Beam Profiler FAQ’s

Cameras

06/01/15

The BeamGage laser beam analyzer product is provided in a tiered structure with features and capabilities designed to meet application criteria options versus cost. The BeamGage license resides within each camera which is sold along with the BeamGage software as a system. When purchasing a license for a higher tier, the functionality for the lower tiers is also available, but when purchasing a lower tier, the functionality for the higher tiers must be additionally purchased as an upgrade.

06/01/15

The Pyrocam III needs a window for protection against foreign objects entering the camera, and destroying the crystal. This could happen by someone poking a brush or Q-tip to clean off lint, etc. The window also protects the sensor from the effects of humidity. The window must have anti-reflection coating, or the two surfaces of the window will create interference fringes from a collimated light source which show up on the sensor as ripples in the beam. With anti-reflection coating the reflections, and thus the interference fringes, are minimized, and the sensor sees only the beam energy.

06/01/15

Enabling more results is done by clicking on the results category in the white results window such as Spatial and placing a check mark next to the result you want to enable. Rest your mouse over the result you are considering enabling will produce a pop up box with a brief description of what this result is. NOTE: Enabling results requires more computer processing power so care should be taken not to enable so many results that it causes poor performance. Turning off results that are not necessary will help to increase performance.

05/28/15

Data provided by a customer: "We only have a gauge that goes down to 10 mTorr. So it works at least to that level, but the vacuum was probably lower".

06/01/15

The problem we are seeing in the images you provided is what is referred to as "image tarring". This occurs when there is another process going on during the data acquisition from the camera. We also see that there are two beams on the screen at the same time. Some of which are of the same intensity and some which are what we call "Ghost Beams". These occur from a couple of things. One, it could be from a beam splitter causing a back reflection and we are picking it up on the camera. Two, it is more likely that this is a ghost beam from the laser being pulsed. We see this when the triggering on the camera is not properly set such that we are having the pulse arrive during the reset time of the array. Third this could be from using too much electronic shutter. The electronic shutter can be used as a slight attenuator, but when two much electronic shutter is used, we typically see vertical blooming.

My recommendations would be for running the camera synced to the laser pulse via the connection on the side of the camera. This will also help when trying to do single shot acquisition. The camera needs to be pre triggered by 12 uS so the camera is readied and has just started integrating when the laser pulse arrives at the CCD imager.

By putting the software into Single Shot mode it will only take one frame from the camera. However, by putting the camera into triggered mode, it waits until the trigger pulse arrives at the camera to start the integration of the CCD imager. Once the pulse arrives, the camera takes the image and stops. This mode is probably the most difficult to setup and function properly. We typically recommend that the software be set to Video Trigger and the camera to run in CW mode if you are trying to avoid seeing blank images coming from the camera until you are more comfortable with the operation of the equipment. Once you are more comfortable with how the interaction with the software, camera, and laser are working then making changes to the setup like externally triggering the camera and doing single shot data acquisition are a little easier. 

06/01/15

Yes, Blooming occurs in the near-IR wavelengths and exhibits as a vertical stripe through the most intense portion of the image. Blooming may sometimes be to faint to notice but may still distort the beam width measurement. Blooming can be mitigated by increasing the Exposure control to the maximum frame period

06/01/15

Yes. Since we remove the protective glass cover over the CCD camera sensor the full spectrum of the Silicon sensor can be used. This allows the cameras to operate as low as 190nm. But UV wavelengths are very abusive to the CCD sensor and over time the CCD sensor will become less responsive in the area where the UV laser is impinging on the sensor. Steering the beam around the sensor will reveal the low response area and unfortunately the CCD sensor will need to be replaced. In these cases, we recommend using a UV converter of some kind to convert the wavelength to a less abusive wavelength to lengthen out the life time of the CCD sensor.

06/01/15

Yes our windowless silicon cameras and Pyrocams are sensitive to UV light. Silicon cameras eventually become desensitized and will eventually fail with long term exposure. The shorter wavelengths create faster degradation.

  • Avoid saturation and needless exposure to prolong the life of cameras working with UV light or use one of our UV convertors to eliminate silicon camera issues at wavelengths shorter than 300nm
05/28/15

Ophir-Spiricon goes to great lengths to qualify scientific quality cameras with blemish free imagers. We also remove the protective windows from the CCD imagers to provide full spectral response and distortion free performance. These options are not available from commercial camera manufacturers. While commercially available cameras cost less, they do not provide the performance levels the Ophir-Spiricon cameras are capable of providing.

06/01/15

No. The camera has a CCD sensor coated with phosphor that responds to 1440nm – 1605nm. The CCD sensor will see wavelengths from 190nm – 1100nm, but since the phosphor coating is on the front of the CCD sensor, it limits the usable range of the camera to only 1440nm – 1605nm. Attempting to use the camera at other wavelengths can distort the image and/or put the CCD sensor and phosphor coating at risk of damage due to the attenuating affects of the phosphor coating at wavelengths outside 1400nm – 1605nm.

