Working Distance（W.D.）
The distance from the end of the lens barrel to the object.
Object side N.A." and image side N.A.'. The formula is established in the figure below, where u is the half-angle that object size entrance pupil extends to the object side, u' is the half-angle that the exit pupil extends to the image side, and n is the refractive index on the object side and n' is the refractive index on the image side. NA=sin u xn NA'=sin u' x n'
Object to Imager（O/I）
Distance between object images. Total optical length between object and imager.
Numerical Aperture (N.A.)
C-mount CS-mount F-mount M72-mount
Flange back 17.526 mm JIS standard screw Flange back 12.5 mm JIS standard screw Flange back 46.5 mm JIS standard screw Flange back depends on each camera manufacturer
Camera Mount
u
u'
Object side
Image side
Flange Back
Camera Mount
Image Circle
For finite lenses, it can be calculated by NA=M/(2xF) and NA'=1/(2xF) in relation to W.F/#. The relationship between NA and NA' can be expressed as NA=NA'x Opt. Mag or NA'=NA/Opt. Mag.
Range of the object side visible with the camera used. Camera effective sensor size(V) / Opt.Mag(M) = FOV(V) Camera effective sensor size(H) / Opt.Mag(M) = FOV(H) * The FOV range in this technical data is a value calculated from general numerical values of camera sensor dimensions. Strictly speaking, the standard dimensions differ depending on the camera specifications. Calculate with " Camera effective sensor size (V) or (H) = 1 pixel size of camera x number of effective pixels (V) or (H) ".
O/I
The brightness of the center of the image side of the optical lens is 100%, and the ratio of the brightness of the periphery is expressed in %.
Relative Iluminance
Field of view (FOV)
ＷＤ
Telecentricity is a magnification error in the depth direction of an object. It is said that the smaller the magnification error, the higher the telecentricity. Telecentric lenses are used for various purposes such as dimension measurement, but it is very important to know the telecentricity of the lens before using it. Since the principal ray of a telecentric lens is parallel to the optical axis of the lens, it is very useful for workpieces with different heights. If the telecentricity is poor, the appearance will change between the edge and the center of the screen, and the depth and front in the height direction, and the effect of using the telecentric lens will not be obtained. To confirm the telecentricity, it is possible to confirm it relatively easily by using the work shown in the figure below.
Field of View
DOF is a range of object distance the image appears to be sharp & focused even if the object surface moves back and forth.Similarly, the range on the image side (camera sensor side) is called depth of focus. The specific depth of field value depends on how far the image allows blur. Tolerable level of blur is called Permissible Circle of Confusion and varies depending on the camera used. The numerical values in this technical data are calculated values as shown in the margin of the specification table.
Telecentricity
Depth of Field (DOF)
Low telecentricity
High telecentricity
Camera
Permissible COC NA x Opt. Mag
= DOF 2 Permissible COC × Effective F Opt. Mag x Opt. Mag
= DOF
Lens Chef ray
Distance from rear principal point (H2) to the image plane. When filming a wide area with a short working distance (WD), a lens with a short focal length is often used. When filming a subject in such a way that it takes up a large amount of the image space using a long WD, a lens with a long focal distance is often used.
Focal Length
Telecentric lens has parallel chief ray to its optical axis. There are object-side telecentric, image-side telecentric, and double-sided telecentric lenses.
Telecentric Lens
Focal Length Short Long
Field of View Wide Narrow
Even an ideal lens without any aberrations cannot reproduce an object detail. Diffration will limit the resolution possible. The smallest achievable spot from a lens is called Airy Disk. The radius r of the spot is given by wavelength λ and numerical aperture NA: ｒ= 0.61λ/NA The longer wavelength of the illuminating light has larger spot. ex) A lens with NA0.07 at wavelength 550nm. r = 0.61 x 0.55 / 0.07 = 4.8µm. The resolution on the specification sheet of VST is given by this equation.
Intensity profiles of diffraction limit
Airy Disk pattern
Value indicating the brightness of a lens when focused to infinity. The smaller the number, the brighter the image and the shallower the depth of field. The larger the number, the darker the image and the deeper the depth of field. FNO = Focal Length / Entrance Pupil diameter or Effective Aperture = f/D
F Number (F/#)
Airy Disk and Resolution
Working F defines the brightness of lens at a finite distance. When filming at a specific WD other than infinity, the image brightness and depth of field are confirmed using the effective F, not the FNO. W.F/# = (1 + Opt. Mag) x FNO ※Relationship between W. F/# and F/# W.F/# = 1 / (2NA / Opt. Mag)
r
Working F/# ( W.F/#)
Airy Disk
178
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