**7. Conclusion**

92 Holograms – Recording Materials and Applications

(,) sin -

In the extreme case, when *z* → ∞ (or 2 2 *x y* + → 0 ) equations (6 and 7) become quite simple:

Equations (8) can be used for holograms of up to 1.5x1.5 cm in size, with holograms of larger sizes demonstrating a noticeable color distortion and irregularity of the brightness of pixels

In the photos presented in Fig.24, one can see two holograms of the same size recorded on the basis of the same original image, a uniform background of a certain color. In case of Fig.24a, calculation was made according to the formulas in (8), and in case of Fig.24b, taking into account the formula in (7). It is clearly seen that in the first case, the brightness of pixels in the direction of observation strongly depends on the position of pixels in the hologram.

Fig. 24. Photos of a recovered image from a dot-matrix hologram recorded on As40S20Se40

Calculation of pixel parameters for stereograms or kinematic effects is similar to the considered case. It is only necessary to take into account a new position of observation of the hologram that can be achieved by replacing the old variables (,) *x y* in formulas (4)-(7) by the new ones (,) *x xy y* −Δ −Δ , where ( , ) Δ Δ *x y* indicate displacement of the observer in the

b) Orientation angle of diffraction grating depending on the position of pixels

photoresist. a) Orientation angle of diffraction grating of all pixels

*x*

*z y*

ϕ

θ

<sup>1</sup> (,) <sup>1</sup>

*<sup>y</sup> fxy f dxy z*

( , ) sin

= ≈−

θ

(,) 0 *x y* ≈ (8)

<sup>≈</sup> , (7)

ϕ *= 0* 

> ϕ *= K x*

, where <sup>1</sup>

0 0 *<sup>f</sup> <sup>d</sup>*<sup>−</sup> <sup>=</sup> (6)

, or the equivalent 0

*x y*

<sup>0</sup> *dxy d* (,) ≈ and

with the distance from hologram to observer, as mentioned above, 30 *z cm* ≈ .

ϕ

<sup>0</sup> (,) 1

in the hologram area.

observation plane.

≈ −

and

*<sup>d</sup> dxy <sup>y</sup>*

sin

θ

*z*

The developed and assembled optical devices for dot-matrix holographic and image-matrix recording have been successfully used for scientific purposes as well as for producing holograms for the protection and identification of industrial products and documents. Its compact dimensions, reliability and low cost price may be interesting for the needs of small and medium size business enterprises.

The possibilities of hologram recording on As-S-Se chalcogenide films have been studied. The obtained results show that the above mentioned chalcogenides may be successfully used in applied dot-matrix and image-matrix holography as an excellent alternative to organic photoresists for producing high-quality security holograms with high diffraction efficiency up to 65%. The increase in film sensitivity with increase of the exposure power density has been discovered. It makes the application of pulse recording attractive.

#### **8. Acknowledgments**

This research was partly supported by the ESF project "Starpdisciplinārās zinātniskās grupas izveidošana jaunu fluorescentu materiālu un metožu izstrādei un ieviešanai" Nr. 2009/0205/1DP/1.1.1.2.0/09/APIA/VIAA/152

### **9. References**


**5** 

*Japan* 

**Azobenzene-Containing Materials for Hologram** 

With the development of information technology, quick rate of data transfer and high capacity of data storage are expected for advanced recording media. Although data storage media and technique have been developed from soft discs, hard disk, CD-ROM and DVD-ROM to multi-layered blue-ray discs, undoubtedly, holography is one of the most fascinating and attractive techniques. As shown in Figure 1, which illustrates comparison of media in data storage and holographic ones. The optical holography is based on a threedimensional storage method (Bieringer, 2000; Kogelnik, 1969). This provides unique opportunities for the next-generation storage technique by a simple recording and reading

Fig. 1. Comparison of several data storage media (above) and scheme of holographic storage

**1. Introduction** 

process.

(below).

*Top Runner Incubation Center for Academia-Industry Fusion and Department of* 

*Materials Science and Technology, Nagaoka University of Technology,* 

Haifeng Yu and Takaomi Kobayashi

