Image Capture Tool

Introduction

The Image Capture Tool (AxsunImageCaptureTool.exe) is a software interface for users of the Axsun Ethernet/PCIe DAQ. It provides a tab- and button-based GUI to easily view the captured image data transmitted from the DAQ device by exposing functionality in the AxsunOCTCapture API. It supports image capture over Gigabit Ethernet and PCIe interfaces, as well as DAQ imaging mode controls over the PCIe interface only.

The Image Capture Tool ("ICT") is not intended to be a fully-featured OCT image capture and analysis application, but rather a springboard for integrating the AxsunOCTCapture library ("Capture API") functionality into the user's custom OCT imaging application. The Image Capture Tool's primary functions include:

• Retrieve and display data transmitted by the DAQ and buffered in RAM

  • Supports all data types (8-bit, 16-bit, 32-bit, complex)

  • Supports image cropping and averaging during retrieval

  • Supports raw unprocessed fringe data or processed intensity OCT images

• Indicate DAQ imaging mode, status of data buffer, and status of Image_sync synchronization trigger

• Save and load data buffers to and from disk

• Export captured images to a variety of file types

• Control DAQ imaging mode and FPGA registers (PCIe interface only)

• Expose secondary AxsunOCTCapture API features such as:

  • OpenGL-based rendering, scan conversion, etc.

  • Control 2-axis galvo raster scan pattern via some NI USB multi-function I/O devices

Compatibility Requirements

Host PC: The Image Capture Tool is compatible with Windows OS versions 10 and 11. An available 1Gbps Ethernet port is required for connecting to the Ethernet DAQ via network interface, or an available PCIe Gen 1 x8 port is required for connecting to the PCIe DAQ.

Because the Ethernet/PCIe DAQ performs FPGA-based OCT image formation on the DAQ board, computer computational requirements such as CPU speed, processor cores, and available RAM are typically satisfied by "consumer-level" personal computer platforms available from 2014 onward.

FPGA bitstream: Modern versions of the Image Capture Tool (i.e. based on AxsunOCTCapture version 3.x or newer) do not support all legacy FPGA bitstream versions. Keep your FPGA version current to take advantage of new DAQ functionality and modern versions of the ICT.

Camera Link DAQ Support: The Image Capture Tool and the AxsunOCTCapture library do not support the Axsun Camera Link DAQ. A third-party PCIe frame grabber and its associated software is required to capture image data transmitted from the Camera Link DAQ. More information on the Axsun Camera Link DAQ can be found here.

Installation

The AxsunOCTCapture library/API (and therefore also the Image Capture Tool) relies on some external third-party dependencies which must be installed for full functionality: pcap (for Ethernet network packet capture), TurboJPEG (a JPEG decompression codec), OpenCV (for image exporting), and the Microsoft Visual C++ Run-Time. The Image Capture Tool (but not AxsunOCTCapture) relies on one additional dependency: the LabVIEW Run-Time Engine.

Install the Packet Capture Library (Ethernet interface only)

If you plan to capture image data from the Axsun DAQ via Gigabit Ethernet network interface, you must install a pcap (packet capture) library as described here.

Install the JPEG Decompression Library (optional)

If you plan to transmit JPEG-compressed image data using the Ethernet interface, the AxsunOCTCapture library requires a dependency called TurboJPEG, a highly-optimized JPEG decompression utility based on the industry-standard libjpeg API. If you plan to transmit image data in a mode which is not JPEG-compressed or are using the DAQ's PCIe interface, installation of this dependency is not needed.

Run the downloaded installer, confirm any Windows Security Warning requests, and select a location for installation (the default location is acceptable or you can choose a different preferred location). A library file named turbojpeg.dll will be installed in your C:\Windows\System32\ directory.

Install OpenCV (optional)

The fully-featured image export functionality of the Image Capture Tool and AxsunOCTCapture library depends on installation of OpenCV. Export options will be limited if OpenCV is not installed.

After extracting the archive, navigate to the extracted folder: ..\opencv\build\x64\vc15\bin\.. and copy the two library files named opencv_world4xx.dll and opencv_videoio_ffmpeg4xx_64.dll (where "xx" indicates a specific version number) into either:

• your C:\Windows\System32\ directory, or

• the directory containing the AxsunOCTCapture.dll and AxsunImageCaptureTool.exe files (see below), or

• any other directory for which you've configured Windows to search for dynamically linked libraries.

