Eur. Phys. J. Appl. Phys. 44, 261–272 (2008) DOI: 10.1051/epjap:2008172 T HE EUROPEAN P HYSICAL JOURNAL APPLIED PHYSICS Real-time optical 2D wavelet transform based on the JPEG2000 standards A. Alkholidi 1 , A. Cottour 1 , A. Alfalou 1, a , H. Hamam 2 , and G. Keryer 1 1 Laboratoire Brest-ISEN (L@BISEN), Institut Sup´ erieur d’ ´ Electronique et du Num´ erique de Brest, France 2 Facult´ e d’Ing´ enierie, Universit´ e de Moncton, Canada Received: 22 August 2007 / Received in final form: 5 May 2008 / Accepted: 28 August 2008 Published online: 24 October 2008 –c  EDP Sciences Abstract. In image processing, the Wavelet Transform (WT) is largely used. However, time requirements for large two-dimensional image transforms are hard to meet with sequential implementations. Parallel implementation decreases the processing time and allows to reach a real-time operation in image coding. Unfortunately, this parallel coding increases the hardware complexity. We propose an optical implementa- tion of the JPEG2000 compression using a special implementation of the WT. Special attention is paid to propose a simple all optical setup carrying out the optical implementation of JPEG2000 compression for gray-level images. Finally, an adaptation of our technique to colored images is proposed. PACS. 42.30.Kq Fourier optics – 42.30.Va Image forming and processing – 42.30.Tz Computer vision; robotic vision Wb 1 Introduction Multimedia data do not cease to grow in the fields of com- puting, internet or televisual environment, and they now reach new markets, such as mobile network. This increase in the volume of data is associated with a very strong de- mand for flexibility of data handling in order to offer a better service to the user. One of the forms of data is the image, which can stand alone or be an element of a video sequence. To store and facilitate the exchange of images in various fields as satellite photography, medical imag- ing, color telefax or cartography..., it is necessary to set up a standard and international format for these images. For this purpose, intensive research has been carried out to select relevant information, numerically or by using co- herent optics. For digital solutions, we quote two typical algorithms of compression: JPEG, and JPEG2000. Currently, JPEG is a standard that is commonly used in the field of fixed image compression (digital photog- raphy). It is very competitive today for low or medium compression ratios. However it has several limits: 1. the image is severely altered (low image quality) for high compression ratios; 2. standard JPEG does not allow to code by area of in- terest; 3. the images that include some texts have low quality when they are compressed by standard JPEG because high spatial frequencies, i.e. edges, are badly com- pressed. a e-mail: ayman.al-falou@isen.fr As a consequence, it was necessary to develop other com- pression standards based on more appropriate transforms. Among various possibilities, the Wavelet Transform (WT) attracted particularly the attention of the concerned sci- entific committee. Indeed, wavelet transforms are used in many practical applications [1] in signal processing, im- age processing, pattern recognition, and feature extrac- tion. Because the wavelet transform of an image is funda- mentally given by a correlation of this image with a family of daughter wavelets, any real-time correlator can be able to implement the wavelet transform. The wavelet trans- form is an important linear time-frequency representation. It allows to represent a signal both in time and frequency planes. It has become a highly efficient tool for time fre- quency analysis of short transient signals. The WT has also appeared to accurately describe the response curves of the human eye and it has proved to be applicable to dif- ferent fields, such as pattern recognition, sound analysis, fractal aggregates, and image compression [2–4]. Limits of JPEG and advantages of WT motivated the JTC (Joined Technical Committee) to call, in March 1997, for contributions to launch a new standard. Thus, the JPEG2000 was born to overcome these limits. Since December 2000, the JPEG2000 has been used as an in- ternational standard. This standard offers many advan- tages [4]: 1. it overcomes the initial limits of the JPEG format; 2. it enables a progressive display, i.e. we can display an image either by increasing visual quality gradually, or by increasing the image resolution gradually. Article published by EDP Sciences