The blue light hazard (BLH) to human eye’s retina is now a new issue emerging in applications of artificial
light sources. Especially for solid state lighting sources based on the blue chip-LED(GaN), the photons with
their energy more than 2.4 eV show photochemical effects on the retina significantly, raising damage both in
photoreceptors and retinal pigment epithelium.
The photobiological safety of artificial light sources emitting optical radiation has gained more and more
attention worldwide and addressed by international standards IEC 62471-2006(CIE S009/E: 2002).
Meanwhile, it is involved in IEC safety specifications of LED lighting products and covered by European
Directive 2006/25/EC on the minimum health and safety requirements regarding the exposure of the workers
to artificial optical radiation. In practical applications of the safety standards, the measuring methods of
optical radiation from LED products to eyes are important in establishment of executable methods in the
industry. In 2011, a new project to develop the international standard of IEC TR62471-4,that is “Measuring
methods of optical radiation related to photobiological safety”, was approved and are now under way. This
paper presents the concerned methods for the assessment of optical radiation hazards in the standards.
Furthermore, a retina radiance meter simulating eye’s optical geometry is also described, which is a
potential tool for blue light hazard assessment of retinal exposure to optical radiation. The spectroradiometric
method integrated with charge-coupled device(CCD) imaging system is introduced to provide more reliable
Traditional light sources were required to provide stable and uniform illumination for a living or working environment
considering performance of visual function of human being. The requirement was always reasonable until non-visual
functions of the ganglion cells in the retina photosensitive layer were found. New generation of lighting technology,
however, is emerging based on novel lighting materials such as LED and photobiological effects on human physiology
To realize dynamic lighting of LED whose intensity and color were adjustable to the need of photobiological effects, a
quantitative dimming method based on Pulse Width Modulation (PWM) and light-mixing technology was presented.
Beginning with two channels’ PWM, this paper demonstrated the determinacy and limitation of PWM dimming for
realizing Expected Photometric and Colorimetric Quantities (EPCQ), in accordance with the analysis on geometrical,
photometric, colorimetric and electrodynamic constraints. A quantitative model which mapped the EPCQ into duty
cycles was finally established. The deduced model suggested that the determinacy was a unique individuality only for
two channels’ and three channels’ PWM, but the limitation was an inevitable commonness for multiple channels’. To
examine the model, a light-mixing experiment with two kinds of white LED simulated variations of illuminance and
Correlation Color Temperature (CCT) from dawn to midday. Mean deviations between theoretical values and measured
values were obtained, which were 15lx and 23K respectively. Result shows that this method can effectively realize the
light spectrum which has a specific requirement of EPCQ, and provides a theoretical basis and a practical way for
dynamic lighting of LED.
Two methods for colorimetric characterization of color scanner are proposed based on the measures of perceptual color difference error. The first method is used to minimize the total color differences between the actual and predicted color samples. The second one, which is a generalization of the existing cubic-root preprocessing technique, derives the mapping between the p'th root of scanner responses and Commission Internationale de l'Eclairage L*a*b* (CIELAB) values. The experiment results indicate that the color accuracies of the proposed methods, especially the second one, are better than those of the traditional CIE XYZ (CIEXYZ)-space-based characterization methods.
The methods based on the laser diffraction are more noticeable in the measurement of particle size distribution. In present laser particle sizing system, particles are treated as a group of spheres with various diameters, in order to inverse the particle size distribution. Actually, the shapes of most measured particles are non-spherical, so obvious differences would occur in the assumption of sphere. In this paper, after the description of the principle of laser particle sizing, problems existing in using above methods to measure the non- spherical particles are discussed. Then it is presented that the measurements based on the spherical, linear, rectangular particle diffraction would be applied to inverse the particle size distribution, according to the shape of measured particles. Through the measurement of samples, it is indicated that the results measured are consistent with those by the auto-electron microscope. In additionally, the values and diagrams obtained by these methods are presented, and the errors with different diffraction models are discussed in this paper.