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A microdensitometer is an optical instrument used to measure optical densities in the microscopic domain. J. C. Dainty and R. Shaw, ''Image Science'' (Academic, New york, 1974).T. H. James, ''The Theory of the Photographic Process'' (Eastman Kodak, Rochester, 1977).
F. J. Duarte Francisco Javier "Frank" Duarte (born c. 1954) is a laser physicist and author/editor of several books on tunable lasers. His research on physical optics and laser development has won several awards, including an Engineering Excellence Award in ...
, ''Tunable Laser Optics'' (Elsevier Academic, New York, 2003) Chapter 10. A well-known microdensitometer, used in the photographic industry, is a granularity instrument or granularity machine. The
granularity Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is su ...
measurement involves the use of an optical aperture, 10-50 micrometers in diameter, and in the recording of thousands of
optical density Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". Alternatively, for samples which scatter light, absorbance may be defined as "the negative lo ...
readings. The standard deviation of this series of measurements is known as the ''granularity'' of the measured transmission surface, optical film, or photographic film, in particular . An alternative version to the traditional point-by-point microdensitometer is the beam expanded laser microdensitometer.F. J. Duarte, Electro-optical interferometric microdensitometer system, US Patent 5255069 (1993). This instrument can illuminate simultaneously an area a few centimeters wide with an ultra thin height, in the micrometer regime. Advantages include increased depth of focus, significant increases in data collection speed, and superior signal to noise ratios. In
microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of mi ...
applications, this type of ultra thin beam-expanded illumination can also be known as light sheet illumination or selective plane illumination. This measurement technique, using ultra-thin expanded laser beams, is particularly useful to detect microscopic imperfections in optical coatings or transmission optical surfaces.F. J. Duarte, ''Tunable Laser Applications'' (CRC, New York, 2009) Chapter 12.


See also

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Densitometer A densitometer is a device that measures the degree of darkness (the optical density) of a photographic or semitransparent material or of a reflecting surface. The densitometer is basically a light source aimed at a photoelectric cell. It determi ...
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Microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of mi ...
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N-slit interferometer The ''N''-slit interferometer is an extension of the double-slit interferometer also known as Young's double-slit interferometer. One of the first known uses of ''N''-slit arrays in optics was illustrated by Newton. In the first part of the twentie ...
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Particle size Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles (''bubbles''). The notion of particle size applies to particles in colloids, in ecology, in ...


References

{{reflist Optical metrology Microscopy Measuring instruments