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VisTrak IR V Stereo

VisTrak Stereo Bar

The VisTrak IR V Stereo and the VisTrak Stereo Bar have the same function.

Just the casing and price is different

Optional extra Stereo Bar projector mount $ 99

Instead of the standard 4 inch Stereo bar mounts, a projector mount can be added to extend the system down 1.5ft for those that have higher ceilings

VisTrak Stereo upgrade

to the VisTrak Eagle

Optional extra Stereo camera bar mount $99

If you already have a VisTrak camera, then you can add the stereo cameras to it.

Stereo camera spacing is 40 to 42 inches.

Video swing playback after every shot

You have the option to view the swing playback in the VisTrak video playback window.

You can also check each frame - one by one - in the cameras window.

VisTrak IR V Stereo / Stereo Bar

Installation

Camera wiring

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There are 3 cameras in the VisTrak IR Stereo and the Stereo Bar systems.

1 USB3 VisTrak camera - high speed camera

2 Hi Res Stereo cameras with USB2 / Cat5 camera cabling - camera

The VisTrak USB3 camera is connected to the the PC via the supplied USB3 cables

The Stereo USB2 / Cat5 cameras are connected to the PC via the supplied Cat 5 cables and the Cat5 transmitter adapters

VisTrak IR Stereo Mounting

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Use the ball swivel joint on the Projector mount to angle the VisTrak IR V Stereo directly

at the place where you will be playing the ball from.

VisTrack IR V Stereo system setup

Principle of operation

The VisTrak IR V Stereo consists of 3 cameras: The VisTrak Eagle camera and 2 Stereo cameras

The stereo cameras measure ball vertical launch angle

and the VisTrak Eagle camera measures ball speed, and path plus club face angle, speed and path.

The stereo cameras capture 3 frames.

Frame 1 is of the ball at launch position on the hitting mat (the reference frame)

Frames 2 and 3 are freeze frames of the bail in flight shortly after ball strike

In the VisTrak camera Control Panel (CP)

camera 1 is the stereo left camera,

camera 2 is the stereo right camera,

camera 3 is the VisTrak Eagle camera.

The above screen shots shows the most important settings.

Shutter Speed

In contrast to the regular VisTrak Stereo system that has a long camera exposure time to capture ball traces,

the IRV Stereo captures freeze frames of the ball in flight. Thus the shutter speed setting is set to a low 200 us.

Camera Gain

As the shutter speed is very fast, we set the camera's Gain to its max of 24 db

Scale

In order to measure the distance the ball has moved forward on the horizontal plane

from its launch position on the hitting mat and the position it is in when the camera captures it in flight,

we have to convert the distance measured in pixels in the image to real world distances.

To set the correct scale, an image of the ball is grabbed on the floor

and the scale is adjusted so that the ball size in pixels is converted to 42 mm.

The Ball Size is shown near top right in the panel.

Trigger delay

In contrast to the regular VisTrak Stereo system that features a line scan trigger camera,

the stereo cameras in the IRV Stereo are triggered by the VisTrak camera itself.

As the VisTrak camera will send a trigger signal to the stereo cameras immediately after it detects a ball strike,

a trigger delay time has to be set on the stereo cameras in order to allow the ball some time to move forward and gain height.

Currently this setting's value is 5 ms.

Camera aiming

Both stereo cameras and the VisTrak camera have to be aimed at a ball on the hitting mat

so that the image of the ball in both cameras line up with the center line of the image.

The stereo cameras should be aimed so that the ball on the mat appears at the far right of the frame on the center line.

The VisTrak camera (the center camera) should be aimed so that the ball on the mat appears around 2/3 rds of the way back.

VisTrak Stereo camera aiming

In order to simplify the stereo camera aiming, a 2 axis only mount is now being used

instead of the ball joint mount shown in the images on this page.

Camera orientation

For those that are assembling their own stereo system,

both the Left and Right cameras are mounted as shown above.

The blue USB3 cable on the VisTrak camera shows the direction of play.

If the unit is mounted sideways, then the camera orientaion is as shown above.

If mounted forwards, the VisTrak Camera is rotated 90 degrees.

Unit orientation

Currently, we're recommending a horizontal (sideways) orientation.

