• I Book revJeuJs

Description without sel

' A l p h a n u m e r i c dA~lays' G.F. Weston, R. Bitt leston, Granada, 1982, pp 194, £16.50

Display technologies are of growing importance, and the rate of change in development is creating a need for continual updating for practising scientists, engineers, and for those planning and teaching specialist courses. This book aims to fnlfil the need for the technologies poten- tially of use for the display of alphanumeric information.

The book deals effectively with the description and specification of both active and passive displays and reviews in some detail the fundamentals of each technology. With the exception of electro- mechanical systems, virtually all the current technologies and those in development are covered. Other chapters then deal with addressing techniques, alternative drive cir- cuits and the encoding and organi- zatiou of data.

In general the book is clear and readable, but there are a number of technical inconsistencies and omissions. Thus, in chapter six we are told that the electrical characterization of all LEDs is simi- lar, with breakdown voltages of around 15 V. Chapter seven then states that reverse breakdowns can be as low as 5V, whereas the Figure shows a diode with a very leaky reverse breakdown around 1- 2 V. The switching time of LCDs is quoted, but we are not told that this parameter is very sensitive to low temperatures. Filament displays are discussed, but the problems of dim- ruing are overlooked. In the detailed discussion of LED technol- ogy the importance of transparent GaP substrates on device perfor- mance is poorly explained.

:tion

3re serious, however, is tk ab- e of any practic~ guidanc fol ~ engineer with a choice 1 m; ~eliability is not discusso an :e is little attempt to rank tl va,= technologies in terms their..,,~mmoes and dJsadva~ and the reletive ccets of the displ_. and its drive electro~:s. The fact that LEDs cannot readily provide a simple large-area display, with a character height of say aS mm, while LCDs and electrolumines- cence can, is not obvious from the text. The writers also fail to distin-

guish sufficiently between the rela- tive technologies in terms of their development status - - are they readily available with a mature technology, or are they still very much in the research stage, more written about than produced and used?

As a result, the book falls short of the ambitious claim made on the jacket, that it will provide an invalu- able practical guide to all engineers engaged on displays. It does, how- ever, provide a useful and readable introduction to the subject for engineers and students.

Cerebral overload for students

'Fundamentals of interactive computer graphics' J.D. Foley, A. Van Dam, Addlnon- Wesley, 1982, pp 664, £15.95

To review a book like this properly would require considerable time for study and sufficient opportunities to employ some of the techniques and procedures outlined. This reviewer has taken the easy way out using a text well known and loved for com- parison as a benchmark. The benchmark text is 'Principles of interactive computer graphics' by Newman and Sproull, 1973 and 1979.

An examination of the indexes of each book reveals a 60 per cent hit rate with probably a further 20 per cent obscured by synonyms. The index to Foley and Van Dam is less thorough than Newman and Sproull's, for example, missing 'pipelining' mentioned on pages 30, 140, 141, etc from the listing. The 30 per cent difference appears to be due to the fact that Foley and Van

Peter Hart

Dam have introduced some more modern material, graphics stan- dards and colour to their text.

Both text titles do not do justice to their contents, as both go further than 'fundamentals' or ~rinciples' of interactive graphics. Many profes- sional graphics programmers and CAD package designers are known to delve into texts of this level for ideas and problem solutions.

Each book claims to fit the same marketplace, namely:

1. Earlier chapters for initial undergraduate teaching;

2. Earlier and central chapters for final-year undergraduate teaching;

3. Central and later chapters for post-graduate teaching.

They both do more than thisl In fact, in my opinion and that of col- leagues, much of the materialwould be too intensive for most students and would require careful presenta- tion to prevent cerebral overload.

188 DISPLAYS. JULY 1984