An optical instrument either processes light waves to enhance an image for viewing, or analyzes light waves (or photon

Photon

In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...

s) to determine one of a number of characteristic properties.

Image enhancement

The first optical instruments were telescope

Telescope

A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

s used for magnification of distant images, and microscope

Microscope

A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

s used for magnifying very tiny images. Since the days of Galileo and Van Leeuwenhoek, these instruments have been greatly improved and extended into other portions of the electromagnetic spectrum

Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....

. The binocular

Binoculars

Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...

 device is a generally compact instrument for both eyes designed for mobile use. A camera

Camera

A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

 could be considered a type of optical instrument, with the pinhole camera

Pinhole camera

A pinhole camera is a simple camera without a lens and with a single small aperture – effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box...

 and camera obscura

Camera obscura

The camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...

being very simple examples of such devices.

Analysis

Another class of optical instrument is used to analyze the properties of light

Light

Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

 or optical materials. They include:

• Interferometer for measuring the interference properties of light waves
• Photometer
  Photometer
  In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...
  
   for measuring light intensity
• Polarimeter
  Polarimeter
  A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance....
  
   for measuring dispersion or rotation of polarized light
• Reflectometer
  Reflectometer
  Some scientific instruments commonly designated Reflectometer are:*Vector Network Analyser *Spectrophotometer: in optics, an instrument for measuring the reflectivity or reflectance of reflecting surfaces*Optical time domain reflectometer...
  
   for measuring the reflectivity
  Reflectivity
  In optics and photometry, reflectivity is the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength...
  
   of a surface or object
• Refractometer
  Refractometer
  A refractometer is a laboratory or field device for the measurement of an index of refraction . The index of refraction is calculated from Snell's law and can be calculated from the composition of the material using the Gladstone-Dale relation....
  
   for measuring refractive index
  Refractive index
  In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
  
   of various materials, invented by Ernst Abbe
• Spectrometer
  Spectrometer
  A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
  
   or monochromator
  Monochromator
  A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input...
  
   for generating or measuring a portion of the optical spectrum, for the purpose of chemical or material analysis.
• Autocollimator
  Autocollimator
  An autocollimator is an optical instrument for non-contact measurement of angles. They are typically used to align components and measure deflections in optical or mechanical systems. An autocollimator works by projecting an image onto a target mirror, and measuring the deflection of the returned...
  
   which is used to measure angular deflections.
• Vertometer
  Vertometer
  Vertometer was the trade name of an instrument made by Bausch & Lomb and later by Reichert.Lensometer was the trade name of the nearly similar instrument made by American Optical.Neither the Vertometer or the Lensometer is now being made....
  
   which is used to determine refractive power of lenses such as glasses, contact lenses and magnifier lens

DNA sequencer

DNA sequencer

A DNA sequencer is a scientific instrument used to automate the DNA sequencing process. It can be also considered an optical instrument as it generally analyses light signals originating from fluorochromes attached to nucleotides....

s can be considered optical instruments as they analyse the color and intensity of the light emitted by a fluorochrome attached to a specific nucleotide of a DNA strand.

Surface plasmon resonance

Surface plasmon resonance

The excitation of surface plasmons by light is denoted as a surface plasmon resonance for planar surfaces or localized surface plasmon resonance for nanometer-sized metallic structures....

-based instruments use refractometry to measure and analyze biomolecular interactions.

See also

• Scientific instruments