question: Why do people see a red or blue glow on edges of objects on wearing glasses (looking sideways towards the object)?
comment: Chromatic aberration, it is due to light of different frequency being bent different amounts by a lens. It is why a prism can be used to split light into a rainbow, and it is attempted to be minimized for optical lenses (but usually shows up at the edges regardless).
passages: This type of devices are commonly used in chemical laboratories for identification of substances and for quality control. Handheld variants are used in agriculture by, e.g., wine makers to determine sugar content in grape juice, and inline process refractometers are used in, e.g., chemical and pharmaceutical industry for process control.
   Many types of glass have been developed to reduce chromatic aberration. These are low dispersion glass, most notably, glasses containing fluorite. These hybridized glasses have a very low level of optical dispersion; only two compiled lenses made of these substances can yield a high level of correction.
  
  The use of achromats was an important step in the development of the optical microscope and in telescopes.
   BULLET::::- Purkinje's blue arcs are associated with the activity of the nerves sending signals from where a spot of light is focussed on the retina near the fovea to the optic disk. Look at the right edge of a small red light in a dark room with your right eye (left eye closed) after dark-accommodating your eye for about 30 seconds and you should see two faint blue arcs starting at the light and heading towards the blind spot. Look at the left edge and you will see a faint blue spike going from the light to the right.
   Scheerer’s phenomenon can be easily distinguished from floaters ("muscae volitantes"). 
   BULLET::::- Electrochromic effect: creation of an absorption band at some wavelengths, which gives rise to a change in colour
  
  BULLET::::- b) change of the refractive index and permittivity
  
  BULLET::::- Pockels effect (or linear electro-optic effect): change in the refractive index linearly proportional to the electric field. Only certain crystalline solids show the Pockels effect, as it requires lack of inversion symmetry
   Section::::Methods of study.:Optical Spectroscopy.
  
  Section::::Methods of study.:Optical Spectroscopy.:UV Spectroscopy.
   A blue-shifted channelrhodopsin has been discovered in the alga "Scherffelia dubia". After some engineering to improve membrane trafficking and speed, the resulting tool (CheRiff) produced large photocurrents at 460 nm excitation. It has been combined with the Genetically Encoded Calcium Indicator jRCaMP1b in an all-optical system called the OptoCaMP.
  
  Section::::Designer-channelrhodopsins.:Ion selectivity.
   In a patient with microtropia, the patient may see one light and two lines, with one of the lines having a small break in it. This is due to foveal suppression.
  
  Section::::Results.:Esotropia.
  
  In a patient with an unsuppressed esotropia, the patient will see two lights with one line through each light. The line corresponding to the right eye will be on the right side, meaning the images are uncrossed.
  
  Section::::Results.:Exotropia.
   Indeed, various experiments have revealed most of the factors responsible for these visual angle illusions, and a few different explanations for them have been published (Baird, Wagner, & Fuld, 1990, Enright, 1987, 1989, Hershenson, 1982, 1989, Komoda & Ono, 1974, McCready, 1965, 1985, 1986, 1994, Ono, 1970, Oyama, 1977, Reed, 1984, 1989, Restle, 1970, Roscoe, 1985, 1989).
   "Lateral" or "transverse" chromatic aberration is caused because the refraction at glass surfaces differs for light of different wavelengths. Blue light, seen through an eyepiece element, will not focus to the same point but along the same axis as red light. The effect can create a ring of false colour around point sources of light and results in a general blurriness to the image.
   Section::::Interpretation of results/ recording.
  
  Section::::Interpretation of results/ recording.:Normal response.
  
  If the patient's eyes are aligned and is bifoveal, the shifting of the image caused by the prism will produce a movement towards the apex of the prism (of the eye under the prism), and the fellow eye will have an outward movement in the same direction of the same magnitude due to Hering's law of equal innervation. Simultaneously the fellow eye produces a fusional convergence movement as there is no central suppression of that fellow eye. This is a result of overcoming the diplopia experienced.
   Cones are responsible for colour vision. They require brighter light to function than rods require. In humans, there are three types of cones, maximally sensitive to long-wavelength, medium-wavelength, and short-wavelength light (often referred to as red, green, and blue, respectively, though the sensitivity peaks are not actually at these colours). The colour seen is the combined effect of stimuli to, and responses from, these three types of cone cells. Cones are mostly concentrated in and near the fovea. Only a few are present at the sides of the retina. Objects are seen most sharply in focus when their images fall on the fovea, as when one looks at an object directly. Cone cells and rods are connected through intermediate cells in the retina to nerve fibres of the optic nerve. When rods and cones are stimulated by light, they connect through adjoining cells within the retina to send an electrical signal to the optic nerve fibres. The optic nerves send off impulses through these fibres to the brain.
   Section::::Theory.
   and the above condition ensures this will be the focal length of the doublet for light at the blue and red Fraunhofer F and C lines (486.1 nm and 656.3 nm respectively). The focal length for light at other visible wavelengths will be similar but not exactly equal to this.
   In a patient with an unsuppressed exotropia, the patient will see two lights with one line through each light. The line corresponding to the right eye will be on the left side of the results, meaning the images are crossed.
  
