Rigid and flexible endoscopes for three dimensional measurement of inside machine parts using fringe projection

Posch, Andreas E.; Schlobohm, Jochen; Matthias, Steffen; Reithmeier, Eduard

doi:10.1016/j.optlaseng.2016.05.023

Cited by 15 publications

(7 citation statements)

References 12 publications

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“…7 Since coloured over-projection cannot be used with a single-colour projector, we use the phasemap of the uncalibrated projector to determine the correspondences between projector and cameras.…”

Section: Calibration Of the Fringe Projection Systemmentioning

confidence: 99%

3D geometry measurement of hot cylindric specimen using structured light

Quentin

Beermann

Posch

et al. 2017

Optical Measurement Systems for Industrial Inspection X

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We present a fringe projection system to measure glowing hot hybrid components in between production processes. For this a high power green light projector, based on TI DLP technology, is used to create the highest possible contrast between fringes on the red glowing specimen. It has a resolution of 1140 x 912 pixels with a maximum frame rate of 120 images per second for fast measurement. We use a green bandpass filter (525 nm) on the camera lens to block unwanted incoming radiation from the specimen caused by self-emission. Commercial measurement standards are not calibrated for temperatures other than 20• C, so they cannot be used to validate measurement data at the required temperatures of up to 1000• C since thermal expansion invalidates the geometry specification from the calibration data sheet. In our first development we use a uniformly heated pipe made of stainless steel as a dummy specimen to examine the measured geometry data. A pyrometer measures the temperature of the pipe so the expansion can be easily calculated using the thermal expansion coefficient. Different impact and triangulation angles are investigated to identify the effects of hot ambient air on the measurement. The impact of the induced refractive index gradient is examined to check the need for pre-processing steps in the measurement routine.

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Section: Calibration Of the Fringe Projection Systemmentioning

confidence: 99%

3D geometry measurement of hot cylindric specimen using structured light

Quentin

Beermann

Posch

et al. 2017

Optical Measurement Systems for Industrial Inspection X

Self Cite

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“…Imaging in minimally invasive surgery is usually performed video endoscope, which is an essential imaging mode in medical image areas. Although some 3D endoscopies based on the stereo vision principles accomplished 3D imaging via the polarized glasses [1] , they failed to provide 3D information of organs due to the short baseline of the 3D endoscope. Recently, a great deal of attention has been given to the light field-based 3D endoscope that has the potential to acquire 3D information.…”

Section: Introductionmentioning

confidence: 99%

Depth constraints in two-step calibration method based on line features

Xu¹,

Xu²,

Zhou³

et al. 2023

International Conference on Optical and Photonic Engineering (icOPEN 2022)

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Calibration is essential for the three-dimensional light field endoscope, and the two-step calibration method based on line features was proposed by us to accomplish it before. In the second step of the two-step calibration method, the relationship between the projections of virtual feature points on the microlens image and the central sub-aperture image was used to calibrate the parameters about the microlens array, but we find that the feasibility of the calibration method has a depth constraint on the border of the checkerboard. In this paper, we deduce and demonstrate this constraint, and an optimization algorithm is designed to improve the accuracy of the second step calibration due to the inaccurate black-and-white boundary detection. Experimental results show that our method is effective and accurate for the calibration of the three-dimensional light field endoscope.

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“…Such an approach can be used when structured light is delivered through a rigid endoscope, e.g. [12,13], or a high-resolution fiber bundle, e.g. [14,15].…”

Section: Introductionmentioning

confidence: 99%