Navigation beacon light / navigation beacon light intensity measurement and light range calculation
1 Subject content and scope of application
This standard specifies the principle and method of light intensity measurement for navigation aids and the calculation method of light range. This standard applies to all kinds of circular and directional navigation lights. Other similar lamps can be used as reference.
2 Reference standard
GB12708 navigation mark light signal color
JJG245 Illuminance Meter Verification Regulations
3 Navigation beacon light intensity measurement
3.1 Measuring principle
Outside a certain range of distance measurement, the beacon light is regarded as a point light source, and then according to the inverse square law of distance:
E=I×cosθ/l2………………( 1)
where: E——the limit on the receiving surface of the illuminance meter (Lx);
I——The light intensity of the beacon light under test (cd);
L——The distance from the center of the light source of the beacon light under test to the receiving surface of the illuminance meter (m);
Θ——The angle between the beam of the navigation mark and the normal of the receiving surface of the illuminance meter. When the angle θ is equal to zero, the formula (l) becomes:
I=El2……………………………………(2)
The light intensity I of the beacon light is calculated by the measured illuminance value E and then calculated according to formula (2).
3.2 Measuring equipment and installation location
3.2.1 Measuring equipment
A. Optical track (or other corresponding measuring device)
includes a trolley equipped with an illuminance meter receiver. After the light track is adjusted, the straightness error is not more than lmm per meter length.
B. Illuminance meter
Meet the technical requirements of the secondary illuminance meter specified in the JJG245 Verification Regulations promulgated by the State Bureau of Technical Supervision, and the minimum reading is not greater than 0.1lx.
C. Turntable
can be equipped with the lamp under test, at the same time it has the function of rotating 360o horizontally and 30o vertically around the luminous center of the lamp under test. The minimum graduation of the horizontal dial is 1o, and the minimum graduation of the vertical dial is 0.5o, and it can be adjusted up and down according to the size of the lamp under test.
D. Power
DC stabilized power supply, the output voltage instability within 10 minutes is not more than 0.5%; AC power supply, the output voltage change within 10 minutes is not more than 1%.
E. He-Ne laser collimator or level.
3.2.2 The installation location of the measuring equipment can refer to the following diagram 1.
3.3 Measurement environment
The measurement can be carried out in a dark room or outdoor environment. The measuring light track in the dark room should work at 20±5℃, and a number of screens should be set between the lamp under test and the illuminance meter receiver to ensure that the stray laser light does not irradiate the illuminance meter receiver. Darkroom walls, test equipment, screens and other test accessories must be painted in matt black.
When measuring outdoors, the stray light entering the illuminance meter receiver should be limited within the allowable error range.
3.4 Measuring method
3.4.1 Equipment adjustment before measurement
A. Operate the illuminance meter according to the requirements of use, and check the zero return error and zero drift. The zero return error shall not exceed 0.5% of the full scale, and the zero drift within 30 minutes shall not exceed 2% of the full scale. The illuminance meter using AC power supply should be warmed up for 15 minutes.
B. The beacon light under test should be preheated under the rated voltage. The incandescent tungsten filament lamp should be preheated for 5 minutes, and the gas discharge lamp should be preheated for 15 minutes.
c. Place the lamp under test on the center of the turntable and fix it, adjust the center of the bulb filament to the focal point of the lens, and then use the laser collimator to adjust the plane of the illuminance meter receiver and the plane of the lamp under test (the drum lens refers to its axis) , Make their center point on the measuring axis and perpendicular to the measuring axis.
D. The scales of the horizontal turntable and the vertical axis of the turntable are set to zero.
E. Determine the minimum measurement distance according to the test results, that is, gradually increase the distance between the illuminance meter receiver and the lamp under test, until the measured light intensity value I=El2 remains unchanged.
F. Put the illuminance meter receiver in an appropriate position and select an appropriate range.
3.4.2 Drum-shaped lens navigation light
3.4.2.1 Light intensity measurement
Rotate the horizontal turntable, measure a point every 90o, read the illuminance scale, E1, E2, E3, E4 and take the average value, namely:
Ē=ē1+ē2+ē3+ē4/4…………………………(3)
Then according to formula (2), get the value of light intensity I0.
3.4.2.2 Vertical emission angle light intensity distribution value measurement
Rotate the horizontal turntable and measure one point every 90o. Each point needs to rotate the vertical shaft, measure from +5o to -5o, and read an illuminance value every 1o. For example, the eleven illuminance values of the first point are E15, E14, E13, E12, E11, E10, E-11, E-12, E-13, E-14, E-15. The first digit of the foot code represents the position of the horizontal point, the second digit represents a different vertical angle, and the minus sign in front of the foot code represents the vertical angle below the horizontal zero position. Calculate the average illuminance values ē5, ē4, ē3, ē2, ē1, ē0, ē-1, ē-2, ē-3, ē-4, ē-5 corresponding to the vertical angles of four points in a week, and then press the formula ( 2) Calculate the vertical divergence angle light intensity distribution values I5, I4, I3, I2, I1, I0, I-1, I-2, I-3, I-4, I-5, and draw the light intensity distribution diagram . If you need to measure the vertical emission angle light intensity distribution values of soil 10o, soil 15o, and soil 20o, you can also follow the above method, and the measurement interval can be in the range of 1 o to 4 o.
