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measuring the optical density of a substance by shining light on it and measuring its transmission

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/09/30 00:31:36」(JST)

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Densitometry is the quantitative measurement of optical density in light-sensitive materials, such as photographic paper or photographic film, due to exposure to light. Optical density is a result of the darkness of a developed picture and can be expressed absolutely as the number of dark spots (i.e., silver grains in developed films) in a given area, but usually it is a relative value, expressed in a scale.

Since density is usually measured by the decrease in the amount of light which shines through a transparent film, it is also called absorptiometry, the measure of light absorption through the medium. The corresponding measuring device is called a densitometer (absorptiometer). The decadic (base-10) logarithm of the reciprocal of the transmittance is called the absorbance or density.^[1]

DMax and DMin refer to the maximum and minimum density that can be produced by the material. The difference between the two is the density range.^[1] The density range is related to the exposure range (dynamic range), which is the range of light intensity that is represented by the recording, via the Hurter–Driffield curve. In the context of photography, the dynamic range is often measured in "stops", which is the binary logarithm of the ratio of highest and lowest distinguishable exposures; in an engineering context, the dynamic range is usually given by its decadic logarithm expressed in decibels.

Uses

According to the principle of operation of the densitometer, one can have:

spot densitometry: the value of light absorption is measured at a single spot
line densitometry: the values of successive spots along a dimension are expressed as a graph
bidimensional densitometry: the values of light absorption are expressed as a 2D synthetic image, usually using false-color shading

Dual-energy X-ray absorptiometry is used in medicine to evaluate calcium bone density, which is altered in several diseases such as osteopenia and osteoporosis. Special devices have been developed and are in current use for clinical diagnosis, called bone densitometers.

References

^ ^a ^b Davies, Adrian (2005). The Focal Digital Imaging A-Z. Focal Press. ISBN 0-240-51980-9.

External links

Fundamentals of Densitometry, by Mark Vivino.

UpToDate Contents

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English Journal

Screening of antidepressant activity and estimation of quercetin from Coccinia indica using TLC densitometry.

Randhawa K1, Kumar D, Jamwal A, Kumar S.
Pharmaceutical biology.Pharm Biol.2015 Dec;53(12):1867-74. doi: 10.3109/13880209.2015.1025289. Epub 2015 Apr 7.
CONTEXT: Coccinia indica Naud (Cucurbitaceae) has been traditionally used for the treatment of depression but these claims have not been validated.OBJECTIVES: The objective of this study is to investigate antidepressant activity of various extracts and fractions of C. indica aerial parts, and to est
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Bone's Material Constituents and their Contribution to Bone Strength in Health, Disease, and Treatment.

Bala Y1, Seeman E.
Calcified tissue international.Calcif Tissue Int.2015 Sep;97(3):308-26. doi: 10.1007/s00223-015-9971-y. Epub 2015 Feb 25.
Type 1 collagen matrix volume, its degree of completeness of its mineralization, the extent of collagen crosslinking and water content, and the non-collagenous proteins like osteopontin and osteocalcin comprise the main constituents of bone's material composition. Each influences material strength a
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Can Cytoprotective Cobalt Protoporphyrin Protect Skeletal Muscle and Muscle-derived Stem Cells From Ischemic Injury?

Wilson HM1, Welikson RE, Luo J, Kean TJ, Cao B, Dennis JE, Allen MD.
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BACKGROUND: Extremity trauma is the most common injury seen in combat hospitals as well as in civilian trauma centers. Major skeletal muscle injuries that are complicated by ischemia often result in substantial muscle loss, residual disability, or even amputation, yet few treatment options are avail
PMID 26070773

Japanese Journal

Chaotic Analogies in the Operation of Churn?Turbulent Bubble Columns and Bubbling Fluidized Beds (Special Issue for Multiscale Multiphase Process Engineering (MMPE) 2011)

NEDELTCHEV Stoyan
Journal of chemical engineering of Japan 45(8-12), 765-771, 2012-12-00
NAID 40019532256

吸湿過程にある木材および木質材料の厚さ方向の水分分布の経時変化(第3報)合板およびシージングボード内部に形成される水分分布の非破壊測定

田中孝,信田聡
木材学会誌 58(5), 271-278, 2012-09-00
NAID 40019446367

CO_2濃度計測に基づくミュージアム来場者数の推定(<特集>サイバースペースとVR)

ソンヨンア,成谷峻,橋田朋子,苗村健
日本バーチャルリアリティ学会論文誌 17(2), 129-132, 2012-06-30
Estimating the number of visitors in museums is an important issue. This paper proposes to solve this problem by measuring CO_2 concentration in a museum. The CO_2 concentration is mainly affected by …
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