Researcher:
Kavaklı, Koray

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PhD Student

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Koray

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Kavaklı

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Kavaklı, Koray

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2021 - 202310

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Researcher Of Publications: search.filters.isAuthorOfPublication.009290dc-8c9b-499a-b713-bcc0c6acbfc8

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    Introduction to odak: a differentiable toolkit for optical sciences, vision sciences and computer graphics
    (Optica Publishing Group, 2022) Akşit, Kaan; N/A; Kavaklı, Koray; N/A; N/A; N/A
    This paper introduces Odak, an open-source toolkit that provides various differentiable simulation models for optical sciences, vision sciences, and computer graphics for gradient-based optimizations.
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    PublicationMetadata only
    Perceptually guided computer-generated holography
    (Spie-Int Soc Optical Engineering, 2022) Aksit, Kaan; Walton, David; Steed, Anthony; Dos Anjos, Rafael Kuffner; Friston, Sebastian; Weyrich, Tim; Ritschel, Tobias; N/A; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579
    Computer-Generated Holography (CGH) promises to deliver genuine, high-quality visuals at any depth. We argue that combining CGH and perceptually guided graphics can soon lead to practical holographic display systems that deliver perceptually realistic images. We propose a new CGH method called metameric varifocal holograms. Our CGH method generates images only at a user’s focus plane while displayed images are statistically correct and indistinguishable from actual targets across peripheral vision (metamers). Thus, a user observing our holograms is set to perceive a high quality visual at their gaze location. At the same time, the integrity of the image follows a statistically correct trend in the remaining peripheral parts. We demonstrate our differentiable CGH optimization pipeline on modern GPUs, and we support our findings with a display prototype. Our method will pave the way towards realistic visuals free from classical CGH problems, such as speckle noise or poor visual quality.
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    PublicationMetadata only
    Vision simulator for cataract screening using holographic near-eye display with pupil tracker
    (Association for Research in Vision and Ophthalmology (ARVO), 2021) N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; N/A; Kavaklı, Koray; Aydındoğan, Güneş; Şahin, Afsun; Ürey, Hakan; PHD Student; Researcher; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; College of Engineering; School of Medicine; College of Engineering; N/A; N/A; N/A; 171267; 8579
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    PublicationOpen Access
    Wearable multi-color RAPD screening device
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2023) Department of Electrical and Electronics Engineering; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan; Hasanreisoğlu, Murat; Kavaklı, Koray; Küçüködük, Abdullah; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; School of Medicine; Koç University Hospital; N/A; N/A; 171267; 8579; 182001; N/A; N/A; N/A; N/A; N/A
    In this work, we developed a wearable, head-mounted device that automatically calculates the precise Relative Afferent Pupillary Defect (RAPD) value of a patient. The device consists of two RGB LEDs, two infrared cameras, and one microcontroller. In the RAPD test, the parameters like LED on-off durations, brightness level, and color of the light can be controlled by the user. Upon data acquisition, a computational unit processes the data, calculates the RAPD score and visualizes the test results with a user-friendly interface. Multiprocessing methods used on GUI to optimize the processing pipeline. We have shown that our head-worn instrument is easy to use, fast, and suitable for early-diagnostics and screening purposes for various neurological conditions such as RAPD, glaucoma, asymmetric glaucoma, and anisocoria.
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    PublicationOpen Access
    Pupil steering holographic display for pre-operative vision screening of cataracts
    (Optica Publishing Group, 2021) Ulusoy, Erdem; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Aydındoğan, Güneş; Kesim, Cem; Hasanreisoğlu, Murat; Şahin, Afsun; Ürey, Hakan; Teaching Faculty; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; Koç University Hospital; N/A; N/A; N/A; 182001; 171267; 8579
    Cataract is the most common cause of preventable blindness and vision loss where the only treatment is surgical replacement of the natural lens with an intraocular lens. Computergenerated holography (CGH) enables to control phase, size, and shape of the light beam entering through the eye-pupil. We developed a holographic vision simulator to assess visual acuity for patients to experience the postoperative corrected vision before going through surgery. A holographically shaped light beam is directed onto the retina using small non-cataractous regions of the lens with the help of a pupil tracker. A Snellen chart hologram is shown to subjects at desired depth with myopia and hyperopia correction. Tests with 13 patients demonstrated substantial improvements in visual acuity and the simulator results are consistent with the post-operative vision tests. Holographic simulator overperforms the existing vision simulators, which are limited to static pinhole exit pupils and incapable of correcting aberrations.
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    PublicationOpen Access
    Metameric varifocal holograms
    (Institute of Electrical and Electronics Engineers (IEEE), 2022) Walton, D.R.; Dos Anjos, R.K.; Swapp, D.; Weyrich, T.; Steed, A.; Ritschel, T.; Aksit K.; Department of Electrical and Electronics Engineering; Ürey, Hakan; Kavaklı, Koray; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 8579; N/A
