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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Now showing 1 - 10 of 16
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    PublicationOpen Access
    Autocolor: learned light power control for multi-color holograms
    (SPIE, 2024) Zhan, Yicheng; Sun, Qi; Akşit, Kaan; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Graduate School of Sciences and Engineering; College of Engineering
    Multi-color holograms rely on simultaneous illumination from multiple light sources. These multi-color holograms could utilize light sources better than conventional single-color holograms and can improve the dynamic range of holographic displays. In this letter, we introduce AutoColor, the first learned method for estimating the optimal light source powers required for illuminating multi-color holograms. For this purpose, we establish the first multi-color hologram dataset using synthetic images and their depth information. We generate these synthetic images using a trending pipeline combining generative, large language, and monocular depth estimation models. Finally, we train our learned model using our dataset and experimentally demonstrate that AutoColor significantly decreases the number of steps required to optimize multi-color holograms from > 1000 to 70 iteration steps without compromising image quality. © 2024 SPIE.
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    Publication
    Flexible modeling of next-generation displays using a differentiable toolkit
    (SPIE, 2023) Akşit, Kaan; Kavaklı, Koray; Graduate School of Sciences and Engineering
    We introduce an open-source toolkit for simulating optics and visual perception. The toolkit offers differentiable functions that ease the optimization process in design. In addition, this toolkit supports applications spanning from calculating holograms for holographic displays to foveation in computer graphics. We believe this toolkit offers a gateway to remove overheads in scientific research related to next-generation displays. © 2023 SPIE.
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    Publication
    Wearable multi-color RAPD screening device
    (SPIE-Int Soc Optical Engineering, 2023)  ; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Gülersoy, Arda; Tuzcu, Ahmet Berk; Gündüzalp, Doğa; Kavaklı, Koray; Küçüködük, Abdullah; Güleser, Ümit Yaşar; Aygün, Uğur; Hasanreisoğlu, Murat; Şahin, Afsun; Ürey, Hakan; Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; Koç University Hospital
    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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    Publication
    Artificial eye model and holographic display based IOL simulator
    (SPIE-Int Soc Optical Engineering, 2023)  ; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Akyazı, Deniz; Kavaklı, Koray; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan;  ; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering;  
    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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    Publication
    Enhancing brightness with multi-color holography
    (John Wiley and Sons Inc, 2024) Shi, Liang; Matusik, Wojciech; Akşit, Kaan; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Graduate School of Sciences and Engineering; College of Engineering
    Holographic displays traditionally project full-colored holograms time-sequentially to achieve colored images. Time-sequential image formation limits the achievable brightness levels. This work introduces a new method to achieve brighter images in holographic displays. Unlike the usual approach, our method allows three light sources to simultaneously illuminate the displayed holograms at different intensity levels. We optimize phase holograms along with the required intensity levels for each frame using our gradient-descent based optimization pipeline. © 2024, John Wiley and Sons Inc. All rights reserved.
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    Publication
    Improving defocus blur in holographic displays
    (John Wiley and Sons Inc, 2023) Itoh, Yuta; Akşit, Kaan; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; Graduate School of Sciences and Engineering; College of Engineering
    In this paper we present a novel multiplane computer generated hologram calculation approach that enables artifact free and realistic-looking defocus blur for optical reconstructions in a holographic display. We introduce a new targeting method and a loss function that evaluates the focused and defocused parts of the reconstructed images. We demonstrate that our method is applicable to various standard hologram generation routines such for both iterative and non-iterative CGH calculation methods. We also demonstrate our new gradient descent-based optimization with double phase constraint combined with our targeting scheme and loss function provides the best image quality. We validate our findings for both the numerical reconstructions and optical captures that are acquired from our holographic display prototype. © 2023, John Wiley and Sons Inc. All rights reserved.
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    Publication
    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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    Publication
    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; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Ürey, Hakan; PhD Student; Faculty Member; 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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    Publication
    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; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Aydındoğan, Güneş; Şahin, Afsun; Ürey, Hakan; PHD Student; Researcher; Faculty Member; Faculty Member; 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; Department of Electrical and Electronics Engineering; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan; Hasanreisoğlu, Murat; Kavaklı, Koray; Küçüködük, Abdullah; Faculty Member; Faculty Member; Faculty Member; 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.