The objective of this introductory paper is to lay a foundation for the papers to follow by providing the reader with some of the basics in the topics covered in this critical review. Specifically, the methods employ interferometry, holography, Doppler effect, and coherent optics. The principles of many optical diagnostics measurements can be understood simply and with very little mathematics, by using moird analogies. The dissemination of a technology can be limited by its complexity and difficulty of understanding by practitioners who would use the technology more if they simply understood it better. Therefore, simpler methods of teaching and understanding the technology and its limitations can themselves be considered breakthroughs in the technology.
In the past, holometry methods have been used primarily for problem solving in structures that were already in production, often where limited opportunities existed to make expensive modifications to existing tooling. Infrequently holometry was used by knowledgeable engineers to develop optimized components in the prototype stage even without the current CAE methods. The opportunity and challenge of our day is to closely couple CAE (FEA, EFA, BEA) methods and experimental methods (Computer Aided Holometry (CAH), modal, etc.) to optimize structural performance in the upstream product development process where necessary tooling modifications can and will be made. Holometry is used by American, European and Japanese automobile manufactures and several commercial sources for equipment and software are now available.
The capabilities of Ford USA’s CAH system for stepped phase interferometry are presented. Holographic test equipment and facilities are briefly reviewed. Fringe analysis algorithms and procedures for practical semiautomated processing of stepped phase interferograms of complex real life structures for quantitative measurement of deformation and shape are discussed. Several automotive applications illustrating the fringe analysis technique are presented.
Optical inspection is of increasing interest in industry since quality demands of the customer and safety regulations require to replace the human inspection by an automated quality control. This paper reviews the optical inspection technologies and methods used in industry refering to the four basic components of an automated inspection system: illumination, interaction of light with materials, detection and evaluation. Examples of practical solutions are given for explanation.
Diffraction moire interferometry involves the replication of a diffraction grating onto a specimen and the measurement of subsequent distortions of the grating through optical interferometry. The method is elegant, simple, easily applied and yields high quality data. Many devices have been developed to exploit this method, often for very specialized applications. There have also been several attempts to produce general purpose research instruments some of which have been offered commercially.
This paper will attempt to review the historical development of diffraction moire instrumentation, the current state of the art and future directions. A companion paper in this volume (SPIE CR-46) by JS Epstein will give a more complete review of specific uses of the subject.
The first portion of this review on moire interferometry concerns optical instrumentation aspects;1 the second deals with use of moire interferometry in recording material deformation and the implications of this deformation for assessing material reliability from a solid mechanics viewpoint. This review concentrates on a number experiments that demonstrate moire interferometry's ability to detect material deformation in a unique manner-we review the use of moire interferometry by the experimental mechanics community to answer questions posed by material scientists. Our review concludes with issues regarding moire interferometry and its transition from a basic research laboratory tool to applied technology arenas.
Holography is expected to become a potential tool for achieving in very near future scientific and industrial three-dimensional cinematography. First, we describe the use of 35-mm to 126-mm films for recording cineholograms with single exposure of time-varying reflecting objects at a frequency of 25 Hz. Thereafter, we report on double-exposure interferometric cineholography for non destructive testing applications.
Recent developments of interferometric techniques for industrial inspection in Japan are reviewed, with special emphasis on automatic fringe analysis, use of unique interferometers, use of advanced devices.
Infrared imaging and radiometry in the commercial sector have been available since the mid 1960's. Since that time, there has been an increase in the number and types of equipment available, and the applications for which infrared is used. This paper presents an overview of the technology itself and many of the current applications.