[Technical classification of projection screens] Projection screens

From the projection method, the screen is divided into two categories: front projection screen (reflective) and back projection screen (transmissive). The front projection screen is not limited by size (customizable), but it will be affected by ambient light and cause a serious drop in picture contrast. The rear-projection screen has a strong overall picture, which is not affected by ambient light and can accurately reflect the quality of the information, so the picture is colorful and lifelike. The largest single optical rear-projection screen is 200 inches, and the effective image range is 4034mm × height. 3018mm.

Front projection screens and rear projection screens are divided into the following types from the optical structure:

Front projection screen: curved screen (metal arc screen), flat screen (glass bead screen/metal soft screen/pure white screen)

Rear projection screen: hard rear projection screen (transmission screen), soft rear projection screen (transmission screen)

The gain of the front projection plane screen is small, the viewing angle is large, and the ambient light must be weak; the arc-type screen has a large gain, the viewing angle is small, and the ambient light can be strong, but the incident light reflected by the screen varies in all directions. Moreover, the high temperature generated by light focusing can easily cause the distortion of the image color. In terms of texture, it is divided into glass curtain, metal curtain, embossed plastic curtain and so on.

Rear projection screens are classified into optical rear projection screens, diffuse screens and soft rear projection screens. These rear projection screens with different imaging principles overcome the shortcomings of many front projection methods: the projector is installed on the screen The darkroom at the back will not cause any imbalance in the decoration, and also shield the noise generated by the operation of the projector. At the same time, it is not easy to be disturbed by ambient light.

It is worth mentioning that the latest Sigma series of optical rear projection screens produced by Danish DNP company. The matt anti-glare surface can effectively absorb background light, effectively resist the light emission from windows and artificial lighting equipment, and make the projection effect unaffected. The impact of ambient light has become a reality.

Scattering screens rely on scattering particles to complete the distribution of projected light. Therefore, scattering screens have the following obvious shortcomings:

The utilization rate of light energy is low, which wastes the brightness output of the projector

The bright spot effect (solar effect) is obvious, and the brightness uniformity is poor

The color drift phenomenon is serious, the contrast is very low

The viewing angle is small, not suitable for large-scale imaging

Diffusion screens are not widely used in the market. There are mainly two imported brands in the country: Vivi-tech (http://www.vivitech.co.kr) in South Korea and Reversa in the UK (http://www. reversa.tv).

Optical rear-projection screens rely on micro-optical mechanisms to complete the distribution of projected light energy. It is currently recognized as the best display method. Fresnel lens technology is widely used in the manufacturing process of optical screens. The ear lens structure can converge the incident light into parallel rays, increasing the brightness of the screen within a certain viewing angle range.

Cylindrical lens technology is also widely used in the manufacturing process of optical screens. Through the cylindrical lens structure on the front of the screen, the horizontal and vertical light distribution can be controlled, and the viewing angle can be expanded. Customers can Design the best angle between the projection light path and the screen focus to obtain the best light path coverage angle range (for details, please refer to 'DNP Design Guide').

The only disadvantage of the optical rear projection screen is that in order to obtain the best image focus, a projector lens with a matching focal length range must be selected (the projection distance is required). All optical rear projection screens produced by Danish DNP company have a variety of focal lengths to choose from, covering the focal length range of most projector lenses.

The rear projection soft curtain is formed by spraying with high light transmittance film. Typical foreign brands include American DA-LITE, American Deaper\American Stewar.

The rear projection soft screen has the advantages of cheap, seamless (size can be customized), convenient transportation and installation (foldable), and no requirement for the focal length of the projector lens. It is usually used in the rental industry. Because the rear projection soft screen also applies the imaging principle of diffuse reflection of light, it is inevitable that there are also the shortcomings of the diffuse screen: poor brightness uniformity, serious 'sun effect, Small viewing angle, etc. Low resolution and low contrast make the rear projection soft screen unsuitable for data display applications. At the same time, in terms of the physical properties of the materials, the soft rear projection screen has the following shortcomings:

Stability is easily affected by temperature, humidity and airflow, which can cause image shaking

Prone to wrinkles, discoloration, deformation, mildew, and aging, and the quality assurance period is short

Due to the need to ensure the viewing range (usually nominally 160?), the gain is low (usually nominally around 1.5)