Stray light (flare) documentation pages
Introduction | Intro to stray light testing and normalized stray light | Outputs from Imatest stray light analysis | History
Background | Examples of stray light | Root Causes | Test overview | Test factors | Test Considerations | Glossary
Calculations | Metric image calculations | Normalization methods | Light source mask methods
Instructions | High-level Imatest analysis instructions (Master and IT) | Computing normalized stray light with Imatest | Motorized Gimbal instructions
Settings | Settings list and INI keys/values | Configuration file input
This page provides a list and description of the settings for Imatest stray light source analysis, as well as corresponding INI field-value pairs.
Page Contents
Calculation Settings
|
Calculation |
The type of stray light calculation. The default is Transmission. |
calculation |
Normalization Options
|
Normalization Method |
The type of normalization to perform. The default is None. |
normalization |
Level Normalization Options
|
Normalization Level |
The normalization level in units of digital number (DNs). The default is 1 (same as None normalization). |
Number (greater than 0) |
norm_level_value |
Reference Image Normalization Options
|
Image Filename |
The fully-qualified path to the reference image. |
Path to a valid image file |
norm_refim_filename |
|
Normalization Aggregation |
The methodology for aggregating the masked pixels into a normalization factor. This setting can only be set in the INI. The default is Median. |
norm_refim_aggregation |
|
|
ND Measurement Type |
The type of neutral density (ND) measurement used for the reference image capture. The default is None. |
norm_refim_comp_nd_type |
|
|
ND Density Value |
The density of the neutral density filter(s) used for the reference image capture. Used if ND Measurement Type is set to ND Density. The default is 0 (no ND filter used). |
Number (greater than or equal to 0, less than or equal to 100) |
norm_refim_comp_nd_density_value |
|
ND Transmission Value |
The transmission percentage [0-100] of the neutral density filter(s) used for the reference image capture. Used if ND Measurement Type is set to ND Transmission. The default is 100 (no ND filter used). |
Number (greater than 0, less than or equal to 100) |
norm_refim_comp_nd_transmission_value |
|
Integration Time Ratio |
The ratio of the reference integration time to the analysis integration time (i.e., value for reference image divided by value for analysis image). The default is 1 (test and reference images have the same integration time). |
Number (greater than 0) |
norm_refim_comp_int_time_ratio |
|
Gain Ratio |
The ratio of the reference gain to the analysis gain (i.e., value for reference image divided by value for analysis image). The default is 1 (test and reference images have the same gain). |
Number (greater than 0) |
norm_refim_comp_gain_ratio |
|
Light Level Ratio |
The ratio of the reference light level to the analysis light level (i.e., value for reference image divided by value for analysis image). The default is 1 (test and reference images have the same light level). |
Number (greater than 0) |
norm_refim_comp_light_level_ratio |
Test Image Mask Options
|
Mask Method |
The methodology for masking out the light source in the image(s). The default is None. |
mask_method |
Test Image – Two-Pass Circle (Radius) Mask Options
|
Mask Radius |
The radius in pixels for the mask. The default is 10 (this is an arbitrary number and should be updated for each system under test). |
Number (greater than 0) |
mask_options_radius |
Test Image – Image Processing Mask Options
|
Level Threshold Type |
The type of threshold used for localizing the light source in the image. |
Level Threshold Type Enumeration |
mask_improc_level_thresh_type |
|
Level Threshold (Value) |
The threshold above which is considered the image of the light source, in units of digital number (DN). |
Number (greater than or equal to 0) |
mask_improc_level_threshold |
|
Level Threshold (Percent) |
The threshold above which is considered the image of the light source, as a percentage of the maximum image value. |
Number (between 0 and 100) |
mask_improc_level_threshold_pct |
|
Minimum Source Level |
The minimum image value (digital number) that can be considered a direct image of the light source. |
Number (greater than or equal to 0) |
mask_improc_minimum_source_level |
|
Image Close Radius |
