Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
I have a green laser pointer, labelled "Orion Skyline". It's rated = 5 mW
output power. I don't have a way to measure actual output, but I'll assume that it's operating at approximately rated power when it's nice and bright and the brightness is steady. Unfortunately, the brightness is constant only when it has "warmed up". If it sits in a cool room (say 15 degrees C) for a while before I use it, the inital brightness of the beam appears quite low - perhaps 10% or less of maximum output. If I keep it turned on, it will flicker - becoming brighter then dimmer again multiple times, remaining at one brightness for a fraction of a second to a couple of seconds before abruptly changing brightness again. After about a minute of operation, it seems to come to full brighness and remain there, without flickering. It's not due to bad batteries or poor electrical contact on the batteries - I've swapped in new alkalines, tested with a battery tester, with just-cleaned terminals. But it *does* seem to be related to temperatu if I hold the laser-containing end of the pointer in my hand for a minute before use, warming it through skin contact while it's still turned off, it comes on at full brightness (or close to it) immediately. So what is likely causing the brightness changes? I can think of 3 plausible explanations (there may be more). 1. A bad electrical contact somewhere in the circuit. When cold, it has high resistance that prevents sufficient current from getting to the power supply. 2. The constant-current supply for the IR laser diode is flakey and IR output is changing, which results in changes in the amount of green light generated. 3. The IR laser output is constant, but there's some sort of problem in the 1064 nm laser or the frequency doubler crystal that makes its efficiency very temperature-sensitive. Anyone who has seen this problem care to guess what's happening in mine? Also, how is it likely to be held together? The main body of the pointer is a brass tube. Batteries are inserted by unscrewing an end cap from one end. The laser assembly *looks* like it's screwed into the other end of the tube, but it's not willing to budge with just hand force attempting to unscrew it. Dave |
#2
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
In article , Dave Martindale wrote: I have a green laser pointer, labelled "Orion Skyline". It's rated = 5 mW output power. I don't have a way to measure actual output, but I'll assume that it's operating at approximately rated power when it's nice and bright and the brightness is steady. Unfortunately, the brightness is constant only when it has "warmed up". The KTP frequency-doubling crystal may be more temperature-sensitive than is normal. This is a known characteristic, but perhaps the crystal is damaged or improperly aligned. |
#4
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
|
#5
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
|
#6
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
|
#7
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
"If it sits in a cool room (say 15 degrees C) for a while before I use
it, the inital brightness of the beam appears quite low - perhaps 10% or less of maximum output. If I keep it turned on, it will flicker - becoming brighter then dimmer again multiple times, remaining at one brightness for a fraction of a second to a couple of seconds before abruptly changing brightness again. After about a minute of operation, it seems to come to full brightness and remain there, without flickering." Laser pointer needs to be preheated before pointing if the room temperature is lower than 25 degrees C.Usually you can hold the laser in hands tightly about 30 seconds before pointing. The low temperature might cause unstable and lower power pointing in operation. |
#8
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
Laser pointer needs to be preheated before pointing if the room
temperature is lower than 25 degrees C. Usually you can hold the laser in hands tightly about 30 seconds before pointing. The low temperature might cause unstable and lower power pointing in operation. My condo is unheated, and is currently around 60 degrees F. (It has been as low as the high 40s during this winter.) All the laser-optical devices in my condo work properly -- including the DVD players in my computers, the DVD player in my bedroom, the BD player in the living room, and even a 25-year-old LV player. The idea that a semiconductor laser has to be at a minimum temperature to work strikes me as decidedly odd. I'd expect the pointer to work if it were dropped in liquid nitrogen (at least until the battery froze). |
#9
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
On Wed, 27 Mar 2013 06:39:37 -0700, "William Sommerwerck"
wrote: The idea that a semiconductor laser has to be at a minimum temperature to work strikes me as decidedly odd. I'd expect the pointer to work if it were dropped in liquid nitrogen (at least until the battery froze). "5mw Green laser warmup - highter power trick" http://www.youtube.com/watch?v=J4hqPII-tsY The common green laser pointer starts with an 808 nm IR laser, which excites a crystal to produce 1064 nm light, which then feeds a frequency doubling crystal to produce green 532 nm. http://en.wikipedia.org/wiki/Diode-pumped_solid-state_laser Both crystals are temperature sensitive. I have an early model green pointer which I use to boresight align mountain top dish antennas. My personal best is 5 miles, although others have gone much further with high power green lasers. The instructions didn't say anything about warming up the laser, so my first attempt on a 6400 ft mountain top in Smog Angeles failed due to lack of light output. I eventually figured it out and now have a small battery operated hand heater and temp controller to keep around room temperature. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#10
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
