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Automated laser optoelectronic system of face-on-skull reconstruction

 

R. M. Galiulin, B. G. Ilyasov, M. G. Mugattarov «OPTEL» Со., Ltd, Dep. of technical cybernetics, Ufa State Aviation Technical University, 12, K. Marx. Str., Ufa, 450000, Republic Bashkortostan, Russian Federation

 

ABSTRACT

 

In the article the information technology of the automated laser optoelectronic system of face-on-skull reconstruction are described. The information technology of the automated system as a whole is considered. The ways of solution of some problems, such as the laser non-contact measuring system are offered. The basic idea of the method consists in finding the main cranial points of a skull and relative ratio analysis of coordinates.

 

1. INTRODUCTION

 

The reconstruction of the face on skull can be executed by different methods. Usually the three methods of reconstruction are used: sculptural, graphical and combined-graphical with using the appearance elements figures.

The sculptural method is realized with the aid of rules of reconstruction, which had been developed by Gerasimov1. The graphics method can be executed by the expert, who possesses abilities to draw. The slides of a skull, which are used for comparison, and standard elements of appearance on transparent films with possibility for dimensioned drawing of separate individual tags are used in the combined graphical method. The main demand for using the above-described methods is execution of reconstruction made by expert in the field of anthropology, medicine, who has abilities of the artist - sculptor. The important step of reconstruction is the detailed investigation of common (floor, age, race), group (metrical and morphological tags) and individual tags of skull.

Thus, a knowledge level of expert determines reliability of used methods. And process of reconstruction takes long time and is very labour intensive.

The automated face on skull reconstruction consists of three main stages:

  а) the optoelectronic measurement of a skull shape and skull surface points2-3 ( Fig.1);

  b) the data analysis;

  c) the computer modelling of human face.

 

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Figure 1. The skull points model (a) and skull surface model (b) as result of optoelectronic measurement

 

The implementation of the second stage consists in definition of main cranial points on skull surface.

 

2. INFORMATION TECHNOLOGY OF FACE-ON-SKULL RECONSTRUCTION

 

The laser optoelectronic spatial computer-aided method of face-on-skull reconstruction is developed4. Application of triangulation and "shape from shadow" measuring methods in combination with source of laser beam of small diametre, conversion of the optical signal into video signal and its processing in the large dynamic range allows to carry out the measurements of objects. The complex-shaped objects, made from various materials, of various roughness and surface color can be measured too.

The informational technology of automated face-on-skull reconstruction is developed. This technology consists in stages of creation and transformation mathematical models of skull, face and face elements. For this purpose the following models are developed:

  {S0} – initial skull points model, which point coordinates are given in the Cartesian coordinates system;

  {S} – skull points model in cylindrical coordinates system;

  {S, T} – skull surface model, texture model data;

  {Znorm} – skull model as the normalized chain codes;

  {P} – identification skull model, which contains the characteristic attributes data of skull model;

  {S*, T*} – textured model of reconstructed surface;

  {REP} – base points coordinates array, in which it is necessary to move coordinates of face elements models;

  {SE, TE} – textured model of face element;

  {S*, T*, REP, SE1, TE1, …, SEk, TEk} – surface models of human face, which include surface, reconstructed on skull, the surface of human face and models of face elements, where k is a number of face elements.

According to the above-mentioned denotations, the developed information technology as face-on-skull reconstruction is shown in Figure 2 as stages of models creation and transformation.

The first stage during the automated face-on-skull reconstruction is initial skull points model creation. The initial skull points model {S0} is formed according to results of analysis of the measuring information based on the profile data. Each skull profile contains the three-dimensional skull surface points coordinates information.

The next stage is transformation from Cartesian coordinates system to cylindrical one according to initial skull points model. Then the skull surface model {S, T} by skull point model {S} is calculated. The next stage is to create the skull model as the normalized chain codes norm The identification skull model {P} is formed further. Information about geometrical distances attributes between craniometrical points and the characteristic craniometrical points are included in identification skull model {P}.

With the aid of existing rules of face on skull reconstruction on skull points model in a cylindrical coordinate system {S} the human face reconstruction {S*} is carried out and the reconstructed surface of human face {S*, T*} is formed.

The final stage of reconstruction process is the creation of human surface {S*, T*, REP, SE1, TE1, …, SEk, TEk} with face elements models {SE, TE}, which is based on the base points coordinates array {REP}.

Thus, during the automated face-on-skull reconstruction based on measuring information analysis results the human face model, which includes basic human face elements models: mouth model, nose model, left eye model, right eye model, etc., is formed.

 

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Figure 2. The stages of mathematical models transformation.

 

3. VERIFICATION OF DESIGNED AUTOMATED INFORMATION SYSTEM

For the purpose of developed automated face-on-skull reconstruction method verification the practical experiments of skull points measurement and automated reconstruction were carried out.

The visualization of measurement information as points and surface skull models is shown in Fig.1. The frame skull model is shown in Fig.3a. The result of automated face-on-skull reconstruction is shown in Fig.3b as an example of face elements set.

 

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Figure 3. The frame skull model (a) and result of face-on-skull reconstruction (b).

 

4. CONCLUSION

 

The problems caused by creation of automated face-on-skull reconstruction system are similar to common problems of expert systems design.

First, the creation of knowledge base with physiological interrelation between soft tissue and skull. Second, the pattern recognition system design for automated determination of characteristic metric skull points. Third, the creation of system, in which the possibility of additional learning and self-training will be stipulated.

Thus, designed automated face-on-skull reconstruction system solves the important applied scientific problem and can be used in criminalistics, anthropology areas, etc.

 

REFERENCES

 

1. M. M. Gerasimov, Bases of face on skull restoring, Moscow:"Sov. nauka", 1949.

2. Rav. M. Galiulin, Risch. М. Galiulin, Zh. М. Bakirov Possibilities of application of new laser measuring computer systems in antropology, in 2nd international congress of the ethnographers and anthropologists: The summary of the reports and messages (June 1-5, 1997), Vol.2, pp 61-62, Ufa:"Vostochnyj universitet", 1997.

3. Rav. M. Galiulin, Rish. M. Galiulin, Zh. M. Bakirov, "A fast laser digital systems for measuring geometry of biomedical objects," in Proceedings of 10th International Symposium on Development in Digital Measuring Instrumentation (ISDDMI'98) and 3th Workshop on ADC Modeling and Testing, IMEKO TC-4 Technical Committee on Measurement of Electrical Quantities, Naples, University of Naples Federico II, Volume III, 1998, pp. 917-919, Naples, Italy.

4. B. G. Ilyasov, R. M. Galiulin, M. G. Mugattarov Design of the automated system of face-on-scull reconstruction, in Proceedings of the Workshop on Computer Science and Information Technologies (CSIT'2000), Vol.1, pp. 294-296, Ufa, USATU, 2000.

 

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