Glossary of terms

Glossary of terms in optics and photometry, microclimate and metrology

  • A – a  source, the relative spectral energy distribution of which in the visible region of the spectrum corresponds to the radiation of an absolutely black body at a temperature of 2856 K (GOST 7721-89).
  • Anemometer  is a measuring device designed to determine the wind speed, as well as to measure the speed of directed air and gas flows.
  • Anemometric  measurements  – measurements of the speed of air movement at different points: at the outlet of the wick, to determine the shape of the wick, to determine the speed of movement in natural hoods, at the entrances to the air intake, etc. There are measurement rules depending on the tasks.
  • Arshin  is  the Federal Information Fund for Ensuring the Uniformity of Measurements of ROSSTANDART. It includes data from various sources of Rosstandart, All-Russian Research Institute of Metrological Service, State Corporation Rosatom and other organizations. In official language, Arshin is the second stage of the Federal Information Fund for ensuring the uniformity of measurements. Located at this address: .
  • Atmospheric pressure  is the pressure of the gas shell of our planet, the atmosphere, which acts on all objects in it, as well as the earth’s surface. Pressure corresponds to the force that acts in the atmosphere per unit area. In the International System of Units, atmospheric pressure is measured in pascals (Pa). Also in Russia, units such as bar, millimeters of mercury and their derivatives are used. Their use is due to the instruments with which the pressure is measured – mercury barometers. 1 mm Hg corresponds to about 133 Pa.
  • Watt per square centimeter (W / cm²)  is a multiple of the SI derived unit of watts per square meter, also known as heat load. By definition, a watt per square meter is the heat flux of one watt passing through one square meter of area perpendicular to the direction of flow.
  • Watt per square meter (W / m²)  is the SI derived unit for measuring heat flux density, also called heat load. (Example of conversion of dimensions: 5 mW / cm² = 50 W / m²).
  • The weighted radiance from blue light L B  and the weighted radiance of the burn hazard L R  are weight functions for numerical comparison of the photobiological hazard indicator from different light sources in accordance with GOST R IEC 62471-2013.
  •  Air humidity  is the content of water vapor in the air. It is usually characterized by two values: absolute humidity and relative humidity.
  • Air  – 78.03% nitrogen, 20.99% oxygen, 0.94% argon, 0.03% carbon dioxide, 0.001% hydrogen, water vapor.
  • Overall brightness  – the brightness of the emitting element of the surface, taking into account the non-luminous gaps of this element, for example, the brightness of one LED is 10  cd / m 2 , and the brightness of one cluster of five similar LEDs is 10 4  cd / m 2… If the radiating body (surface) has the form of a spiral or chaotically (orderly) located radiating elements, then not only the area of ​​the radiating elements, but also the areas of non-radiating gaps between them are taken as the radiation area. The brightness of light sources is measured in stilb (sb). To measure the brightness of illuminated surfaces, in addition to the stilbe, the apostilbe (asb) unit of brightness is used: 1 sat = 32,000 asb. The overall brightness of projection incandescent lamps is approximately 1000-1500 sb. The overall brightness is always less than the brightness of a spiral or a single pixel.
  • A hygrometer  is a device used to measure air humidity.
  • Chromaticity graph  is a graphical image on a plane, where the points determined by the chromaticity coordinates unambiguously correspond to the chromaticities of the color stimulus.
  • Radiation dose (or energy exposure)  is the product of the flux intensity value by the exposure time (unit of measurement – W · sec / m 2  or J / m 2 ). The concept of “dose” or “exposure” is very important in occupational health and safety, since the risk of radiation exposure is determined by two factors – the intensity and time of exposure, and the term “radiation dose” actually combines these two factors.
  • The dominant wavelength is  used to represent color in CIE coordinates and is measured in nanometers (nm). It is essentially the color actually perceived by the human eye.
  • Permissible intensity of radiation  (irradiation) is the amount of radiation that, when exposed to a person during a work shift and in the course of work, does not cause functional and acute injuries in workers, leading to a violation of the state of health immediately during work or in long-term periods.
  • E – a   source, the relative spectral energy distribution of which is constant in the visible region of the spectrum.