The radius of an image close morphology step. This helps to remove holes in the mask. Set to 0 to skip this step. This setting can only be set in the INI. |
Number (greater than 0) |
mask_improc_image_close_radius |
|
Multiple CC Strategy |
The strategy for how to deal with multiple connected components when computing the mask. This setting can only be set in the INI. |
mask_improc_multiple_cc_strategy |
|
|
Mask Area Threshold |
The minimum number of pixels that the direct image of the light source should be (minimum area in pixels for the mask). |
Number (greater than 0) |
mask_improc_mask_area_threshold |
Reference Image Mask Options
|
Mask Method |
The methodology for masking out the light source in the reference image(s) |
refmask_method |
Reference Image – Two-Pass Circle (Radius) Options
|
Mask Radius |
The radius in pixels for the mask. |
Number (greater than 0) |
refmask_options_radius |
Reference Image – Image Processing Mask Options
|
Level Threshold Type |
The type of threshold used for localizing the light source in the image. |
Level Threshold Type Enumeration |
refmask_improc_level_thresh_type |
|
Level Threshold (Value) |
The threshold above which is considered the image of the light source, in units of digital number (DN). |
Number (greater than or equal to 0) |
refmask_improc_level_threshold |
|
Level Threshold (Percent) |
The threshold above which is considered the image of the light source, as a percentage of the maximum image value. |
Number (between 0 and 100) |
refmask_improc_level_threshold_pct |
|
Minimum Source Level |
The minimum image value (digital number) that can be considered a direct image of the light source. This setting can only be set in the INI. |
Double(greater than or equal to 0) |
refmask_improc_minimum_source_level |
|
Image Close Radius |
The radius of an image close morphology step. This helps to remove holes in the mask. Set to 0 to skip this step. This setting can only be set in the INI. |
Number (greater than 0) |
refmask_improc_image_close_radius |
|
Multiple CC Strategy |
The strategy for how to deal with multiple connected components when computing the mask. This setting can only be set in the INI. |
refmask_improc_multiple_cc_strategy |
|
|
Mask Area Threshold |
The minimum number of pixels that the direct image of the light source should be (minimum area in pixels for the mask). This setting can only be set in the INI. |
Number (greater than 0) |
refmask_improc_mask_area_threshold |
Other Calculation Settings
|
Crop LRTB |
The number of pixels to crop off the left, right, top, and bottom of the image. |
Number (list of four values greater than or equal to 0) |
crop_lrtb |
|
Percentile Ranks |
The percentile ranks [0-100] (e.g., 95 = 95th percentile) to calculate. |
Number (list of values greater than 0, less than 100) |
pctl_ranks100 |
|
Level Count Thresholds |
The thresholds of stray light level for producing results that show the number of pixels worse than said threshold. |
Number (list of values) |
level_count_thresh |
Batch Output Settings
|
Output Directory |
The path to the save results to. Note: inclusion of the following characters may result in failure to save .fits output files (metric images and masks): “(*:<>?[| |
The fully qualified path to a folder/directory or the name of a folder in which output files will be saved. Note: If just the name of a folder is entered, Imatest will create a new folder with that name in the same directory as the test images, and save the outputs to that folder. |
output_dir |
Result Files
|
Save Summary Results Files |
The results files to save. |
result_files |
|
|
Save Metric Image Files |
Enable to save out a FITS file containing the metric image data for each image. |
Boolean |
save_metric_image |
|
Save Mask Files |
Enable to save out a FITS file containing the binary mask of the source for each image. |
Boolean |
save_mask |
|
Mask Prefix |
A string to be prepended to the mask file(s). This setting can only be set in the INI. |
String |
mask_prefix |
|
Mask Postfix |
A string to be appended to the mask file(s). This setting can only be set in the INI. |
String |
mask_postfix |
|
Metric Image Prefix |
A string to be prepended to the metric image file(s). This setting can only be set in the INI. |
String |
metric_image_prefix |
|
Metric Image Postfix |
A string to be appended to the metric image file(s) This setting can only be set in the INI. |
String |
metric_image_postfix |
Level Plot
Note: level plots require two or more test images.
