White light or laser – what makes the best dental 3D scanner?

[NicelyMKV]

I get cases produced with 3shape and they never seem to fit the tissue area of a Pontic or preps with a rough surface. I'll take white light any day.

 

[YMS96]

I get cases produced with 3shape and they never seem to fit the tissue area of a Pontic or preps with a rough surface. I'll take white light any day.

Sounds like a design/manufacturing issue. I'm doing bridges all day on a D700 and I can set the gingival cut on pontics to 0.01 mm away and it fits perfect.

 

[charles007]

Sounds like a design/manufacturing issue. I'm doing bridges all day on a D700 and I can set the gingival cut on pontics to 0.01 mm away and it fits perfect.

Does this mean we can stop scraping ridges on models and just change the gingival cut off setting on the scanner... Can you do this when docs asks to cut teeth off the model, then later trim ridge to fit the milled frame, and on resent extracted teeth ? this would be more precise than scraping for sure. If this can be done, would be nice to learn the setting.

 

[xjhou]

a nice post, learned

 

[Toothman19]

Was this debate ever resolved?

 

[Marcusthegladiator CDT]

Combo, laser/light.

 

[2thm8kr]

Combo, laser/light.

Laser light show at the planetarium.

 

[aqdental]

Dear 3 Shape Guy
can you please explain , if is true what you are telling us, why 3 Shape which is making laser scanners for some time now (10 years?),made the decision to move away from it with the new d900.
Just a walk on the wild side?

 

[harmonylab]

Was this debate ever resolved?

3shape's best scanner is now a light scanner. /thread

Sent from my LG-P769 using Tapatalk

 

[Ken Knapp]

Hi guys
I have been following the discussions about technology vs. performance for different kinds of dental scanners. I really find everybody’s input very interesting.

I would like to contribute to the discussion by throwing some additional light on the technical differences between “White Light scanners” and “Laser scanners”.


The plain answer first: It really doesn’t make a difference – other factors are decisive for scanner performance.

Now for the detailed story. In general, there is a lot of confusion about supposed technical advantages of various kinds of light and light sources. Let’s have a look at this.


White light images are sharper:
The opposite is true. Optical lenses refract light of different colors differently. As white light is a combination of all colors, not all these colors can be in perfect focus. This phenomenon is called chromatic aberration [1]. Its effect can be minimized by careful design and assembly of a scanner’s lens system, but it will never disappear completely, and thus it will limit the accuracy of a white light scanner. Lasers, in contrast, are single color light sources and hence don’t suffer from chromatic aberration.


White light penetrates objects less and is reflected better:
An object that appears white reflects all colors equally well. Gypsum casts are at least close to white. As one can easily see, gypsum is very matte which indicates that there is essentially no light penetration through gypsum in general. So all colors work equally well with gypsum. The debate may be muddled by confusion of white light dental scanners with white light interferometers [2] or white light confocal microscopes [3]. These latter instruments are indeed very accurate (and expensive),but they exploit other physical phenomena than dental white light scanners, which are based on the simple principle of fringe projection.


White light sensors are preferred in industry:
Not correct. The majority of scan heads for coordinate measurement machines, which are the reference standard in industrial metrology with accuracies down to 3-5 micron, use lasers. Note that coordinate measurement machines are the most widely used high-accuracy measurement devices. In addition, some industries use white light and laser 3D scanners for less demanding measurement tasks.


White light sources have a longer life time:
The opposite is true. Halogen lights have a mean lifetime of thousands of hours and usually have to be replaced, whereas lasers and LED’s generally outlast other electronics components [4].


White light gives better resolution than laser light:
Camera resolution is what really matters, i.e. how many megapixels the camera sensor has. High end dental scanners have 5 megapixels, typical dental scanners have 1.3 megapixels.


Lasers are imprecise due to speckle:
Again, true in theory, but the effects are too small to matter in practice. Speckle is an effectively random variation in laser light intensity across a dot or line of laser light, resulting in some uncertainty in detecting its center in a scanner’s camera. However, lasers in dental scanners can be driven in such a way that the magnitude of this uncertainty is only approximately 1 micron [5]. Furthermore, advanced image processing algorithms can correct for speckle artifacts, such that the overall effect is negligible.


White light scanners save one axis in the motion system:
Somewhat true - if you are willing to live with a serious disadvantage. White light scanners project a multi-line pattern from a central light source, while a laser only gives a single line and thus has to be moved along a linear axis. However, the additional degree of freedom gives better coverage. From the extreme position of the linear axis, the laser can illuminate regions that are shadows when illuminated from a central position only. As linear axes can be built to be very precise (1-2 micron),the advantage comes at no noticeable accuracy cost.


White light sensors capture data faster:
There is no reason why this should be true. A sensor’s frame rate has nothing to do with the color of light that it senses. In fact, several white light scanners in the dental market are much slower than some laser scanners.