  • Measurement  – a set of operations performed to determine the quantitative value of a quantity.
  • The index of thermal load of the environment (TNS-index)  is an empirical indicator characterizing the combined effect of microclimate parameters (temperature, humidity, air velocity and thermal radiation) on the human body, expressed as a numerical indicator, in degrees Celsius, in which they are summed up, with certain weights, values ​​of temperatures of a wet bulb, radiation and air, is used to assess the possible thermal overheating of a person during a period characterizing his vigorous activity, but is not used to assess thermal overheating for very short periods of time or to assess thermal overheating close to comfort zones.
  • Color rendering index is a measure of the correspondence of visual perceptions of a colored object illuminated by the investigated and standard light sources under certain observation conditions (taking into account the chromatic adaptation of the observer) (see GOST R 8.827-2013 and GOST R 56228-2014). The objective characteristic here is the value of the color rendering index  Ra , the maximum possible value of which is 100. The higher the index, the more accurate the perception of colors will be. It is better to compare different sources in terms of Ra  values  at similar color temperatures. To determine the value of  Ra, 8 (or 14) standard reference colors specified in DIN 6169 are selected from the environment, which are illuminated by the lamp under test and then by a standard lamp having the same color temperature. The smaller the difference in color rendition between the test colors, the better the color rendition of the test lamp.
    Tested colors: R1 – Withered rose
    R2 – Mustard
    R3 –
    Light green R4 – Light green
    R5 – Turquoise
    R6 – Sky blue
    R7 – Purple aster
    R8 – Lilac
    Additional test colors
    with saturated colors:
    R9 – intense red
    R10 – intense yellow
    R11 – intense green
    R12 – intense blue
    R13 – Skin color
    R14 – Leaf green
  • Integrating Sphere –  means “collecting light in all directions”; the inner surface is painted with a special substance that reflects more than 95% of the light in the entire visible spectrum of radiation; reflection occurs diffusely: light, falling on any part of the surface, is scattered, repeatedly re-reflected, and as a result, the surface of the sphere is almost uniformly illuminated over its entire area; the light falling on the built-in photodetector turns out to be proportional to the entire flux emanating from the measured light source (lamp or LED).
  • The intensity of radiation (irradiation) is the  surface energy flux density falling per unit of the irradiated area at the workplace (measured in energy units – W / m 2 , W / cm 2  (1 W / m 2  – 10 (-4)  W / cm 2 In addition, in practice, in the literature on occupational health and safety, including reference and regulatory and methodological documentation, two similar in essence, but still different terms are often used – radiation and irradiation. , energy illumination.
  • Calibration of measuring  instruments – a set of operations performed in order to determine the actual values ​​of the metrological characteristics of measuring instruments.
  • Colorimetry  is the science of methods for measuring and quantifying color, the scientific measurement and determination of the color characteristics of LEDs. Colorimetric parameters of LEDs are usually expressed in chromaticity coordinates or wavelengths. Human color perception is very difficult, since it depends not only on the various physical properties of light, but also on the surrounding objects, the mechanical properties of the emitter, the physiological response of the observer’s eye and his psychological state. In 1931, the International Commission on Illumination (CIE) measured the reactions to color of several thousand people and introduced the concept of the “standard observer”. The reaction of such an abstract observer to colors of a different spectrum was described in terms of tristimulus – three curves called X, Y and Z.
  • Color coordinates are the   number of three primary colors required to obtain colorimetric equality with the measured color.
  • Chromaticity coordinates – the  ratio of each of the three color coordinates to their sum. Typically, chromaticity coordinates are determined only by the X and Y axes. But if the LED does not have a “white” glow, most of the specifications provided by the manufacturers do not contain the chromaticity coordinates, but rather the  peak  and  dominant  wavelengths.
  • The correlated color temperature  T kts  is the temperature of the Planck emitter, the perceived color of which most closely characterizes the given color radiation under the same lightness and the same standard observation conditions. The correlated color temperature is based on an idea of ​​what light looks like when emitted by a black body heated to different temperatures expressed in degrees Kelvin (K). In practice, it is the color temperature obtained by determining on an equal-contrast color plot the point on the black body line closest to the point representing the chromaticity of the light source in question. “CCT: Temperature of a Planck emitter (black body) having chromaticity coordinates closest to the chromaticity coordinates corresponding to the spectral distribution of the object in question . ” (see GOST R 56228-2014 Artificial lighting. Terms and definitions). Correlated color temperature measurement method according to  GOST R 55703.
