DVD burners that rock for diodes.

[IgorT]

IR LD has same "wings" in beam (with other optic)

I was wondering, how you view the IR LD's beam? With a CCD camera?

Optic is not involved, because with other LD's witch has no lines in beam - has no "wings".

A very intriguing pattern.. I like it actually, but i know it probably bothers you, cos you want all of the light in one single point..


I have exectly the oposite problem. Without optics the light from the LD is the usual nice oval shape..

With the optics i get these weird (star like) "lines" going away from the point on the wall, and if i turn the laser the "lines" turn with it.

It this spread pattern usual for a narrow collimated beam (2mm diameter)?

I'll attach a pic..

Unfortunatelly i didn't manage to get the focus right, so the spot looks much larger than it actually is, while the "lines" are much longer, like 500mm dia at 5m...

This is not a reflection from the spot, cos it turns with the laser and it get's wider, the further away the wall is, while the spot remains the same size (2mm).

Is this normal, or is my lense messed up?

 

[IgorT]

As I have no idea what the specs of my red 'gem' are, I'm reluctant to run it much higher than 150mA. Even at that current, using a lens and a body from a $1 key-chain pointer, it is able to ignite matches in a second and punch a hole through a black floppy disk at a distance of 10 cm in less than a minute with a well focused beam.
A well-desined ARC lens will yield even more power and focusing precision. Some of those chinese cheapos never quite managed to focus in a well-defined spot without many side artefacts... A good source is Roithner, Austria. They ship collimator lenses in any quantity.

You seem to know A LOT about electronics in general and the lasers as well. I would just like to point out one thing... We call the laser diodes "LDs", so as not to mix them up with LEDs.. LED is Light Emmiting Diode, while LD is a Laser Diode.. I'm sure you already know all that, so please don't take this wrong. I just pointed it out, cos it could be confusing to a newbie..

Igor, I saw the photo of your 'blaster' and I noticed that the beam aperture is somewhat narrow. I used a similar set-up for my experiments and I discovered that the 'burning efficiency' increased when I increased the diameter of the aperture on the focusing nut. Pehaps a small circular aperture makes the projection more dot-like, as opposed to the 'bar-like' spot produced by most low-power leds...however this may effectively prevent some of the 'burning power' from escaping the aperture.

Thank you! I was also considering this as a cause of the problem (hole too small in diameter to allow all the light to get out)

I will make the hole bigger, since i have to mod that thing anyway. I messed up my calculations (distance between the LD and the lense).

This means i also have to make an indentation in the inside of the focusing nut, to be able to screw it in further and allow for better focusing.

I'll also make the hole bigger now. Thanks for the hint!

BTW: Do you think this too small hole could also be the cause of the lines going away from the point on the wall (in my pic above)? Like reflections from the edges of the inside of the too small hole, for example? Well, i'll know for sure in a few minutes anyway...

I will soon be buying a 20x LG drive. Wonder what the LEDs are going to be like. I am beginning to want a closed-can specimen for the sake of reliability. Open-can leds may dissipate heat better, but are susceptible to mechanical damage and environmental contaminants...
My goal now is to find good lenses. I bought all key-chain lasers in my town and only one or two had satisfactory lenses without much scratches and other frightening optical defects......

Since my lense assembly is also from a cheap laser pointer, i'm afraid, this is the cause of many of my problems..

I just hope the AixiZ modules arrive soon.

 

[Phenol]

Igor,
I have tested like 7 lenses and each produced a unique pattern on the wall. Most of them, when slightly defocused, produce a not well-defined blurry spot with 'protuberances'. Only 2 were able to produce a tiny spot with distinct edges and very few dim side patterns. Ideally, you should obtain a single spot with nothing around it / haze.../. If i were you i would examine the lens for scratches and dust. try defocussing it until you project a fairly large spot on the wall, like 5cm across, and look for dark spots and non-uniformities.

 

[IgorT]

Igor,
I have tested like 7 lenses and each produced a unique pattern on the wall. Most of them, when slightly defocused, produce a not well-defined blurry spot with 'protuberances'. Only 2 were able to produce a tiny spot with distinct edges and very few dim side patterns. Ideally, you should obtain a single spot with nothing around it / haze.../. If i were you i would examine the lens for scratches and dust. try defocussing it until you project a fairly large spot on the wall, like 5cm across, and look for dark spots and non-uniformities.

