Using YOLO (a convolutional neural network) for camouflage evaluation in combination with a genetic algorithm (GA) we investigated what details and colours are important for visual camouflage of a soldier. Depending on the distance, details like the face and legs or the soldier’s silhouette appeared most important for detection. GA optimization yielded a set of optimal colours that depended on whether the evolution targeted a specific location or (average over a) scene, as the immediate background in a scene differs per location. We validated our results in a human observer experiment.
Natural scenes are typically highly heterogeneous, making it difficult to assess camouflage effectiveness for moving objects since their local contrast varies with their momentary position. Camouflage performance is usually assessed through visual search and detection experiments involving human observers. However, such studies are time-consuming and expensive since they involve many observers and repetitions. Here, we show that a (state-of-the-art) convolutional neural network (YOLO) can be applied to measure the camouflage effectiveness of stationary and moving persons in a natural scene. The network is trained on human observer data. For each detection, it also provides the probability that the detected object is correctly classified as a person, which is directly related to camouflage effectiveness: more effective camouflage yields lower classification probabilities. By plotting the classification probability as a function of a person’s position in the scene, a ‘camouflage efficiency heatmap’ is obtained, that reflects the variation of camouflage effectiveness over the scene. Such a heatmap can for instance be used to determine locations in a scene where the person is most effectively camouflaged. Also, YOLO can be applied dynamically during a scene traversal, providing real-time feedback on a person’s detectability. We compared the YOLO-predicted classification probability for a soldier in camouflage clothing moving through a rural scene to human performance. Camouflage effectiveness predicted by YOLO agrees closely with human observer assessment. Thus, YOLO appears an efficient tool for the assessment of camouflage of static as well as dynamic objects.
In order to assess camouflage and the role of movement under widely ranging (lighting, weather, background) conditions simulation techniques are highly useful. However, sufficient level of fidelity of the simulated scenes is required to draw conclusions. Here, live recordings were obtained of moving soldiers and simulations of similar scenes were created. To assess the fidelity of the simulation a search experiment was carried out in which performance of recorded and simulated scenes was compared. Several movies of bushland environments were shown (recorded as well as simulated scenes) and participants were instructed to find the moving target as rapidly as possible within a time limit. In another experiment, visual conspicuity of the targets was measured. For static targets it is well known that the conspicuity (i.e., the maximum distance to detect a target in visual periphery) is a valid measure for camouflage efficiency as it predicts visual search performance. In the present study, we investigate whether conspicuity also predicts search performance for moving targets. In the conspicuity task, participants saw a short (560 ms) part of the movies used for the search experiments. This movie was presented in a loop such that the target moved forward, backward, forward, etcetera. Conspicuity was determined as follows: a participant starts by fixating a location in the scene far away from the target so that he/she is not able to detect it. Next, the participant fixates progressively closer to the target location until the target can just be detected in peripheral vision; at this point the distance to the target is recorded. As with static stimuli, we show that visual conspicuity predicts search performance. This suggests that conspicuity may be used as a means to establish whether simulated scenes show sufficiently fidelity to be used for camouflage assessment (and the effect of motion).
Targets that are well camouflaged under static conditions are often easily detected as soon as they start moving. We investigated and evaluated ways to design camouflage that dynamically adapts to the background and conceals the target while taking the variation in potential viewing directions into account. In a human observer experiment recorded imagery was used to simulate moving (either walking or running) and static soldiers, equipped with different types of camouflage patterns and viewed from different directions. Participants were instructed to search for the soldier and to make a speeded response as soon as they detected the soldier. Mean correct search times and mean detection probability were compared between soldiers in standard (Netherlands) Woodland uniform, in static camouflage (adapted to the local background) and in dynamically adapting camouflage. We investigated the effects of background type and variability on detection performance by varying the soldiers’ environment (like bushland, and urban). In general, performance was worse for dynamic soldiers compared to static soldiers, confirming the notion that motion breaks camouflage. Furthermore, camouflage performance of the static adaptive camouflage condition was generally much better than for the standard Woodland camouflage. Also, camouflage performance was found to depend on the background. When moving across a highly variable (heterogenous) background, dynamic camouflage turned out to be especially beneficial (i.e., performance was better in a bush environment than in an urban environment). Interestingly, our dynamic camouflage design was outperformed a method which simply displays the ‘exact’ background on the camouflage suit, since it is better capable of taking the variability in viewing directions into account. By combining new adaptive camouflage technologies with dynamic adaptive camouflage designs such as the one presented here it may become possible to prevent detection of moving targets in the (near) future.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.