables one or more cameras to be aligned to the same field of view. Two or more cameras can be tested sequentially or, using beam splitting technology, well known in the trade, simultaneously in groups of one to three cameras. A second support mechanism comprising pre-programmed components, enables two and three dimensional reference test targets to be moved at varying speeds within the cameras' field of view. The reference test targets include life-size or scaled down 3-D reference test targets/human replica, along with test patterns incorporating color, resolution, dynamic range, framing elements as known in the trade. To illuminate the test targets under real-world conditions, multiple light sources positioned within or adjacent to the apparatus, provide illumination having color and brightness characteristics designed to match the brightness and spectral characteristics of typical real-world light sources, sunlight, incandescent, fluorescent, LED for example. To maintain the same lighting angle multiple illuminants having different spectral or brightness characteristics, should emanate from the same housing.
As long as man has been reproducing visual images on cave walls, the reproductions have fallen into two categories, accurate reproduction of a scene, or enhanced reproduction of the scene to produce a more pleasing image.
The identical situation exists in modern photography; precision reproduction of an image for accurate identification, or artistic enhancement and intentional distortion for visual effect.
Accurate image reproduction is particularly important in law enforcement and medical imaging where the accuracy of reproduction can mean the difference between life and death.
While today's digital imaging technology provides greater potential for accurate image reproduction, film based photography of the last century benefitted from a more stable image recording system, because cameras all used essentially the same image recording media and technology. Additionally, whereas previous illuminants, essentially sunlight or tungsten, were full spectrum light sources, today's illuminants such as LED and fluorescent, have discontinuous energy spectrums.
Digital imaging in different cameras not only uses different types of image sensing technology, CCD and CMOS for example, but there are variations within those systems such as sCMOS. This along with variability in the characteristics of the light sources illuminating a scene can result in significant differences in the images produced by such cameras.
While technology exists to test multiple cameras by recording the same test image in each camera and comparing results, cameras perform very differently one to another in real world conditions, particularly when photographing moving images.
The invention provides robotic test targets as identical moving objects, in this embodiment being shown as replicas of a human being, along with other reference images. By photographing an identical sequence of movements, of he same robotic target, under identical lighting conditions with different movie cameras, the invention enables performance differences between such movie cameras to be identified and quantified, facilitating selection of the most suitable camera for use in a particular application. For example, security cameras used in an airport would typically be operating under similar conditions of lighting both for brightness level and spectral characteristics, whereas a police officer's body camera needs to produce accurate constantly moving images under a wide variety of conditions from bright sunshine to a dimly-lit dark alley at night.
The invention is described by way of illustration with reference to the accompanying drawings in which:
Member (5) is attached to a cross frame (6) which is supported by beam member (7). Beam (7) is supported at each end on rails (1).
Three primary motor drives (8a), (8b), and (8c) enable rotatable member (5) and a robotic target, which in this embodiment is shown as a human replica, and/or other test target/s (4a) hanging from the member (5).
The target will typically have some movable components, such as the arms and legs. However the target may in fact be held stationary and the camera may be moved relative to the target. This may simulate a situation such as the body camera of a police officer, for example. The motor drives (8) are operable so that the target can be moved anywhere within the confines of the main frame (1) along both x and y axes and can be rotated 360 degrees. Other stationary or moving test targets (4b) may be included within the camera's field of view.
Thus the target can be moved across the field of view or advanced or returned, or moved in a diagonal direction, or rotated, by the primary motors (8).
Secondary motors (9a) and (9b) support the left and right side of test target (4) to provide vertical control of the target (4), while motors (9c), (9d), (9e) enable movement of other target elements, such as arms, legs and the like within or attached to test target (4).
The primary (8) and secondary motors (9) are controlled by software programs to provide, in this embodiment, a lifelike motion to the target, in this case the human replica. This is accomplished in part, in this case, by the secondary motors (9), which are operable to provide a side to side movement component, and an up and down movement component as the robotic target or human replica moves forward or backward or turns.
