Aquatic information display and its applications for behavioral biology experiments

This paper proposes a new display that forms information screen in water or around a water tank. The information screen is formed with aerial imaging by retro-reflection (AIRR). AIRR employs three elements, which are a light source, a beam splitter, and a retro-reflector. The retro-reflector converges the retro-reflected lights to the plane-symmetrical position of the light source regarding the beam splitter. AIRR features a wide viewing angle, a large-size scalability, and a low cost with mass-productive process. An information screen inside a water tank can be formed with the following three types of optical systems. In Type I, we place a beam splitter above the water surface to reflect lights from the light source and transmit the retro-reflected lights. Type II uses the water surface as a beam splitter because the intersection between water and air causes reflection and refraction. Type III uses the bottom of the water tank as a beam splitter. Preliminary experimental results show that Type III forms a clearer and stable image inside water. By use of a coneshaped beam splitter and a flat panel display, we have formed an omni-directional information screen that surrounds a cylindrical water tank. We have utilized this omni-directional display to investigate optomotor reaction of fish for the visual stimuli. A medaka in the water tank followed to the rotating stripes shown on the surrounding screen. Furthermore, a medaka reacted to a biological motion image that was shown in water. Thus, the proposed display is useful for behavioral biology experiments.