The dependence of spectral response on wavelengths ranging from visible to infrared was observed using a thermal radiation detector whose surface had been covered with gold-black absorbent. Conical cavity type detectors decrease the effective reflectance through repeated reflections. Data concerning the correlation between the cone vertex (90°, 60°, 45°) and the various reflectances (0.1-0.6) of the absorbent on the cone were obtained.
In a past study, we developed a laser radar system for estimating slant visibility, which is the visibility along the glide path of an airplane and proposed the new laser radar equation, considering the divergence of the transmitting laser beam in bad weather conditions, like rain, fog and snow, in order to obtain the exact slant visibility in various weather conditions. This equation corresponds well to practical data and estimated visibilities coincide well with actual ones in various weather conditions. In the present study, to confirm the appropriateness of the new laser radar equation, the scattering angle characteristics of a laser beam propagating through fog is measured by using an optical Fourier transform system and an artificial fog generator. As a result of this experiment, the spatial spread functions of broadening of the forward beam caused by the fog scattering are derived from the obtained data as angle distribution. Using these spread functions, the analysis of broadening of a laser beam propagating through fog in laser radar operation using a computer. This computer analysis reveals the alternation of the pattern of the transmitting laser beam through fog. As a result, broadening and scattering characteristics of the transmitting beam in foggy condition were found and the spreads of transmitting beam derived from the calculated results well explain the concept of the new equation. The analyzed results compared well with practical data for laser radar. And the slant visibilities derived from the analyses well coincided the actual ones.
The color image reproducted on a CRT monitor does not have exactly the same color appearance as the real object under illumination. This is mainly because there is no simple formula for predicting exactly the state of chromatic adaptation to various illuminants and the color appearance of such kinds of color stimuli (object color or color monitor display). In this study, the CIE chromatic adaptation transform, taking into account the adaptation coefficient for incomplete chromatic adaptation was applied to color image reproduction. The color photographic images included a woman's face, which is one of the most important objects for color reproduction evaluation. As a result, the color image reproduction was easily displayed with the same color appearance as the object color under illumination, adjusting only for the adaptation coefficient for incomplete chromatic adaptation.
It is hypothesized that the apparent lightness of an object is determined relative to the size of the Recognized Visual Space of Illumination (RVSI), which is constructed in the human brain for an illuminated space. The apparent lightness of a test patch was matched with that of a reference patch; they were respectively located in a test room and a reference room, which were both illuminated at 600lx. Two kinds of reference patches were employed, with N4.0 and N6.0 respectively. When the size of the RVSI of the test room was made smaller than the reference room by furnishing the walls, floor, and furniture in the test room with lower lightness of N1.5 compared to the reference room, the test patch with lowered lightness by about NO.5 in the case of N4.0 and about NO.7 in the case of N6.0 matched the reference patch, showing that the lightness in the test room was evaluated as higher because of the smaller size of the RVSI of the test room, thus confirming the hypothesis of the lightness recognition. When the RVSI was enlarged by furnishing the furniture in the test room with chromatic surfaces in addition to increasing the lightness by N1.5, although without changing the wall or the floor, the matching point shifted toward a higher lightness of the test patch as expected and excluding the description for the lowered lightness of the test patch with the simultaneous contrast.
The wavefront synthesizing method was used to analyze the real physical phenomena of a laser beam scattering in fog. The analyses were performed by steady state in the standing waves. The wavefront synthesizing method is simple, and the calculation time and accuracy do not depend on the size or number of particles being analyzed, so it is possible to analyze stably. Using this method, the intensity distributions and phase distributions inside and outside a single fog particle are obtained. The analysis results were comparable to ones calculated by Mie theory with a long distance. We also extended this analysis to many particles of different sizes in a fog space. For a fog space, the bold approximation was applied. This approximation method was validated by comparing the water content of natural fog. The analyzed results compared well with experimental results for the intensity distribution of a scattering beam. This study could quantitatively evaluate the propagation of a laser beam in fog, and it also proved the appropriateness of the proposed laser radar equation for real weather conditions, considering the divergence of the transmitting laser beam.
