The new revolution of e-teaching: analysis of rear projection large screen projection technology

The biggest feature of the rear projection large screen projection technology is ultra-high resolution, ultra-large display screen, ultra-high resolution. This advantage makes the edge fusion projection large screen have unprecedented advantages in the field of electric teaching.

1. Is the rear projection screen a single-focus screen or a multi-focus screen?

An important part of the rear projection screen is the projection screen. The projection screen is not simple, but it is directly related to the focal length of the screen. Especially in the rear projection system, it is a special and main parameter.

In the manufacturing process of the optical curtain, the Fresnel lens on the back is cut in the direction of concentric circles to control the incident angle of light. To form a good image focus on the rear projection screen, there will be a certain limit to the distance of the light source. Projection within this range can make the image obtain good focus and resolution, and avoid image blur or ghosting. If the focal length of the screen does not match the projection distance, the traces of lens cutting are easier to show as a spiral stripe background on the screen, and the four corners of the screen are prominent.

The rear projection screen has a single focal length range called a single focal length screen; the rear projection screen can have a variety of different focal length ranges, as far as possible without being limited by the screen focal length is called a multiple focal length screen, such as the United States 3M and Denmark DNP rear projection screen.

When designing solutions for customers, engineers must consider this aspect, otherwise, they are not professional!

2. How to design the screen focal length and the best view point?

The screen focal length has a close optical relationship with the projector lens. In general, the screen focal length is not recommended to be greater than the lens focal length under any circumstances. If it is really affected by the environment, the lens focal length is allowed to be controlled within 1.4 times the focal length of the screen. Within this range, the selection of projector lenses with different focal lengths will directly affect the viewing position of the best viewpoint.

3. When the space behind the rear projection screen is narrow, how to choose a refractor?

A common problem encountered in rear-projection large-screen projection projects is the use of refractors to save space.

I do n’t know if people use ordinary mirror reflection, which will have a very poor effect, because most of the mirror surface uses a mercury coating on the back. The interaction of the mercury coating and the glass surface will form multiple refractions and reflections of the optical path, causing image ghosting blur. Professionals use vacuum-coated mirrors for one or more refractions.

At present, the reflectivity of good vacuum-coated mirrors is as high as 94%, so the second refraction projection will not cause significant loss of brightness.

4. How to calculate the distance between the refractor, projector and rear projection screen?

Many engineers use some probabilities to estimate the projection distance that can be shortened by one or more refractions, but they lack a scientific and rigorous attitude, because this data is related to the screen installation height, projection method (off-axis or off-axis), projector volume, mirror Area is closely related. After we have mastered all the environmental data related to projection, it is a very effective, fast and accurate method to use AutoCad software for simulation drawing.

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