Views: 55 Author: Site Editor Publish Time: 2022-11-10 Origin: Site
Projector inspection needs to be tested with professional instruments. The following are several aspects of projector inspection.
The projector "brightness" mentioned in our test sheet is not exactly the same as the true brightness in optical knowledge. To keep it simple, the brightness we tested is the sum of all the light the projector throws, in lumens.
9 test sites
Illuminance is a unit reflecting the intensity of light. Its physical meaning is the luminous flux irradiated on a unit area. The unit of illuminance is the number of lumens (Lm) per square meter, also called Lux: 1Lux=1Lm/m2
We used the ANSI standard 9-point method for testing. The projector projected an image with 9 test points onto the screen. The average of the illumination evenly distributed across the 9 test points on the screen was the average illumination of the entire screen. Use the illuminometer to test the illuminance value of 9 points respectively, and then get the average illuminance value of the projection screen (the amount of light received per unit area, unit: lux). Multiply the average illuminance by the size of the picture, and get the total light received on the screen, that is, the total amount of light emitted by the projector. This amount is the "brightness" in the data table.
Optimize the difference between brightness and maximum brightness
The difference between optimal brightness and maximum brightness is quite simple. The former is determined by testing the projector with ANSI optimized adjustment, while the latter is determined by testing the projector with both contrast and brightness set to maximum.
Contrast ratio (ANSI contrast, FOFO contrast)
Contrast ratio is the ratio of white to black, which is the gradient from white to black. The higher the ratio, the more gradations from white to black, and the richer the color representation.
ANSI contrast 16 test points
FOFO Contrast test (white/black)
There are two ways to test contrast in projector testing:
One is ANSI Contrast, which uses the ANSI standard test method to measure contrast. The ANSI contrast test method uses 16-point black and white color blocks. The ratio between the average brightness of 8 white areas and the average brightness of 8 black areas is the ANSI contrast ratio.
The other is the all-white/all-black contrast test, which tests the brightness ratio (FOFO contrast) of the all-white screen and all-black screen output by the projector.
Using these two contrast tests on a projector yields a much lower ANSI contrast ratio than the FOFO contrast ratio, which is quite different. But there is little difference between the two methods for testing an LCD monitor or LCD TV. The reason is that there are inevitable defects in the optical path of the projector itself. Because it is a reflective display, it is easy to be affected by the light reflected, scattered or refracted from the bright area around, especially the black picture is greatly affected, often can not get pure black, which easily makes the contrast is not as high as the test with all white and all black.
Color saturation indicates the depth of color or brightness of the light projected by the projector. Depending on the white light content in the color, the higher the white light content, the lower the color content, the lower the color saturation, its value is a percentage, between 0
- Between 100%. Pure white light has a color saturation of 0, whereas pure color light has a saturation of 100 percent.
A variety of color gamut ranges
To test the color saturation of the projector, we used a similar method to test the display. By measuring the chromaticity value of the RGB three primary colors, the color performance range of the projector can be drawn on the color space visible to the human eye. Then the percentage of this color range compared with the NTSC color range is used as the result of color saturation. After Microsoft released the sRGB standard, many products and devices on the market comply with the sRGB specification. The sRGB color range is 71%NTSC, which is also the mainstream LCD and CRT monitors can achieve the color range.
Zone A is brighter than zone B
As can be seen from the figure above, region A is brighter than region B, and the color saturation of these two places is different. We can measure this uneven situation more accurately through professional instruments.
There are 4 more test points for non-uniformity
In the test of brightness unevenness and color unevenness, using the same 9 test points and brightness test, in addition to add 4 points in the corner, because these 4 points are the weakest place of the projector light, the 4 points are also included in the scope of investigation can more accurately test the brightness and color unevenness.
Unevenness of brightness: It is the reflection of the uneven distribution of the brightness of the projector on the whole projection picture. The ratio of the maximum and minimum illuminance values of the center 9 points is the unevenness score of the center area, while the ratio of the maximum and minimum illuminance values of all thirteen points plus the four points of the corners is the unevenness score of the corner brightness.
Projectors to project large-size pictures, there will certainly be some uneven picture brightness, generally speaking, the center of the projector unevenness score is less than 1.5 can be accepted, less than 1.2 when the human eye is almost imperceptible.
Color inconsistency: Similar to brightness inconsistency, we use Minolta color illuminance meter to test the chromaticity values of the center 9 points and corner 4 points of the white picture, and then the chromaticity coordinates of each point x, y and the center point chromaticity deviation square sum, obtained is chromaticity deviation. Human eyes can generally distinguish 0.003 deviation, in fact, as long as the deviation value is within the range of 0.001-0.010, reflect the actual picture of the color deviation is acceptable.
When talking about pollution in the past, you may think of water pollution, air pollution... now a new term is born: noise pollution! Other forms of pollution often arrive unnoticed and take people by surprise; However, noise pollution is on the contrary. Its strong entry, beating drums and even waving flags and Shouting, makes people helpless against it.
Noise is everywhere
Preparation for noise testing
Before the test, we first let the projector warm up for 30 minutes, and then in the front, back, left, right and upper five directions of the machine 50 cm away from the projector with the noise meter to test the working noise of the projector, the test result is the average of these five directions.