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Lens Selection Guide

The key is to examine the working conditions required for the image application, which is also the core element of correctly selecting image equipment. Common parameters and dimensions are shown in the figure.

spec1

Camera

  • Area Array or Line Array Sensor
  • Sensor Size/Flange Distance
  • Mount/Black and White or Color, etc.

Lens

  • Lens Type (depending on the application)
  • Fixed Aperture or Adjustable Aperture
  • Fixed Magnification or Adjustable Magnification
  • Lens Size etc.

Light Source

  • Light Source Type
  • Lighting Method
  • Light Source Working Distance, etc.

Working Environment

  • Vibration, Shock, Unwanted Ambient Light
  • Dust, Moisture, Temperature, Humidity

Sensor Size

Sensor Size = Pixel Size (V) or (H) x Number of Effective Pixels (V) or (H)


Example)

Pixel Size: 4.4μm x 4.4μm
Number of Effective Pixels: 1600 x 1200

 

Sensor Size (V) = 0.0044×1200 = 5.28mm
Sensor Size (H) = 0.0044×1600 = 7.02mm
Sensor Size = 7.04 x 5.28mm

sensor size-1

Lens Selection

 

Find the optical magnification(Mag.) from the field of view(FOV) of the object you want to photograph and the camera you are using (preparing to use).

 

Mag. = Ratio of the FOV of the object to be photographed to the sensor
Mag. = Sensor (V) or (H)  /  FOV  (V) or (H)

 

After calculating the optical magnification, the next step is to confirm the conditions such as the installation distance of the space camera of the device and the working distance of the lens.

1. Calculation method of lens focal length

f  (Focal Length) = WD x Mag. (Senosr  Size (V or H) / FOV (V or H))

2. Use focal length to calculate the shooting range

FOV (V or H) = WD x Sensor Size (V or H) / f  (Focal Length)

f = 2000mm x Mag. (= Sensor Size (4.8mm) / FOV (200mm)) = 48mm

FOV = 1500 x 4.8 / 50 = 144mm

* However, the result obtained by this calculation formula is only an estimate and is provided for reference only. Especially when shooting at close range (WD 300mm or less), there is a possibility that it will deviate greatly from the accurate value. Please contact our staff or refer to the HP for details.

According to these relationships, for the same working distance (WD), the smaller the focal length (f), the wider the field of view (wide-angle lens), and the longer the focal length, the smaller the field of view. In addition, when shooting objects of the same size, the smaller the focal length, the shorter the WD, and the longer the focal length, the longer the working distance (telephoto lens).