  • Illumination ripple coefficient , Kp,% – a criterion for assessing the relative depth of illumination fluctuations as a result of the change in time of the luminous flux of the IC in the op amp when powered with alternating current (see GOST R 56228-2014).
  • Rayleigh’s criterion –  two spectral lines are considered allowed if the dip of the total contour is 20% or more, but in practice, it is very problematic to find two lines with the same intensity and line width next to each other. Therefore, in practice, a good estimate of the Rayleigh spectral resolution ΔλR is the so-called “half-width” of the spectral single line δλR. Line FWHM is defined as the spectral line FWHM. The line height Imax is the intensity of the maximum of the spectral contour, measured from the spectral background. (see right figure) ΔλR ≅ δλR.
  • изменения во времени светового потока ИС в ОУ при питании их переменным током (см. ГОСТ Р 56228-2014).
  • The Relay criterion – two spectral lines are considered allowed if the failure of the total contour is 20% or more, but in practice it is very problematic to find two lines of the same intensity and width nearby. Therefore, in practice, a good estimate of the Rayleigh spectral resolution ΔαR is the so-called “half-width” of the spectral single line δαR. The half width of the line is defined as the width of the spectral line at half height. The height of the Imax line is the intensity of the maximum spectral contour counted from the spectral background. (refer to the right figure) ΔαR ≅ δαR.
  • Luxmeters  are measuring devices that control the level of illumination in different types of rooms and in the open air. Instrumental measurements of illumination are made by means of measurement, with minimal deviations of the relative spectral sensitivity from the relative spectral luminous efficiency, and the correcting cosine nozzle must take into account the influence of light obliquely (at an angle) incident on the photocell. When working with a luxmeter, the sensor of the device, the receiving plate of the photocell must be placed on the working surface in the plane of its location (vertical, horizontal or inclined).
  • Measurement technique  – a set of specifically described operations, the implementation of which ensures the receipt of measurement results with established accuracy indicators; are developed to describe measurements, with the exception of measurements in which the value of the quantity is obtained directly from the measuring instrument in accordance with the operational documentation for the measuring instrument.
  • Measurement method  – a reception or a set of methods for comparing a measured value with its unit or scale in accordance with the implemented measurement principle. According to the general methods of obtaining measurement results, methods are distinguished into: direct and indirect. In accordance with the Law of the Russian Federation “On Ensuring the Uniformity of Measurements” (Article 9), measurements must be performed in accordance with duly certified procedures. “Measurements related to the sphere of state regulation of ensuring the uniformity of measurements must be carried out according to certified measurement procedures (methods), with the exception of measurement procedures (methods) intended for direct measurements.” (From Federal Law No. 102-FZ “On Ensuring the Uniformity of Measurements” Part 1 of Article 5) Confirmation of compliance of these methods with mandatory metrological requirements is carried out in the process of approving the types of these measuring instruments (GOST R 8.563-2009 State system for ensuring the uniformity of measurements. Methods (methods) of measurements).
  • Calibration techniques for measuring instruments: a document regulating the calibration procedure for measuring instruments. The fact and results of the calibration of the measuring instrument are certified by the Calibration Certificate: a document issued by the organization performing the calibration. Requirements for the content and presentation of methods for calibrating measuring instruments are established by GOST R 8.879-2014. The result of the calibration is the determination of the actual values ​​of the metrological characteristics of the measuring instruments. Calibration of measuring instruments is carried out if the measuring instrument is not included in the State Register and for this reason its verification is impossible. Calibration is not a mandatory procedure and is carried out by the user of the device at his discretion, if it is necessary to establish the actual values ​​of the metrological characteristics. Therefore, the calibration interval is not regulated.
  • Methods of verification of measuring  instruments – the main document for verification of measuring instruments, which is an algorithm for carrying out verification, documented in accordance with the established rules.
  • The microclimate  is a complex of physical factors that affect the heat exchange of a person with the environment, his thermal state and determine well-being, working capacity, health and labor productivity.
