1. SILICON VIDEO® 643M, 643C Video Adjustments

 

1.1. Gain & Offset Normalization

The SILICON VIDEO® 643M and 643C cameras, as do most CMOS sensors, exhibit fixed pattern noise; an image aberration where different columns have varying black (i.e. offset) levels.

From the PIXCI® Image Viewer, click:

    Capture
    Adjustments
    FFC
For most common conditions:

  1. Select:
        Pixel Normalization: Offset
    

  2. Cover the lens, adjust the Black Offset so pixel values are low but not zero. Click:
        Extract Offset Ref(erence)
    

  3. Click: Normalization On

CMOS sensors also exhibit slight differences in individual pixel sensitivity. For better image quality:

  1. Select:
        Pixel Normalization: Gain & Offset
    

  2. Cover the lens and click:
        Extract Offset Ref(erence)
    

  3. Uncover lens and point the camera at a flat grey target[1] with even illumination yielding 70% to 95% of maximum pixel values (i.e. bright white but not saturated) and click:
        Extract Gain Ref(erence)
    

  4. Click:
        Normalization On
    

The camera's fixed pattern noise will change, and the above procedure should be repeated, after changing any of the camera's Pixel Clock, AOI Left, AOI Width, AOI Top, AOI Height, Scan Direction, Gain, or Black Offset controls (below).

 

1.2. Video Resolution

Reducing the video resolution (the number of pixels captured per line and column) allows capturing more video frames in a given size of frame buffer memory. From the PIXCI® Image Viewer, click:

    Capture
    Adjustments
    Res(olution)
Click:
    Set Video Window
and draw the new desired area to be captured by left clicking and dragging over the displayed image. Click:
    OK
to accept the new capture resolution. Note: Changing the capture resolution will destroy any images previously captured in the frame buffers!

The

    Capt(ure)
    Frame Buffers
shows the number of frame buffers available with the current selections.

 

1.3. Saving the Video Configuration

The selections under the PIXCI® Image Viewer:

    Adjustments
are automatically saved when the PIXCI® frame grabber is closed, and/or XCAP is exited. When the PIXCI® frame grabber is next opened, clicking (from the XCAP Main Window):
    PIXCI®
    PIXCI® Open/Close
    Camera & Format
Choose:
    Open w. last used Video Setup
to use the previous video setup, or choose:
    Open w. default Video Setup
to start afresh with the default video format and resolution.

 

1.4. Camera Controls

XCAP integrates controls for both the PIXCI® frame grabber and the SILICON VIDEO® 643 camera within the Capture & Adjust window. The left side of the Capture & Adjust window contains controls for the PIXCI® frame grabber. The right side of the Capture & Adjust window provides camera specific controls.

The Black Offset allows adjusting the camera's black level. An increased offset causes black areas of the scene to appear as grey, leading to a ''washed out'' appearance. A decreased offset causes loss of detail in the dark areas of the scene. When using Pixel Normalization Pixel Normalization the Black Offset should be set so that an image captured with the lens closed, and with Pixel Normalization disabled, results in low, but not zero, pixel values. This is to maintain the linearity of pixel values, avoiding ''clipping'' or so-called ''negative offsets''; pixels whose value is clipped can not be properly corrected by PixelNormalization.

The Gain allows adjusting the camera's gain. Increased gain allows capturing dark scenes, but at the expense of decreased image quality (random and fixed pattern noise); Whenever possible, increase illumination or increase exposure instead of increasing gain.

The Exposure allows adjusting the camera's exposure (shutter) period. When using AC powered lighting, an Exposure which is a multiple of half of the power line's period (i.e. 16.6/2 msec. in the U.S. and other locations using 60 Hz, 20.0/2 msec. in Europe and other locations using 50 Hz) is suggested to prevent varying image brightness due to the illumination's cyclical change of brightness. Selecting Exp. Mult. of 1/50 or Exp. Mult. of 1/60 automatically forces the Exposure to a multiple of the corresponding period. The Exp. Mult. ... is not useful when operating the SILICON VIDEO® 643M and 643C at frame rates faster than the power line frequency; a high frequency or DC powered illumination source is recommended.

The AOI Left, AOI Width, AOI Top, and AOI Height allow selecting an area of interest which is read-out and captured. Capturing fewer lines or columns decreases the image size and allows a faster frame rate. If Center Aoi L(eft)-R(ight) or Center Aoi T(op)-B(ottom) is selected, the AOI Left or AOI Top, respectively, is automatically adjusted so as to center the capture AOI, the AOI Width or AOI Height, within the camera's field of view.

The Subsampling allows selecting vertical subsampling (decimation) of the AOI by a factor of 2, producing an image of lower resolution with smaller size, and allowing a faster frame rate.

The Pixel Clock allows specifying the pixel clock rate. A faster pixel clock increases the allowable frame rate, but with reduced image quality (increased fixed pattern noise); a slower pixel clock increases the allowable exposure periods for longer integration and greater sensitivity.

The Video Mode allows selecting Free-Run or Controlled frame mode. In Free-Run mode the camera exposure and read-out is free-running; continuously exposing and sending frames to the frame grabber at a constant frame rate without need of a trigger. In Controlled mode the Controlled Frame Rate, Continuous, and Single Shot provide frame rate and triggering control through the PIXCI® SI1, SI2, or SI4 frame grabber.

 

1.5. Color Cameras

For color cameras with so-called ''Bayer format output'', it is XCAP software which performs color adjustments and white balancing, not the camera.

From the PIXCI® Image Viewer, click:
    Capture
    Adjustments
    Color (or Clr)
For most common conditions:

  1. Select one of the pre-defined correlated color temperatures, either based on best appearance, or matching the color temperature of the current illumination. The 5000°K selection is average overcast daylight, the 4100°K selection is a typical cool white fluorescent bulb, and the 2800°K selection is a typical 60 to 100 watt tungsten bulb.

  2. Choose one of the predefined color qualities, trading quality for speed.

  3. If none of the predefined settings is satisfactory, start with the best setting and click:
        Customize
    
    Cover the camera's lens and click:
        Black Balance
    
    Finally point the camera at a white target (but preferably not a target using fluorescent brighteners) and click:
        White Balance
    

 

1.6. Automatic Exposure Control

The AEC controls provide automatic adjustment of the camera's exposure as the image intensity changes. From the PIXCI® Image Viewer, click:
    Capture
    Adjustments
    AEC

Click:
    AEC On
to enable AEC.

2. Footnotes

[1]
Defocusing the lens is sometimes helpful - especially when the target is textured - so that the camera doesn't see the texture.