In conclusion, there is no fundamental law in physics that determines that one type of dental scanners is better than others. What really matters for obtaining optimal accuracy are advanced image processing software algorithms, high-resolution cameras, a well-designed mechanical motion system, and sound craftsmanship. To ascertain a consistent level of quality in every-day use, it is furthermore imperative that scanners are supplied with a reference / calibration object and procedure



References

[1] Chromatic aberration - Wikipedia, the free encyclopedia

[2] Encyclopedia of Laser Physics and Technology - white light interferometers, dispersion measurement, low-coherence interferometry

[3]Frank JH, Elder AD, Swartling J, Venkitaraman AR, Jeyasekharan AD, Kaminski CF: A white light confocal microscope for spectrally resolved multidimensional imaging, Journal of Microscopy, vol 227, pt 3 September 2007, p. 203–215.

[4] Sony Global - Laser Diode

[5] Dorsch, RG, Häusler G, Herrmann JM: Laser triangulation: fundamental uncertainty in distance measurement, Applied Optics, vol 33, no 7, March 1994, p. 1306 – 1314. (See Figure 7. In dental scanners, lasers can be driven to behave like an LED.)

3shapesupportguy,

I agree with you.

The key is a cost effective scanner technology that satisfies the end use application quality requirements.

A well built laser system will exceed the accuracy and precision of structured light technology. However, this would be cost prohibitive for dental applications and the quality beyond what is necessary.

The structured light scanner is very low cost compared to a laser system yielding the same quality. Structured light and time of flight scanners will dominate dental applications in the near future because of cost, speed and ease of fabrication.

I like laser systems too. I cut my optical teeth on laser interferometers back in the 80's.

Ken

Knapp Laboratories

 

[DMC]

I find nothing exotic, or expensive about Lasers.....?
OK, back in the 80s yes....but for 2013....they are a dime a dozen.
No more expensive than a common flashlight. LOL

Where are the crazy expensive, super accurate laser scanners you speak of?
I never have seen any?
I have seen many $100k+ Light scanners though.

I completly disagree with Laser being more accurate, or any more expensive to produce.


Light scanners are more accurate on small objects. Period. I doubt you will find any documentation or articles to suggest otherwise.

I mean, where is this awesome, accurate laser scanner? If it exists?
Who sells/sold it?

Please read this.....
http://www.exactmetrology.com/laser...gy-examines-which-is-better-for-your-project/

I have this pretty sweet Laser at my river house...only a couple hundred.
Very fancy scanning system! Very intricate patterns and moving shapes.
Dual laser (Two color) at that!

Also Two fog machines, disco-ball, and nice karaoke set-up....

 

[Ken Knapp]

I find nothing exotic, or expensive about Lasers.....?
OK, back in the 80s yes....but for 2013....they are a dime a dozen.
No more expensive than a common flashlight. LOL

Where are the crazy expensive, super accurate laser scanners you speak of?
I never have seen any?
I have seen many $100k+ Light scanners though.

I completly disagree with Laser being more accurate, or any more expensive to produce.


Light scanners are more accurate on small objects. Period. I doubt you will find any documentation or articles to suggest otherwise.

I mean, where is this awesome, accurate laser scanner? If it exists?
Who sells/sold it?

Please read this.....
http://www.exactmetrology.com/laser...gy-examines-which-is-better-for-your-project/

I have this pretty sweet Laser at my river house...only a couple hundred.
Very fancy scanning system! Very intricate patterns and moving shapes.
Dual laser (Two color) at that!

Also Two fog machines, disco-ball, and nice karaoke set-up....

https://www.youtube.com/watch?v=Z-ZSSBoGXmI

?[/quote]


***,

Laser interferometers are hardly outdated. One needs to keep up with the technology by staying educated.

Phase detection laser interferometers have a resolution in the (2-10) nm range. These imaging systems can profile surfaces and can be equipped with a goniometer. However they are relatively slow. These systems cost about $100,000.

You really should read a little more before you start shooting your mouth off.

Ken

Laser Interferometers

Click to learn more about ZYGO's complete selection of interferometer accessories.
Laser interferometers from ZYGO were first introduced commercially over 35 years ago. Today, ZYGO continues to maintain the leadership role in surface form metrology using laser interferometry. Thousands of ZYGO interferometers are installed worldwide and relied upon daily to provide accurate production measurements of optical components and assemblies, things that affect our daily lives. Applications span across a wide range of industries, including consumer electronics, ophthalmology, semiconductor and defense & aerospace. ZYGO is the one optical metrology company that is trusted across the globe to qualify the world's most critical and precise optics. Shouldn't you be using a ZYGO laser interferometer.

 

[cadfan]

Hi Ken Knapp maybe you can bring a little light in the discussion that the problem of dental laser scanners is to measure edges and nook like sharp margins or occlussal edges because off the speckle and therefore white light is better and maybe although the parallel processing off laser scanners and not matching after finishing measurement like stripe light scanners do to be better able sorting good and bad data in normal noise ,lateral and z resolution.I hope you understand what i mean i am only technician and german so maybe two problems. Thanks John

 

[primus]

Neat, but now back to the thread in which we are discussing 3d scanning of small objects for data points to be meshed, and then modeled in CAD.

Not measuring the flatness of surfaces. Completly different thing and different application.

What you show is more of a 2D scanner.

Just tells how flat a surface is. Right??

Are there any super-awesome Laser scanners for small objects??

I am pretty sure they are all structured light now. Almost certian of it.

The cost is not the issue.