This will count as one of your downloads.
You will have access to both the presentation and article (if available).
Method of optical encryption with spatially incoherent illumination does not have drawbacks inherent to coherent techniques but provides lower security.
State of the art encryption techniques implement asymmetric encryption which entails that there is no exchange of encryption keys between the sender and receiver. In case of interception of encrypted messages hacker will not be able to decrypt them. There are several asymmetric optical encryption techniques based on DRPE technique. Typically light phase distribution serves as an open key, while amplitude distribution serves as a secret key. However there are no such techniques implementing spatially-incoherent illumination due to limitation to amplitude only registration. We propose for the first time asymmetric optical encryption technique implementing spatially-incoherent illumination. Procedure is described as follows. User 1 optically encrypts information using key 1 and sends it to user 2. User 2 encrypts received data using key 2 and sends it back to user 1. In order to verify identity of user 2, user 1 checks if received data correspond to certain parameters which are unique to user 2 and serve as an additional secret key. If identity check is passed, user 1 decrypts received data using key 1 and sends it back to user 2. Finally, user 2 decrypts received data using key 2 and obtains information. Results of computer simulations of asymmetric optical encryption implementing spatially incoherent illumination are presented.
The evaluation shows that not every DMD-chip has acceptable optical quality for its application as display device for Fourier holograms. It was determined that major factor of reconstructed image quality degradation is a curvature of surface of SLM or its safety glass. Ranging hologram size allowed to estimate approximate size of sufficiently flat area of SLM matrix. For tested SLM it was about 1.5 mm. Further hologram size increase led to significant reconstructed image quality degradation.
Developed and applied a technique allows to quickly estimate maximum size of holograms that can be displayed with specific SLM without significant degradation of reconstructed image. Additionally it allows to identify areas on the SLM with increased curvature of the surface.
Method of optical encryption with spatially incoherent illumination does not have drawbacks inherent to coherent systems, however, as only light intensity distribution is considered, mean value of image to be encrypted is always above zero which leads to intensive zero spatial frequency peak in image spectrum. Therefore, in case of spatially incoherent illumination, image spectrum, as well as encryption key spectrum, cannot be white. If encryption is based on convolution operation, no matter coherent light used or not, Fourier spectrum amplitude distribution of encryption key should overlap Fourier spectrum amplitude distribution of image to be encrypted otherwise loss of information is unavoidable.
Another factor affecting decrypted image quality is original image spectrum. Usually, most part of image energy is concentrated in area of low frequencies. Consequently, only this area in encrypted image contains information about original image, while other areas contain only noise. We propose to use additional encoding of input scene to increase size of the area containing useful information. This provides increase of signal-to-noise ratio in encrypted image and consequentially increases quality of decrypted images.
Results of computer simulations of test images optical encryption with spatially incoherent illumination and additional input amplitude masks are presented.
Increasing quality of computer-generated kinoforms using direct search with random trajectory method
View contact details
No SPIE Account? Create one
