# Leica confocal microscopes TCS 4d, SP1, NT

This is part of the Backprojected Pinhole Calculator.

## Pinhole reported as P_8 parameter

See below in case the pinhole is reported in Airy disk units.

### Details

This applies to the Leica TCS4d. This information is believed to be valid for the SP1 and NT models too, but this is not confirmed.

The pinhole size is given by the microscope as an 8-bit number which maps to the side length of the square physical pinhole as in the following table:

Reported parameter (P_8) Diameter (µm)
0 20
255 630 (earlier reported as 500)

Use the reported value as an input in the calculator below, it will be translated accordingly to that relationship automatically.

The shape factor is $$c=1/\sqrt{\pi}\approx 0.5642$$.

The system magnification is reported to be 4.5.

### Calculator

 Reported parameter (P_8) Objective magnification

## Pinhole reported in Airy disk units

The size of the square pinhole can be reported by the microscope in Airy Disk units. Then the equation is r_b = 0.69 λ_ex N_Airydisks / NA with NA the Numerical Aperture and λ_ex the reference WaveLength, which in Leica systems is 580 nm. This does not change with the user changing laser wavelength. 580 was chosen as it is the middle of the range of wavelength at which the system operates.

 Number of Airy disks Lens numerical aperture