Double ten on the measurement of laser brightness
Date：2022/8/5 8:44:58 / Read： / Source：本站
Brightness is one of the luminosity characteristics of a light source that is often measured. The luminosity of the luminescent body and its surface condition,
The uniformity of luminescence characteristics, the direction of observation, etc., is the unit light source area in the normal direction, the unit stereo
The flux of light emitted in the Angle. Brightness is for the light source (point light source), and point light source is not bright
The degree concept. The luminance depends not only on the luminous flux of the source, but also on the convergence of the equivalent luminous area and emission
Degree. For example, the laser pointer, although its power is very small, but the degree of convergence is very high, so the brightness is very high
High. Luminance refers to how much light flows uniformly through an area, whether active or passive (reflective)
For this reason, the area should be obtained relatively small. In addition, brightness does not depend on distance, but on the direction of the observer
Luminance is often measured by first measuring illuminance and other photometric physical quantities, and then according to its and illuminance
The relationship between the luminance is calculated by the method. Hence the helioscopic method and the objective method. It can also be taken directly with known luminance
A comparative approach.
1. The terrorist! Depending on the method of
Luminance meter and illuminometer are two kinds of instruments and cannot be replaced directly. A luminometer measures the brightness of a luminous object
And the illuminometer measures the illuminance of the place being irradiated. But, if you want to know the larger ones
Luminance, such as the brightness of a light box, can be directly attached to the luminance with the probe of the illuminometer to read the Lux value
And then you multiply it by a coefficient, which is the nite value of brightness. All helioscopic luminance measurements are based on the comparison of luminance as
Basis. Figure 4.24 shows the principle of luminance measurement by helioscopic method.
During the measurement, the measured luminance LC and the comparison luminance Lv respectively illuminate half of the field of view of the two photometers and adjust the reduction
CD opening Angle (PC, observe the brightness of the two half fields of view of the photometer until equal. And then use what you know
The standard luminance Ls replaces the original measured luminance LC, and also adjusts the diurnal Angle of the reduced disc 'Ps to make two halves of the view
The photometric balance of the field. Finally, the brightness is calculated according to the opening Angle of the disc (A C and A S) before and after two subtractions.
This method requires small surface areas for both the luminance source to be measured and the standard luminance source, and requires both
The area elements are equal. The measured brightness is the average brightness of the measured area. The required light source is a standard source, so the
Mostly used for laboratory measurement.
I >. The objective law
1) Measure the illuminance to determine the brightness
Figure 4.25 shows a simple method of measuring luminance with an illuminometer by adding a translucency in front of the luminescence
An aperture of area △S through which the luminous surface emits hemispheric radiation. At the plane element AS 'd from the diaphragm
The illuminance value measured by the illuminometer is E. "The daily aperture is much smaller than D, defined by illuminance and solid Angle
Law, the average brightness value in △S can be obtained.
2) Measure brightness with a luminometer
It's hard to fix the diaphragm and make direct contact with the light source and △S at zero distance, so you can use a lens
Image, use the image △S of the light source on the right to determine the brightness of the light source, as shown in Figure 4.26.
The luminance at △S 'can be obtained by measuring the illuminance E at △S, the lens area S and the image distance U. here
On the premise that the law of conservation of brightness is established, that is, when there is no loss of optical radiation energy in medium transmission, it is transmitted in light
The path takes two surfaces, their brightness is connected, this is the conservation of radiant brightness. And the image distance u
Is fixed and does not change with distance. The luminance meter made in accordance with the above principles is shown in Figure 4.27
4.28 shows its structure diagram.
The photomultiplier tube is subjected to the action of light to produce photocurrent, which is amplified by the emitter and determined by the scale and brightness of the meter
Can be used to read out its brightness value. You can use a higher precision luminance meter or light intensity standard lamp and ideal diffuse
Calibration of shot plate. The light intensity standard lamp can be used with a known light intensity standard lamp or a known brightness standard lamp. In the calibration
Before, must make the adjustment, the specific method is: illuminate the white diffuse plate with light intensity standard lamp, change the standard lamp and
A series of brightness values can be obtained from the distance L of the whiteboard. The instrument can be divided by different brightness values, i.e
Calibration of luminance meter. Do not allow stray light to enter the receiving device of the luminance meter to avoid errors. The light of modern
The calorimeter has adopted a new generation of fully digital measurement technology, which does not include any analog part, and overcomes the traditional luminance meter
It is difficult to avoid the zero drift problem, with the strong anti-interference ability of digital system and high conversion accuracy, and the instrument
The digital V (A) sensor with large dynamic range is adopted to eliminate the range switching error of the traditional luminance meter.
It is widely used to measure light source brightness and display screen lighting effect.
The full digital luminance meter adopts the aiming measurement method, which aims at the target by direct heliogaze of the human eye and adjusts the focus
Distance, Angle of view and other methods to measure the daily standard, reduce the artificial or external error in the measurement process. Within the
Including RS232 interface, calibrated by computer software, and can be used for computer remote online monitoring, the system is stable
Sex is high.
Full digital luminance meter can be used for instrument calibration and real-time data acquisition, with a friendly graphical interface. mining
With graphical entity data display, data can be printed out. It can measure the dynamic range of brightness
Large, from red laser pointer 20 000 000 000 nits (int= LCD "M) and solar surface 2000
000 ooont into the moonless night sky