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Optical Inner Wall
Metrology System

Optical Inner Wall Metrology System

The importance of inner peripheral surface evaluation has been increasing for precision pore-machined parts such as fuel injection nozzles in aerospace instruments, hollow parts in medical devices, precision nozzles in analyzers, and hydrodynamic bearings.
Existing measuring instruments can evaluate inner diameter, roundness, surface roughness, and shape of machined parts with relatively large inner diameters. However, these instruments are not able to gauge the pore-machined parts unless the bodies of the parts are cut in half.

Orbray has developed the “NMH-02”an OCT inner peripheral surface measuring instrument that enables the visualization of the inner peripheral surfaces of pores using optical interference of near infrared light.

This unique invention was possible thanks to our micro motor technology and optical communication technology. It combines our world's smallest φ0.9mm motor with our patented optical imaging probe, and is equipped with our patented tilt correcting algorithm. It has the following new capabilities: (1) Measurement of inner diameter as small as φ1.1mm; (2) simultaneous measurement of inner diameter, roundness, and shape; (3) repeatability to an accuracy of σ=0.2μm; (4) ready-to-use convenience.

Our instrument is not only able to observe and measure the inner peripheral surfaces of pore-machined parts, but can also simultaneously evaluate inner diameter, roundness, surface roughness, and shape, which used to require using separate instruments for each. These features significantly reduce the measurement time from about 30min to 30sec, and contribute to the improvement of measurement throughput for customers.


  • Smallest inner diameter measurable: 1.1mm
  • Repeatability with accuracy of σ=0.2μm
  • Setting free:work's inclination automatically adjusted by original computing.
  • Measuring time:30min (conventional) reduced to 30sec
    (simultaneous measurement of inner diameter/circularity/shape)

Comparison to conventional method

Comparison to conventional method
  • Measurable Minimum Diameter φ1.1mm over
    world's smallest φ0.9mm motor installed.
  • Repeated Measurement Accuracy: 0.2μm
    Minimizing optical vibration and fluctuation by translucent standard pipe.
  • Setting free measurement
    Auto- adjusting a work's inclined and eccentric state by arithmetic processing.

Measurement example

Link gauge

Link gaugeGauge diameter:


3D picture

Measured result:
(Center value)

2D inner diameter data2D inner diameter dataInner diameter data
at Z axis direction

Hydrodynamic bearing

Link gaugeInner diameter:


3D picture Measured result:

2D picture2D pictureAuto-detection of
dynamic pressure groove

Auto scratch detection

Inner diameter:φ3.900Inner diameter:


Dent detection

Dent detection

Vertical scratch detectionVertical scratch detection

Optical Inner Wall Metrology System


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