How to understand the concept of a cheap laser pointer?

Question

Electronics

It is necessary to start the laser from a penny laser pointer. There are two scarves with an emitting diode at the end. In the case, they received (as I understand it) a plus from the case, and a minus from a spring soldered on the protruding edge of the board (three standard button batteries). In the photo, the spring and the clock button are removed. As soon as I did not apply power and ground, the diode does not start. Any ideas? Can anyone give me a wiring diagram or a wiring diagram?
I am attaching a photo of the boards:

Answer 1

Still sometimes, manufacturers expect that the diode can simply burn out _from batteries_ and from a power supply unit of the same voltage.
1. PSUs have ripples when turned on
2. Batteries have their own internal resistance...