Small range motion sensor

I bought a PIR sensor that has a range of several meters but I need to detect motion at maximum distance of 40cm. I reduced its sensitivity by putting polyethylene sheets in front of the sensor but I'm getting very inconsistent inputs and I don't know whether to continue on this path.

I want to add some LEDs activated by the motion sensor to my bedside table because I always knock something off when I'm reaching for my glasses or my phone.

The problem is that all the sensors that I saw have a much longer range that what I need.
I want a small sensor to make it more hidden as possible and whit a small range so it doesn't get triggered when I'm sleeping

Is it worth continuing to use the sensor I already have or are there sensors that are more suitable for what I have to do?

Thanks

With a Time Of Flight sensor you can program the distance you need.
Reflective IR sensors (obstacle avoidance for toy cars) might also work.
Leo..

Do you see the little lenses all over the cover of the PIR sensor? When a warm object moves in front of the sensor, the sensed heat goes up and down as the object moves from lens to lens. This varying signal is what indicates movement. You would have to change the lenses to limit the distance.
You do not indicate if the sensor works at 40 cm or not.

Paul

It’s a really cool sensor but it would be triggered by any object (my glasses for example) and the leds would never go out

I removed the stock lens and I 3D printed a cap whit a small hole in front of the sensor hoping to further reduce sensitivity, then I began stacking some thin polyethylene sheets in front of the hole

I get very inconsistent results, I place my hand in front of the sensor and there’s a 30% possibility that is not detected. Sometime it stops detecting motion for a few seconds no matter what I do.
It still detect motion at more than 40cm but since I'm wasting a lot of time I wanted to know if this is the right way or is there a more correct method