06/01/15

It is recommended that the camera be sent back on a yearly basis to be recertified for continued assurance of high quality measurements as a beam profiling camera. When the camera is sent back to Ophir-Spiricon, part of the recertification process is that we inspect and clean the camera sensor to make sure it is reporting "as new" measurement results.

06/01/15

Camera Defects Policy
Ophir-Spiricon, LLC (OSL) is a supplier of laser beam analysis tools that employ commercial-industrial solid-state cameras. OSL attempts to supply cameras with as few pixel defects as possible. OSL tests for and corrects defective pixels that may have an adverse effect when used for its intended purpose. OSL does not guarantee that a supplied camera will be defect free, or that they will remain defect free during its normal lifetime and under normal use.

It is not uncommon for modern megapixel camera imagers to develop point defects as they age, even when not subjected to abuse. Imagers without windows often experience point defects at rates typically greater than imagers with their cover glass left in place. Point defects can also appear more frequently when operating at higher rather than lower ambient temperatures, and higher relative humidity. Such defects can occur even when the camera is in storage and not being used.

Cameras supplied by OSL will be certified for use in laser beam analyzer applications. When defects occur, the ability to make certain measurements under certain conditions may be compromised. However, depending upon the nature of the defect, most measurement can still be performed without loss of accuracy. In some instances the effects of defects can be eliminated or significantly reduced by adjusting the manner in which the camera is being employed.

Ophir-Spiricon, LLC offers a camera recertification service. This service can help to extend the useful life of your camera and correct some point defects that may show up over time. This service can not correct cameras with serious laser damage or imager degradation. Whenever possible OSL will restore the camera to our "as new" level of certification; and if not possible, we will indicate to the user how to avoid areas of the imager that may not perform to "as new" standards.

Defects, Solutions and Workarounds
The following list contains examples of typical camera point defects that may occur over time, and suggested methods of compensating for them if they are troublesome:

Defect type Description of the Problem Recommended Solution
See Note 1 below
Bright Pixel Pixels with this defect will indicate being illuminated even when no signal is present. These are the most troublesome when attempting to make accurate peak fluence and peak fluence location measurements because they represent a false signal. Most other measurements are not adversely affected by this type of defect. This type of defect is screened for during our regular camera inspection process. All pixels that exceed a set limit are corrected, if possible, before the camera ships. See Note 1 below. Our QA department will often reject cameras if the pixel can not be corrected and it exceeds our acceptance criteria.
  1. Ultracal/baseline correction will subtract out the defective pixel.
  2. Reposition the camera to remove the defective pixel from the measurement region and employ a manual aperture to isolate the pixel from the area of interest.
  3. Return the camera to OSL to have the bad pixel corrected and the camera re-certified.
Twinkling Pixel This is an intermittent version of the Bright Pixel defect. These often appear as the camera warms up. May disappear if the camera is run in cooler environments. Usually predicts a pixel that will soon be a permanently bright pixel defect.

These are the hardest to detect and as such may get past our camera inspection process.

Same as above.

If returned to OSL to be corrected please send a full frame data file showing the pixel as it is malfunctioning. This will aid in our ability to find and fix it.

Dark Pixel Dark pixels have low responses compared to the amount of illumination that they receive. Isolated instances of these types of defects do not pose a serious beam analysis problem and they are generally not in need of correcting. This type of defect will not significantly impact a beam measurement result unless the beam is very very small and the defect falls inside of the beam profile. Reposition the camera to remove the defective pixel from the measurement region.
Dead Pixel Dead pixels have no response at all and may output a raw pixel value of zero (0) counts. This type of defect is screened for during our regular camera inspection process. All pixels that exceed a set limit are corrected, if possible, before the camera ships. This type of pixel may create a warning message when performing Ultracal operations. Ignore the warning and proceed as in the Dark Pixel case described above.
Dark Clusters These dimmer than normal clusters involving about a dozen or fewer pixels are often caused by dust particles and can usually be removed by cleaning of the imager. Sometimes these can be very difficult to impossible to remove. In the latter case they are may be melted into imager

If this is the result of laser damage then imager replacement is the only solution.

These usually do not cause serious measurement problems and can be treated with the Dark Pixel workaround described above. They can sometimes be dislodged with very gentle puffs of dry air. If you return a camera to be re-certified we have a few special methods for cleaning these, but success is not 100% guaranteed.
Regions of non-uniform response When large areas of an imager yield reduced signal levels this usually indicates laser damage. Long term exposure to ultraviolet radiation or overexposure to high laser power or peak energies are common causes. This type of degradation is not repairable and either the camera or the camera imager must be replaced.



