Photometric standards can be realized using silicon photodiodes whose absolute spectral responsivity is self-calibrated. However the conventional method required laborious measurements at many wavelengths over the visible region. To simplify such calibration procedures, a new method is investigated in which the responsivity [A/1m] for the photometric quantity of a silicon photodiode, which is combined with a V (λE)-correction filter having a known spectral transmittance, can be self-calibrated by measuring the surface reflectance and the recombination losses of the photodiode for white light. The derived equation for this method requires that the spectral responsivity of the reference detector for surface reflectance measurements be proportional to wavelength. This requirement is approximately fulfilled by using high quality silicon photodiodes, but this approximation causes a systematic error. To clarify this error, a computer analysis has been made using measured spectral data of commercially available silicon photodiodes both for the self-calibration sample and for the reference detector, and of V (λE)-correction filters. The analysis revealed that the systematic error was less than 0.2%, and that this method was promising for simple and accurate realization of the photometric scale.
It is important to satisfy the visibility needs of visual tasks on a working place (such as a desk top) as well as to make comfortable office lighting. Visual tasks may include desk top work, VDT work or even talking to another person, in which case, the face of the person becomes a visual task surface. A series of experimental studies, with subjective appraisals, were carried out to clarify a preferable face illuminance against background wall illuminance in an office room, especially while using task and ambient lighting (general lighting with a local lighting on a desk top). In this experiment, background wall illuminance against an illuminance on the desk, is set at a lower limit value for nearly 90 percent of observers, and the face illuminance is adjusted by the obsever. The experiments' results are as follows: (1) Preferable face luminance against the background wall luminance can not be expressed simply. (2) For a plan of task and ambient lighting in the office, it is desirable to have a preferable range of face illuminance for illuminance on the desk top on condition that wall illuminance is fixed. As a guideline for typical lighting design in the office, an optimum illuminance range for the face should be 450-6201x; for an illuminance of the desks: 7501x, and minimum illuminance range for walls should be 270-3001x; for an illuminance on the desk: 1000 lx, on condition that preferable range of illuminance on the desk top should be 750-1000 lx and wall reflectance is 0.3-0.8.
Photometric measurements of floodlights with HID lamps (high pressure sodium lamp and metal halide lamp) were done by the different measurement methods. Also, examination were made at various operating positions. In the case of high pressure sodium lamp, there is no influence in the photometric performance according to the operating position nor the measurement method. In the case of metal halide lamp, there is no influence in the luminaire efficiency but there are differences in luminous intensity distribution. It is considered that result are largely affected by arc conditions of the lamps used in the measurements. Therefore, with respect to floodlights aiming to control luminous intensity distribution accurately, disigning of optical system and the measurement method should be selected correctly in consideration of operating position.
A model for the analysis of a lead-peaked ballast characteristics is developed. The model is derived using the equivalent circuit method of magnetic circuit. The magnetic path is divided into nine parts, and are expressed by equivalentinductors respectively. Iron loss at each part is represented by an equivalent resistance. For a discharge load, the discharge voltage-current model is adopted. Using the developed model, input and output characteristics are calculated and compared with the measured values at no load, short c circuit load and discharge load condition, respectively. The calculated results agree well with the measured results both in waveforms and effective values.
To investigate the relationship between the equivalent lightness and the color appearance of colored objects, 39 colored chips were used as stimuli to measure the equivalent lightness and the three attributes of whiteness, blackness and chromaticness at illuminance levels from 0.01 to 3000 lx. The first method, which has already been reported by the authors, is the determination of the equivalent lightness of colored objects by using heterochromatic brightness matching. In this paper, the color appearance of a colored object was measured by the values of its whiteness, blackness and chromaticness. It was observed that the whiteness corresponding to illuminance is directly related to the theoretical achromatic lightness, and the chromaticness corresponding to illuminance is also directly related to chromatic lightness. Consequently, the equivalent lightness corresponding to illuminance can be explained by adding the chromaticness to the whiteness.