Aerial Imaging By Retro-reflection Research Articles

P‐122: Dependence of Aerial image quality on Display parameters in aerial Display system

In this paper, we report the relationship between the imaging spatial resolution and display parameters of the AIRR (aerial imaging by retro‐reflection) system, which we constructed using displays of different brightness, luminance spatial distribution and pixel pitch, respectively, and a line‐pair MTF‐based measurement method is applied to the system. The MTF measurement results show that the spatial resolution depends on the display pixel period size, luminance intensity and luminance spatial distribution.

Reducing thickness of long-distance aerial display system in AIRR using Fresnel lens

Aerial displays for providing road information require long-distance image formation and a compact installation space. This paper proposes a compact optical system for forming long-distance floating images by introducing a Fresnel lens in an aerial imaging by retro-reflection (AIRR) optical system. In the conventional AIRR optics, since the aerial image position is the plane-symmetrical position of the light source with respect to the beam splitter, the installation space for forming a long-distance aerial image becomes huge. Our proposed method uses the virtual image formed by a Fresnel lens as the light source in an AIRR optical system. This leads to a much longer distance from the beam splitter to the aerial image than the distance from the beam splitter to the light source. We developed a prototype long-distance floating aerial display system using a large-scale Fresnel lens. As a result, the distance from the LED panel to the beam splitter was halved. Furthermore, we used two beam splitters to form two aerial images by using a single LED panel. Long-distance floating images could be formed 3.4 m and 4.6 m away from the beam splitters and could be seen with the naked eye.

Formation of multiple aerial LED signs in multiple lanes formed with AIRR by use of two beam splitters

We propose multiple aerial imaging system by use of two beam splitters in the optical system of aerial imaging by retro-reflection (AIRR). The AIRR optical system consists of a light source, a beam splitter, and a retro-reflector. Use of two-layered beam splitters enables us to show multiple aerial signs to drivers in multiple driving lanes. The purpose of this paper is to confirm feasibility that an aerial display by use of AIRR for a novel traffic information provision. First, we explain an optical configuration to show aerial images to multiple road lanes, a driving lane and an overtaking lane with AIRR by use of two beam splitters. Next, we have developed a prototype optical system by use of two large beam splitters and a large high-brightness LED sign that is designed to be used for actual road displays. The light source was an LED display with a height of 450 mm and a width of 390 mm, which shows a character. We observed aerial images by naked eyes as experiments. And we discuss the issues for practical application that the experiments have revealed.

54‐3: Reduced Solar‐Loading Using Micro‐Mirror Array in Automotive HUD

Automotive head‐up displays (HUDs) use windshields as part of the display system and are used as partial reflectors for reflecting the images formed inside the dash board towards the driver. The locations of the aerial images are usually at the bumper of the vehicle and beyond, depending on the requirements. One of the major issues with such HUD system is the solar loading created by sunlight shining into the system through the image forming optics with focusing properties especially when the sun is shining into the HUD system in an off‐axis manner. This paper describes a HUD system where the imaging system uses a Micro‐Mirror Array Plate (MMAP) with an optical design that eliminates the issues associated with the off‐axis sunlight. Solar loading is an important design criterion as the HUD optics concentrate the sunlight to levels that can damage the display panel. Based on the aerial imaging properties of MMAP, this design would be applicable to the use of Dihedral Corner Reflector Array (DCRA), and Aerial Imaging by Retro‐Reflection (AIRR). Bench‐top system has been set up using MMAP from ASKA3D, Japan with the expected imaging properties. A complete prototype is being fabricated and will be reported.

Examination of deblur processing according to optical parameters in aerial image

We propose a pre-processing method of source image to reduce blur of aerial image that is formed with aerial imaging by retro-reflection (AIRR). The image blur in the AIRR optical system depends on the optical elements and the incident angle. In this paper, the point spread function (PSF) was measured by changing the optical arrangements and the retro-reflectors. A deconvolution processing based on the obtained PSF was applied on the aerial image. The accuracy of the deconvolution processing was quantitatively evaluated by use of three types of image quality indices. These numerical experimental results show the possibility of removing the blur of the aerial image by applying the deconvolution process based on the PSF of AIRR optical system.