The Monte Carlo method, which has recently been widely used to predict the illuminace distribution of a room arranged in a complicated way with furniture, is easier than others in terms of algorithm and is suited to simulating the various states of lighting in a room. The accuracy of the illuminance distribution is affected by the number of particles that replace the luminous flux of the light source and the number of elements on the room surfaces. Therefore, we investigated the suitable number of the particles and elements considering the CPU time and error rate of the illuminance calculation when a shadow caster assumed to be a worker's head was set up at an arbitrary position in a rectangular parallelepiped model room. A new method, which uses the incident particles on the surrounding elements of the calculation point, was developed to decrease the CPU time and calculation error. We examined various reflectances of the room surfaces, positions and diameters of the shadow caster, and sizes of the shadow caster and light source. As a result, using only 1/10 the CPU time of previous methods, we found that the suitable number of particles is five million and the suitable number of the elements on the floor is 40×40 to 60×60.
Cold cathode discharge lamps are usually operated by the condenser ballast, and are supplied by a high-frequency sinusoidal voltage. At some frequencies of the supply voltage, the current waveform of the positive period differs from that of the negative one and the luminance of the lamp is lower than when the current waveform is symmetrical. In a asymmetrical waveform, the current waveform in one half-cycle is pulse-like with a high peak and the waveform in another half cycle has a low amplitude. We calculated the equation of a simple equivalent circuit, and found that the discharge current consists of a sinusoidal steady component and a transient pulse component which increases as the delay time for re-ignition increases. The asymmetrical waveform of the discharge current occurs, when the supply voltage, the operating frequency, the lamp diameter, or the capacitance of the ballast is decreased. Since decreasing the value of those parameters increases the delay time for re-ignition in one half-cycle, the reignition voltage drops and the delay time becomes shorter in the other half-cycle.
This paper examines how a driver's behavior, such as gazing at an in-vehicle navigation display device, affects safety driving. We carried out two types of experiments. The first one examined the response time of the driver from the time when the stop lamps of the preceding vehicle went on, under the conditions that the driver was instructed to look at the in-vehicle display device as long as possible. We found that it was almost impossible for the driver to recognize the traffic conditions in front when gazing at the display device. The other experiment examined an ordinary driver's behavior of diverting his line of vision from the front. Based on the results, we also conducted an analysis to obtain quantitatively the delay in response time when the driver is ordinarily shifting attention from in front to the display device.
A prediction method of the Helmholtz-Kohlrausch effect is developed by using the CIELUV formula, and it can predict the effect for object and luminous colors in the whole chromaticity gamut including spectral colors. The method gives equivalent lightness values to chromatic object colors with a constant luminance factor, and equivalent luminance values to chromatic luminous colors with a constant luminance. This condition of prediction is called the Variable-Achromatic-Color method. The predicted results by the developed method agree well with the corresponding experimental results reported so far.
The Helmholtz-Kohlraush effect was estimated for object and luminous colors in the case of the variable-chromaticcolor method. This method specifies luminance-factor values of various chromatic object colors with the same equivalent lightness, and luminance values of various chromatic colors with the same equivalent luminance. The predicted results showed that the effect in the variable-chromatic-color (VCC) method was twice as large as that in the variable-achromaticcolor (VAC) method in Part 1 of the present studies. The method also predicted well the experimental results done by Sagawa et al. using the VCC method. In addition, it was confirmed that the VCC method was more effective than the VAC method in practical visual photometry.
There are two methods of representing the Helmholtz-Kohlrausch (H-K) effect, the VAC method (Variable-Achromatic-Color method) and the VCC method (Variable-Chromatic-Color method). This paper (1) describes how to use and adapt the prediction equations of the two methods to their practical applications, (2) theoretically derives the prediction equations in both methods, and (3) clarifies the relationships between the numerical coefficients used in the prediction equations for the two methods.