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VisTrak Installation VisTrak Eagle VisTrak Vcam VisTrak Spin cam VisTrak Vcam B VisTrak KX VisTrak LX VisTrak Stereo Camera Installation Installation and setup

 

Setup and Theory

The S cam is a hi-resolution camera that - when used in conjunction with the hi-res Vcam camera -

can calculate spin rate from the two images.

 

VisTrak Vcam B

Add-on to the VisTrak Eagle for LA and Spin detection

$ 1,999

Contact us to purchase

The Vcam B is the same is a Vcam plus an Spin cam but mounted in a carry case

 


Measuring ball spin using the ball's logo.

The Vcam B captures 3 frames with the two floor mounted cameras.

Frame 1: the ball at launch position (captured when the VisTrak camera detects a ball on the mat).

Frame 2: the ball in flight after the trigger delay

Frame 3: the ball in flight after the base trigger delay plus an additional Cam1 to Cam2 delay

Cam 1 to Cam 2 trigger delay

The trigger delay difference between camera 1 and camera 2 is used to calculate the ball spin

It is set independently from the base trigger.

Both cameras have the same base trigger delay - in order that the ball in flight is captured in the FOV of the cameras - but camera 2 has this additional delay added to it.

This difference in trigger delay time is used as the time taken for the ball to rotate in the ball spin images and directly effects the spin calculations.

Most will probably not want to use specially marked balls so we have developed the Bcam system to use the standard ball logo on the ball to measure ball spin and spin axis.

New logo matching end detection.

An issue with measuring ball spin using the ball's logo is that the correct matching ends of the logo must be detected in order to correctly measure the amount of rotation within the time frame..

i.e. if one end of the logo is found in image 1 then that same end has to found in image 2. Failing to do this can result in very different ball spin rate measurements.

The above two images show a ball spinning at a rate of 8321 rpm. We know this because the amount of rotation within the 1 ms frame delay was 149.78 degrees.

And we only know the correct amount of rotation because the Letter "C" in the Calloway logo has been detected correctly in both frames. This is shown by the two red cross hairs over the letter "C".

Without this new "Matching logo end detection" feature, the CP image processing may well get the ends mixed up and then a totally different amount of rotation will be measured

(i.e. 30.22 degrees here) and thus a totally different and false ball spin rate will be calculated. (Note that the two sets of images are from the same shot.)

As can be seen from the above two images, the letter "C" in the Calloway logo has not been detected in image 2 (i.e. there's a green cross hair on the "C" instead of a red cross hair).

And thus a false spin rate measurement was calculated (i.e. 1678 rpm instead of the real 8321 rpm).

It should be noted that not all ball logos have a dominant end and thus it may be required to use a black magic marker or black ink pen to accent one end of the logo.

Note that measuring ball spin using the logo (or any marked balls like those with About Golf systems) is the only way a camera method of ball spin detection is able to do this in real time. i.e. without a long 2 to 4 second or so lag time (SkyTrak / GC2 etc).

While radar systems (Trackman, FlightScope etc) require metallic dots be applied to the ball and the ball be placed with the dot facing upwards.

VisTrak Vcam B setup

 

VisTrak: Multiple camera setups

The VisTrak Vcam B is using 3 cameras:

1. The ceiling mounted hi-speed VisTrak camera

2. Two hi-resolution ball spin and vertical launch angle detection cameras.

When the system is functioning correctly, all status blocks of the cameras shown in the Control Panel's main window will turn from red to green

Camera assignments

It is essential that the correct camera assignments are made.

An error message is displayed if any of the cameras are incorrectly assigned.

Correct camera assignments for the VisTrak Vcam B are:

Cams 1 and 2 are the Hi Res ball spin cameras and Cam 3 is the VisTrak camera.

To check for correct camera assignments for the VisTrak Vcam B,

go to the cameras window in the CP and successfully click on the cameras 1, 2 and 3.

If one of the these cameras is incorrectly assigned, a large error message will be shown.

If you find that cameras are not being assigned in the correct order then you can manually re-assign the cameras.

To do this, select the camera in the CP cameras window, hold both the shift and ctrl keys down,

and press the left or right arrow keys to move the camera up or down the sequence.

Fixed assigns

Ensure that the "Fixed Assigns" option in the camera 1 window is OFF when re-assigning camera functions.

When assignemnt adjustments are completed, switch this option back ON so that the camera assignements are stored.

Auto camera assignments

This new feature eliminates the need to manually assign the cameras

Simply switch on the Auto Camera Assigns option and restart the CP.

Vcam B Setup

Measuring ball spin using the ball's logo.

The Vcam B captures 3 frames with the two floor mounted cameras.

Frame 1: the ball at launch position (captured when the VisTrak camera detects a ball on the mat).

Frame 2: the ball in flight after the trigger delay

Frame 3: the ball in flight after the base trigger delay plus an additional Cam1 to Cam2 delay

Cam 1 to Cam 2 trigger delay

The trigger delay difference between camera 1 and camera 2 is used to calculate the ball spin

It is set independently from the base trigger.

Both cameras have the same base trigger delay - in order that the ball in flight is captured in the FOV of the cameras - but camera 2 has this additional delay added to it.

This difference in trigger delay time is used as the time taken for the ball to rotate in the ball spin images and directly effects the spin calculations.

Most will probably not want to use specially marked balls so we have developed the Bcam system to use the standard ball logo on the ball to measure ball spin and spin axis.