  Section::::Results.:Hypertropia/Hypotropia.
  
  In a patient with an unsuppressed vertical deviation, one line will appear higher than the other. If the image of the right eye is higher than that of the left, this means the right eye is lower than the left. This could be either a right hypotropia or a left hypertropia.
  
  Section::::Results.:Harmonious Abnormal retinal correspondence.
   When interpreting results, the line associated with each eye is the line perpendicular to the lens in front of that eye. If the lens in front of the right eye is at 135 degrees, then the line on the results representing the right eye will be at 45 degrees.
  
  One light: If the patient sees one light, that means that either they have fused the two images from each eye together, or are suppressing of one of the images.
   Varilux Experience demonstrates the technologies used to produce Varilux lenses, which are quite similar to those used in research laboratories, so as to provide an effective communication aid for optical professionals and their customers with presbyopia.
  
  In a theater showing a 3D film, viewers wearing polarized, stereoscopic glasses follow in the footsteps of a young man with presbyopia. Stage-by-stage, he experiences the vision produced by single-vision and bifocal lenses, and then that of standard progressive lenses, and ultimately Varilux lenses.
   Section::::In imaging.
  
  In photographic and microscopic lenses, dispersion causes chromatic aberration, which causes the different colors in the image not to overlap properly. Various techniques have been developed to counteract this, such as the use of achromats, multielement lenses with glasses of different dispersion. They are constructed in such a way that the chromatic aberrations of the different parts cancel out.
  
  Section::::Pulsar emissions.
   Optical lift
  
  Optical lift is an optical analogue of aerodynamic lift, in which a cambered refractive object with differently shaped top and bottom surfaces experiences a stable transverse lift force when placed in a uniform stream of light.
  
  Section::::Discovery.
   This optical illusion is caused by the fact that the human optic nerve responds to changes in light at about 10 cycles per second, so changes about double of this are registered as motion instead of being separate distinct images.
  
  Section::::Examples of use.
  
  One example of the beta movement effect would be a set of LEDs, as shown at the adjacent picture. The LEDs, electronically, are individually controlled, but our eyes and brains perceive them as a snake running clockwise around the four edges of the square picture. This is also seen commonly on LED displays.
  
  Section::::Experiment.
   where "V" and "V" are the Abbe numbers of the materials of the first and second lenses, respectively. Since Abbe numbers are positive, one of the focal lengths must be negative, i.e., a diverging lens, for the condition to be met.
  
  The overall focal length of the doublet "f" is given by the standard formula for thin lenses in contact:
   Although diffraction spikes can obscure parts of a photograph and are undesired in professional contexts, some amateur astronomers like the visual effect they give to bright stars – the "Star of Bethlehem" appearance – and even modify their refractors to exhibit the same effect, or to assist with focusing when using a CCD.
   In English, the idiom "rose-colored glasses" or "rose-tinted glasses" is also sometimes used to refer to the phenomenon of rosy retrospection. Usually this idiom occurs as some variation of the phrase "seeing things through rose-tinted glasses" or some other roughly similar phrasing.
  
  Rosy retrospection is also related to the concept of declinism.
  
  Section::::Experiments.
   Aberrations fall into two classes: "monochromatic" and "chromatic". Monochromatic aberrations are caused by the geometry of the lens or mirror and occur both when light is reflected and when it is refracted. They appear even when using monochromatic light, hence the name.
  
  Chromatic aberrations are caused by dispersion, the variation of a lens's refractive index with wavelength. Because of dispersion, different wavelengths of light come to focus at different points. Chromatic aberration does not appear when monochromatic light is used.
  
  Section::::Overview.:Monochromatic aberrations.
  
  The most common monochromatic aberrations are:
  
  BULLET::::- Defocus
  
  BULLET::::- Spherical aberration
  
  BULLET::::- Coma
  
  BULLET::::- Astigmatism
  
  BULLET::::- Field curvature
   Section::::Appearance and observation.:Brocken spectre.
  