1. SILICON VIDEO® 20C-CL, 20M-CL Video Adjustments

 

1.1. Video Resolution

Reducing the video resolution (the number of lines captured) 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. The SILICON VIDEO® 20C-CL and 20M-CL cameras only support vertical AOI reductions, width of the AOI can't be changed. 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.

 

1.2. 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.

 

1.3. Camera Controls

XCAP integrates controls for both the PIXCI® frame grabber and the SILICON VIDEO® 20C-CL and 20M-CL cameras 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 Analog Gain allows adjusting the camera's analog gain. Increased gain allows capturing dark scenes, but at the expense of slightly decreased image quality (increased random noise); using (Analog Gain) Normal to force recommended analog gain values provides optimal linearity and minimal pixel noise. Whenever possible, increase illumination or increase exposure instead of increasing gain.

The ADC Gain allows adjusting the camera's A-D converter to obtain more gain; using (ADC) Normal to force recommended ADC values provides optimal linearity and minimal pixel noise. Use of ADC Gain less than 1.4 or 2.0 (depending on Data Mode) is not recommended, as the full range of pixel values may not be usable regardless of illumination and exposure settings.

The Dark Level allows adjusting the camera's black level or pixel offset.

The Exposure allows adjusting the camera's exposure (shutter) period. When using AC powered lighting, use of 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 Enable Long Exposure alters the range of the Exposure to allow extended exposures; extended exposures exceed the nominal frame period and will reduce the frame rate.

The AOI 1 Top, AOI 1 Height through AOI 8 Top, AOI 8 Height allow selecting one or more areas of interest which are read-out and captured. Capturing fewer lines decreases the image size, and also allows a faster frame rate. Up to eight areas of interest of different heights are allowed, but can't overlap vertically. The camera's horizontal area of interest can't be changed, the AOI Width and AOI Left shows the width and horizontal position of the area of interest, but neither is adjustable.

The Subsampling allows selecting vertical subsampling (decimation) of the AOI by a factor of 2, 4, 8, or 16 producing an image of lower resolution with smaller size, and allowing a faster frame rate. The Scan Direction allows adjusting the direction in which pixels are read-out, allowing inversion of the image.

The Data Mode allows selecting the number of bits per pixel, the number of taps used (i.e. number of pixel values output per clock), and the Camera Link mode. Any Data Mode selections not supported by the current PIXCI® frame grabber are corrected.

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, Trigger Input, Continuous, Single Shot, and Min(imum) Retrigger Period provide frame rate and triggering control through the PIXCI® E1, E1DB, E4, E4DB, E4G2-2F, E4G2-4B, E4G2-F2B, E4TX2-2F, E4TX2-4B, E4TX2-F2B, E8, E8DB, e104x4-2f, e104x4-4b, e104x4-f2b, EB1, EB1G2, EB1-PoCL, EB1G2-PoCL, EB1mini, miniH2B, miniH2F, miniH2x4F, mf2280, EC1, ECB1, ECB1-34, ECB2, EL1, or EL1DB frame grabber.

The Black Sun Protection allows protecting against ''black sun'' artifacts, where a very bright object is partially black instead of saturated white (and regardless of the Exposure). A value of 0 disables protection, larger values offer increasing levels of protection but also increased levels of fixed pattern noise (FPN).

1.3.0.1. High Dynamic Range

The High Dynamic Range allows selecting Disabled, Two-Slope, or Three-Slope exposure modes. The High Dynamic Range options provides for greater effective dynamic range, allowing imaging of a scene with both very bright and dark areas without losing the details of the dark areas and without saturating the bright areas. A common example is imaging a bright scene through a window while simultaneously imaging the dark wallpaper around the window.

In the Two-Slope mode, the Exposure effectively controls the exposure of dark pixels, the Exposure Knee 1 and the DAC Knee 1 effectively controls the exposure of bright pixels.

In the Three-Slope mode, the Exposure effectively controls the exposure of dark pixels, the Exposure Knee 1 and the DAC Knee 1 effectively controls the exposure of bright pixels, and the Exposure Knee 2 and the DAC Knee 2 effectively controls the exposure of very bright pixels.

More precisely, the Exposure Knee 1 specifies the additional exposure after bright pixels reach the DAC Knee 1 pixel value, and the Exposure Knee 2 specifies the additional exposure after very bright pixels reach the DAC Knee 2 pixel value.

The DAC Knee 1 and DAC Knee 2 are specified as a percentage of maximum pixel value. The Exposure Knee 1 and Exposure Knee 2 can be specified in milliseconds, as is Exposure, or can be specified as a percentage of the Exposure, allowing them to track the Exposure value.

1.3.0.2. Lookup Table (LUT)

The lookup table (LUT) feature allows remapping pixel values - after the sensor A/D conversion and before reduction (if used) to 8 or 10 bits.