3.4.3 Bull's eye lens navigation light
3.4.3.1 Light intensity measurement
Place the bull's eye lens navigation beacon light according to 3.1.4.IC regulations, and measure the illuminance E. If there are n faces, each face needs to be measured once, and the average value of n times of illuminance value is taken;
Ē=1/n×∑ni=1 Ei……………………………………(4)
Then calculate the exit light intensity I0 according to formula (2).
3.4.3.2 Horizontal divergence angle light intensity distribution value measurement
The horizontal turntable and the vertical rotation axis are based on the measurement axis of the bull's eye lens plane of the lamp being tested perpendicular to the optical track as the reference zero. Turn the horizontal turntable. Rotate to the left and right, measure an illuminance value every 3o, 15o for the left and right, a total of 11 illuminance values. According to formula (2), obtain the light intensity distribution value of the horizontal divergence angle, and draw the light intensity distribution diagram. If there are several surfaces, the average illuminance value of the corresponding horizontal angle of each surface is used to obtain the light intensity distribution value of the horizontal divergence angle according to formula (2), and the light intensity distribution diagram is drawn.
3.4.3.3 Vertical divergence angle light intensity distribution value measurement
The horizontal turntable and the vertical rotation axis are based on the measurement line where the bull's eye lens plane of the lamp under test is perpendicular to the optical track. Rotate the vertical shaft, rotate up and down respectively, measure the illuminance value every 3o, 15o up and down respectively, a total of eleven values. According to formula (2), the vertical divergence angle light intensity distribution value can be obtained, and the light intensity distribution map can be drawn. Similarly, if there are n surfaces, the average illuminance value of each surface corresponding to the vertical angle is used to obtain the vertical emission angle light intensity distribution value according to formula (2), and the light intensity distribution map is drawn.
3.4.3.4 The light intensity measurement and horizontal and vertical divergence angle light intensity measurement methods of lens-type or reflective beacon lights are basically the same as those of bull's eye lens navigation lights. When measuring the light intensity distribution value, the measurement interval can be based on the measured The divergence angle of the lamp is divided into 9 to 11 equal parts.
4 The beacon light has a light intensity calculation
4.1 When the instantaneous light intensity of a flashlight changing with time cannot be directly measured, the effective light intensity of the flash can be calculated using the "Blondel-Rey" formula:
Ie=i0t/a+t……………………………………(5)
In the formula: Ie——the effective light intensity of the flashlight (cd);
IO——the maximum value of the light intensity at the moment of flashing, that is, the fixed light intensity (cd);
T——The duration of the flash, S, for a group of flashes composed of different durations, the shortest duration of the flash should be calculated;
A——The visual time constant, at night, the flash produced by shielding or switch a=0.2, and the flash produced by rotating the optical device a=0.3.
4.2 The effective light intensity calculation after the light passes through the color shade and lamp shade
When the light passes through the color cover (such as color filter glass, colored lens, colored bulb, etc.) and or lamp cover (such as lamp housing glass, plastic cover), the light will be attenuated, and the effective light intensity after the attenuation can be obtained by formula (6) get.
If=bcIe…………………………………………(6)
In the formula: If——the effective light intensity after attenuation (cd);
B——The transmittance of the color mask, generally red mask b=0.2, green mask b=0.2, yellow mask b=0.6, the color of the light passing through the color mask, its color coordinates should be in the chromaticity zone specified by GB12708;
C——The transmittance of the lampshade, generally glass C=0.85, plastic, C=0.9.
5 Calculation of light range of navigation mark
5.1 The light range of the navigation beacon light refers to the illuminance E produced by the light on the naked eye when the distance is 10nmile (corresponding to the atmospheric transmission coefficient T-0.74) under the condition of 005 contrast and under the dark conditions. The distance at 0.2uLx.
5.2 Adopt "Allard’s law" (Allard’s law) to find the range of the light according to the intensity of the light:
I=ED2/TD……………………………………(7)
In the formula: D——light range (n mile);
I——Light intensity (cd), substitute the effective light intensity in the calculation
T——Atmospheric transmission coefficient, T=0.4;
E——Illuminance threshold, E=0.686.
Substituting the above coefficients into:
I=0.686D2/0.74D………………………………(8)
Formula (8) is the calculation formula for the light range of the navigation beacon light.
The conversion table of night light intensity and range for T=0.4 is shown in Appendix A, Table A.