I thought so as well. But first i need to fix my focusing nut and make the hole bigger, to see if makes a difference.

BTW: I cleaned the lense with ethanol before putting it in. But i noticed something weird on it...

It has something that looks like the dried vapours of CA glue on it. It's a narrow line, but it might also be a cause of this..

The CA vapours definatelly didn't get there during my glueing, since the lense was nowhere close to the parts i was glueing together..

It also has a tiny scratch, which could have been my fault.


Thanks for the hints!

Igor


EDIT: I just tried what you suggested (making a wider spot on the wall) and noticed A LOT of disturbance in the beam.. This lense really sucks! And besides, where i live it's nearly impossible to get any kind of laser pointer at all. I just wish AixiZ would finally respond to my inquiry.. I made a payment, but still got no answer..

 

[Phenol]

EDIT: I just tried what you suggested (making a wider spot on the wall) and noticed A LOT of disturbance in the beam.. This lense really sucks! And besides, where i live it's nearly impossible to get any kind of laser pointer at all. I just wish AixiZ would finally respond to my inquiry.. I made a payment, but still got no answer..

I just want to lay my hands on a couple of those Roithner lenses. They also have anti-reflection coating.

 

[IgorT]

I just want to lay my hands on a couple of those Roithner lenses. They also have anti-reflection coating.

What is that good for? So the beam can not get back into the LD?


BTW: I just moded the focusing nut, and made the hole bigger, like you suggested.
Now it's not a round spot anymore, but at least more light is coming out..
The star pattern also decreased, so i believe it was related to this.
But this lense is really bad. I can not focus it into a small dot. Nothing works...

What is the usual diameter of the opening in front of the lense, for example in the AixiZ modules?

EDIT: Does anyone know the distance between the LD and the lense in the aixiz module? I have to put my lense very far away from the LD so i'm worried not all of the light is actually being focused in the first place...

 

[Phenol]

What is that good for? So the beam can not get back into the LD?


BTW: I just moded the focusing nut, and made the hole bigger, like you suggested.
Now it's not a round spot anymore, but at least more light is coming out..
The star pattern also decreased, so i believe it was related to this.
But this lense is really bad. I can not focus it into a small dot. Nothing works...

What is the usual diameter of the opening in front of the lense, for example in the AixiZ modules?

Anti-reflective coating does reduce beam reflection back to the LD. This could be useful when the built-in photodiode is implemented in an APC circuit for instance. Such coating would reduce eventual loop disturbances when the position of the lens is altered. In our case, we dont use that monitor photodiode for automatic power control /my LD doesnt even have one built-in/, so the only benefit would be the increased transmission of the lens/reduced reflection losses/, ie, more burning capability and cool "bluish" aspect of the lens when viewed at an oblique angle...

I have never seen AixiZ module. I have extracted the LD holder from an old not-so-cheap pointer. It accommodates standard collimating lenses. The adjustment is done with a nut that exposes as much as 80% of the area of the lens

Igor, perhaps the LD is not well-cenetred with respect to the lens....

 

[IgorT]

Igor, perhaps the LD is not well-cenetred with respect to the lens....

The centering was the hardest part of the entire process.. I took great care, to put it in the "perfect" spot. But i did try moving it around and not much changed, except for the worse...

80% of the lense exposed you say... I'm still far away from that... Damn, more drilling..


BTW: Do you know the approximate distance between the LD and the lense in your assembly?

 

[Phenol]

The centering was the hardest part of the entire process.. I took great care, to put it in the "perfect" spot. But i did try moving it around and not much changed, except for the worse...

80% of the lense exposed you say... I'm still far away from that... Damn, more drilling..


BTW: Do you know the approximate distance between the LD and the lense in your assembly?

Not really sure :duh2: about that... My LD came from a lite-on drive and it looks exactly like MatajumotorS's photos. Its base is flush with the holder. The rest with the chip pedestal protrudes inside the cavity of the holder as far as a standard closed-can 5.6mm LD would, I reckon... I will measure this as soon as I get home. Anyway, I have been able to achieve focusing from 8cm to ~infinity (well.... kinda) with any collimator i scavenged from those cheap pointers. In general, the farther from the LD the lens goes, the closer it focuses. My objective was to produce a focused dot some 10cm from the aperture and I achieved it with ease without having the lens pop out.

