Fumio Okuyama

Evaluation of stereoscopic display with visual function and interview

The influence of binocular stereoscopic (3D) television display on the human eye were compared with one of a 2D display, using human visual function testing and interviews. A 40- inch double lenticular display was used for 2D/3D comparison experiments. Subjects observed the display for 30 minutes at a distance 1.0 m, with a combination of 2D material and one of 3D material. The participants were twelve young adults. Main optometric test with visual function measured were visual acuity, refraction, phoria, near vision point, accommodation etc. The interview consisted of 17 questions. Testing procedures were performed just before watching, just after watching, and forty-five minutes after watching. Changes in visual function are characterized as prolongation of near vision point, decrease of accommodation and increase in phoria. 3D viewing interview results show much more visual fatigue in comparison with 2D results. The conclusions are: 1) change in visual function is larger and visual fatigue is more intense when viewing 3D images. 2) The evaluation method with visual function and interview proved to be very satisfactory for analyzing the influence of stereoscopic display on human eye.

Extraction Method of Retinal Border Lines in Optical Coherence Tomography Image by Using Dynamic Contour Model

In the field of ophthalmology, the needs of retina diagnosis using optical coherence tomography (OCT) images have been growing, and the automatic measurement of a retina thickness and its quantitative evaluation are desired for the diagnosis of retinal diseases. Previously, the automatic measurement methods of the retinal thickness have been reported for retinal OCT images. These previous methods can extract the retinal border lines (ILM and RPE) appropriately in most cases of normal OCT image. However these methods caused the tracking error to some OCT images with large noises. In this paper, we propose a new automatic measurement method of a retinal thickness in OCT image. The method employs ODAN (One Directional Active Net) to extract ILM and RPE. ODAN employs a new energy function to extract the retinal border lines exactly and all nodes of ODAN moves only to one direction to minimize the total energy repeatedly. The energy function consists of (1) the conformity characteristics energy of image and (2) the internal strain energy. We confirmed the usefulness of the ODAN by the experimental results for ten OCT images with large noises. We compared the positions of retinal border lines by the proposed method with the positions in a manual trace by ophthalmology specialist. In the comparative result, the proposed method is useful as the basic method for the detection of retinal diseases.

Telemedicine Imaging Collaboration System with Virtual Common Information Space

The computerization of the clinical record and the realization of the multimedia has brought improvement of the medical service in medical facilities. It is very important for the patients to obtain comprehensible informed consent. Therefore, the doctor should plainly explain the purpose and the content of the diagnoses and treatments for the patient. We propose and design a Telemedicine Imaging Collaboration System which presents a three dimensional medical image as Xray CT, MRI with stereoscopic image by using virtial common infomation space and operating the image remotely. This system can offer a comprehensible three-dimensional image of the diseased part. Therefore, the doctor and the patient can easily understand it, depending on the their demand. In this paper, we described the examination situation of the system design

A Retinal Layer Structure Analysis to Measure the Size of Disease Using Layer Boundaries Detection for Optical Coherence Tomography Images

In the field of ophthalmology, optical coherence tomography (OCT) is rapidly becoming popular in clinical applications to diagnose retinal disease. In this paper, we proposed a new profile analysis to evaluate the size of the retinal disease using the number of layer boundaries. The number is established by a new analysis method of a gray level profile scanned in longitudinal direction for an OCT image. We employed the proposed method for 50 OCT images of normal retina and 50 OCT images of abnormal retina. The experiment result showed that a significant difference was obtained in the significance level at 1%, when we employed Mann-Whitney U method on the standard deviation of the number of layer boundaries for normal and abnormal retinal images group. Therefore, we confirmed that the proposed method becomes one of the indexes to evaluate the size of the retinal disease. In addition, we confirmed that our system can measure the size of abnormal part in horizontal direction using the number of layer boundaries.

Response of accommodation and vergence to electro-holographic images

Studies on measuring accommodation and vergence responses of human vision are important to evaluate three-dimensional (3D) display technologies. Electro-holography is expected to be an ideal 3D display. However, there has been little research on measuring responses to it. In this study, the static responses to electro-holographic images with a large visual field and correct stimuli were measured. In addition, responses to real objects were measured for comparison with those to displayed images. There were more subjects than in conventional studies for statistical analysis. The experimental results statistically confirmed the equivalence of the responses to electro-holographic images and those to real objects. Therefore, it was experimentally suggested that electro-holography enables human vision to perform correct accommodation and vergence responses in accordance with the depths.