Note 1: The following camera models can be re-certified and can have bad pixels corrected:
GRAS20, SP620, L11058, L230, Pyrocam III, Xeva
Each of the above cameras will have a maximum number of pixels that can be corrected. Once this limit is exceeded the camera imager or the camera must be replaced in order to meet OSL "as new" certification standards. If a large cluster of defective pixels appear, then bad pixel correction may not be able to repair the defect. The following cameras do not have, or have very limited, bad pixel correction capabilities:
SCOR20, SP503, FX50, FX33, FX33HD 

06/01/15

The Pyrocam III uses a +5VDC 2A rated universal power supply with a standard 5 mm barrel plug. The +5VDC is listed both on the power supply and on the Pyrocam III at the power input port. Because the 5 mm barrel plug is a standard size plug used for many power supplies, typically in the 12VDC to higher VDC power rangers, it is possible to connect a higher VDC rated power supply with this same 5 mm barrel plug into the Pyrocam III. However, if the more-than +5VDC power supply is powered-on and connected to the Pyrocam III, it does damage the Pyrocam III electronics to where the Pyrocam III malfunctions. In known occurrences of connecting a powered-on more-than +5VDC power supply, the Pyrocam III will still communicate and connect to the host PC, but functionality is compromised, for instance the chopper typically will not operate correctly, nor will the Pyrocam III produce a valid image or any image at all. If a powered-on more-than +5VDC power supply has been connected to the Pyrocam III and it becomes damaged, then it must be returned to the manufacturer and repaired by replacing the damaged internal electronic circuit boards to restore good operation and full functionality.

06/01/15

Usually this is because the camera has not been connected correctly. On desktop computers power can be pulled directly over the 6 pin to 6 pin FireWire cable. On laptops, you must use the supplied "Y" power adapter cable. The 6 pin to 6 pin FireWire cable must connect into the back of the camera and then connect into the female connection on the "Y" power adapter cable. Then the male connection of the "Y" power adapter cable is plugged into the laptop computer card. The same configuration is used for laptop computers that have built in IEEE 1394 except the 6 pin to 4 pin connector is used instead of the laptop adapter card. The round power connection must also be connected for the camera to show up in the camera list.

06/01/15

Upon initial startup the Pyrocam III defaults to pulsed mode operation. In order for the Pyrocam III to "run" in pulsed mode operation it must have a repetitive frequency trigger-in signal connected to the Pyrocam III trigger-in BNC connector. Another option is that you can select chopped mode, and once the optical chopper blade synchronizes in ~30 seconds, the Pyrocam III will "run". 

The Pyrocam III is a pyroelectric matrix array detector camera which operates on the principle of heating and cooling of the pyroelectric detector in order to output a video signal. This heating and cooling is accommodated with pulsed mode lasers and requires a trigger-in signal from the laser to synchronize to it. With a CW laser, the Pyrocam III is set to chopped mode which engages an internal optical chopper blade to interrupt the beam in order to provide heating and cooling. 

09/05/16

Below is a picture of an imager that has a lot of dust on the detector. The best thing that can be done is to return the camera to Ophir-Spiricon to go through our Camera Recertification process where we will clean the imager and check for any damage or defects in the imager that might impact the performance of your system.

Please contact our Service Department at Service@us.ophiropt.com to get an RMA number to send your camera in for evaluation.

06/01/15
  • CCD camera manufacturers typically quote a signal-to-noise ratio of 50 to 60db. This refers to the peak signal before saturation divided by the RMS noise. This is a 20 log function, so 60db would be equivalent to a dynamic range of 1000, whereas 50db would be a dynamic range of about 300. However, it should be noted that this is comparing peak signal to RMS noise. The peak-to-peak noise is about 6 times the RMS noise. Therefore, the dynamic range in terms of peak signal to peak-to-peak noise ranges from about 50 to 180. With 8-bit digitizers, i.e., 256 counts, this means that the bottom 2-5 counts in the digitizer are noisy.
     
  • The Pyrocam III pyroelectric camera also has a 60db signal-to-noise ratio. However, this is a worst case pessimistic specification. Typically the dynamic range is about 70db, which means the dynamic range is about 500 relative to peak-to-peak noise. This makes the camera very useful with 10 and 12-bit digitizers
06/01/15

The CCD in the camera will saturate at room light levels, so it is important to keep the amount of power/energy being directed towards the CCD well below these levels. Typical saturation levels of a CCD are only single digit µW/cm2 or single digit nJ/cm2, but can vary from camera model to camera model. Please consult the data sheets for your Ophir-Spiricon cameras for saturation levels for save power/energy levels for your specific camera.