  • Normal atmospheric pressure  is 760 mm Hg or 101 325 Pa at 0º C at sea level (45º latitude). At the same time, for every square centimeter of the earth’s surface, the atmosphere acts with a force of 1.033 kg. A 760 mm high mercury column balances the mass of this air column. Pressure is more often displayed in hectopascals instead of mmHg. st .: 1 mm = 133.3 Pa = 1.333 hPa.
  • Optical radiation  is an electromagnetic study of a source in the range from 1 nm (in our consideration, from 200 nm) to 1 mm, covering the ultraviolet (UV), visible and infrared (IR) spectral regions.
  • Illumination  is a physical quantity that is numerically equal to the luminous flux falling on a unit of surface, the unit for measuring illumination in the SI system is lux (lx).
  • Relative air humidity  is the ratio of the actual mass of water vapor contained in the air to the maximum possible (saturating) mass in a given volume of air at a given temperature; relative humidity is expressed as a percentage. It is the relative humidity that is important for us, since the rate of evaporation of moisture from human skin, from wooden furniture, etc. depends on it.
  • Parameters  microclimate  (determining) – temperature, relative humidity, air temperature mobility and fences (walls etc.), when the deviation is compensated by changing any parameter other.
  • The peak wavelength  is the wavelength of the maximum spectral intensity. The peak value is easy to determine and is therefore the most common parameter specified by LED manufacturers. However, the peak wavelength is of less practical importance for applications in the spectral region perceived by human vision: two LEDs may have the same peak wavelength, but will be judged by humans to have different colors.
  • Verification of  measuring instruments – a set of operations performed in order to confirm the compliance of measuring instruments with metrological requirements.
  • Confirmation of conformity  – the activities of a testing laboratory aimed at establishing compliance with the requirements of technical regulations, national standards or contract terms.
  • You can show the relationship between height and pressure  using a simple formula:
  • Thus, when you rise 9 meters, the pressure level decreases by 1 hPa. This indicator is called the pressure stage. Standard atmospheric pressure – 1013 hPa (can be rounded up to 1000).
  • A permanent workplace  is a place where a worker is the majority (more than 50% or more than 2 hours continuously) of his working time. If at the same time work is carried out in different points of the working area, the entire working area is considered a permanent workplace.
  • The flux density of thermal radiation  inside a room is the amount of radiation energy per unit volume of space, in the SI system it is measured in W / m 2 .
  • The density of the photosynthetic photon flux  PPFD  (Photosynthetic Photon Flux Dencity) is the number of photons per second per square meter in the wavelength range from 400 to 700 nm (in  µmol / s / m² ).
  • Direct measurement method  – measurement in which the desired value of the quantity is obtained directly from the measuring instrument. Federal Law No. 102-FZ (as amended on 12/08/2020) does not require certification of direct measurement techniques used in the field of state regulation. Direct measurements are carried out according to the operational documentation for the used measuring instrument. Confirmation of compliance of these methods with mandatory metrological requirements is carried out in the process of approval of the types of these measuring instruments.
  • Consumption (air) – the  amount of air required for different purposes: for example, in aspiration in order to carry all the chips away from the machine at a given speed and pressure. The amount of air passing through ducts and ducts or supplied by a fan is usually expressed in m 3  per hour.
  • Luminous flux is the total amount of light emitted by a source in the visible wavelength range, measured in lumens (lm). The light flux is determined by the radiation flow on selective receiver – eye whose spectral sensitivity is normalized relative spectral luminous efficiency of monochromatic radiation function for photopic vision (L> 10 cd / m 2 ) and for night vision (L <0.01 cd / m 2 ), taken experimentally.
  • Luminous intensity I  –  (unit of measurement – cd) value characterizing the intensity of the source of visible radiation (light). In general, the luminous intensity is different for different directions from the light source and is equal to the ratio of the luminous flux dF V propagating from the source inside the elementary solid angle, which contains the given direction, to this solid angle.
  • Air speed is the air speed  averaged over the volume of the serviced area; the unit of speed measurement in the SI system is m / s.
