3D-L4000 Series Vision System Wizard – Sensor Settings

The 3D-L4000 Series Acquisition Wizard contains the sensor properties of the 3D-L4000 series vision systems on its Sensor tab. These settings allow you to set the exposure, sensitivity or HDR settings of the acquisition, and fine-tune the sensor's Z-axis detection zone as well. You can modify these settings both before and after field correction is performed.

Tip: Cognex recommends adjusting these settings each time you acquire a different object. Using the minimal required Region of Interest (ROI) for your object will allow you to acquire faster and speed up the spreadsheet job, as the acquisitions will contain less points for inspection. Similarly, Cognex recommends adjusting the Exposure setting when a new object is inspected (depending on the reflectivity of the object), to get a more accurate reconstruction in the acquisition.

Setting	Description
Exposure	Sets the exposure time for every profile acquisition (in ms), that is the time that the sensor's imager will use to acquire each raw image to find a laser profile. The value range is between 0.011 – 25, and the default value is 0.1. Tip: Higher values let the vision system collect more information about the laser line reflected from the surface of the object under inspection. Therefore, use those values for surfaces that are less reflective. Use the acquired raw image to help set an Exposure value that prevents saturation in the acquired profile, and keeps the grayscale value of the laser line between 200-800. Click the Auto button to let the sensor automatically set the Exposure value (or multiple exposure values, if any of the HDR exposure sliders are enabled), based on the detected light conditions. If only the Exposure property is used, the Auto tune returns one optimal value. If the HDR settings are also enabled, it returns multiple optimal values. This parameter affects the Max Profile Rate (that is the acquisition rate), with lower exposure values resulting in faster profile rates. Typically, configuring the Exposure value correctly is enough for most acquisitions. However, if the resulting acquisitions return under- or oversaturated surfaces regardless of the Exposure and Sensitivity settings, configure HDR exposure as well to fine-tune acquisition. Use the (Peak Saturation) button on the Raw display toolbar to check if any peak is saturated or not. You can also modify this property on the spreadsheet with the ApplyAcquisitionSettings function.
HDR	The HDR Low and High Exposure sliders allow you to configure multiple exposures to generate peak data if the target surface has varying reflectance, and using only the Exposure setting results in under- or oversaturated areas. Enabling both HDR Low and High Exposure lets you acquire image data with 3 different exposure settings. HDR Low Exposure: Allows you to configure an additional HDR exposure (in ms) lower than the regular Exposure setting. If the value of this slider is set higher than the Exposure slider or the HDR High Exposure slider (if enabled), they will be automatically adjusted to a higher value. HDR High Exposure: Allows you to configure an additional HDR exposure (in ms) higher than the regular Exposure setting. If the value of this slider is set lower than the Exposure slider or the HDR Low Exposure slider (if enabled), they will be automatically adjusted to a lower value. Note: The acquisition rate (indicated with Max Profile Rate) is affected by the number of exposures and their configured values as well. Therefore, enable HDR only if the results of a single exposure are insufficient.
Detection Zone	Sets the lower and upper bounds of the vision system's measurement range (in mm) in which shapes and surfaces are detected, and image data is generated. Use the sliders to manually adjust the size, or enter a specific value. The Z min value (specifying the lower bound of the working section) cannot be higher than the Z max value, and likewise, the Z max value (specifying the upper bound of the working section) cannot be lower than the Z min value. Tip: Decreasing the Detection Zone interval (that is, using Z min and Z max values that are closer to each other) speeds up acquisition, and increases the Max Profile Rate. Cognex recommends configuring the detection zone by: Acquiring a Raw 2D image and roughly adjusting the detection zone there, and then Acquiring a full 3D point cloud, and finalizing the detection zone on the 3D Image Viewer. Otherwise, you will need to acquire the full Point Cloud with the entire working area of the device set, which negatively impacts the Max Profile Rate. You can modify the detection zone in the 3D Image Viewer too, if 3D mode is selected. Simply click the (Edit ROI) button to toggle showing the device's working space (1), then click and hold either the top or bottom Z-plane of the detection zone (shown in blue) to drag it to the desired position (2). You can also modify this property on the spreadsheet with the ApplyAcquisitionSettings function.
Binning	Enables 2x2 binning that treats 2x2 pixel data as one pixel on the raw image. If this setting is enabled, it halves the resolution of the acquired profiles, resulting in a coarser point cloud, but in faster Exposure values and a higher Max Profile Rate.
Advanced Settings
Selected Peak	Defines how the sensor will select the peak data for height calculation: Strongest: Selects the peak with the maximum intensity. This is the default setting. Top: Selects the peak that is closest to the vision system. Bottom: Selects the peak that is farthest from the vision system. Tip: Set the Top or Bottom settings to reduce possible false peaks if you are sure that the nearest/farthest peak in the intensity image column is the correct surface to use. This is useful if the profile contains strong but false peaks. For example, if you are measuring the height of a semi-transparent cover on top of an opaque object, the acquisition would contain a weak peak from the cover and a stronger peak from the object beneath the cover. However, since you want to measure the cover, and not the object under it, you should use the Top setting.
Sensitivity	Sets the laser detection sensitivity, that is a lower threshold for laser line intensity detection. The value range is 0 – 1, and the default value is 0.9. Tip: Lower values prevent mistaking noise for the laser line in areas where the laser is obscured. Higher values make the laser line easier to detect without setting higher Exposure values, improving performance and allowing a higher Max Profile Rate. You can also modify this property on the spreadsheet with the ApplyAcquisitionSettings function.
Peak Width Threshold	When enabled, it specifies an upper width threshold (in pixels) for laser line detection. As such, this setting can reduce the chance of detecting false peaks by removing spikes that are commonly characterized by wide laser lines due to multiple reflections. The value range is 1 – 100, and the default value is 5. Note: Peak data generated out of a laser line with a width higher than the specified value will be filtered out. All other peak data will be kept.