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In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using line field spectral domain optical coherence tomography. The conventional Fourier domain optical coherence tomography system requires a single scanner for two-dimensional cross-sectional images and two scanners for volumetric images. Our developed line field spectral domain optical coherence tomography has the advantage of needing only a single scanner for volumetric images, while two-dimensional cross-sectional images are obtained by the parallel acquisition of an illuminated line on a sample using an area camera. Further, the image acquisition speed was enhanced by implementing a high speed camera (340 frames per seconds) with improved quantum efficiency at near infrared region enabling two-fold frame rate. Cross-sectional and volumetric images were acquired to detect the internal sublayer defects in the optical thin films, which are difficult to observe using visual or machine vision-based inspection methods. The developed pseudo code for defect identification in optical thin films was well-utilized here for the defect inspection. The system characterization is demonstrated using United State Air Force (USAF) resolution target. The results indicate the possible application of the proposed system in touch screen panel inspection for the quality assurance of products at the consumer end.

An adaptive optics optical coherence tomography (AO-OCT) system with a non-modulated pyramid wavefront sensor (P-WFS) is presented. The P-WFS is implemented as add-on to a Shack Hartmann (SH) WFS based AO-OCT system, where the AO loop is driven by either sensor. Equivalent performance of the AO-OCT is demonstrated with the P-WFS and the SH-WFS by visualizing the mosaics of different retinal cell types in image data obtained in-vivo at the fovea of a healthy volunteer. Contrary to the SH-WFS, the pupil sampling of P-WFS is flexible and may be adjusted in order to further increase the sensitivity of the sensor.

An adaptive optics optical coherence tomography (AO-OCT) system with a 3-sided pyramid wavefront sensor (P-WFS) is presented. Compared to the Shack-Hartmann WFS, the P-WFS promises better sensitivity in low-light scenarios and greater flexibility in pupil sampling. Key feature of the presented set-up is that part of the imaging light is used to illuminate the WFS. The double pass enables closed loop correction without beam modulation and speckle patterns in the sensor read-out are averaged out during scanning. The developed instrument is demonstrated with retinal images obtained in-vivo, where the cone mosaic is clearly visualized at ~4° eccentricity from the fovea.

Adaptive optics (AO) systems for retinal imaging have a small field of view (FoV) of 1°-2°. To increase the FoV we developed a multi-conjugated AO-system. By choosing different scanning patterns, aberrations introduced by the eye at different locations within the FoV can be measured by a Shack Hartmann wavefront sensor. A second deformable mirror that is conjugated to a plane anterior to the retina corrects for varying aberrations across the field. Retinal imaging using spectral-domain optical coherence tomography is performed with 4o x 4o FoV and imaging data including the visualization of the cone mosaic is presented.

We developed a tunable laser diode for an optical coherence tomography system that can perform three-dimensional profile measurement using an area scanning technique. The tunable laser diode is designed using an Eagleyard tunable laser diode with a galvano filter. The Littman free space configuration is used to demonstrate laser operation. The line- and bandwidths of this source are 0.27 nm (∼110 GHz) and 43 nm, respectively, at the center wavelength of 860 nm. The output power is 20 mW at an operating current of 150 mA. A step height target is imaged using a wide-area scanning system to show the measurement accuracy of the proposed tunable laser diode. A TEM grid is also imaged to measure the topography and thickness of the sample by proposed tunable laser diode.

Actuator lens industries have gained an enormous interest with the enhancement of various latest communication devices, such as mobile phone and notebooks. The quality of the aforementioned devices can be degraded due to the internal defects of actuator lenses. Therefore, in this study, we implemented swept-source optical coherence tomography (SS-OCT) system to inspect defects of actuator lenses. Owing to the high-resolution of the SS-OCT system, defected foreign substances between the actuator lenses, defective regions of lenses and surface stains were more clearly distinguished through three-dimensional (3D) and two-dimensional (2D) cross-sectional OCT images. Therefore, the implemented SS-OCT system can be considered as a potential application to defect inspection of actuator lens.