In article , William Sommerwerck wrote: Laser pointer needs to be preheated before pointing if the room temperature is lower than 25 degrees C. Usually you can hold the laser in hands tightly about 30 seconds before pointing. The low temperature might cause unstable and lower power pointing in operation. My condo is unheated, and is currently around 60 degrees F. (It has been as low as the high 40s during this winter.) All the laser-optical devices in my condo work properly -- including the DVD players in my computers, the DVD player in my bedroom, the BD player in the living room, and even a 25-year-old LV player. The idea that a semiconductor laser has to be at a minimum temperature to work strikes me as decidedly odd. I'd expect the pointer to work if it were dropped in liquid nitrogen (at least until the battery froze). Hint: In a DPSS laser assembly, it isn't the semiconductor component that is the heat-sensitive factor. |
#11
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
On 3/27/2013 9:30 AM, Jeff Liebermann wrote:
On Wed, 27 Mar 2013 06:39:37 -0700, "William Sommerwerck" wrote: The idea that a semiconductor laser has to be at a minimum temperature to work strikes me as decidedly odd. I'd expect the pointer to work if it were dropped in liquid nitrogen (at least until the battery froze). "5mw Green laser warmup - highter power trick" http://www.youtube.com/watch?v=J4hqPII-tsY The common green laser pointer starts with an 808 nm IR laser, which excites a crystal to produce 1064 nm light, which then feeds a frequency doubling crystal to produce green 532 nm. http://en.wikipedia.org/wiki/Diode-pumped_solid-state_laser Both crystals are temperature sensitive. I have an early model green pointer which I use to boresight align mountain top dish antennas. My personal best is 5 miles, although others have gone much further with high power green lasers. The instructions didn't say anything about warming up the laser, so my first attempt on a 6400 ft mountain top in Smog Angeles failed due to lack of light output. I eventually figured it out and now have a small battery operated hand heater and temp controller to keep around room temperature. One of the printed circuit boards we build for a local customer is a heater board for their green diode laser. The board is .090 thick, with silver plated traces. 4 wire wound resistors surround a hole where the laser diode goes. These are for a outside, cold winter, application. Paul |
#12
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
Thanx to Jeff and Mike for the clarifications.
|
#13
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
On Wed, 27 Mar 2013 06:39:37 -0700, "William Sommerwerck"
wrote: Laser pointer needs to be preheated before pointing if the room temperature is lower than 25 degrees C. Usually you can hold the laser in hands tightly about 30 seconds before pointing. The low temperature might cause unstable and lower power pointing in operation. My condo is unheated, and is currently around 60 degrees F. (It has been as low as the high 40s during this winter.) All the laser-optical devices in my condo work properly -- including the DVD players in my computers, the DVD player in my bedroom, the BD player in the living room, and even a 25-year-old LV player. The idea that a semiconductor laser has to be at a minimum temperature to work strikes me as decidedly odd. I'd expect the pointer to work if it were dropped in liquid nitrogen (at least until the battery froze). Greetings William, When the green laser pointers first cam out I got curious, bought one, and read a lot about how they work. They use two crystals to get green. First one crystal takes the 808 nm IR light in and lases at 1064 nm. Then this light goes into a KTP (potassium titanyl phosphate) crystal which doubles the frequency and so 532 nm laser light comes out. This second crystal is quite sensitive to temperature and won't put out as much light if too cold or too hot. Also, especially in the cheaper laser pointers, the IR laser draws a lot of current when it first is powered, and some type of cheap current limiter then cuts the current, so when the laser is cold pressing the button will result in a short duration bright beam which then dims rapidly. I don't remember if the laser also needs to be up to a certain temp to lase well. I do know that if they get too hot their life is shortened. I also know that repeatedly pressing the button on a cold laser with a couple seconds between pushes will warm the laser faster and thus be brighter than just pressing and holding the button down. Another fault of some of the cheap pointers is the chrome plating on the threads of the battery compartment. The chrome plating develops a high resistance oxide coating very fast. So if the laser is dim after sitting around a few days unscrewing and screwing back together the two halves of the laser will abrade away this coating and the laser will be much brighter. I discovered this on pointers I had bought and I'm sure I'm not alone. Eric |
#14
Posted to sci.electronics.repair
|
|||
|
|||
erratic output from green laser pointer
wrote:
"If it sits in a cool room (say 15 degrees C) for a while before I use it, the inital brightness of the beam appears quite low - perhaps 10% or less of maximum output. If I keep it turned on, it will flicker - becoming brighter then dimmer again multiple times, remaining at one brightness for a fraction of a second to a couple of seconds before abruptly changing brightness again. After about a minute of operation, it seems to come to full brightness and remain there, without flickering." Laser pointer needs to be preheated before pointing if the room temperature is lower than 25 degrees C.Usually you can hold the laser in hands tightly about 30 seconds before pointing. The low temperature might cause unstable and lower power pointing in operation. Mine goes dim when warm, after trying to use it or a while. Greg |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Erratic output on Kenwood KR-A5030 | Electronics Repair | |||
Edge-cutting Laser Pointer Plus Laser Presenter Boosts User Ability | Electronics Repair | |||
Edge-cutting Laser Pointer Plus Laser Presenter Boosts User Ability | Woodturning | |||
How to Check CD Player Laser Output | Electronics Repair | |||
Laser pointer use in scroll saws. | Woodturning |