Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1984-02-02
1985-11-26
Evans, F. L.
Optics: measuring and testing
By particle light scattering
With photocell detection
356341, 356371, 356434, 356442, 356446, 356447, G01N 2147
Patent
active
045551782
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a method for the measurement of the difference in the optical properties dependent on the light direction of two samples, in which method one or several sources of light as well as one light detector are used. By means of the method in accordance with the invention, the difference is obtained by means of one measurement.
The samples for which the method in accordance with the invention is suitable may be solid, liquid or gaseous volume samples, or faces that reflect light, or films transparent to light.
The invention comes out in more detail from the following description and from the attached drawings, wherein
FIG. 1 illustrates an embodiment in which unevenness of the skin is measured on the occasion of local pimpledness of the skin in allergic reactions, and
FIG. 2 illustrates an embodiment in which the difference in turbidness of two liquid samples is measured. As an example in the description of the method, a measurement of the difference in unevenness of two face samples is used. The way in which the nature of the samples affects the details of the performance of the method is obvious for a person skilled in the art. Likewise, it is obvious that this method can also be applied in the ultraviolet and infrared ranges.
In the method in accordance with the invention, two lights are used per sample, the angles between the directions of incidence and dispart of the said lights being different. The directing of the lights takes place in a way well known to a person skilled in the art, such as, e.g., by means of mirrors or prisms if one or two sources of light are used, or merely by means of positioning of the sources of light and of the lenses related to them, if any, if four sources of light are used. One of the face samples is called the face to be studied and the other one the reference face. Both of the faces are illuminated simultaneously, one of them with light of one direction and the other one with light of the other direction, and the lights reflected from both faces are allowed to act simultaneously upon one light detector. The directions of the lights are alternated with each other at an appropriate frequency, which frequency is selected, for example, within the range of 1 c/s to 10,000 c/s, so that both the electrical or mechanical control of the light direction and the light detector and the related electronics, such as amplifiers, are capable of operating at the frequency concerned reliably and precisely. Owing to the linearity of the light detector, the information on the difference between the reflection factors is retained, and if the unevenness of the faces is different, i.e. if the difference between the reflection factors of one face, with the two directions of light to be used, is different as compared with the corresponding difference in respect of the other face, the light detector yields an AC signal, whose frequency is the same as the frequency of alternation of the light directions and whose amplitude is proportional to the difference in unevenness between the faces. The result of the measurement is independent from the darkness of the sample, i.e. from its component neutral in respect of the direction of the absorption, and also independent from possible differences in colour between the samples.
It is evident for a person skilled in the art that, in general, in this method, the selection of the direction of the measurement light may also be performed after the sample, whereat the samples would be illuminated constantly by means of light of one direction.
Generally speaking, in the method in accordance with the invention, in order that the darkness of the sample should not affect the measurement result, it is necessary to adjust the intensity of the sources of light illuminating the same sample to such a level that lights of different directions produce an equally strong signal in the light detector. The adjusting takes place in practice so that a white calibration face is placed in the place of one of the samples and a black calibration fac
REFERENCES:
patent: 3892492 (1975-07-01), Eichenberger
Evans F. L.
Labsystems Oy
LandOfFree
Method for the measurement of the difference in the optical prop does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the measurement of the difference in the optical prop, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the measurement of the difference in the optical prop will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-267513