A dual-path handheld system is proposed for cornea and retina imaging using spectral domain optical coherence tomography. The handheld sample arm is designed to acquire two images simultaneously. Both eyes of a person can be imaged at the same time to obtain the images of the cornea of one eye and the retina of the other eye. Cornea, retina, and optic disc images are acquired with the proposed sample arm. Experimental results demonstrate the usefulness of this system for imaging of different eye segments. This system reduces the time required for imaging of the two eyes and is cost effective.

A wavelength-swept laser is constructed using a free space external cavity configuration coupled with a fiber-based ring cavity at the 850 nm region. The external cavity filter employs a galvo-mirror scanner with a diffraction grating for wavelength selection. The filter is connected to a ring cavity through an optical circulator. The ring cavity contains a broadband semiconductor optical amplifier with a high optical output. The performance of this laser is demonstrated with broad bandwidths and narrow linewidths. The 3 dB linewidth and the bandwidth of this source are 0.05 nm (～20 GHz) and 48 nm, respectively. The maximum output power is 26 mW at 160 mA current.

Using adaptive optics optical coherence tomography, human photoreceptors and retinal pigment epithelium (RPE) cells are typically visualized on a small field of view of ∼1° to 2°. In addition, volume averaging is required for visualizing the RPE cell mosaic. To increase the imaging area, we introduce a lens based spectral domain AO-OCT system that shows low aberrations within an extended imaging area of 4°×4° while maintaining a high (theoretical) transverse resolution (at >7 mm pupil diameter) in the order of 2 µm. A new concept for wavefront sensing is introduced that uses light mainly originating from the RPE layer and yields images of the RPE cell mosaic in a single volume acquisition. The capability of the instrument for in vivo imaging is demonstrated by visualizing various cell structures within the posterior retinal layers over an extended field of view.

Adaptive optics plays an important role in the correction of high-order aberrations to enhance lateral resolution. An OCT system coupled with a programmable phase modulator is designed to verify lateral resolution improvement. The Hamamatsu high-resolution, non-pixelized, optically addressed light modulator (PAL-SLM) PPM X7550 series is used to correct aberrations, utilizing a simple method based on phase information from OCT images. The advantages of this method are its high simplicity and low cost. A raster scanning technique is adopted to scan samples covered with scattering suspension. Metal lines covered with scattering suspension are imaged, and a respective correction is applied to remove the aberration. Results demonstrate an improvement in lateral resolution on metal grid samples.

The conventional Fourier domain optical coherence tomography system requires single scanner for two dimensional cross-sectional image and two scanners for volumetric image. Parallel spectral domain optical coherence tomography has advantage of single scanner for volumetric image, while two dimensional cross-sectional images are obtained by parallel acquisition of illuminated line on sample using area camera. In this study, the industrial inspection of optical thin film on touch screen panels was demonstrated using parallel spectral domain optical coherence tomography. The cross-sectional and volumetric images were acquired to detect the internal sub layer defects in optical thin film which are difficult to observe using visual or machine vision based inspection methods. The results indicate the possible application of the proposed system in touch screen panels inspection for quality assurance of product at consumer end.

A dual illumination system is proposed for cornea and retina imaging using spectral domain optical coherence tomography (SD-OCT). The system is designed to acquire cornea and retina imaging with dual illumination with limited optics and using a single spectrometer. The beam propagation for cornea and retina imaging in dual illumination enables to acquire the images of different segments. This approach will reduce the imaging time for separate corneal and retinal imaging. The in vivo imaging of both the cornea and retina of a health volunteer shows the feasibility of the system for clinical applications