Eyepiece-type full-color electro-holographic display for binocular vision

Head-mounted type 3-D displays are expected to be useful with Augmented Reality techniques to provide visual information. However, because these displays use the stereoscopic method to provide 3-D vision, observers tend to experience eye discomfort when viewing 3-D images due to the disparity between accommodation and convergence. Electro-holography is a rival technique that displays holograms on electrical devices such as a spatial light modulator and enables observers to view ideal 3-D images in comfort for many hours. In the current study, we applied the holography technique to an eyepiece-type display in order to solve the disparity problem. Our system can represent 3-D images at arbitrary depths and displays large reconstructed images by using a Fourier transform optical system. We also adopted the time division color method to reconstruct full-color images. In computer generated holography, holograms for each color are calculated considering with the distance between their wavelength. In this paper, we describe our calculation algorithm and report the fabrication of an eyepiecetype full color electro-holographic display for binocular vision. To confirm the effectiveness of the proposed system, the reconstructed images were evaluated both objectively and subjectively. Results of experiments show that reconstructed full-color images are located at the correct depth.

Dynamic visual responses of accommodation and vergence to electro-holographic images

Electro-holography can display images without inducing fatigue and three-dimensional (3D) sickness, i.e., visual discomfort due to viewing a stereoscopic display. Thus, this technology is expected to be applied to 3D media. However, there are no studies that have shown the agreement between the dynamic responses of accommodation and vergence to the reconstructed images of electro-holography and those to the real targets. This paper describes the measurement results of these responses using a developed system that can simultaneously measure the dynamic responses of accommodation and vergence. Moreover, statistical analysis for associating the accommodation and the vergence responses was achieved, and our study confirmed that these responses were in agreement.

Application of PC stereoscopic image viewer for informed consent

Informed consent for patients becomes important clinics where the doctor explains diseases and treatments. But patients have difficulty understanding medical images, i.e. X-rays, CT or MRI because the patient is not expert in reading these medical images. In this paper, we tried to reconstruct the stereoscopic image of CT and MRI and display these using a simple and low cost auto-stereoscopic viewer.

Extraction of Disease Area from Retinal Optical Coherence Tomography Images Using Three Dimensional Regional Statistics

We propose a new extraction method of the macular disease area in the human retinal layer from OCT images using three dimensional regional statistics. In previous researches, we extracted disease area by using the mean and standard deviation of the two dimensional disease part pointed out by a clinical doctor. However, the previous method cannot extract disease area for some disease OCT images precisely. In this paper, we propose a new extraction method of the disease area using three dimensional regional statistics. We use a set of 128 images (3D-OCT image) consisted of 2 dimensional OCT retinal image about one retina of a patient. The regional mean and regional standard deviation of gray level are calculated in the three dimensional region of interest (ROI, 125 (=5 × 5 h 5) pixels) in the abnormal area pointed by a clinical doctor. These values are compared with every ROI in the abnormal area to extract the disease area, and the proposal system measures the volume of the disease area. We apply the proposed method to OCT images of 5 patients with retinal diseases. As a result, we can measure the volume of the abnormal area with 80.7% average accuracy.

Calculation method of CGH for Binocular Eyepiece-Type Electro Holography

We had researched about eyepiece-type electro holography to display 3-D images of larger objects at wider angle. We had enlarged visual field considering depth of object with Fourier optical system using two lenses. In this paper, we extend our system for binocular. In the binocular system, we use two different holograms for each eye. The 3-D image for left eye should be observed like the real object observed using left eye and the same for right eye. So, we propose a method of calculation of computer-generated hologram (CGH) transforming the coordinate system of the model data to make two holograms for binocular eyepiece-type electro holography. The coordinate system of original model data is called the world coordinate system. The left and the right coordinate system are transformed from the world coordinate system. We also propose the method for correcting the installation error that occurs when placing the electronic and optical devices. The installation error is calculated and the model data is corrected using the distance between measured position and setup position of the reconstructed image Optical reconstruction experiments were carried out to verify the proposed method.