How much do you know about this projector? A brief question!
Are projector lenses convex or concave?
The lens of the projector is a convex lens! So what are its imaging rules?
Convex Lens Imaging Rules
The imaging rule of a convex lens is an optical law. In optics, the image that is formed by the gathering of practical light and can be presented on the light screen is called a real image; the image that is formed by the reverse extension of the light and cannot be presented on the light screen is called a virtual image. When narrating the difference between real and virtual images, there is often mentioned such a method of difference: "Real images are all upside down, while virtual images are upright."
If it is a thick meniscus concave lens, the situation will be more messy. When the thickness is large enough, it is equivalent to a Galilean telescope, and when it is thicker, it is equivalent to a positive lens.
lens difference
structure
Convex lens: thin edge, thick center, at least one surface must be spherical, and both sides can be spherical. It can be divided into three types: biconvex, planoconvex and meniscus.
Concave lens: The edge is thick and the center is thin. At least one surface must be spherical, and both sides can be spherical. It can be divided into three types: bi-concave, plano-concave and convex-concave lenses.
effect on light
The convex lens mainly concentrates light.
The concave lens mainly scatters light.
Imaging properties
Convex lens is refraction imaging, and the formed image can be upside down and reduced real image; upside down and equal-sized real image; upside down and expanded real image; upright and expanded virtual image. Convergence of light.
A concave lens is a refracting image, and can only form an upright, reduced virtual image. Divergence of light.
Rule 1: When the object distance is greater than 2 times the focal length, the image distance is between 1 times the focal length and 2 times the focal length, forming an inverted and reduced real image. At this time, the image distance is smaller than the object distance, the image is smaller than the object, and the object image is on the opposite side.
Application: camera, camcorder.
Rule 2: When the object distance is equal to 2 times the focal length, the image distance is also 2 times the focal length, forming an upside-down, equal-sized real image. At this time, the object distance is equal to the image distance, the size of the image and the object are equal, and the object image is on the opposite side.
Use: measure the focal length.
Rule 3: When the object distance is less than 2 times the focal length and greater than 1 times the focal length, the image distance is greater than 2 times the focal length, forming an inverted and expanded real image. At this time, the image distance is greater than the object distance, the image is larger than the object, and the object image is on the opposite side.
Application: projector, slide projector, movie projector.
Rule 4: When the object distance is equal to 1 times the focal length, the image will not be imaged and will be emitted as parallel light.
Rule 5: When the object distance is less than 1 times the focal length, it becomes an upright and extended virtual image. At this time, the image distance is greater than the object distance, the image is larger than the object, and the object image is on the same side.
Use: Extender.
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