  • Spectral characteristic  – the relative spectral sensitivity of the optical radiation receiver, corrected for the eye sensitivity curve or “U-shaped” view in the UV region of the optical spectrum.
  • A spectroradiometer  is a spectral instrument designed to measure photometric characteristics (flux, illumination, luminous intensity, brightness, etc.) of optical radiation sources.
    Structurally, in general, it is similar to a spectrophotometer, however, with functions that allow comparing the flow under study with the flow from a reference source (photometry), which can be a table of one of the reference sources from the device memory or an external source. For most modern spectroradiometers, all types of spectroradiometric measurements are available, including: photometric; colorimetric (colorimetric); radiometric. Through the use of software, further processing is carried out and color coordinates, color rendering index, color temperature are determined.
  • Average radiation temperature (average temperature of radiation, effective temperature of surrounding surfaces ) is the temperature of an imaginary (virtual) homogeneous environment, in which the transfer of heat by radiation from the human body is equal to the transfer of this heat in an actual inhomogeneous environment. It is equal to the temperature of an absolutely black body, the integral brightness of which is equal to that of the observed body.
  • Measuring  instrument – a technical instrument intended for measurements.
  • Ultraviolet radiation  – electromagnetic radiation of the optical range with a wavelength from 200 to 400 nm and a frequency from 10 13  Hz to 10 16  Hz, subdivided depending on the biological activity into the UV-A region (400-315 nm), UV-B (315 – 280 nm) and UV-C (280-200 nm). Refers to the field of non-ionizing radiation.
  • A point source  is a radiation source whose dimensions are so small compared to the distance to the irradiated surface that they can be neglected in calculations and measurements.
  • PAR (Photosynthetic Active Radiation  PAR ) is a falling quantum flux in the range from 400 to 700  nm  without involving any experimental plant reaction.
  • Photon  is an elementary particle of radiation, the energy of which [quantum] is equal to the product of Planck’s constant h and the frequency of electromagnetic radiation.
  • Photometer  – a device for measuring any of the photometric quantities, more often than others – one or more light quantities. When using a photometer, a certain spatial limitation of the radiation flux is carried out and its registration by a radiation receiver with a given spectral sensitivity. Illumination is measured with luxmeters, brightness – with brightness meters, luminous flux and light energy – using an integrating photometer. Instruments for measuring the color of an object are called colorimeters.
  • A photometric sphere  (“integrating sphere” or “Ulbricht’s sphere”)  is a  part of an integrating photometer in the form of a hollow sphere with an inner surface covered with diffuse and possibly less selective, most often white paint, which has a hole through which photometry is usually carried out on a small inner part of the sphere with using a photometer; a shield located inside the sphere protects the observed field from the direct rays of the source.
  • Photosynthetic photon flux  (ang Photon Flux Photosynthetic.  PPF ) – the number of photons in a second wavelength range from 400 to 700 nm ( mol / s ).
  • Color purity  is the percentage of dominant wavelength in a standard light source. The closer the color purity is to 100%, the closer it is to the dominant wavelength.
  • Color  – the concept of color is subdivided into: color perceived by the eye, and psychophysical color. Perceived color is a property of visual perception that combines chromatic and achromatic features. This property of visual perception can be described using the names of chromatic colors (yellow, orange, red, pink, green, blue, violet, etc.) or the names of achromatic colors (white, gray, black, dull, light, dark) or a combination of them. Psychophysical color – determination of a color stimulus using experimentally determined values ​​of quantities (for example, three color coordinates).
  • Chromaticity is a  characteristic of a color stimulus, determined by its chromaticity coordinates or the dominant wavelength and color purity.
  • Color or light stimulus –  visible radiation entering the eye and causing the sensation of color or light, respectively.
  • The energy intensity of light  I (radiation intensity) – (unit of measurement – W / sr) characterizes the radiation of the source in a certain direction, is equal to the ratio of the radiation flux propagating from the source inside the elementary solid angle containing the direction in question to this elementary solid angle. This concept is applicable when the distance from the source is much greater than its size, and when the law of “inverse squares” is fulfilled.
  • Energy illumination (irradiance)  is a physical quantity determined by the ratio of the radiation flux incident on a small area of ​​the surface containing the point under consideration to the area of ​​this area.