PSF Lab is a software program that allows the calculation of the illumination Point Spread Function

Point spread function

The point spread function describes the response of an imaging system to a point source or point object. A more general term for the PSF is a system's impulse response, the PSF being the impulse response of a focused optical system. The PSF in many contexts can be thought of as the extended blob...

 (PSF) of a confocal microscope under various imaging conditions. The calculation of the electric field vectors is based on a rigorous, vectorial model that takes polarization effects in the near-focus region and high numerical aperture

Numerical aperture

In optics, the numerical aperture of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, NA has the property that it is constant for a beam as it goes from one...

 microscope objectives into account.

The polarization of the input beam (assumed to be collimated and monochromatic) can be chosen freely (linear, circular, or elliptic). Furthermore, a constant or Gaussian shaped input beam intensity profile can be assumed. On its way from the objective to the focus

Focus (optics)

In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...

, the illumination light passes through up to three stratified optical layers, which allows the simulation of an immersion oil/air (layer 1) objective that focusses light through a glass cover slip (layer 2) into the sample medium (layer 3). Each layer is characterized by its (constant) 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....

 and thickness. PSF Lab can also simulate microscope objectives that are corrected for certain refractive indices and cover slip thicknesses (design parameters). Thus, any deviations from the ideal imaging conditions for which the objective was designed for are properly taken into account.

The following optical parameters can be selected:

• Input beam
  • Wavelength
    Wavelength
    In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
    
    
  • Gaussian profile filling parameter (0 = constant profile)
  • Polarization (linear, circular, elliptic)
• Outputs
  • Individual field components
  • Squared field components
  • Intensity
• Microscope objective
  • Numerical aperture
• Optical media
  • Refractive index (design and actual)
  • Thickness (design and actual)
  • Depth (focus position within medium 3)

The program calculates only 2D section of the PSF, but several calculations can be stacked (with a third party program) to obtain the full 3D PSF. Calculations are organized in "sets", each with its own set of parameters. Loops can be set up such that PSF Lab calculates one or several sets, increasing the resolution

Image resolution

Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....

 of the calculated images in each new iteration. The resulting image is displayed in PSF Lab in linear or logarithmic

Logarithmic scale

A logarithmic scale is a scale of measurement using the logarithm of a physical quantity instead of the quantity itself.A simple example is a chart whose vertical axis increments are labeled 1, 10, 100, 1000, instead of 1, 2, 3, 4...

 color scale with user-selectable color map, and the intensity, individual field components, or squared field component distributions can be exported into various formats (data formats: .mat, .h5 (HDF5), .txt (ASCII); image formats: .fig, .ai, .bmp, .emf, .eps, .jpg, .pcx, .pdf, .png, .tif).

See also

• Point spread function
  Point spread function
  The point spread function describes the response of an imaging system to a point source or point object. A more general term for the PSF is a system's impulse response, the PSF being the impulse response of a focused optical system. The PSF in many contexts can be thought of as the extended blob...
  
  
• Optical microscope
  Optical microscope
  The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
  
  
• Confocal microscopy
  Confocal microscopy
  Confocal microscopy is an optical imaging technique used to increase optical resolution and contrast of a micrograph by using point illumination and a spatial pinhole to eliminate out-of-focus light in specimens that are thicker than the focal plane. It enables the reconstruction of...
  
  
• Confocal laser scanning microscopy
  Confocal laser scanning microscopy
  Confocal laser scanning microscopy is a technique for obtaining high-resolution optical images with depth selectivity. The key feature of confocal microscopy is its ability to acquire in-focus images from selected depths, a process known as optical sectioning...
  
  

External links

• PSF Lab, download.
• The One Molecule Group, authors' web site.
• Molecular Expressions, introduction to deconvolution using PSFs.