 

[petah]

Can anyone tell what is the type of laser diode in an LG-H10A dvd-burner?
i'd like to dissect my dvd-burner but i'm not sure what to expect.

hey laserblue!!!!

the LG-H10A model uses a 16x LD, I have one mounted in a flashlight shape housing, It's doing just fine running @ 300ma - 3.4V . I use it in short duties though... but it's pretty powerfull, don't know the exact output power but I was told that it might be around 200mw when batteries are fresh, I feed it with rechargeable ones....
good luck with yours!!!

 

[petah]

IgorT

EDIT: Does anyone know the distance between the LD and the lense in the aixiz module? I have to put my lense very far away from the LD so i'm worried not all of the light is actually being focused in the first place... [/quote]


Hi mate,
the distance between the LD and the lens in my AixiZ module is something like 5mm or even less, pretty close!

 

[petah]

....

 

[VaThInK]

BTW: I was talking about my LD in comparison to yours.. Mine gets 3V, yours gets >5V. The power is therefor greater at the same current.. (P=U*I)


Besides, it seems i confused your circuit with the Daedal's driver circuit (from laserpointerforums), which is not using a low drop out regulator, and has a voltage drop of almost 3V in it..

Sorry for the confusion...


EDIT: In this case i would like to see the circuit you're using.. Is it posted somewhere?

Ah I see what you're trying to say. However, as I said before, my LD only eats ~3V and not the whole 5V even though I supply 5V to it. So the wattage would still be the same not greater than yours. Try it if you don't believe me :naughty:.

I believe Daedal's circuit uses LM317 and its voltage drop is around 1.2V not 3V. His circuit uses 2x LM317 to regulate current and voltage. That's why its outputting at 3V.

Hope this clear things out.

EDIT: Btw, I use Die4Drive for each LDs because I need them to be modulated for laser show. This LD driver gives out around 4.5V with 5V input due to voltage drop. For testing purposes I normally just use the 5V rail from PC PSU with 25W wire wound potentiometer in series to limit the current.

 

[IgorT]

Hi mate,
the distance between the LD and the lens in my AixiZ module is something like 5mm or even less, pretty close!

Thanks..

This means my lense totaly sucks... It must have a totaly different dioptry.. Cos i think my distance is bigger, so a lot of the light gets lost before it even enters the lense..

No wonder it cant burn anything..


BTW: While i was mowing the lawn i left the laser on in my pocket for 20 minutes by mistake. I even thought "did i leave it on" but didn't check...

When i found it was on, i immediatelly checked for the temperature. I opened the enclosure and measured different spots, but nowhere was the temp greater than 35 degrees centigrade.. And this is from driving it at 200mA..

So at least my heatsinks work.. Anyone know the safe operating temperatures for these LDs?


BTW: Did you order your module from aixiz directly or dealextreeme? Is aixiz reliable? (i ordered directly, but got no reply)

 

[IgorT]

I have to correct myself..

I managed to focus the beam to a very narrow spot at 25 cm and put a piece of paper in front of it (that i painted black first of course).

It made a hole clean through.. I do have a burning laser! Even with the cheap puny lense..

I can imagine it will get even better with the aixiz housing.. I can hardly wait!

Unfortunatelly there are no matches or baloons in the house..

 

[IgorT]

Ah I see what you're trying to say. However, as I said before, my LD only eats ~3V and not the whole 5V even though I supply 5V to it. So the wattage would still be the same not greater than yours. Try it if you don't believe me :naughty:.

I did try it, when testing this LD. Initially i limited the current to 200mA on my lab PSU. Then i raised the voltage to raise the power, but since the current was limited, the voltage stayed the same.. Then i allowed a little more current, and checked the voltage and it went to 4.2V (from 3.6V in the beginning) Only this way the current was able to go to 280mA (without removing or changing the resistor).

So if you raise the voltage, the current also raises (I= U/R), and so does the power (P=U*I), just like with any other electric components. Of course all this only applies when driving the LD directly, without any circuitry..

With a dual LM317 circuit it is possible to regulate the voltage and then the current, to make it constant, no matter what you feed into the circuit (within limits of course), if this is what you meant..

I believe Daedal's circuit uses LM317 and its voltage drop is around 1.2V not 3V. His circuit uses 2x LM317 to regulate current and voltage. That's why its outputting at 3V.

