Investigation of photobiological safety of blue light of LED image projector of household use

Light emitted in the wavelength range of 400–500 nm causes a very significant photochemical effect on the retina. At certain doses of blue light energy can cause damage to the retina, so the study of the safety of blue light projectors used in domestic conditions is an urgent task. The aim of this work is to study the photobiological safety of light image projectors with light emitting diodes. The paper analyzes the requirements for photobiological safety of tube systems and methods for assessing the danger of blue light of projectors that use LED light sources. The information is provided on the equipment for measurement of spectroradiometric and photometric parameters of beams of projectors, as well as features of radiance and irradiance measurement of lamp systems in which lens optics is used. The results of research of photobiological danger levels of blue light of image projectors intended for use in household conditions are presented. It is shown that at a distance of 1 m from the projector (the distance for which the level of photobiological safety of blue light is normalized), the investigated type of projector belongs to the risk group RG1 (insignificant risk). When the distance is reduced to 0.5 m and 0.2 m, the risk of blue light increases to the RG2 group (medium risk). The features of the requirements for photobiological safety of blue light of image projectors used in everyday life, educational institutions and in other conditions are analyzed. In particular, the risk group at a distance of 1 m from the collimator lens should not exceed RG1, and it is recommended to put an additional label on the projector indicating the risk group RG1 and mark this information in the user manual. Conclusions are made on the compliance of the studied low-power image projectors with the safety conditions of blue light, established by the international standard IEC 62471-5 (Photobiological Safety of Lamps and Lamp Systems – Part 5 Image Projectors).

Can Liquid Lenses Increase Depth of Field in Head Mounted Video See-Through Devices?

Wearable Video See-Through (VST) devices for Augmented Reality (AR) and for obtaining a Magnified View are taking hold in the medical and surgical fields. However, these devices are not yet usable in daily clinical practice, due to focusing problems and a limited depth of field. This study investigates the use of liquid-lens optics to create an autofocus system for wearable VST visors. The autofocus system is based on a Time of Flight (TOF) distance sensor and an active autofocus control system. The integrated autofocus system in the wearable VST viewers showed good potential in terms of providing rapid focus at various distances and a magnified view.