Improvement of aerial image by simulations

We measured the contrast of standard charts using two different types of retro-reflectors in an AIRR (Aerial imaging by retro-reflection) system, and examined the results to be reproduced by optical simulation. As a result, it became possible to reproduce the effect of retro-reflector diffraction on the Aerial image quality of the AIRR system by optical simulation.

Proposal of moire-free aerial display based on the LED panel and apertured retro-reflector

We have realized a novel optical system to form a large aerial image in front of a full-color LED panel that is covered with retro-reflector. The retro-reflector has square apertures through which lights from the LED pixels pass. Our optical system is based on aerial imaging by retro-reflection (AIRR). The aerial image formed with AIRR is visible over a wide viewing angle without using 3D glasses. To reduce the system volume, a beam splitter is placed parallelly in front of the LED panel covered with the retro-reflector. Because the apertured retro-reflector is placed on the LED panel, no moire occurs between the apertures in the retro-reflector and black regions on the LED panel. We have analytically clarified the optimal aperture ratio in the proposed optical system to increase the luminance of the aerial image. Furthermore, we have developed a prototype for experimental confirmation of our optical system and measured of the luminance intensity of the aerial images. Consequently, we have confirmed measured results are consistent with our analysis. Showing aerial signage in front of an LED panel reduces the foot space, which is suitable for the installation of a large-scale aerial display for advertisement and exhibitions.

Reduction of retro-reflector and expansion of the viewpoint of an aerial image by the use of AIRR with transparent spheres

This paper proposes a novel optical system to form an aerial image over a transparent sphere. The proposed optical system is composed of two transparent acrylic spheres in the light path of the aerial imaging by retro-reflection (AIRR) device. The first sphere collects the diverging light rays from a light-source display. The second sphere converges retro-reflected light rays to the aerial image. Raytracing simulation results shows that the area of light entering the retro-reflector can be reduced. Furthermore, this reduction of retro-reflector has been confirmed with a prototype aerial display by the use of a piece of retro-reflector. Thus, the proposed optical system features reduction in the area of expensive retro-reflector.

Influence of incident angle, anisotropy, and floating distance on aerial imaging resolution

We measure the image resolution of aerial images formed with an AIRR (aerial imaging by retro-reflection) system. Using three different types of retro-reflectors inside the AIRR system, we measure the aerial image modulation transfer function (MTF) via the slanted knife edge method, showing that the resolution of depends on the angle of incidence on the retro-reflector, the retro-reflector's anisotropy, and the aerial image's floating distance.

Aerial Imaging by Retro-Reflection for Mid-Air Image Display and Camera Viewpoint Transfer

Previously, a telepresence system, called Levitar, was proposed to allow communication through computer-graphics (CG) avatars in real space. Levitar employs micro-mirror array plates (MMAPs) to display mid-air images and optically transfer the camera viewpoint to the mid-air image-display position optically. This system captures the first-person view of a mid-air image avatar; however, it has a limitation that the stray light caused by MMAPs reduces its range. Therefore, in this study, we propose an optical system to capture a wider range of mid-air viewpoints. The proposed optical system uses aerial imaging by retro-reflection (AIRR) instead of MMAPs for mid-air image display and camera viewpoint transfer. AIRR is a mid-air imaging system that includes a beam splitter and retro-reflector. However, in contrast to MMAPs, it does not generate stray light. The optical transfer of the camera viewpoint by AIRR enables the capture of a large area. To evaluate the range of the capturing area when using cameras with MMAPs and AIRR, we conducted experiments under different camera gaze directions and effective angle of view. The results indicate that AIRR maintains a constant resolution up to 40° of the camera gaze direction, whereas MMAPs have a lower resolution above 30°, and the area of the marker detection rate of over 80% is approximately 54% larger for AIRR than for MMAPs. This implies that AIRR achieved a wider imaging range than MMAPs for mid-air telepresence systems.