There are a number of new options for the VisTrak Vcam B system in the Setup window:

1. You have the option to use a line scan camera top trigger the Vcam an Spin cameras.

If this option is not ON then the trigger signal will come from the VisTrak camera which requires a trigger delay setting.

2. You can now manually set the launch position for the Vcam camera instead of the system auto detecting the ball on the mat.

This is done because the ball on the mat may not always be in the FOV of the Vcam.

3. if not using a Line Scan camera, then the trigger can either be via a Soft Trigger instruction to the Vcam and Spin cameras or via a GPIO trigger line

Default is soft trigger.

Trigger frame and trigger delays

The Vcam B is triggered to capture 2 freeze frames from the VisTrak Eagle camera.

It is important to set the timing of this trigger signal so that the Vcam B ball images are within the FOV of the Vcam B cameras.

If the trigger signal is fired too soon then the ball images will be before the FOV of the camera and if fired too late

the ball images will be beyond the FOV of the Vcam B cameras.

Trigger delay options for VisTrak Stereo or Vcam systems

There are two methods of setting the camera trigger delays:

1. a single global trigger delay setting for all shots and clubs

2. a club depedent trigger delay that changes the delay when a new club is selected or used

You can switch the club dependent Vcam or Stereo camera trigger delays on or off from the CP's main window.

Note: this feature is as of CP version 9.5.2.2 Beta

If off, then the regular Vcam trigger delay - as displayed in the Vcam window - will be used.

You may have to experiment a bit to find the ideal trigger delay so that the ball in-flight is in the FOV of the cameras for all shot speeds.

A trigger delay of around 10 ms should be good though.

Club dependent Trigger delays for VisTrak Stereo and VisTrak Vcam

To set club trigger delays:

1. click on the club image to select the club

2. use the +/- red and green butons to set the trigger delay for the selected club.

3. repeat the procedure for all clubs.

4. Finally, switch the "Club Trigger Delays" option ON

If the trigger delay is too short, then the ball will be too near to the club for the cameras to detect it correctly.

Trigger delays can also be automatically set depending on how close the ball is to the pin during a game.

Minimum ball speed for VisTrak Vcam.

If the measured ball speed from the VisTrak Eagle is less than this user defined minimum speed,

then data from the Vcam camera will be ignored

and all launch data will be derived from the VisTrak Eagle.

This is done because data from the Vcam camera with small chips cannot be guaranteed to be correct

due to either the ball being too close to the club or the ball trajectory is already on the downwards path by the time the cameras capture the ball images

and thus the measured vertical launch angle will not be correct.

Use the left/right arrows keys to adjust the min speed for Vcam when selected.

Use the up/down arrow keys for overall min ball speed.

Thusly, the trigger signal has to be delayed somewhat but not be delayed too much.

Some experimentation will be required to get the settings just right.


Side Spin and spin axis detection

Note that in reality a ball cannot have both back spin and side spin at the same time. In reality a ball has only spin and spin axis.

Never-the-less, a theoretical side spin rate can be measured by the amount of horizontal rotation within a certain time period.

And a back spin rate can be measured by the amount of vertical rotation within a certain time period.

Side spin theory

Side spin is imparted on the ball by the club face striking the ball with a relative-to-club-path face angle that is not square - i.e. open or closed.

This open or closed club face relative to the club path will cause the ball's backspin rotation axis to shift off center.

The above image shows ball spin without any side spin and 0 degree spin axis. The red line represents a line or logo on the ball.

If the Bcam is overhead mounted (Top View), then the line will only move backwards in each frame if there is no side spin and the line will have the same angle in each frame.

This backward movement is vertical rotation and is used to measure the back spin.

If the Bcam is mounted at floor level (for a side view) and there is no side spin, the red line will continue to rotate around the initial center of rotation

and the amount of rotation within a certain time period is used to calculate the back spin rate in rpm.

The "ref frame" is a frame of the stationary ball on the ground or tee before being struck.

The above image shows ball spin with side spin.

If the Bcam is overhead mounted (Top View), then the line angle will have changed from the initial image of the ball on the ground or tee

to a different angle after launch. This change in angle within a certain time frame is used to calculate the amount of side spin in rpm.

If the Bcam is side mounted (side view), then the line will be seen as rotating around a different axis compared to the initial axis the line was on when on the ground or tee.

We use this shift in spin axis to then calculate the side spin rotation in rpm.

Spin axis theory

Note that spin axis is never always on one plane. i.e. spin axis can have both a vertical and horizontal component to it. Thus spin axis is a 3D value.

So when you see a launch monitor displaying a spin axis of 4 degrees left or right, it is not known whether this value is on the vertical or horizontal plane.

As the real spin axis value can only described by a mathematical 3D vector - which most average golfers will have difficulty comprehending - it is simplified by reducing it to just the one plane.

Just like side spin: it's not real but we can at least grasp its meaning.

Bcam side view images

The above shows real balls - viewed from the side - with a back spin rotation and rotation axis shift.

Side spin can then be converted to spin axis.

Note that both the single camera Bcam and dual camera Bcam Pro are both using reference frames now. i.e. images of the ball on the ground or tee are automatically captured.

Bcam overhead view images

The above images are from the Bcam when mounted overhead.

Bcam overhead mounted images

Left: frame 2 of full shot with 3 wood - Right: frame 1 of ball on mat hitting position

Left: frame 2 of open faced 3 wood. Right: Composite of frames 1 and 2.

 


Bcam side mounted images

Left: 9 iron shot using spin dots on ball ---------------------- Right: White head driver using line marking on ball

 


 

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