Optical implementation of partially negative filters using a spectrally tunable light source, and its application to contrast enhanced oral and dental imaging

Hyttinen, Joni; Fält, Pauli; Jäsberg, Heli; Kullaa, Arja; Hauta-Kasari, Markku

doi:10.1364/oe.27.034022

Cited by 8 publications

(4 citation statements)

References 21 publications

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“…The difference is that the defect area cannot be objectively quantified in all images [9]. In 2019, Hyttinen et al [10] reported a method that can be used to implement the positive and negative parts of optical filters separately and apply the effect from a partially negative optical filter for imaging purposes. The partially negative filters are split into positive and negative parts that can then be implemented optically.…”

Section: Introductionmentioning

confidence: 99%

Optical Interference Filters Combined with Thin Film Residual Stress Compensation for Image Contrast Enhancement

Tien

Cheng

et al. 2023

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We propose two single-wavelength notch filters and one dual-wavelength (480 and 620 nm) notch filter to enhance image contrast. The stack structure of the notch filters was designed as (Ta2O5/SiO2)4Ta2O5 in Essential Macleod thin film simulation software. Dual-electron-beam evaporation with ion beam-assisted deposition was used to prepare optical interference filters with different center wavelengths. A multilayer notch filter with a center wavelength of 620 nm was deposited on the front surface of the glass, and then a notch filter with a center wavelength of 480 nm was coated on the rear surface of the same glass. The proposed dual-wavelength (480 and 620 nm) notch filter is a combination of two single-wavelength notch filters coated on a double-sided glass substrate to compensate for residual stress. The transmittance, residual stress, and surface roughness of the proposed notch filter were evaluated using different measuring instruments. The experimental results show that the residual stress of the dual-wavelength notch filter could be reduced to 10.8 MPa by using a double-sided coating technique. The root-mean-square (RMS) surface roughness of the notch filters was measured by using a Linnik microscopic interferometer. The RMS surface roughness was 1.80 for the 620 nm notch filter and 2.09 for the 480 nm notch filter. The image contrast obtained with the three different notch filters was measured using an optical microscope and a CMOS camera. The contrast value could be increased from 0.328 (without a filter) to 0.696 (dual-wavelength notch filter).

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Section: Introductionmentioning

confidence: 99%

Optical Interference Filters Combined with Thin Film Residual Stress Compensation for Image Contrast Enhancement

Tien

Cheng

et al. 2023

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“…Although wide-angle imaging systems provide richer information, they always suffer from several problems, especially the transmitted color of light change from different angles. The optical filter is a critical component of imaging systems, which has various applications, including depth camera [ 9 ], chemical analysis [ 10 ], color imaging [ 11 ], medical imaging [ 12 ], etc. Unfortunately, the wavelength transmittance in an optical filter, especially the band-pass filter, does not always guarantee steady performance at a wide angle.…”

Section: Introductionmentioning

confidence: 99%

Wide-Angular Tolerance Optical Filter Design and Its Application to Green Pepper Segmentation

Shu

Kurihara

2023

Sensors

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The optical filter is critical in many applications requiring wide-angle imaging perception. However, the transmission curve of the typical optical filter will change at an oblique incident angle due to the optical path of the incident light change. In this study, we propose a wide-angular tolerance optical filter design method based on the transfer matrix method and automatic differentiation. A novel optical merit function is proposed for simultaneous optimization at normal and oblique incidents. The simulation results demonstrate that such a wide-angular tolerance design can realize a similar transmittance curve at an oblique incident angle compared to a normal incident angle. Furthermore, how much improvement in a wide-angular optical filter design for oblique incident contributes to image segmentation remains unclear. Therefore, we evaluate several transmittance curves along with the U-Net structure for green pepper segmentation. Although our proposed method is not perfectly equal to the target design, it can achieve an average 50% smaller mean absolute error (MAE) than the original design at 20∘ oblique incident angle. In addition, the green pepper segmentation results show that wide-angular tolerance optical filter design improves the segmentation of the near-color object about 0.3% at 20∘ oblique incident angle compared to the previous design.

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“…Successful data-analysis can allow the design of optimized optical imaging solutions for targeted diagnostic analyses. In the simplest cases, spectral images can be used to design systems that enhance the visibility of a targeted feature, for example, by applying different weights on the bands while computing a color image representation [7], or by optimizing contrast to produce optimal optical filters [8,9]. The selected spectra could also be used in training targeted diagnostic imaging systems, like spectral filter array cameras [10], or in automatic diagnostic image segmentation based on deep learning [11].…”

Section: Introductionmentioning

confidence: 99%

“…The annotations were made by dental experts, who used an annotation tool built for the project. We have successfully used the database to develop a prototype optical imaging system based on partially negative filters derived from principal component analysis of healthy and diseased tissue [9], and in automatic image segmentation and classification based on a convolutional neural network [11].…”

Section: Introductionmentioning

confidence: 99%

Oral and Dental Spectral Image Database—ODSI-DB

et al. 2020

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The most common imaging methods used in dentistry are X-ray imaging and RGB color photography. However, both imaging methods provide only a limited amount of information on the wavelength-dependent optical properties of the hard and soft tissues in the mouth. Spectral imaging, on the other hand, provides significantly more information on the medically relevant dental and oral features (e.g. caries, calculus, and gingivitis). Due to this, we constructed a spectral imaging setup and acquired 316 oral and dental reflectance spectral images, 215 of which are annotated by medical experts, of 30 human test subjects. Spectral images of the subjects’ faces and other areas of interest were captured, along with other medically relevant information (e.g., pulse and blood pressure). We collected these oral, dental, and face spectral images, their annotations and metadata into a publicly available database that we describe in this paper. This oral and dental spectral image database (ODSI-DB) provides a vast amount of data that can be used for developing, e.g., pattern recognition and machine vision applications for dentistry.

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Optical implementation of partially negative filters using a spectrally tunable light source, and its application to contrast enhanced oral and dental imaging

Cited by 8 publications

References 21 publications

Optical Interference Filters Combined with Thin Film Residual Stress Compensation for Image Contrast Enhancement

Optical Interference Filters Combined with Thin Film Residual Stress Compensation for Image Contrast Enhancement

Wide-Angular Tolerance Optical Filter Design and Its Application to Green Pepper Segmentation

Oral and Dental Spectral Image Database—ODSI-DB

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