The Lookup Table Mapping allows Disabling or Enabling the lookup table transformation on pixel values.

The LUT Type selects the lookup table values to be loaded, and thus the pixel remapping. If Gamma is selected, a nonlinear power curve specified by gamma correction curve with gamma of LUT Gamma is loaded. If Gamma Invert is selected, an inverted nonlinear power curve specified by gamma correction curve with gamma of LUT Gamma is loaded. A LUT Gamma less than 0 is often used with 8 or 10 bit output modes, assigning a greater range of pixel values to dark areas of the scene and assigning fewer pixels values to bright areas of the scene - where the human is less sensitive to small differences.

If 1 Knee is selected, a piecewise curve of two linear segments, with slopes Lut Knee Slope 1 and Lut Knee Slope 2 applied before & after the ''knee'' pixel value of LUT Knee 1, is loaded. If 1 Knee Invert is selected, an inverted 1 Knee curve is loaded.

If 2 Knee is selected, a piecewise curve of three linear segments, with slopes Lut Knee Slope 1, Lut Knee Slope 2, and Lut Knee Slope 3 applied before & after the ''knee'' pixel values of LUT Knee 1 and LUT Knee 2 is loaded. If 2 Knee Invert is selected, an inverted 2 Knee curve is loaded.

If Linear is selected, a linear curve is loaded; however, simply disabling the Lookup Table Mapping has the same effect on the camera's pixel values. If Linear Invert is selected, an inverted linear curve is loaded.

If Lookup Table Loading is Disabled, a lookup table is not loaded; if Lookup Table Mapping is enabled, then the camera's current lookup table values are used. This option allows minimizing serial communication with the camera, by not reloading the lookup table values.

The graph of the lookup table curve selected by LUT Type and related parameters is displayed, with original pixel value on the abscissa (horizontal) axis and modified pixel value on the ordinate (vertical) axis.

 

1.4. 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, as part of the (post)capture process.

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
    

 

1.5. Automatic Gain & Exposure Control

The AGC controls provide automatic adjustment of the camera's gain or exposure as the image intensity changes. From the PIXCI® Image Viewer, click:
    Capture
    Adjustments
    AGC
Select whether gain, or exposure, or both, should be modified to darken a too-bright image or brighten a too-dark image:
    AGC Adjusts Gain
    AGC Adjusts Adc Gain
    AGC Adjusts Exposure
Using only gain adjustments avoids increased blur due to moving objects when exposure is increased. Using only exposure adjustments avoids increased pixel noise at high gain settings. If using both gain and exposure adjustments, the
    AGC Adjust Priority
allows selecting whether gain or exposure should be adjusted first for an image which is too dark (the opposite is done for an image which is too bright); again trading off image blur versus noise. Finally click:
    AGC On
to enable AGC.

 

1.6. Image Quality

The SILICON VIDEO® 20C-CL and 20M-CL cameras, as do other high resolution and high performance sensors, use multiple ''taps'' to process multiple pixel values in parallel. The behavior of individual taps of individual sensors varies; on the 20C-CL and 20M-CL cameras this is seen as an intensity difference between the left and right halves of the image, and to a lesser degree, an intensity difference between odd and even lines.

To enable software compensation for the tap differences, click:

    Capture
    Adjustments
    FFC
Select:
    Pixel Normalization: Tap Balance
Close the lens aperture or install the lens cap. Click:
    Extract Offset Tap Balance
Uncover and open the lens and point the camera at flat grey or white target, with even illumination (but not saturated). Click:
    Extract Gain Tap Balance
and select:
    Normalization On
It may be difficult to arrange for the entire camera's field of view to be ''flat''; use:
    Set Tap AOI
to select a relatively flat portion of the image before tap balancing.

Virtually all high resolution CMOS sensors (as well as most CCD sensors), has several pixels which are totally or partially unresponsive. The number and pattern of pixels is unique for each camera and sensor. Software can compensate for the unresponsive pixels. While some cameras hide the unresponsive pixels' existence, the SILICON VIDEO® 20C-CL and 20M-CL default to showing all pixel values as output by the sensor, so that the user can be aware of these unique pixels.

To select software compensation for bright, unresponsive pixels, dark unresponsive pixels, as well as tap differences, select:

    Pixel Normalization: Offset & Gain & Defect
Close the lens aperture or install the lens cap. Click:
    Extract Offset Ref.
Uncover and open the lens and point the camera at flat grey or white target, with even illumination (but not saturated). Click:
    Extract Defect Ref.
    Extract Gain Ref.
and select:
    Normalization On
While this procedure will also compensate for the tap differences, the ''Pixel Normalization: Offset & Gain & Defect'' requires more overhead when images are displayed, processed, or saved than use of ''Pixel Normalization: Tap Balance''.