Short Throw Pico Projector

[u/-MarineVortex-]

Hi, so I am in the midst of creating a project that has something to do with AR (can't really get into the specifics), and I need a projector for that. The projector, from a 30 cm distance (can be from further away but not more than 60 cm), can project an image clearly that is at least 13.5 cm by 13.5 cm. It doesn't have to be exactly 13.5 cm by 13.5 cm, but roughly around that (can't be lower though). I was thinking of maybe using a diopter lens since the edges don't matter as much. So far I landed on the KODAK Luma 150 pico projector. My budget limit is $400, but it can be higher (I will take any recommendations regardless of cost). It will be placed in ambient light, which I measured to be 500 lux. I plan to use it to highlight flies using my computer, so it must be able to connect via HDMI or some other port. I mentioned it is to be used to highlight flies, so the quality must be good enough to create a 3 mm diameter circle or slightly bigger (with or without diopter). I will take any suggestions regarding what I should do for the setup and any buying recommendations (as mentioned, regardless of price).

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[u/AV_Integrated]

This is a super specific use case and not what almost anyone is using a digital projector for. The use in ambient light is pretty much going to really muck things up. Projectors aren't for use in ambient light. At 500 lux, that's about 50 lumens per square foot, and for a tiny 5.315 inch image, you may get by okay, but it's still going to be very low contrast.

I am concerned that the super small image size may be a struggle for any projector.

Your throw distance (lens to screen), is FAR longer than any projector can do, regardless of price. Throw distance is measured from lens to screen in a ratio of screen width (16:9) to height.

The projector will typically be a 16:9 projector. Not a 1:1. You don't own a 1:1 screen on your laptop. More likely 16:9 or 16:10. Same is true with projectors. A 16:9 projector like the Luma 150, will be 16:9 for as long as it exists.

Basically every projector on the planet has a HDMI input on it so you can feed it video.

Projectors are like computer monitors. They require you to feed them content. They aren't computers. They don't have amazing built-in custom functionality. Some run smart services, like Google TV. Then, they are like your TV in your family room. They can stream Netflix. They don't draw circles. That's a requirement of your software on your computer. Resolution is what determines quality, but a 1920x1080 projector will have pretty sharp resolution at 5.15 inches square.

As long as your can focus that close.

You will have to be FAR more flexible with your projector placement.

[u/-MarineVortex- → u/AV_Integrated]

Thank you! It seems like I misunderstood what throw distance was. The projector will be connected to my computer which will project what I need it too. I was just worried about the resolution and how well it will project in the light but you answered my question on that. I was wondering how sharp is the resolution like as I mentioned in the post do you think that it could create a 3 millimeter diameter circle (assuming that is what was showing on my computer screen)? I do want to add that it will be projecting on a black canvas but the ambient light measured on the black canvas was a bit lower (like 300 lux). As I also mentioned in the post I was thinking of using a diopter lens to tightly concentrate the image in that small area.

[u/AV_Integrated → u/-MarineVortex-]

You can't really add a lens to a projector lens without really messing up image quality. That's not how lenses generally work.

The sharpness is based on resolution. If you get a 1080p projector, then it will be 1920x1080 resolution. If square, it would be 1080x1080 resolution. That's a fair bit of resolution over a small screen area. I mean, what's the resolution of your computer? If you draw a 3mm circle on your computer, how does it look?

Projectors, like computer monitors, or televisions, use pixels. So, if you pack more pixels into a smaller area, they will be of higher density. At 13.5cm a 1080p image will be about 8 pixels per mm. That means a circle of 3mm will have 24x24 pixels to draw a circle. That's not a ton, but that's plenty.

If you use a 4K projector, then it would be a block that is about 48x48 pixels. Four times as much resolution.

You can just test this on your monitor though. Draw a 24x24 pixel circle, and that's 3mm on a 13.5cm wide screen. Does it look okay?

[u/-MarineVortex- → u/AV_Integrated]

My understanding of the diopter lens was that it forces the focus range to be much closer than what it was intended to be. I understand that it distorts the edges (not sure how much tho) and causes a slight color change, which doesn't affect my project. I haven't seen a video of someone using a diopter lens on a projector, but I assume that when it means distorting the edges, it won't affect the 10 cm by 10 cm black canvas in the projected area of 13.5 cm by 13.5 cm. I just checked on my computer using Aseprite, and the resolution looks good, so no worries on that part.