Spectral characteristics of chromatic confocal imaging systems

Hillenbrand, Matthias; Mitschunas, Beate Dr.-Ing.; Brill, Florian H. H.; Grewe, Adrian; Sinzinger, Stefan

doi:10.1364/ao.53.007634

Cited by 35 publications

(8 citation statements)

References 35 publications

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“…This section is thus limited to a quantitative evaluation of the chromatic confocal module and to several proof-of-principle experiments with the full sensor system. Following the discussion in [55] the spectral peak is selected as the performance criterion for the chromatic confocal module. For the evaluation of the spectral peak the chromatic confocal module was set up without the beam splitter and the illumination and the detection modules.…”

Section: Methodsmentioning

confidence: 99%

Chromatic confocal matrix sensor with actuated pinhole arrays

et al. 2015

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We present two versions of a chromatic confocal matrix sensor for the snapshot acquisition of three-dimensional objects. The first version contains separate illumination and detection pinhole arrays, while the second version uses a single pinhole array in double pass. The discrete lateral measurement points defined by the illumination and detection pinhole arrays are evaluated in parallel with a hyperspectral detection module. As this approach enables the spectrometric evaluation of all lateral channels, multilayer objects can be analyzed. To increase the lateral resolution the pinhole arrays are moved by micromechanical actuators. The paper includes a quantitative evaluation of the chromatic confocal module and proof-of-principle experiments with the full sensor system.

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Section: Methodsmentioning

confidence: 99%

Chromatic confocal matrix sensor with actuated pinhole arrays

et al. 2015

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“…For accuracy improvement, the presented works focused on optical model optimization. Hillenbrand M et al [14] presented a novel mathematical function, called the intensity point-spread function, to reshape the characteristic curve of the chromatic confocal system. Using this method, the measurement repeatability and computation efficiency could be improved.…”

Section: Of 16mentioning

confidence: 99%

Thickness Measurement for Glass Slides Based on Chromatic Confocal Microscopy with Inclined Illumination

Zhang

Shang

et al. 2021

Photonics

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Chromatic confocal microscopy is a widely used method to measure the thickness of transparent specimens. In conventional configurations, both the illumination and imaging axes are perpendicular to the test specimen. The reflection will be very weak when measuring high-transparency specimens. In order to overcome this limitation, a special chromatic confocal measuring system was developed based on inclined illumination. This design was able to significantly improve the signal-to-noise ratio. Compared with conventional designs, the proposed system was also featured by its biaxial optical scheme, instead of a coaxial one. This biaxial design improved the flexibility of the system and also increased the energy efficiency by avoiding light beam splitting. Based on this design, a prototype was built by the authors’ team. In this paper, the theoretical model of this specially designed chromatic confocal system is analyzed, and the calculating formula for the thickness of transparent specimen is provided accordingly. In order to verify its measurement performance, two experimental methodology and results are presented. The experimental results show that the repeatability is better than 0.54 μm, and the axial measurement accuracy of the system could reach the micron level.

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“…A comprehensive study of chromatic confocal signals, based on a similar approach as described in [17,18] discusses a spatially incoherent wave-optical model for chromatic confocal imaging systems [19]. The assumption of invariant intensity point spread function (IPSF) in isoplanatic regions [20] allows the calculation of the radiant flux in any arbitrary plane in the image space simply by convolving the ideal pinhole image with the local IPSF.…”

Section: Introductionmentioning

confidence: 99%

A wave-optical model for chromatic confocal sensing using multimode fibre incoherent illumination

Nizami

Claus

2021

J. Opt.

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This paper presents a wave-optical model for chromatic confocal signals based on multimode optical fibre data acquisition. It is shown that the emitted light from a multimode fibre can be modelled as a point source grid. The confocal signal can be obtained by incoherent summation of the intensities of the reflected fields in the detector plane. In this manner, this two-dimensional wave-optical model encompasses the temporal incoherence of the light source due to the usage of a broadband light source and the spatial incoherence due to the application of a multimode fibre. In fact, this model enables the modelling of different degrees of coherence. Therefore, to our knowledge, it represents the most thorough modelling tool for chromatic confocal signals. Physical parameters such as the spectral distribution of the polychromatic light source, the lateral distribution of point sources on the grid, and the strength of longitudinal aberrations, and their influences on the chromatic confocal signal have been evaluated in detail. Consideration of all these parameters results in simulated chromatic confocal signals, which almost perfectly match the experimentally recorded chromatic confocal signals. The results obtained will be very useful for the development of a deeper understanding of chromatic confocal sensing, to optimise the setup parameters with regard to a particular application and to reinterpret the results, possibly in combination with artificial intelligence algorithms, in order to increase the measurement precision and to reduce the demands imposed on the manufacturing quality of the optical elements.

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Spectral characteristics of chromatic confocal imaging systems

Cited by 35 publications

References 35 publications

Chromatic confocal matrix sensor with actuated pinhole arrays

Chromatic confocal matrix sensor with actuated pinhole arrays

Thickness Measurement for Glass Slides Based on Chromatic Confocal Microscopy with Inclined Illumination

A wave-optical model for chromatic confocal sensing using multimode fibre incoherent illumination

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