    Computer-Generated Holography (CGH) offers the potential for genuine, high-quality three-dimensional visuals. However, fulfilling this potential remains a practical challenge due to computational complexity and visual quality issues. We propose a new CGH method that exploits gaze-contingency and perceptual graphics to accelerate the development of practical holographic display systems. Firstly, our method infers the user's focal depth and generates images only at their focus plane without using any moving parts. Second, the images displayed are metamers; in the user's peripheral vision, they need only be statistically correct and blend with the fovea seamlessly. Unlike previous methods, our method prioritises and improves foveal visual quality without causing perceptually visible distortions at the periphery. To enable our method, we introduce a novel metameric loss function that robustly compares the statistics of two given images for a known gaze location. In parallel, we implement a model representing the relation between holograms and their image reconstructions. We couple our differentiable loss function and model to metameric varifocal holograms using a stochastic gradient descent solver. We evaluate our method with an actual proof-of-concept holographic display, and we show that our CGH method leads to practical and perceptually three-dimensional image reconstructions.
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    PublicationOpen Access
    Learned holographic light transport: invited
    (The Optical Society (OSA) Publishing, 2021) Akşit, Kaan; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579
    Computer-generated holography algorithms often fall short in matching simulations with results from a physical holographic display.Our work addresses this mismatch by learning the holographic light transport in holographic displays. Using a camera and a holographic display, we capture the image reconstructions of optimized holograms that rely on ideal simulations to generate a dataset. Inspired by the ideal simulations, we learn a complex-valued convolution kernel that can propagate given holograms to captured photographs in our dataset. Our method can dramatically improve simulation accuracy and image quality in holographic displays while paving the way for physically informed learning approaches.
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    PublicationOpen Access
    Artificial eye model and holographic display based IOL simulator
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2023) N/A; Department of Electrical and Electronics Engineering; N/A; Şahin, Afsun; Ürey, Hakan; Aygün, Uğur; Kavaklı, Koray; Akyazı, Deniz; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; School of Medicine; College of Engineering; Graduate School of Sciences and Engineering; 171267; 8579; N/A; N/A; N/A
    Cataract is a common ophthalmic disease in which a cloudy area is formed in the lens of the eye and requires surgical removal and replacement of eye lens. Careful selection of the intraocular lens (IOL) is critical for the post-surgery satisfaction of the patient. Although there are various types of IOLs in the market with different properties, it is challenging for the patient to imagine how they will perceive the world after the surgery. We propose a novel holographic vision simulator which utilizes non-cataractous regions on eye lens to allow the cataract patients to experience post-operative visual acuity before surgery. Computer generated holography display technology enables to shape and steer the light beam through the relatively clear areas of the patient’s lens. Another challenge for cataract surgeries is to match the right patient with the right IOL. To evaluate various IOLs, we developed an artificial human eye composed of a scleral lens, a glass retina, an iris, and a replaceable IOL holder. Next, we tested different IOLs (monofocal and multifocal) by capturing real-world scenes to demonstrate visual artifacts. Then, the artificial eye was implemented in the benchtop holographic simulator to evaluate various IOLs using different light sources and holographic contents.
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    PublicationOpen Access
    Applications of augmented reality in ophthalmology [invited]
    (Optical Society of America (OSA), 2021) Artal, Pablo; Department of Physics; Department of Electrical and Electronics Engineering; Aydındoğan, Güneş; Kavaklı, Koray; Ürey, Hakan; Şahin, Afsun; Faculty Member; Faculty Member; Department of Physics; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; N/A; N/A; 8579; 171267
    Throughout the last decade, augmented reality (AR) head-mounted displays (HMDs) have gradually become a substantial part of modern life, with increasing applications ranging from gaming and driver assistance to medical training. Owing to the tremendous progress in miniaturized displays, cameras, and sensors, HMDs are now used for the diagnosis, treatment, and follow-up of several eye diseases. In this review, we discuss the current state-of-the-art as well as potential uses of AR in ophthalmology. This review includes the following topics: (i) underlying optical technologies, displays and trackers, holography, and adaptive optics; (ii) accommodation, 3D vision, and related problems such as presbyopia, amblyopia, strabismus, and refractive errors; (iii) AR technologies in lens and corneal disorders, in particular cataract and keratoconus; (iv) AR technologies in retinal disorders including age-related macular degeneration (AMD), glaucoma, color blindness, and vision simulators developed for other types of low-vision patients.
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    PublicationOpen Access
    Mitigating edge fringe effects in multiplane holography
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2023) Akşit, Kaan; Itoh, Yuta; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579
    This poster presentation was prepared for the Optical Architectures for Displays and Sensing in Augmented, Virtual, and Mixed Reality (AR, VR, MR) IV Conference at the SPIE AR | VR | MR 2023 Symposium.