There are some for sale on ebay.
place the lens cap in place.
Assuming that the lens is not adjusted, the picture will become smaller as the projector is moved towards the screen. The size of the picture is related quite precisely to the distance, so moving the projector to half the distance will result in an image half the width and half the height. This applies to projectors of all types, not just movie projectors. Most video and some movie projectors have zoom lenses so the image size can be adjusted without moving the projector. Alternatively, if the projector is moved, the lens can be adjusted to restore the original image size (within certain limits).
An overhead projector is used to project an image of a transparency onto a wall or screen by means of an overhead mirror. There are also "slide projectors" that are used to display photographic slides on a wall or screen. A "projector" or "digital projector" would be used similar to a computer monitor or a television screen that would display an inputted image from a variety of sources (blu-ray player, computer, laptop, dvd players, game console, etc.). In the case of a projector the image is projected with the help of a light apparatus shining through a small silicon ship and projected through a lens to create an image on your wall or projector screen.
Conventional projection uses a projector in front of the screen, hence the term "front projection". It is also possible to project from the rear of a translucent screen, "rear projection". The problem with rear projection is that the image will be reversed left to right. Video projectors all have a menu setting that allows the image to be reversed before it is projected so the resulting screen image will be seen the right way round. The question mentions movie projectors suggesting a film projector rather than a video projector. Because a film projector is fully optical there are no electronic methods to reverse the image but it can still be done. Most projectors allow alternative lenses to be fitted. Using a specialist reversing lens will correct the image orientation but they are expensive. The image can also be reversed using a mirror in the light path. The mirror needs to be a front silvered mirror, one that has the reflective coating on the front rather than the rear as this avoids double images. This is much the same process as a reversing lens which has a mirror or prism inside the lens housing. Front projection distances tend to be large, with the projector being at the rear of a room. Rear projection rooms or cabinets are generally much shorter so wide angle lenses are often used to produce a large image from a short distance. A movie projector should have a short focus lens to reduce the required projection distance if possible. However, by using a mirror, the projection distance can be extended as the effective distance is the sum of the distance from the projector to the mirror and the mirror to the screen. Careful positioning of the projector and mirror will be needed and this is not as simple as it first appears. It may well be worth looking at dedicated mirror mounts to get the right result.
A bright light lights the slide (a prepared positive cut from the original film). The light travels through a lens to focus it and on to a screen. There are many mechanisms to change slides, from manual insertion, to rotary and linear slide trays.
projector have concave or convex
No, a movie projector uses a convex lens.
There are many websites that provide DIY projector plans, But none offer a way to repair a Projector Lens. I would look into how much it is to replace the Lens or the projector all together.
To make the projector image smaller, you can adjust the lens by moving it closer to the projector. This will focus the light and reduce the size of the image displayed on the screen.
Convex lens because i said so
Convex lens because i said so
The lens focuses light on the retina (fish have one)
place the lens cap in place.
To select a Fresnel lens for a home projector, first determine the desired projection size and distance from the lens to the screen. Look for a lens with a suitable focal length that matches your projection setup, typically around 10-20 inches for small projects. Ensure the lens has a high-quality optical clarity to minimize distortion. Finally, consider the lens size and shape to fit your projector design and housing.
since you need to show the image on a big screen so you require a diverging lens i.e. a concave lens
since you need to show the image on a big screen so you require a diverging lens i.e. a concave lens
A projector lens diagram typically includes components such as the lens barrel, lens elements, aperture, and focal length. The functions of these components are to focus and project light onto a screen, control the amount of light passing through the lens, and determine the size and clarity of the projected image.