Install the Microsoft Visual C++ Run-Time Library

The Microsoft Visual C++ Run-Time Library (2015-2022, 64-bit) must be installed in either your C:\Windows\System32\ directory or in the same directory as the application which is calling AxsunOCTCapture.dll. This is a common run-time library which likely already exists on your system from installation of an unrelated program or from your original Windows OS installation (depending on the OS version).

If it is not already present on your system, you can download it directly from Microsoft at: https://aka.ms/vs/17/release/vc_redist.x64.exe

Install the National Instruments LabVIEW Run-Time Engine

The Image Capture Tool requires installation of the LabVIEW Run-Time Engine which is available for download from National Instruments.

OPTIONAL: If you plan to use the DAQmx-based scanner control features provided by the AxsunOCTCapture library and Image Capture Tool, you must also download and install the NI-DAQmx driver from National Instruments.

Confirm Successful Installation

After the external dependencies have been installed, perform a host system restart.

Download the Axsun Image Capture Tool and extract the .zip archive contents to your preferred location (there is no installer but you must keep the files in the extracted folder together). Launch the Image Capture Tool GUI application (AxsunImageCaptureTool.exe). If all dependencies were installed correctly, the AxsunOCTCapture.dll library will be loaded by this application and its main window will launch without any pop-up warnings to indicate missing dependencies. If missing dependencies are reported, review and repeat the installation instructions above or refer to the Troubleshooting page in the DAQ Reference Manual.

Using the Image Capture Tool

• Physically connect and power-up the Axsun devices.

• Launch the Hardware Control Tool application to access high-level functionality provided by the DAQ board and any connected Laser Engines (optional).

• Launch the Image Capture Tool (AxsunImageCaptureTool.exe) and make the appropriate selection when prompted for either the Ethernet or PCIe capture interface:

• The Image Capture Tool window will show a blank image and the selected session type will be indicated at the top of the window:

• If errors were encountered when selecting the interface, the Image Capture Tool will provide relevant information in a pop-up dialog and then support review of previously-saved data files only (but not new data collection from a connected DAQ). See the DAQ Troubleshooting page to overcome the errors and then try again to select the desired interface by pressing either the Ethernet or PCIe button:

Image Capture Status Indicators and Image Request Controls

The bottom left corner of the Image Capture Tool window has lights to indicate the following DAQ and buffer states (also see Capture API documentation for axGetStatus()):

• Imaging: data is actively being enqueued into the Main Image Buffer, either transmitted from the DAQ or loaded from a previously-saved data file.

• Burst Recording: image data is currently being acquired from the DAQ in Burst Record mode.

• Loading: image data is currently being loaded into the Main Image Buffer from a previously-saved data file.

• Image_sync Trigger Too Fast: the frequency of the trigger signal connected to the Image_sync input exceeds the allowable maximum (≈390 Hz for a laser with 100 kHz A-line rate).

• Image_sync Too Slow (Force Trig): the frequency of the trigger signal connected to the Image_sync input is too slow relative to the configured Force Trigger timeout period, and thus the newest frame has been displayed in unsynchronized Force Trigger mode (see Capture API documentation for axSetTrigTimeout()).

• Move the white Requested Image # slider control to request an image to be retrieved from the Main Image Buffer for display. This can be a unique image number, or it can be set equal to 0 to display the most recently enqueued image in the buffer (typical for real-time low-latency display in Live Imaging mode). Numeric indicators show the actual Returned Image #, and the Width (A-scans) & Height (Pixels) dimensions of the displayed image (see Capture API documentation for axGetImageInfo() and axRequestImage()).

• A general purpose message indicator shows relevant information, warnings, or errors that may occur when requesting images.

• Press the SHOW MORE INFO button to display a pop-up window that provides more advanced information about the displayed image, including timestamp, image dimensions before and after cropping, data type, ADC channel, pipeline mode, and other details:

• If Burst Recorded images have been captured or loaded into the Main Image Buffer, a LOOP button will automatically be shown and playback start image (green) and stop image (red) sliders are available to control looping playback behavior. Press the LOOP button to toggle between paused and playback display modes. Numeric controls are also provided for the current requested image (white), start image (green), and stop image (red) to control image playback more precisely than dragging the sliders.

Image Display Window Tabs

The Image Capture Tool window contains tabs for a full 2D OCT B-Scan (i.e. intensity image) as well as a 1D Single A-Scan plot selected from the currently displayed OCT B-Scan.