|
Save Options |
How should level summary plot(s) be created? Choose one or more options. At least one is required to produce this plot. |
level_plot_options_mode_options |
|
|
Save Types |
The image formats to save the plot as. Choose one or more options. At least one is required to produce this plot. |
level_plot_options_mode_save_types |
|
|
Groups |
How to group the data within a plot. Choose one or more options. At least one is required to produce this plot. |
level_plot_options_groups |
|
|
Y Data |
The data to plot on level summary plot(s). Choose one or more options. At least one is required to produce this plot. |
level_plot_options_y_data |
|
|
Include Percentiles |
Enable to include percentiles on the level summary plot(s). |
Boolean |
level_plot_options_include_pctls |
|
Y-Axis Scale |
The scaling of the y-axis of the plot. |
level_plot_options_y_axis_scale |
Count plot
|
Save Options |
How should level summary plot(s) be created? Choose one or more options. At least one is required to produce this plot. |
count_plot_options_mode_options |
|
|
Save Types |
The image formats to save the plot as. Choose one or more options. At least one is required to produce this plot. |
count_plot_options_mode_save_types |
|
|
Groups |
How to group the data within a plot. Choose one or more options. At least one is required to produce this plot. |
count_plot_options_groups |
|
|
Y Data |
The data to plot on count summary plot(s). Choose one or more options. At least one is required to produce this plot. |
count_plot_options_y_data |
|
|
Include Level Counts |
Enable to include level counts on the count summary plot(s), corresponding to value(s) entered for the Level Count Threshold option. |
Boolean |
count_plot_options_include_level_counts |
|
Y-Axis Scale |
The scaling of the y-axis of the plot. |
count_plot_options_y_axis_scale |
Summary Videos
Metric Video
|
Save Video Formats |
The formats to save the metric image video as. Note: MP4 is not available on Linux. |
metric_video_opts_video_formats |
|
|
Save Image Formats: |
The image formats to save each frame of the metric image video as. |
metric_video_opts_image_formats |
|
|
Video Frame Rate |
The framerate in frames per second for the metric video. |
Number (greater than 0, less than 40) |
metric_video_opts_frame_rate |
|
Base Name |
A string to prepend to the metric video file. This setting can only be set in the INI. |
String |
metric_video_opts_basename |
Histogram Video
|
Save Video Formats |
The formats to save the histogram image video as. Note: MP4 is not available on Linux. |
hist_video_opts_video_formats |
|
|
Save Image Formats |
The image formats to save each frame of the histogram video as. |
hist_video_opts_image_formats |
|
|
Video Frame Rate |
The framerate in frames per second for the histogram video. |
Number (greater than 0, less than 40) |
hist_video_opts_frame_rate |
|
Base Name |
A string to prepend to the histogram video file. This setting can only be set in the INI. |
String |
hist_video_opts_basename |
Miscellaneous
|
Frame Scaling |
How to scale the frames of the video relative to each other. |
frame_scaling |
|
|
Video Output Scale |
How to scale the data before making video(s). |
video_output_scale |
|
|
Plot Output Scale |
How to scale the data before making the summary metric plot(s). |
plot_output_scale |
|
|
Histogram Output Scale |
How to scale the data before taking a histogram. |
hist_scale |
|
|
Video Prefix |
A prefix added to the video filename(s). |
String |
video_prefix |
|
Video Postfix |
A postfix added to the video filename(s). |
String |
video_postfix |
Enumerations
Single Choice Enumerations
For the following enumerations, choose one of the provided options.
Calculation Type Enumeration
Description
The type of stray light calculation to perform.
Members
| Name | Description | Value |
| Transmission |
The calculation is the image divided by the normalization factor. |
0 |
| Attenuation |
The calculation is the normalization factor divided by the image. Note: 0 is a valid digital number for image data. If choosing reciprocal, any image with 0’s in it will get infinity for the calculated stray light. Summary statistics (e.g., mean, max) of data containing infinity become meaningless. As such Transmission is recommended. |
1 |
Normalization Method Enumeration
Description
The type of normalization to perform.
Members
| Name | Description | Value |
| None |
Perform no normalization. Results will be in digital numbers. |
0 |
| Level | Normalize with a user-provided source level in units of digital number (DN). Using this option requires the Level normalization settings. | 1 |
| Reference Image | Normalize by the level of the direct image of the source from a reference image. This normalization method corresponds to Point Source Rejection Ratio (PSRR) or Extended Source Rejection Ratio (ESRR). Using this option requires the Reference Image normalization settings. | 3 |
Normalization Aggregation Enumeration
Description
The methodology for aggregating the masked pixels into a normalization factor.
Members
| Name | Description | Value |
| Mean |
Use the mean inside the masked pixels as the base normalization factor. |
0 |
| Median |
Use the median inside the masked pixels as the base normalization factor. |
1 |
| Total |
Use the total (sum) inside the masked pixels as the base normalization factor. |
2 |
Neutral Density Measurement Enumeration
Description
The type of neutral density measurement used for the reference image capture.
Members
| Name | Description | Value |
| None |
No ND filter is used for the reference image. |
0 |
| Density |
ND filter(s) are used. The value is the total density of filters. |
1 |
| Transmission | ND filter(s) are used. The value is the total transmission as a percentage [0-100] of the filters. | 2 |
Mask Method Enumeration
Description
The methodology for masking out the light source in the image(s).
Members
| Name | Description | Value |
| None |
Don’t mask the source. Note: this is not available for masking reference images. |
0 |
| Image Processing |
Use image processing to mask the source. |
10 |
| Two Pass Circle (Radius) | Find the center via a “first pass” and then use a circle to mask. The light source is first localized in the image via image processing-based methods. Then, a circle of a specified radius is placed at the center of the localized region and is used as the mask for the image | 13 |
Image Processing Masking Level Type Enumeration
Description
The type of threshold used for localizing the light source in the image.