Forward mounting is also an option if preferred

Lenses

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Current lens tests show:

12 mm lens : ball image size 32px - FOV distance forward range: 2ft 10"

8 mm lens: ball image size 22px - FOV distance forward range: 4ft 6"

Currently, systems are being shipped with 8 mm lenses on the stereo cameras and a 12mm lens on the VisTrak camera

Camera assignments

In the cameras panel, you should see the left camera as camera 1,

the right camera as camera 2,

and the VisTrak camera (VT cam) as camera 3.

If you see this error message flashing when first starting the CP,

then the camera assignments are incorrect.

If you see a warning message like the above, the cameras have to be re-assigned as described in the error message.

Note: when re-assigning cameras, ensure that the "Fixed Assigns" option is OFF.

When the assingments are correct, switch the "Fixed Assigns" option back ON.

Follow the above instructions to re-assign the cameras to their correct positions.

White Screen

If the camera assignments aren't correct, then the CP may hang and just show a white screen when started.

To fix:

1. unplug all cameras from the PC.

2. restart the CP and switch the "Fixed Assigns" option OFF.

3. shut the CP down.

4. plug the cameras back into the PC and restart the CP.

5. Check that assignments are correct.

If it's a 2 camera system, then camera 1 is the Vcam camera and 2 is the VisTrak camera.

If it's a 3 camera system, then camera 1 is the Vcam camera, camera 2 the Hcam camera and 3 is the VisTrak camera.

If re-assigning cameras then the "Fixed Assigns" should be switched back ON again and the CP re-started

Measuring ball speed and path option with the VisTrak IRV Stereo

- V 9.4.7.3 Beta

As of this update, you can now opt to have the system measure ball speed and path as well as LA with the stereo cameras instead of from the VisTrak camera.

A new "Set scale" button automatically sets the correct scaling factor.

Hard and software triggers

The VisTrak IR V Stereo cameras are triggered by the CP and not via a line scan camera.

Important note:

There are two methods of triggering the stereo cameras via the CP: Soft or Hard.

Although both methods are initiated by software commands to the cameras as soon as the CP detects a ball strike in the VisTrak camera,

the SDK SoftTrigger command takes longer to process than the Hardware trigger.

The Hardware trigger sets a GPIO output line that is connected to camera's trigger input line on the cameras high for a split second.

So, for this method to work, a GPIO cable connector that has its output and input lines shorted out, has to be connected to the cameras.

If you don't have this GPIO connector then you must ensure that the "Soft Trigger Stereo Cameras" option is ON.

Otherwise, the cameras won't get triggered and thus the stereo frames 2 and 3 won't be captured.

The VisTrak IRV Stereo uses the regular VisTrak Eagle camera.

Click on the below link to see how to setup the VisTrak Eagle camera.

 

Stereo calibration table

The stereo calibration table for the VisTrak V Stereo consists of just 2 values - Disparity and Height

Note that if both cameras are perfectly aimed at the same center line then disparity at the converging point at floor level will be zero.

This will probably prove to be difficult to achieve but at least the disparity number at floor level should be a low number.

.

A graph plot of disparity to golf ball height shows a non-linear exponential curve.

Stereoscopic vision explained

The above diagram explains the basic stereoscopic principles.

Note: the above diagram shows the stereo cameras for the VisTrak IRV Stereo where the direction of play is from right to left and not from bottom to top as with the regular VisTrak Stereo system.

If the two 2 stereo cameras are aimed precisely at the center line and a ball is placed at floor level, the images of the will appear on top of each other.

The disparity of the ball is then zero (or near zero) and this is known as the "Converging point"

When the ball is elevated, the images of the ball in the camera frames will start to separate. The distance the ball images are apart is the "Disparity".

Using a "disparity to ball height" table and with weighted calculations, the exact height of the ball can be determined.

Knowing where the ball was before ball strike (frame 1) and the trigger delay time on the stereo cameras, the ball LA, speed and path can be determined.

Ball path is simply derived from the divergence the center of the disparity distance is from the center line.

i.e. a perfectly straight shot would show that the 2 ball images are the exact same distance from the center line.

 

 

 

 

 

 

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