Observation tools Flashcards
Microscope scales 2
- Provide information at differing scales ranging, micron to picometer scales
- mikrós - small, skopein - to look
Observation tools - seeing small things in the body 6
- magnetic particle imaging
- magnetic resonance imaging (blodcirculation)
- near infra-red imaging (tumor scanning)
- ophthalmic microscopy (eye surgery)
- Flouroschopy/X-ray imaging
- ultrasound imaging (baby)
Light
- radiant energy or electromagnetic radiation (EMR)
- has both electric and magnetic components
EMR
electromagnetic radiation
- radio, microwave, infrared, visible, ultraviolet, x-ray, gamma ray
- visible 400-700
The nature of light - reflection
Direction change of a wave front at an interface between two dissimilar media s.t. the wave front returns into the medium from which it originated (ex.mirror)
The nature of light - refraction
Direction change of a ray of light from one transparent medium to another with different optical density.
- a less to a more dense medium –> bent perpendicular to the surface, greater deviation for shorter wavelengths.
The nature of light - diffraction
- Light rays bend around edges - new wavefronts are generated at shape edges
- The smaller the aperture, the bigger the diffraction
The nature of light - dispersion
Separation of light into its constituent wavelengths when entering a transparent medium - the change of refractive index with wavelength, such as the spectrum produced by a prism or by water droplets in a rainbow
Contrast - Bright Field (normal) 3
- Full aperture is illuminated
- Does not reveal differences in brightness between
- Light absorption of sample is imaged
Contrast - Dark Field 3
- A central obstruction blocks the central light cone
- Enhances contrast by indirect illumination
- Light scattering at sample is imaged
Chromatic Aberration 3
- “focus all length to the same point”
- Dispersion: An optical lens has different refractive indices for different wavelength (Rainbow color) or…
- Achromatic lenses combine two or more lenses o correct chromatic aberration (single color yellowish)
Spherical Aberration
- Aberration with a spherical lens
- If point spread function = blurriness
Aberration
lenses that causes light to be spread out over some region of space rather than focused to a point.
Aberration
lenses that causes light to be spread out over some region of space rather than focused to a point.
Astigmatism
- Blurred vision
- Not axisymmetric (error in the shape of the optical surface or due to misalignment of the components)
Flourenscene microscopy
- High energy beam (UV) to emit visible light
- down to 2-5nm
- filter for emission and excitation
specimen
laboratorieprov
resolution
defined as the shortest distance between two points on a specimen that can still be distinguished by the observer or camera system as separate entities
NA
light gathering capacities of an obj
depth of field
distance between the nearest and farthest obj that are acceptable in sharp focus in an image (without lossing sharpness) - depends on the resolution
- higher magnification smaller depth of field
Bright field
area which absorb light (e.g. electrons) appear dark whereas the areas with a low interaction btw sample and light appear bright.
Dark field
the light (e.g. electron beam) which barely interacts with the ample does not hit the detector (dark area). Only the light which is scattered at the sample can reach the detector. These appear brights
