HUIDIAN

This document describes the method of using the NOKOV optical motion capture lens to externally trigger a camera, using the MARS2H lens and FL3-U3-13Y3M-C camera as examples.

FL3-U3-13Y3M-C Camera

• The FL3-U3-13Y3M-C camera is a member of the Point Grey (acquired by FLIR) Flea3 USB 3.0 series industrial cameras, with its main features outlined in Table 1 below.

Model	FL3-U3-13Y3M-C
Image Sensor	Onsemi VITA1300 1/2'' CMOS Sensor monochrome global shutter
Pixel Size	4.8μm
Max Resolution/Frame Rate	1.3 Megapixels, 1280x1024 @ 150fps
Optical Lens Interface	C-mount
Data Interface	USB3.0
Memory	32MB DDR frame buffer, 1MB Flash
Exposure Range	0.1129μs to 0.99 seconds
Trigger Modes	Standard，bulb，multi-shot
Power Supply	5V via USB3.0 or 5~24V via GPIO
Camera Size	29mmx29mmx30mm（excluding optical parts）

• The external sync trigger feature of the FL3-U3-13Y3M-C camera is provided through an 8-pin GPIO connector (Hirose HR25 circular connector female socket), as shown in the diagram below.

  

The signal definitions for the FL3-U3-13Y3M-C camera GPIO connector are outlined in the table below.

• We usually use GPIO0 as the Trigger Source to synchronize the camera. According to the table above, GPIO0 is an optically isolated input signal. Based on the internal circuit of the camera, the wiring method for the optically isolated input signal is as follows.

  
• When using GPIO0 as the external input trigger signal, the sync output signal from the MARS2H needs to be connected to pin 1 and pin 6 of the camera GPIO connector.

Description of the 3 external trigger modes supported by the FL3-U3-13Y3M-C camera:

• Standard External Trigger Mode (Mode0) - In this mode, the falling or rising edge of the external input sync trigger signal will initiate the start of exposure for a frame of the image. The exposure time will be controlled by the camera's Shutter register value.

  
• Bulb Shutter Trigger Mode (Mode1) - In this mode, the falling edge of the external input sync trigger signal will start the exposure for a frame of the image. The exposure time will be the duration of the low level of the trigger pulse.

  
• Multi-Shot Trigger Mode (Mode15) - In this mode, an external input sync trigger pulse will initiate the exposure and capture of multiple frames. The number of frames that can be captured is set by the parameter in the mode setting, with a maximum capture frame count of 255.

• Due to the periodic square wave nature of the sync output signal from the MARS2H, after analysis, we select the Standard External Trigger Mode (Mode0) as the external trigger mode for the camera.

Sync Interface of the MARS2H Lens

• The sync input/output interface of the MARS2H lens is achieved through a custom audio cable (one end with a 3.5mm headphone jack split into two, and the other end with two RCA plugs), which can output the corresponding sync output signal. In the diagram below, the white RCA plug serves as the sync signal output terminal, with the inner core of the RCA as the sync output signal and the outer part as the ground signal.

  
• The output sync signal of the MARS2H lens is a periodic square wave. The frequency of the square wave is set to the frame rate of the lens, and the amplitude of the square wave is 5V. In the idle state, the sync signal level remains high, at a voltage of 5V. When the "play" button is clicked in motion capture software (such as Seeker 1.6), the sync signal immediately shifts to a low level, generating a continuous wave with a 50% duty cycle. Once the "stop" button is clicked, the sync output signal returns to a high level. The sync output waveform is shown in the diagram below.

  

Cable Assembly

• You need to create a cable assembly that connects the sync output interface of the MARS2H lens to the corresponding signals on the GPIO connector of the FL3-U3-13Y3M-C camera.

• The connection cable for the GPIO connector interface of the FL3-U3-13Y3M-C camera is shown in the diagram below. It can be purchased on the FLIR official website or on Taobao.

  
• Locate the wires corresponding to Pin 1 and Pin 6 on the connection end of the camera's GPIO cable (the cable should have labeling instructions). Solder an audio RCA female connector to the connection wires, with the inner core of the RCA connector soldered to Pin 1 and the outer part soldered to Pin 6, as shown in the diagram below.

  

Connection between the MARS2H lens and the FL3-U3-13Y3M-C camera

• The connection between the sync output interface of the MARS2H lens and the GPIO interface of the FL3-U3-13Y3M-C camera is as shown in the diagram below. The sync cable from the MARS2H lens is plugged into the sync input/output interface socket of the lens, while the GPIO cable from the FL3-U3-13Y3M-C camera is connected to the GPIO connector of the camera. These two cables are linked via RCA plug and RCA female connector.

  

Software Configuration

• Connect the FL3-U3-13Y3M-C camera to the computer using a USB 3.0 cable. Follow the method described earlier to connect the sync cable of the MARS2H lens to the GPIO cable of the FL3-U3-13Y3M-C camera. Ensure that the MARS2H lens is powered on and connected to the network. Start the XINGYING software. Install the image capture software FlyCapture2 for the FL3-U3-13Y3M-C camera on the computer and launch the FlyCapture2 software.

• The interface of the FlyCapture2 software is shown in the diagram below. Typically, the software displays real-time images captured by the camera as well as relevant information about the camera.

  
• In the "Settings" menu, select the "Toggle Camera Control Dialog" command to enter the camera configuration interface. Click on the "Trigger/Strobe" option on the left to access the "Trigger/Strobe Control" configuration page. Follow the settings below for external trigger functionality: Set Trigger Mode to "0", Trigger Source to "GPIO 0", Trigger Polarity to "Low". Finally, check the "Enable/disable trigger" box in the Trigger Control section to activate the external trigger functionality.

  
• Click on the "Camera Settings" option on the left to enter the "Camera Settings" configuration page. Uncheck the Shutter Auto checkbox, set the Shutter value to around 1ms, uncheck the FrameRate Auto checkbox, and set the FrameRate to the maximum frame rate of 150fps supported by the CMOS sensor at its maximum resolution. Refer to the diagram below.

  
• After these settings, the image displayed by the FL3-U3-13Y3M-C camera will be frozen and static. It will wait for the sync trigger pulse input on GPIO0 to capture an image.

• Subsequently, in the XINGYING software on the computer, connect the MARS2H lens, set the frame rate of the lens to 60fps, and click the "Play" button, as shown in Figure XIV. The MARS2H lens will output a square wave sync trigger signal at 60Hz.