optical window

Examples of optical window in the following topics:

• Visible Light

  • Visible wavelengths pass through the "optical window", the region of the electromagnetic spectrum which allows wavelengths to pass largely unattenuated through the Earth's atmosphere (see opacity plot in.
  • The optical window is also called the visible window because it overlaps the human visible response spectrum.
  • A consequence of the existence of the optical window in Earth's atmosphere is the relatively balmy temperature conditions on Earth's surface.
  • The Sun's luminosity function peaks in the visible range and light in that range is able to travel to the surface of the planet unattenuated due to the optical window.
  • This is again not coincidental; the light in this range is the most plentiful to organisms on the surface of Earth because the Sun emits about half of its luminosity in this wavelength range and it is allowed to pass freely through the optical windows in Earth's atmosphere.

• Properties of Quartz and Glass

  • Glasses are typically brittle and optically transparent.
  • The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica (SiO2) with the addition of sodium oxide (Na2O) from soda ash, lime (CaO), and several minor additives.
  • Glass has the ability to refract, reflect, and transmit light according to the principles of geometrical optics.

• Thermal Radiation

  • Now let's move the material in a position the blocks our window to the enclosure.
  • We know that as light travels through the material the intensity field should approach the source function but we also know that the light emerging from the window must have $I_\nu=B_\nu(T)$.
  • A thermal emitter has $S_\nu = B_\nu(T)$,$B_\nu(T)$ so the radiation field approaches $B_\nu(T)$ (blackbody radiation) only at large optical depth.

• Optic (II) Nerve

  • The optic nerve is also known as cranial nerve II.
  • The optic nerve is the second of twelve paired cranial nerves.
  • As a consequence, optic nerve damage produces irreversible blindness.
  • The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running posteromedially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.
  • An illustration of the brain highlighting the optic nerve and optic tract.

• Development of Vision

  • Development of the optic vesicles starts in the three-week embryo from a progressively deepening groove in the neural plate called the optic sulcus.
  • As this expands, the rostral neuropore (the exit of the brain cavity out of the embryo) closes and the optic sulcus and the neural plate becomes the optic vesicle.
  • The lens then acts as an inducer back to the optic vesicle to transform it into the optic cup and back to the epidermis to transform it into the cornea.
  • Iris is formed from the optic cup cells.
  • After the closure of the tube they are known as the optic vesicles.

• Lasers

  • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback.
  • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback (usually an optical cavity).
  • When a gain medium is placed in an optical cavity, a laser can then produce a coherent beam of photons.
  • The gain medium is where the optical amplification process occurs.
  • The most common type of laser uses feedback from an optical cavity--a pair of highly reflective mirrors on either end of the gain medium.

• Problems

  • At $t=t_0$ the sphere is optically thin.
  • What is the total luminosity of the sphere as a function of $M_0, R(t)$ and $T_0$while the sphere is optically thin?
  • What is the luminosity of the sphere as a function of time after it becomes optically thick in terms of $M_0, R(t)$ and $T_0$?
  • Give an implicit relation in terms of $R(t)$ for the time $t_1$ when the sphere becomes optically thick.

• Enhancement of Microscopy

  • In this section we will discuss both optical and electron microscopy.
  • You have probably used an optical microscope in a high school science class.
  • In optical microscopy, light reflected from an object passes through the microscope's lenses; this magnifies the light.
  • Although this type of microscopy has many limitations, there are several techniques that use properties of light and optics to enhance the magnified image:
  • Electron microscopes use electron beams to achieve higher resolutions than are possible in optical microscopy.

• Limits of Resolution and Circular Aperatures

  • In optical imaging, there is a fundamental limit to the resolution of any optical system that is due to diffraction.
  • However, there is a fundamental maximum to the resolution of any optical system that is due to diffraction (a wave nature of light).
  • An optical system with the ability to produce images with angular resolution as good as the instrument's theoretical limit is said to be diffraction limited.
  • The denominator $nsin \theta$ is called the numerical aperture and can reach about 1.4 in modern optics, hence the Abbe limit is roughly d=λ/2.
  • There are techniques for producing images that appear to have higher resolution than allowed by simple use of diffraction-limited optics.

• Chicago School of Architecture

  • The "Chicago window" originated in this school.
  • It is a three-part window consisting of a large fixed center panel flanked by two smaller double-hung sash windows.
  • The arrangement of windows on the facade typically creates a grid pattern, with some projecting out from the facade forming bay windows.
  • These windows were often deployed in bays, known as oriel windows, that projected out over the street.
  • This steel frame building displays both variations of the Chicago window, its facade is dominated by the window area (limiting decorative embellishments) and it is capped with a cornice, elements which are all typical of the Chicago School.