Intensity image-embedded binary holograms

Abstract

Past research has demonstrated that, by downsampling the source object scene in multiple directions, a binary Fresnel hologram can be generated to preserve favorable quality on the reconstructed image. In this paper, we will show that a binary hologram generated with such an approach is also insensitive to noise contamination. On this basis, we propose a method to embed an intensity image into the binary hologram. To prevent the embedded information from being tampered or retrieved with unauthorized means, scrambling is applied to relocate each pixel to a unique position in the binary hologram according to a random assignment that is only known with the availability of a descrambling key. Experimental results demonstrate that our proposed method is capable of embedding an intensity image that is one quarter the size of the binary hologram without causing observable degradation on the reconstructed image. In addition, the embedded image can be retrieved with acceptable quality even if the binary hologram is damaged and contaminated with noise.

Embedding intensity image in grid-cross down-sampling (GCD) binary holograms based on block truncation coding

“…As demonstrated in [15], the GCD binary hologram can tolerate up to 30% of noise (complementing the binary states of pixels) and still preserve good fidelity with peak-signal-to-noise-ratio (PSNR) of around 28db on the reconstructed image. Based on this finding, a binary image can be embedded in the GCD binary hologram simply by replacing the hologram pixels.…”

“…For clarity of explanation, we shall describe briefly the binary hologram generation process that is based on the down-sampling of the object scene, and adopted in the parent method [15]. To start with, we consider an object scene composing of a threedimensional (3D) surface.…”

“…It has also been demonstrated that a binary hologram generated with such means can tolerate up to 30% of noise contamination (negating the binary state of each corrupted pixel) without causing noticeable degradation on the reconstructed image. Based on this property, as reported in [15], a binary image can be embedded in a binary hologram simply by changing the values (black to white, or vice versa) of some of the hologram pixels. As the hologram pixels are binary, the intensity image to be embedded is first converted into a binary form with error diffusion, a technique that is commonly employed in the printing industry for presenting continuous tone picture with black and white dots.…”

“…The approach is different from existing techniques for hiding or encrypting images into a hologram, such as compressive [16], the joint transform correlator architecture [17], the cascaded Fresnel digital holograms [18,19], random phase encoding scheme [20][21][22][23], and the integration of QPSK modulation and phase shifting holography [24]. In the above-mentioned methods, a gray level hologram is generated to record the embedded image, whereas the scheme in [15] is applicable to a binary hologram. On the downside, the visual quality of the embedded image is substantially degraded after the error diffusion process.…”

“…For clarity of explanation, a brief outline on the binary hologram generation and the intensity image embedding method reported in [15] (hereafter referred to as the parent method) is given in Section 2. Our proposed method to embed an intensity image, through the use of the block truncation coding, into the binary image is presented in Section 3.…”