P‐74: Aerial Signage Formed with AIRR and DS3D Display

This paper proposes a novel aerial 3D display that forms an aerial image augmented in the real space with DS3D (directional scattering 3D) display. The aerial image is formed with AIRR (aerial imaging by retro‐reflection) in see‐through structure. We have demonstrated presenting the position of the aerial image to observers in an easy‐to‐understand method by pointing the position of the aerial image with the arrow of the 3D image. Furthermore, observers can view the aerial image and the real world behind the beam splitter at the same time.

Multiple aerial imaging by use of infinity mirror and oblique retro-reflector

We have realized a new optical system to form multiple aerial images by use of thin optical components. The proposed optical system is based on aerial imaging by retro-reflection (AIRR). The aerial image formed by AIRR is visible over a wide viewing angle without using 3D glasses. In addition to AIRR, we have introduced a technique called infinity mirror in which a mirror and a half mirror are arranged in parallel to form multiple virtual images of a single light source. By combining AIRR and infinity mirror, multiple images are formed in mid-air. By placing a retro-reflector obliquely outside the infinity mirror, our proposed optics improves the brightness of the aerial images by placing.

Development of omnidirectional aerial display with aerial imaging by retro-reflection (AIRR) for behavioral biology experiments

We have realized an omnidirectional aerial display for behavioral experiments. The omnidirectional aerial image is formed using a beam splitter with a cone shape. When an aerial image is shown to medaka and betta fish, they react following the aerial image. Furthermore, we propose a method for changing the position of the aerial image by increasing the distance between the beam splitter and the light source.

Aerial depth-fused 3D image formed with aerial imaging by retro-reflection (AIRR)

We have realized a new type of three-dimensional (3D) aerial image. The aerial image is an image that exists in the mid-air and can be observed without using 3D glasses. We utilized aerial imaging by retro-reflection (AIRR) to form the aerial image. Conventionally, the formed aerial image is a two-dimensional (2D) image. To give depth information, we have designed a new optical system to form two-layered aerial images. We have introduced depth-fused 3D (DFD) display technique. The DFD display is composed of a front image and a rear image. When the front and the rear images are overlapped from the viewing position, the two images are perceived as one depth-fused image. We realized this by overlapping two aerial images, taking advantage of the feature that the aerial image is translucent and we can observe the object behind it while observing the aerial image. Furthermore, we have demonstrated a protruding DFD display which gives depth beyond the gap of the two layers. Thus, we have realized aerial DFD display, which shows a floating 3D aerial image in the mid-air.

再帰反射による空中結像 (AIRR) による空中ディスプレイ

再帰反射による空中結像 (AIRR) による空中ディスプレイ

23-6 再帰反射によるLED 空中像(AIRR)の視域 : 再帰反射シートの角度とLED 空中像の輝度の関係(第23部門 立体映像技術)

23-6 再帰反射によるLED 空中像(AIRR)の視域 : 再帰反射シートの角度とLED 空中像の輝度の関係(第23部門 立体映像技術)

Comparison of Divergence Angle of Retro-Reflectors and Sharpness with Aerial Imaging by Retro-Reflection (AIRR)

Comparison of Divergence Angle of Retro-Reflectors and Sharpness with Aerial Imaging by Retro-Reflection (AIRR)

Floating aerial LED signage based on aerial imaging by retro-reflection (AIRR).

We propose a floating aerial LED signage technique by utilizing retro-reflection. The proposed display is composed of LEDs, a half mirror, and retro-reflective sheeting. Directivity of the aerial image formation and size of the aerial image have been investigated. Furthermore, a floating aerial LED sign has been successfully formed in free space.