• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.706-709
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• 2005

A hybrid focus method with multiple laser slits has been newly proposed and it is based on the integration of DFD and DFF Rough depth information is estimated using DFD equipped with multiple laser slits, and then DFF is applied to only each specific depth range using the depth information resulting from DFD. The proposed hybrid method gives more accurate results than DFD and DFF, and faster measurement than DFF. Its performance has been verified through experiments of calibration blocks with sharp depth discontinuity.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.111-118
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• 2006

A hybrid focus method with multiple laser slits is newly proposed for the measurement of surface morphology with depth discontinuity, and it is based on the integration of DFB and DFF. Rough depth information is estimated through calibration tables which are constructed by DFD with multiple laser slits, and then DFF is applied to only each specific depth range using the rough depth information resulting from DFD. The proposed hybrid method gives more accurate results than DFD and DFF, and faster measurement than DFF in the vicinity of depth discontinuity Its performance is verified through experiments of calibration blocks with sharp depth discontinuity.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.115-122
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• 2005

Errors resulting from magnification variations of a optical system are largely generated in three-dimensional shape measurements based on depth-from-focus. In the case of measuring the surface morphology of tiny objects based on DFF, images are acquired with a very small interval so that magnification changes can be minimized. However, the magnification variations are actually existed in the acquired images and so focus measures are wrongly or ambiguously extracted. In this paper, a methodology with linear magnification calibrations, based on DFF, is proposed to make more accurate measurement in surface morphology with high depth discontinuity, compared with previous ones. Several experiments show that the proposed method outperforms existing ones without magnification calibrations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1500-1503
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• 2004

Errors resulting from magnification variations of optical system are largely generated in three-dimensional shape measurements. In the case of measuring the surface morphology of tiny objects based on DFF, images are acquired with a very small interval and then magnification changes are minimized. However, the magnification variations are actually existed in optical system and so focus measures in DFF are wrongly or ambiguously extracted. in this paper, a methodology based on DFF with the magnification changes is proposed to make more accurate measurement in surface morphology with high depth discontinuity, compared with previous ones. Several experiments show that the proposed method outperforms existing ones without magnification changes.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.17-21
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• 2022

A variety of techniques have been proposed in the literature for depth improvement in depth from focus method. Unfortunately, these techniques over-smooth the depth maps over the regions of depth discontinuities. In this paper, we propose a robust technique for improving the depth map by employing a nonconvex smoothness function that preserves the depth edges. In addition, the proposed technique exploits the mutual structures between the depth map and a guidance map. This guidance map is designed by taking the mean of image intensities in the image sequence. The depth map is updated iteratively till the nonconvex objective function converges. Experiments performed on real complex image sequences revealed the effectiveness of the proposed technique.