The robotic target (4) in this case is a form of marionette, having a torso and head, and having moveable arms and legs.
Test panels (4a), typically having separate segments of different colors and grey scales, known in the art, may be attached to the test target Two or more cameras can be tested sequentially or, using beam splitting technology known in the art, simultaneously in groups of one to three cameras, if desired.
A computer (12) supplies software control signals to motors 8 and 9. The program of movements can be varied to suit the typical situation for which the cameras are to be tested. In this way the movements and sequence of movements can be preselected and set, so that successive cameras can be tested under identical movements and simulated conditions.
Lighting such as lights (3) are supported from frame (6). Preferably four such lights are provided to provide uniform preselected lighting for the target, from all four corners.
Each light (3) may have, for example, four different light sources. These sources, may be LED, and/or fluorescent, and/or daylight and/or incandescent.
A control panel (11) is provided to pre set the light condition for each set of tests. While a manual control (11) is illustrated for the sake of simplicity, it will be understood that these settings could also be provided by the computer (10).
The lights (3) are supported from the frame (6) so that as the frame (6) moves according to the movement sequence selected, the lights will travel with it.
The target is thus illuminated uniformly through each sequence of test movements.
The control panel (11) provides individual manipulation of each color, including brightness, and other light characteristics. It will be appreciated that the actual lighting in any given real life experience may vary by a factor of 10,000 on a bright sunny day, to 1 in a dark alley or cellar. By providing the variety of light sources, and the control panel (11) it is possible to set simulated conditions as close as possible to those which the cameras will be experiencing, in the field.
In order to provide exact timing for the tests a flashing LED light (not shown) provides for exact synchronisation of each test run.
The camera itself is preferably on a movable carriage, and the camera can be rotated, raised or lowered, for various views and scenes.
This system enables scenes to be photographed over a range of 24 F stops, and enables the field of view FOV of each camera to be varied from wide angle to more restricted FOV, depending on the requirements for which the camera is being specified.
An example of the monitor display in
A monitor image from two cameras, A and B, is shown in
A monitor showing differences in shadow detail or color between cameras A and B is shown in
Four graphs in
Graph 1—indicates the Red, Green and Blue color error errors through the visible spectrum, indicated at the bottom of the graph. Camera C performs the best, producing minimal color distortion.
Graph 2—demonstrates the horizontal and vertical resolution reproduction capability of the cameras. Primarily used for body worn cameras, the graphs show resolution from a person standing still and simulated running; camera B gives the best performance of the cameras.
Graph 3—indicates skin tone reproduction accuracy for four different ethnic skin types, Asian, African, Caucasian and Indian. It is evident from the outset camera a reproduces dark African skin tones best.
Graph 4—plots how well a camera reproduces gray tones, both from a brightness perspective and deviation from neutrality, showing the red green and blue components. It is evident that camera A reproduces dark tones darker than it should and camera B. reproduces the same tones lighter than optimum.
It should be noted that these graphs are of one light source only; there would be similar graphs for the other three light sources.
In Operation:
The basic sequence of steps of method of evaluating movie cameras would be as follows:
a. establishing an enclosed space with predetermined controllable lighting conditions;
b. operating at least one robotic object performing a predetermined sequence of movements in the enclosed space under predetermined lighting conditions;
c. recording the scene in the enclosed space of the predetermined sequence of movements of the object with a first movie camera;
d recording the same scene in the same enclosed space with the identical set of predetermined sequence of movements and identical lighting of the object with a second movie camera; and,
e. comparing scenes recorded by said first movie camera with said scenes recorded by said second movie camera.
The foregoing are descriptions of preferred embodiments of the invention which are given here by way of example only.
This application is based on U.S. Provisional application Ser. No. 62/448,670 Title: CAMERA TESTING APPARATUS AND METHOD filed Jan. 20, 2017, the priority of which is claimed.
| Number | Date | Country | |
|---|---|---|---|
| 62448670 | Jan 2017 | US |