Members
| Name | Description | Value |
| Value |
The threshold in digital numbers. |
0 |
| Percentage of Max |
The threshold is a percentage of the maximum value [0-100]. |
1 |
| Otsu’s Method |
Use Otsu’s method to automatically determine a threshold. |
2 |
Image Processing Masking Mulitple Connected Component Enumeration
Description
The strategy for how to deal with multiple connected components when computing the mask.
Default
Pick Biggest
Members
| Name | Description | Value |
| Don’t Mask |
If multiple CCs are found, assume the source is not in the image. |
1 |
| Pick Biggest |
Pick the largest of the connected components. |
2 |
Axis Scaling Enumeration
Description
How to scale the axis of a plot.
Members
| Name | Description | Value |
| Linear |
The axis uses a linear scale. |
0 |
| Log |
The axis uses a log scale. |
1 |
Video Frame Scaling Enumeration
Description
How to scale the frames of a video relative to each other.
Members
| Name | Description | Value |
| Global |
All frames have the same scaling. |
0 |
| Per-Subset |
All frames of the same subset (channel) have the same scaling. |
1 |
| Per-Image |
Each frame of the video will have its own scale. |
2 |
Data Scaling Enumeration
Description
How to scale data.
Members
| Name | Description | Value |
| Linear |
The data are un-transformed. |
0 |
| Log10 |
Take the log10 of the data. |
1 |
| dB |
Convert the data to decibels. |
2 |
Multiple Choice Enumerations
For the following enumerations, choose any of the provided options. The value in the INI is the sum of desired options.
Results File Type Enumeration
Description
The type(s) of summary results file to save.
Members
| Name | Description | Value |
| JSON |
Save a JSON-formated results file. |
1 |
| CSV |
Save a CSV-formatted results file. |
2 |
| HDF5 |
Save an HDF5-formatted results file. |
4 |
Plot Creation Enumeration
Description
Select how to create (display, save) plot(s).
Members
| Name | Description | Value |
| Save |
Save plot(s) to disk. |
1 |
| Display |
Display plot(s) to screen. |
2 |
Plot Save Type Enumeration
Description
The image formats to save the plot as.
Members
| Name | Description | Value |
|
JPEG 24-bit (.jpg) |
1 | |
|
PNG 24-bit (.png) |
2 | |
|
TIFF 24-bit [compressed] (.tif) |
|
4 |
|
TIFF 24-bit [not compressed] (.tif) |
|
8 |
|
BMP 8-bit [256 color, uses a fixed colormap] (.bmp) |
|
16 |
|
HDF 24-bit (.hdf) |
|
32 |
|
PBM 1-bit (.pbm) |
|
64 |
|
PCX 24-bit color [three 8-bit planes] (.pcx) |
|
128 |
|
PGM (.pgm) |
|
256 |
|
PPM (.ppm) |
|
512 |
|
Full page Portable Document Format [PDF] color (.pdf) |
|
1024 |
|
Encapsulated PostScript [EPS] Level 2 color (.eps) |
|
2048 |
|
SVG [scalable vector graphics] (.svg) |
|
4096 |
|
Full-page PostScript [PS] Level 2 color (.ps) |
|
8192 |
| MATLAB Figure (.fig) |
|
16384 |
Plot Grouping Enumeration
Description
How to group the data within a plot. At least one is required to produce this plot.
Members
| Name | Description | Value |
|
All |
All channels will be in the same plot. | 1 |
| By Channel | A separate plot will be made for each channel. | 2 |
Level Plot Data Enumeration
Description
The data to plot on level summary plot(s).
Members
| Name | Description | Value |
|
Minimum |
1 | |
|
Minimum (Non-0) |
Minimum of the non-0 data in the original image. | 2 |
|
Maximum |
|
4 |
|
Mean |
|
8 |
|
Median |
|
16 |
|
RMS |
Root Mean Square |
32 |
|
Std. Dev. |
Standard Deviation |
64 |
Count Plot Data Enumeration
Description
The data to plot on count summary plot(s).
Members
| Name | Description | Value |
|
Total Count |
The number/count of pixels in the region of interest (note: currently, only the total number of pixels in the image is available). | 1 |
|
Source Count |
The number/count of pixels in the masked region (the light source object). | 2 |
Video Save Type Enumeration
Description
The formats to save a video as.
Members
| Name | Description | Value |
|
MP4 |
Note: Not available on Linux | 1 |
|
AVI |
2 |
|
|
GIF |
4 |
Image Frame Save Formats
Description
The image formats to save each frame of a video as.
Members
| Name | Description | Value |
|
PNG |
1 | |
|
JPEG |
2 | |
|
TIFF |
4 |