OCT B-Scan

Processed OCT intensity images (as well as other data representations acquired in different pipeline modes) which are retrieved from the Main Image Buffer will be displayed on the OCT B-Scan tab:

• Press the SAVE IMAGE (.bin) button to save the currently displayed image in a header-less raw binary format. The file formatting details (required for interpreting the saved binary file) will be displayed in the message indicator:

• Press the SAVE IMAGE (.png) button to save the currently displayed image in .png format.

• The Images/Sec (acq.) indicator shows the current image acquisition rate during live image capture (i.e. the rate at which new images are being enqueued into the Main Image Buffer).

• The Images/Sec (disp.) indictor shows the current image display rate (i.e. the refresh rate of the OCT B-Scan indicator).

Single A-Scan

The Single A-Scan tab displays a 1D graph with a single A-scan's amplitude as a function of pixel number (e.g. z-dimension or depth) in a processed OCT image, or as a function of sample number in a pre-FFT (interference fringe amplitude) pipeline mode.

• Select the desired A-scan to view in the 1D graph using the Plot A-Scan # control or drag the yellow vertical cursor on the OCT B-scan thumbnail image.

• Enter the system's scan depth value (in mm) into the X-axis scale to field in order to convert the depth axis display from pixels numbers to physical units.

Control and Indicator Tabs

Additional Image Capture Tool functionality is grouped onto several tabs on the right side of the main window. The following sections highlight the relevant controls and indicators available on each tab, and their associated AxsunOCTCapture API functions. Refer to the AxsunOCTCapture API documentation and function reference for more information on the underlying behavior of these controls and indicators.

Image

The Image tab provides basic display controls for image retrieval and display (including cropping and averaging) as well as OpenGL rendering and window behavior. It is divided into Image Request Preferences and OpenGL Controls sections:

Image Request Preferences

• Press the RESET button to return all values in the Image Request Preferences to their default values.

• Select the desired display behavior using the Mode menu:

  • Retrieve Only copies image data from the AxsunOCTCapture library's Main Image Buffer into the Image Capture Tool application, displaying it on the OCT B-Scan and Single A-scan tabs.

  • Display Only bypasses the retrieval of image data into the Image Capture Tool application and rather renders it directly to an OpenGL window (created by first pressing the axSetupDisplay button). Requested image data will not be displayed on the OCT B-Scan and Single A-Scan tabs. This mode is optimized for speed because direct rendering avoids a memory-copy of the image contents.

  • Retrieve & Disp exhibits both behaviors: it copies the image data into the Image Capture Tool application as well as rendering it directly to an OpenGL window.

• Use the Average # control to calculate the average (arithmetic mean) of up to 10 consecutive images in the buffer during the retrieval & display. Set equal to 1 to disable averaging. Image averaging helps suppress noise in the displayed image but also slows the image display rate. Averaging is unavailable for some data types and is not available in Force Trigger mode.

• Cropping an image during retrieval & display avoids inefficiency associated with copying unwanted pixels (e.g. a galvo scanner fly-back region not suitable for display). Cropping controls the retrieved image dimensions; the original images stored in the Main Image Buffer are unaffected. Set all values equal to 0 to turn off cropping behavior and retrieve images with their original dimensions.

  • Crop Width Offset sets the first A-scan to be retrieved.

  • Crop Width Total sets the total number of A-scans to be retrieved.

  • Crop Height Offset sets the first depth pixel to be retrieved.

  • Crop Height Total sets the total number of depth pixels to be retrieved.

OpenGL Controls

The AxsunOCTCapture library supports direct rendering of images to child windows via OpenGL on platforms which support OpenGL version 3.3 or newer.

• To use OpenGL rendering, first press the axSetupDisplay button to create a window and initialize OpenGL resources.

• Insure that the Mode menu is set to either Display Only or Retrieve & Disp.

• Make additional adjustments to the displayed image properties using the controls listed here:

Buffer

The Buffer tab provides an indication of the current Main Image Buffer status and other information related to session initialization, plus controls for interacting with the buffer, such as the ability to Save and Load buffers to/from a file for offline storage and retrieval, and the ability to Export individual images into common file types.

Scanner

The Scanner tab provides controls for a connected National Instruments USB multi-function I/O device, commonly used to generate a raster-scan waveform for a 2-axis galvo scanner. See the AxsunOCTCapture API documentation for the axScanCmd() function for more details on supported devices, terminal connections, and behaviors.

PCIe

The PCIe tab provides basic controls for DAQ Imaging Mode and low-level FPGA register read/write access when connected to a DAQ via the PCIe interface.

Quitting the Image Capture Tool

To exit the Image Capture Tool simply close the main window by clicking the "x" icon in the upper right corner.