Here we describe the possible application of optical coherence tomography (OCT) to inspect Marssonina coronaria infected apple blotch disease of in situ apple leaves. To fulfill the in situ field inspection requirement, we developed a compact wearable OCT system. For the confirmation of OCT results, simultaneous experiment was performed in realtime using loop-mediated isothermal amplification (LAMP), which is frequently used in agriculture. LAMP method was developed as an alternative approach for the inspection of disease. We performed field inspection for 30 consecutive days, and all the acquired results from both OCT and lamp were compared to confirm the correlation. A clear identification between healthy specimens, apparently healthy but infected specimens, and infected specimens could be obtained through the real-time OCT images, and the correlation between OCT and lamp results was confirmed through the obtained realtime lamp results. Based on this feasibility study, we conclude that the combination of both these diagnosing modalities can be effective for various novel agricultural discoveries.

Adaptive optics is used in optical coherence tomography (OCT) in order to improve lateral resolution based on aberration correction. Experiments were performed to compensate higher order aberrations based on wavefront sensing and correction scheme using adaptive optics. The device utilized for compensation is parallel-aligned nematic liquid crystal spatial light modulator (PAL-SLM), PPM X7550 series. Wavefront of light at the sample path was measured by using OCT for aberration correction. Since the phase information can be obtained from interferogram therefore no additional optics is used. The performance of this device is evaluated for the correction of linear tilt aberration. Further experiments were performed to correct cylindrical aberration for reflective and scattering surfaces using a simplistic method which construct phase map using OCT. This method incorporates the PAL-SLM’s transfer function for the compensation of higher order aberration. The RMS of phase variation of cylindrical aberration without and with adaptive optics for reflective and scattering surface is reduced from 4.1 to 0.8 and 3.46 to 2.44, respectively. Metal grid sample is used to verify the lateral resolution improvement with adaptive optics. Arbitrary aberration can be corrected by using PPM. Purely reflective and scattering samples indicate the performance of OCT with adaptive optics. 25 mm separation of metal lines became distinguishable after correcting aberration by adaptive optics.

We report a wavelength swept laser-based full-field optical coherence tomography for measuring the surfaces and thicknesses of refractive and reflective samples. The system consists of a galvo filter–based wavelength swept laser and a simple Michelson interferometer. Combinations of the reflective and refractive samples are used to demonstrate the performance of the system. By synchronizing the camera with the source, the cross-sectional information of the samples can be seen after each sweep of the swept source. This system can be effective for the thickness measurement of optical thin films as well as for the depth investigation of samples in industrial applications. A resolution target with a glass cover slip and a step height standard target are imaged, showing the cross-sectional and topographical information of the samples.

A method for depth enhancement is presented using a bidirectional imaging modality for spectral domain optical coherence tomography (SD-OCT). Two precisely aligned sample arms along with two reference arms were utilized in the optical configuration to scan the samples. Using exemplary images of the optical resolution target, Scotch tape, a silicon sheet with two needles, and a leaf, we demonstrated how the developed bidirectional SD-OCT imaging method increases the ability to characterize depth-enhanced images. The results of the developed system were validated by comparing the images with the standard OCT configuration (single-sample arm setup). Given the advantages of higher resolution and the ability to visualize deep morphological structures, this method can be utilized to increase the depth dependent fall-off in samples with limited thickness. Thus, the proposed bidirectional imaging modality is apt for cross-sectional imaging of entire samples, which has the potential capability to improve the diagnostic ability.

An application of spectral domain optical coherence tomography (SD-OCT) was demonstrated for a fast industrial inspection of an optical thin film panel. An optical thin film sample similar to a liquid crystal display (LCD) panel was examined. Two identical SD-OCT systems were utilized for parallel scanning of a complete sample in half time. Dual OCT inspection heads were utilized for transverse (fast) scanning, while a stable linear motorized translational stage was used for lateral (slow) scanning. The cross-sectional and volumetric images of an optical thin film sample were acquired to detect the defects in glass and other layers that are difficult to observe using visual inspection methods. The rapid inspection enabled by this setup led to the early detection of product defects on the manufacturing line, resulting in a significant improvement in the quality assurance of industrial products.