05/08/17

With Trigger In mode the camera will only start to expose and transmit a frame of data when a trigger signal is sent to the camera. There generally are timing issues when using photo detectors with pulsed lasers and CCD camera frame acquisition. The BeamGage Trigger In feature provides delay adjustment to move the camera acquisition timing in order to synchronize with the pulsed laser firing. The delay can be set in milliseconds to be either later or earlier in the exposure window. A negative delay entry is settable for pre-triggering when needed. When the beam is present but not displayed, adjusting the delay will allow for good synchronization and a consistent pulsed beam display.

06/01/15

The amount of power or energy that the camera can take depends on the type of camera sensor.

  • CCD cameras typically saturate at about 0.3µW/cm2 CW, and 3nJ/cm2 pulsed
  • Pyroelectric solid-state cameras typically saturate at 3W/cm2 CW and 10mJ/cm2 pulsed
09/14/17

We recommend only using clean, dry, low-pressure dust-off air spray for gently blowing dust specs and contamination away from the CCD camera sensor. Do not use anything that makes physical contact with the sensor surface. The sensor is delicate and is surrounded by micro connecting wire-bond wires which will likely break if anything physical contacts them.

06/01/15

Sampling and attenuating the beam is done in a two-step process.

  • A high quality beam splitter is used to pass typically 90% of the beam through the beam splitter, and reflect or split typically 10% of the beam 90° away from the input path.
    • The beam splitter is typically quartz for the UV to Near IR, and AR coated ZnSe for CO2, or a transmitting or reflecting grating.
    • The beam splitter is typically quartz for the UV to Near IR, and AR coated ZnSe for CO2, or a transmitting or reflecting grating.
    • The splitter can be wedged to eliminate interference from the reflections from two surfaces, or thick enough that the back side reflection does not overlap the front side reflection.
    • The beam splitters are polarization sensitive, and this factor should be considered.
  • This sampled beam is then typically attenuated with high quality uniform neutral density filters.
    • ND filters from 450nm to 2µm can be bulk absorbing BK7 glass, and achieve excellent results.
    • In the UV, quartz plates with surface reflecting coatings can be used. However, great care must be taken to minimize interference fringes.
    • At 10.6µm flats of CaF2 absorb about 50% per mm thickness, and can be used to attenuate CO2 beams.
    • Attenuation in the 2mm to 10mm region is difficult, and is best done by multiple beam splitters.
11/06/17

When a laser has a beam size that is too large to fit onto the CCD it is necessary to use lensing to reduce the size of the beam so it can fit. This can be done in one of two ways, a beam reducer or an imaging system. When direct imaging in front of the camera, like imaging an image projected onto a defusing surface such as a ground glass plate, it is necessary to reduce the image so that it completely fits onto the CCD chip surface. A 25mm or 50mm CCTV lens images an object from a given plane in front of the lens onto the CCD while reducing the size. The lens can image such objects at distances from about 10cm in front of the lens (20cm for the 50mm lens) to 1 meter or more depending on the distance from the lens to the CCD. The distance from the lens to the CCD depends on the camera type and spacers placed between the lens and the CCD. The magnification reduction is dependent on how far the object is from the lens and the amount of distance the lens is to the CCD detector. Below is an example of how this is done and some graphs showing the Object distance vs. Lens spacing and Size reduction vs. Lens spacing.

How do I profile a laser with a beam size that is too big to fit onto the camera CCD detector

06/01/15

When using a camera with a lens, the operator must perform a spatial calibration to obtain accurate dimensional results. To do this, you must set up the camera lens system to view an object of a known dimension. The object to be viewed must contrast against its background to yield well defined edges. Use the following procedure.

  • In the Camera Dialog Box, set the "Pixel Scale" V value to 1.
  • In the Beam Display Toolbar Dialog Box check "Cursors" and "Crosshair"
  • In the Camera Dialog Box set the "Resolution" to 1X.
  • On the Beam Display Toolbar set "Crosshair" to Manual and "Cursor" to Manual.
  • Set the LBA into "CW Mode" and start it "Running."
  • Place an object containing at least one known dimension into the imaging plane of the camera lens system, and focus the optics. (A good object might be a circular disk with a diameter of 1cm.) The object should be large enough to fill over 50% of the display height. You can hardware zoom to enlarge the object if necessary. Orient the object so that the calibration dimension aligns vertically on the Y axis cursor. You can use the Pan and Cursor controls to achieve a good alignment.
  • With the mouse and left button move the cursor to one edge of the object
  • With the mouse and left button move the crosshair to the object's opposite edge. The Delta = value on the screen will contain the pixel count between the known calibration dimensions. Divide this number into the calibration dimension to yield the correct "Pixel Scale" value.
  • For example, if a 1cm distance produced a delta count of 176, then the "Pixel Scale" value would become .00568cm, or 56.8µm.