MEMS accelerometer: noise reduction and improve resolution

Hi to all, I hope to post in the right place.
I have a 14 bit MEMS digital accelerometer, I need 100 sps output rate.
I would like to start tests with LabView before move to microcontroller but first I have these doubts:
First step: sensor could work up to 1200 sps, so I'm thinking about reading data at 1200 sps to increase resolution.
Is there any suitable algorithm specific for this case or just oversample then avarage results to 100 sps?
Second step: I've heard it's possible to use multiple (2-3) sensor at same time to reduce noise (Kellman filter?), right?
If so I haven't found examples on the net, just using sensors grid (isn't my case).
Is there available any example?
Thanks. Michele.

At the end, my final application is measure signal with maximum pk-pk value of 1-1,5g, maximum bandwidth 50Hz.
Target accelerometers has got about 300ng PSD value, at 24 bit resolution, I would likr to know what can I do with commercial accelerometers.
Hi, I've take as example application note AN4075 from Freescale:
- sensor MMA8451 14 bit digital output, +/- 2g fullscale, 0,25 mg/count
PSD = 85ug/SQRT(Hz)
Signal bandwidth = 200 Hz
Sample frequency = 400 Hz
RMS noise = 1,2mg (on 200 Hz bandwidth)
pk-pk noise = RMS noise * 4 = 4,8 mg
I have 2,8 mg of noise where I have a resolution of 0,25 mg/count, so I got at the end efective resolution of 11,05mg.
Other sensors could be BMA180 from Bosch or LIS3LV02DQ from ST (both digital output).
1) can I improve performances of these sensors?
I've read I can increase resolution with oversampling, but I think I would be limited to the maximum sample rate of sensor (1200 SPS for BMA180 or 1600 for LIS3LV02DQ)
If oversampling would be correct way, I think I could use external ADC (due to high SPS I can reach in this way, digital sensors has got maximum SPS up to 1600) to increase SPS value.
But if I increase resolution through oversampling (let's suppose I can reach 24 bit resolution), which would be efective number of bits?
2)I can place sensors much closer, so I think I can get same acceleration reading from 2 (or more) sensors. In this case I would reduce noise throu Kelman filter.
But examples I've fond on the net are based on "estimated" value I suppose, and on "real" value I read from sensor.
So I have no idea how implement Kelman filter.

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Matt Howell wrote:
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Jao, Thank you. I have asked this question elsewhere before. I have recieved replies, maybe I did not follow the directions properly, but they never worked. The sharpening would be disableduntil I went to make another correction. Then back to sharpening Lightroom would go. Your way, sharpening is disabled for all the images and stays that way. Thanks again.
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dorin_nicolaescu wrote:
Luminosity Contrast slider also helps maintain some darker tones.
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i absolutely agree!
Now, in LR3 you can move the sliders very smoothly - but nothing happens for seconds.
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V1.1 Noise Reduction

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>Not at all. There's ABSOLUTELY nothing wrong with that workflow. I would recommend it myself.
>[EDIT] except I prefer Noise Ninja most of the time, and Noiseware in a few cases.
I've discussed this matter with Gordon on another thread, but a few points are worth repeating here. On page 157 of his Image Sharpening with Adobe Photoshop PSCS2, Bruce Fraser states, "Always do noise reduction before sharpening. If you sharpen, you'll almost certainly make the noise worse; the noise reduction tool will have to work harder, and will probably wipe out the sharpening you did anyway."
Most noise reduction tools do not eliminate noise but merely make it less visible. When you sharpen after noise reduction, some or much of the noise may reappear. If you do the sharpening first, this problem is eliminated, but the effect of your sharpening may also be wiped out.
Sharpening and noise reduction are basically inverse processes and work against another. Some of these problems may be eased with the use of masks. You can use a surface mask during noise reduction to help confine the NR to smooth areas where the noise is most noticeable and keep the NR away from the edges where sharpness would suffer. Similarly, you can use an edge mask during sharpening to help confine the sharpening to the edges.
That said, Noise Ninja can work reasonably well on JPEG images that have been sharpened in camera as they often are. In this case, one has to use a different noise profile for the best results.
Bill

How do PS CS3 Noise Reduction Filters compare with dedicated third-party plug-ins?

Am I missing something by not installing a dedicated Noise Reduction application into my PS CS3? Can Neat Image, Noise Ninja, Noiseware Pro, etc. do something that the PS CS3 Noise Filters can't do? Do these third-party aplications do it better?
Since I like flashless photography, and I generally carry with me small-sensor compacts when I travel, I'm frequently confronted with the problem of digital noise. I've always wondered how the third-party noise reduction applications perform in comparison with the Photoshop Noise Filters. I hope someone in this Forum has been able to acquire direct experience on this topic and will be kind enough to share this experience with us.
Kindest Regards,
Conrad

Conrad,
ACR 4.3 has better NR (noise reduction) than previous versions and can handle NR in most normal situations. However, available light photography with a small pixel sensor may require more NR and the specialized plugins such as Noise Ninja, NeatImage, and NoiseWare Pro can do a better job. I have all three and they do an excellent job, but I currently use NoiseWare most of the time.
Here is a demonstration of NoiseWare vs ACR NR, using 100% crops of an image taken with the Nikon D200, 1/320 sec at f/2.8. The image is reasonably sharp at normal viewing conditions, but has quite a lot of luminance noise. It was rendered with ACR and the settings were exposure +0.85, brightness +60. One thing you learn early in this type of shooting is to expose to the right to reduce noise, but this may conflict with stopping action and reducing camera shake. More exposure would have helped this image, and one should try to avoid exposures requiring this amount of positive exposure adjustment.
The results are shown below, followed by some discussion. Other comments are welcome. Color noise is not prominent in this image and I left color NR at its default.
ACR, No sharpening, no NR
ACR, Luminance NR 53, no sharpening
ACR, No NR, No sharpening, NoiseWare default, no sharpening
Noise reduction and sharpening are antagonistic processes. It is important that NR is applied before sharpening--you don't want to sharpen noise. Following NR there is an inevitable loss of detail, and some sharpening is necessary to restore the detail, but this also brings back the noise. One can use masks and blend if sliders in Photoshop in both NR and sharpening to mitigate some of these effects, and Bruce Fraser discusses the details in his excellent book on sharpening.
If you use an add on such as NoiseWare, you should turn off luminance sharpening in ACR. In doing so, you lose all those nifty sharpening features that have recently been added to ACR. I leave color NR at the default. It has a minimal effect on detail.
In adjusting the NR in ACR at 100% viewing, I estimated that a luminance setting of +53 was optimal. Beyond that, blotchy artifacts appear in the image.
For NoiseWarePro, I used the default settings with no sharpening. The NR effect is dramatic, but detail is lost and some sharpening is needed. This could be applied in NoiseWare or in Photoshop, perhaps with a plugin such as PhotoKit Sharpener. Personally, I have found that PK does not work well with this type of image because it bring back noise and produces artifacts.
In all of these examples, sharpening is needed following the NR. One could try to use surface masks to keep sharpening in Photoshop with the unsharp mask away from the edges. However, I find it is difficult to get a good surface mask, and I don't take the trouble.
For now, I use the sharpening built into NoiseWare. I don't know how it works internally, but it does have a slider for detail protection, and you can play with this to get the best result. It would be best to have the robust NR of the add ons built into ACR much like NoiseNinja is built into Bibble Pro. However, this is an ACR forum and I would expect that ACR is the preferred raw converter of those who frequent this forum.
After expending this much effort on the post, I hope to get some helpful feedback.

MEMS accelerometer: noise reduction and improve resolution

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