Fotometriya: Çi ye?

Photometry bîr elmaşî ye ku di hêzên çavkaniyê de nûrê pîvand dide. Ewe ji radiometry, ku di hêzên mutlak de nûr û enerjiya taybetand dide, ve giran e. Photometry tenê di rûnyarên kêmê (nûr) de ku çavkan dikarin bibin.

Çavkan dikarin radîasyonê bi derexê yên 370 nm û 780 nm bibin. Ev derexê "specîfîk visible" an "nûr" hatine nehat. Radîasyon bi derexê kêmter nûr "radîasyon ultraviolet" anam û radîasyon bi derexê zêde nûr "radîasyon infrared" anam. Photometry radîasyon ultraviolet an infrared nehat.

Photometry li ser pîvandiya çavkan la nûrê wekî funksiyonê derexê ya nûrê têne. Çavkan la her derexê nûrê bi yekêna nebibin. Li ser nûrê xerîb dibin û li ser nûrê sor û vîlet bibin. Çavkan da ku bibin ji bo hêzên din jî bêtir. Di navbera çavkan de du mod û şêw û şevî dibin.

Modê şêw çavkan la li ser hêzên zêde, wêje di rojî de an li ser rojhilatên taybetand. Modê şêw reng û detal bibin. Modê şevî çavkan la li ser hêzên kêm, wêje di demîn de an li ser rojhilatên çavkan. Modê şevî reng nebibin û li ser hêzên kêm bibin. Di navbera modê şêw û şevî de modê mesopic heye.

Photometry li ser modelên standartî ya pîvandiya çavkan la nûrê wekî funksiyonê derexê û hêza bibin. Ev modelên "luminosity functions" hatine nehat. Ev modelan bikaranîn taybetandîya nûrê bi derexê yên din dikarin bibin. Luminosity function ên ziyan bikaranîn modê şêw, ku çavkan la li ser hêzên zêde bibin. Modelên din li ser modê şevî û mesopic dibin.

Photometry li ser wan fîldan de bikaranîn. Ev dike nûr û şopandina nûr bibin. Ji bo hêzan û çavkan da ku bibin bikaranîn.

Li navbera vê makaleyan, dike mînaka, princîp, bikaranîn û karkirina photometry bibin. Ji bo pîvanîna photometric bikaranîn alatan û unitên bikaranîn.

Firotina Fiber Photometry

Fiber photometry teknîkî ye ku di neuroscience de bikaranîn taybetandîya neuronan bibin. Ev dike nûrê bi kanînên optical fiber bibin û fluorescence bi kanînên fluorescent bibin.

Indikatoran fluorescent molecule an ku fluorescenceyê bi guherandina parametreyên biolojî bibin, wêje calcium concentration, voltage, neurotransmitters, etc. Bi karînîna indikatoran fluorescent genetically encoded (GEFIs), wêje GCaMPs, mumkin e ku neuronan û navberên brain yên taybetand bike.

Fiber photometry dike pîvandkirina taybetandîya neuronan bibin. Ev dike taybetandîya neuronan bi event û stimulan bibin. Fiber photometry bi teknîkên din bikaranîn, wêje two-photon microscopy an calcium imaging, li ser sade, cost-effective, portable, û scalable.

Lê fiber photometry jî piçeyên hene, wêje resolution kêm, signal contamination, movement artifacts, û tissue damage.

Firotina Flame Photometry

Flame photometry teknîkî ye ku di chemical analysis de bikaranîn taybetandîya ionên metal bibin. Ev dike flame emission spectroscopy an flame atomic emission spectroscopy bibin.

Flame photometry dike principle ku ionên metal karakteristik wavelength bibin. Intensity emitted light proportional to the concentration of the metal ions in the sample.

Flame photometry mainly used for alkali metals (group 1) and alkaline earth metals (group 2), such as sodium, potassium, calcium, lithium, etc. These metals have low ionization energies and can be easily excited by thermal energy from a flame.

To perform flame photometry, a sample solution containing the metal ions is sprayed into a flame (usually an air-acetylene flame). The flame vaporizes and atomizes the sample into its constituent elements. Some of these atoms are then excited to higher energy levels by absorbing thermal energy from the flame. These excited atoms eventually return to their ground state by emitting photons of light with specific wavelengths corresponding to their energy transitions.

The emitted light is then collected by a lens system and passed through a monochromator (a device that selects a narrow range of wavelengths). The monochromator allows only the desired wavelength of light corresponding to the metal ion of interest to reach a detector (usually a photomultiplier tube or a photodiode). The detector converts the light signal into an electrical signal that can be measured by a meter or a recorder.

The concentration of the metal ion in the sample can be calculated by comparing the intensity of the emitted light with a standard curve obtained from known concentrations of the same metal ion.

What is Reflectance Photometry?

Reflectance photometry is a technique used to measure the color or reflectance properties of a surface or an object. It works on the principle that different surfaces reflect different amounts and wavelengths of light depending on their physical and chemical characteristics.

Reflectance photometry uses a light source (usually white light) to illuminate a surface or an object at a certain angle. The reflected light from the surface or object is then measured by a detector (usually a spectrophotometer or a colorimeter) at another angle.

The detector analyzes the spectrum or intensity of the reflected light at different wavelengths and compares it with a reference standard (usually a white surface). The color or reflectance properties of the surface or object can be expressed by various parameters, such as hue (dominant wavelength), saturation (purity), brightness (luminance), chromaticity coordinates (x,y,z), color index (CIE Lab*), etc.

Reflectance photometry can be used for various purposes, such as quality control, color matching, color identification, color communication, etc. It can be applied to various materials and objects, such as paints, textiles, plastics, metals, and ceramics.

What are the Photometric Quantities and Units?

Photometric quantities are derived from radiometric quantities by applying the luminosity function as a weighting factor. The luminosity function represents the relative response of the human eye to different wavelengths of light. The most commonly used luminosity function is the photopic sensitivity function, which models the eye’s response under bright conditions. Other luminosity functions include the scotopic sensitivity function, which models the eye’s response under dark conditions, and the mesopic sensitivity function, which models the eye’s response under intermediate conditions.

What are the Photometric Instruments and Methods?

Photometric instruments are devices that measure photometric quantities using various methods and principles. Some of the common photometric instruments and methods are:

• Photometers: Photometers are devices that measure the relative brightness of light sources or objects by comparing them with a reference standard. Photometers can be classified into different types based on their design and application, such as visual photometers, photoelectric photometers, filter photometers, spectrophotometers, etc.

• Colorimeters: Colorimeters are devices that measure the color of light sources or objects by analyzing their spectral composition. Colorimeters can be classified into different types based on their design and application, such as tristimulus colorimeters, chromameters, spectroradiometers, etc.

• Integrating spheres: Integrating spheres are devices that measure the total luminous flux of light sources or objects by enclosing them in a spherical cavity with a highly reflective inner surface. Integrating spheres can be used for various purposes, such as calibration of light sources, measurement of reflectance or transmittance of materials, measurement of the angular distribution of light sources, etc.

• Goniophotometers: Goniophotometers are devices that measure the angular distribution of luminous intensity or luminance of light sources or objects by rotating them around one or more axes. Goniophotometers can be used for various purposes, such as the characterization of light sources, measurement of optical properties of materials, measurement of glare or contrast ratios of displays, etc.

• Photodetectors: Photodetectors are devices that convert light into electrical signals by using various physical principles, such as the photoelectric effect, photovoltaic effect, photoconductive effect, etc. Photodetectors can be classified into different types based on their design and application, such as photodiodes, phototransistors, photomultiplier tubes, photovoltaic cells, etc.