Quite possibly, but that has to be a different circuit. The one i meant uses only one LM317 and i was told it has a voltage drop of 3V. It is possible the person who explained it to me didn't understand it fully tho..

EDIT: Btw, I use Die4Drive for each LDs because I need them to be modulated for laser show. This LD driver gives out around 4.5V with 5V input due to voltage drop. For testing purposes I normally just use the 5V rail from PC PSU with 25W wire wound potentiometer in series to limit the current.

Which driver is this? Never heard of it before. Can you point me to it perhaps?

 

[Phenol]

I did try it, when testing this LD. Initially i limited the current to 200mA on my lab PSU. Then i raised the voltage to raise the power, but since the current was limited, the voltage stayed the same.. Then i allowed a little more current, and checked the voltage and it went to 4.2V (from 3.6V in the beginning) Only this way the current was able to go to 280mA (without removing or changing the resistor).

So if you raise the voltage, the current also raises (I= U/R), and so does the power (P=U*I), just like with any other electric components. Of course all this only applies when driving the LD directly, without any circuitry..

With a dual LM317 circuit it is possible to regulate the voltage and then the current, to make it constant, no matter what you feed into the circuit (within limits of course), if this is what you meant..


Quite possibly, but that has to be a different circuit. The one i meant uses only one LM317 and i was told it has a voltage drop of 3V. It is possible the person who explained it to me didn't understand it fully tho..


Which driver is this? Never heard of it before. Can you point me to it perhaps?

http://www.die4laser.com/dvd-rec/Die4Drive_files/Die4DriveRev1-2.pdf

mine is similar. ive totally 'flipped it around' as i didnt want to have the LD case hooked to +5V. this one uses a fet as a current sinking component, this way the compliance range is wider compared to a BJT.

 

[VaThInK]

Yeah, that behavior sounds right IgorT. My LDs consume 3V @ 380mA and the voltage will only start to increase slowly if I increase the current. This is when I was only using a resistor in series with the LD. They won't get >3V if I don't overdriven them really hard. This is probably due to different LD internal resistance characteristics. Below is the circuit that I'm using when I properly run my setup for laser light show.

http://www.die4laser.com/dvd-rec/Die4Drive_files/Die4DriveRev1-2.pdf

mine is similar. ive totally 'flipped it around' as i didnt want to have the LD case hooked to +5V. this one uses a fet as a current sinking component, this way the compliance range is wider compared to a BJT.

Care to explain what you mean by flipping it around :thinking:? Isn't the LD case from DVD drives actually ground?

 

[Phenol]

Yeah, that behavior sounds right IgorT. My LDs consume 3V @ 380mA and the voltage will only start to increase slowly if I increase the current. This is when I was only using a resistor in series with the LD. They won't get >3V if I don't overdriven them really hard. This is probably due to different LD internal resistance characteristics. Below is the circuit that I'm using when I properly run my setup for laser light show.



Care to explain what you mean by flipping it around :thinking:? Isn't the LD case from DVD drives actually ground?

I reworked the entire circuit so that the cathode of the LD /its case/ is connected to GND and current is pumped by the transistor from 'above' , i.e., its anode, as opposed to the die4laser circuit in which LD's cathode must be connected to the drain electrode of Q1. The main issue this arrangement poses is that you actually end up having non-ground potential on the case of the LD and its heatsink respectively. I run the circuit off a lab PSU whose negative terminal is connected to its metal case. In this respect, any exposed massive metallic parts at some potential other than ground with respect to PSU's ground/chassis/PC/Scope........are subjected to short-circuit events if accidentally touched to any of these.
The next disadvantage /not really applicable in the proposed circuit/ of not having the LD case hooked to electrical GND is the fact that its case along with the heatsink present a fairly large parasitic capacitance connected to the active element. As this would not be an issue for you laser show experiments using this driver where the beam is likely to be modulated with fairly low frequencies where a couple of picofarads more mean nothing, in a high-speed application /with very short pulses in the nanosecond range/ they may prove critical...not to mention the amount of RFI a big metal case connected to a 'live' high freq terminal would radiate.

 

[VaThInK]

Ah I see what you mean. So you're using P channel FET instead I guess for the reworked circuit. I actually killed my LD once by accident as the result of the ground not being on the same level as the LD cathode. Thanks mate.