The role of the first flaw in the human body infrared sensor:
The Fresnel lens uses the special optical principle of the lens to create an alternating "blind zone" and "high-sensitivity zone" in front of the detector to improve its detection and reception sensitivity.
When someone walks in front of the lens, the infrared rays emitted by the human body alternately move from the "blind zone" into the "high-sensitivity zone", so that the received infrared signal is input in the form of a pulse that is strong and weak, thereby enhancing its energy amplitude. .
There are two Fresnel lens functions: one is the focusing effect, that is, the pyroelectric infrared signal is refracted (reflected) on the PIR, and the second function is to divide the detection area into several bright and dark areas to enter the detection area. The moving object can produce a varying pyroelectric infrared signal on the PIR in the form of a temperature change.
Simply put, there are equidistant ridges on one side of the lens, through which the bandpass (reflection or refraction) of the specified spectral range can be achieved. Traditional bandpass optical filters for polishing optical equipment are expensive. Fresnel lenses can greatly reduce costs.
A typical example is the PIR. PIR is widely used on alarms. If you take a look, you will find a small plastic hat on each PIR. This is the Fresnel lens. The inside of the small hat is engraved with a tooth pattern.
This can limit the peak frequency of incident light to around 10 microns (the peak of human infrared radiation). The light transmitted through the narrow-band interference filter can be focused on the photosensitive surface of the silicon photodiode detector.
The second trick is in the camera's focusing screen:
Today's camera focusing screens are frosted frosted glass, which has the advantage of brightness and uniform brightness. When the focus is not correct, the image on the focusing screen is not clear. In order to focus more accurately, it is generally equipped with a split image and a micro-ring device in the center of the focusing screen.
When the focus is not accurate, the image of the subject in the center of the focusing screen is split into two images. When the two split images are combined into one, the focus is accurate. The standard focusing screen of the AF SLR is generally not provided with a splitting device, but a small rectangular frame is engraved to indicate the AF area.
Some focusing screens are also engraved with a partial metering or spot metering area. When an early AF SLR camera focuses on a dark environment, it is often difficult to see the focus frame. It is difficult to determine which point the camera is used as the focus point. The focus point on the focusing screen of the new generation of SLR will illuminate.
Or have a focus sound prompt to confirm focus in a complex environment. Different types of focusing screens have different uses, shooting portraits may be better with split-image focusing screens, and focusing screens with horizontal vertical lines or scales are suitable for building photography and document remake;
The middle part has no split image and the micro-edge focusing screen is suitable for small aperture lens. It does not have the disadvantage of splitting one side and brightening one side. Many SLR camera focal screens can be replaced by the user. Also known as a threaded lens.
The third role in the LED spotlight:
Fresnel lenses are used in LED light sources to increase light efficiency and increase brightness. Compared with the same lens and LED lamp, different focal lengths and different distances, any arbitrarily set the exit angle, single lamp or multiple array LED lights can be designed according to requirements.
Suitable for LED floodlights, colorful floodlights, lighting, landscape lights, signal lights, various lamps.
Features: Fresnel lens ultra-thin structure, large size, arbitrary shape of cutting, excellent light transmittance and other advantages than traditional convex lens, its weight is smaller than the convex lens, suitable for a variety of occasions.
The role of the fourth ridge in the rear view wide-angle lens:
Fresnel lens wide-angle lens is suitable for trucks, home two-cars, buses, four-wheel drive off-road vehicles and other vehicles without "tails", often do not know what is hidden behind the car.
This lens features a unique FRESNEL lens technology that simply pushes the inside of the rear window for driving
The staff provides a wide-angle view of the obstacles on the blind spot that was previously invisible and increases the range of the rear view.
The role of the fifth ˎ in concentrating photovoltaic solar cells:
The concentrating photovoltaic lens is one of the core components of the third generation of high-concentration photovoltaic solar power generation. As a precision optical device, solar panels can be increased by several times.
Yuying can design Fresnel lenses of different specifications according to the customer's concentration ratio and the size of the solar panel to achieve the desired concentrating effect.
The sixth hexagram plays a role in the field of amplification:
Fresnel magnifier, this is a slim magnifying glass. Made of transparent plexiglass (and of course more materials). Fresnel magnifier made of PVC, the minimum thickness can be between 0.45mm~0.90mm,
Unlike a general magnifying glass, its surface is covered with tiny stripes, and its spiral stripe contains a number of convex lenses (referred to as a ring shape), so that the light passing through it bends to produce a diffractive phenomenon, thereby forming an enlarged image. .
The Fresnel lens is characterized by a higher brightness and a flat surface than a normal lens, and a large radiation area. Generally, the ordinary meniscus lens has a very limited diameter, and Fresnel plays a very good role in the field of the magnifying glass, achieving the effect that ordinary ordinary lenses cannot achieve.
Moreover, the Fresnel magnifier made now has a thickness of only 0.45mm. The main purpose of the portable belt is to reduce the weight and volume of ordinary plexiglass and glass magnifier made by traditional magnifiers.
The seventh is applied to traffic lights:
Due to the popularity of high-power LEDs, the use of a single or a few LEDs as a light source, Fresnel lens with microarray lens as a illuminator to replace multiple LEDs as a light source constitutes a traffic signal has become a trend in the industry. It has been put into use in many countries around the world.
The eighth is applied to 3D glasses:
In order to make the 3D lens thinner and lighter, some 3D glasses use a Fresnel lens. This lens has the same curvature as a normal lens, but it has different sizes of threads on one side. Because the beam is incident on the lens from different angles,
So I feel that the distance between the eyes and things is far, but in fact the distance is not so far.
Using Fresnel lens 3D glasses means you need to make some sacrifices. You can make multi-threaded lenses for a sharper image.
In addition, you can also use Fresnel lenses with less threading to help concentrate the beam and improve contrast, but the sharpness of the image will be compromised, more about the VR lens principle design.