VisTrak Installation VisTrak Eagle VisTrak SCX VisTrak EV VisTrak KX VisTrak LX Video Swing Capture Videos

 

Ball Spin Setup

Selecting the Ball Spin Detection method

Please note:

Ball spin detection is now only performed with the system in TMPix or random dots/markings on the ball.

All other methods have now been removed.

Should the user's camera shutter speed setting be over 200 us, a warning will be displayed stating that

measured ball spin will not be possible due to motion blur.

 

---

VisTrak SCX Ball Spin Detection

Random all around markings or Taylor made Pix balls method

Detecting spin from Taylor Made Pix balls

Current test results show that spin detection works best with the Taylor Made Pix balls

Main reasons are that

1. In contrast to using the ball logo, no matter what ball in flight frames are used to calculate the spin, there are always 2 frames showing the Pix images

2. In contrast to launch monitor proprietary balls with spin dots on them, TaylorMade Pix balls are readily available in any golf store for a regular ball price

Measuring Ball Spin from an overhead ceiling mounted camera

using image pixel shift and rotation matching methods

Taylor Made PIX balls

This method consists of taking an array of pixel levels of the ball image in 2 adjacent frames

and obtaining a match with a series of pixel shifting and rotation procedures.

Using this method, rotation (and thus back and side spin) can be detected even with just a smudge mark on the ball.

i.e. this method is not looking for any specific dots or markings on the ball

so any ball can be used as long as there's something on the ball that is not pure white.

Low and high spin rate detection using TM PIX balls

Note that only well defined and spaced spin dot balls or balls with a strong logo can be used ( as shown above).

Note that camera exposure time (i.e. shutter speed) has to be set at or below 100 micro seconds and frame set to 1500 fps.

Lighting and shutter speed requirements

in order to measure ball spin with the ceiling mounted SCX

Measured ball spin requires clear non-blurry images of the ball in flight so that ball markings can be clearly seen.

This can only be accomplished by reducing the camera's exposure time to below 200 micro-seconds !

which in turn requires strong lighting.

If not using the narrow beam IR lights (as featured in the SCX IR),

the system will have to feature additional lighting.

i.e. 4 LED track lights

-

When using the CM Vision narrow beam angle lights, camera shutter speeds can be reduced to well under 100 micro seconds.

This will ensure that ball motion blur is at a minimum and ball markings are clearly visible

GSA Golf Hi-intensity CM Vision IR narrow beam lights

Track Lighting

4 hi-power LED zoom-able track light system with 800 Lumens per light with track

IR Light spread over the hitting area

It is essential that the SCX or Eagle overhead unit is aimed such that the light is equally spread over the hitting area.

If using IR Light, you can use brown cardboard (use the box that the unit was shipped in for this)

placed over the hitting area to see the light spread with the SCX cameras running in video stream mode.

With the unit aimed such that the light is equally spread, then all balls in the hitting area

will appear bright and will be detected at 200 micro second shutter speed

if the unit is aimed away from the hitting area, then the light spread will not be equal

In this case, balls in the center of the FOV of the camera of left of it won't be detected and the system won't function.

---

Note that the VisTrak systems require that the camera shutter speed has to be at or below 200 micro seconds

if ball spin is to be measured and not calculated.

Side Spin

Note: When the system is unable to determine side spin from marked balls,

then side spin is calculated from the relative club face angle to path and not just from the face angle itself.

Examples:

1.Draw

If club path is 10 degrees in-to-out and face angle is 5 degrees open, then relative club face angle is -5 degrees closed

which results in a negative side spin and the ball will curve back left after starting off right (i.e. a draw)

2. Pull draw

If club path is 10 degrees in-to-out and face angle is -5 degrees closed, then relative club face angle is -15 degrees closed

which results in a negative side spin and the ball will curve left after starting off left (i.e. a pull-draw)

3. Push

If club path is 5 degrees in-to-out and face angle is 5 degrees open, then relative club face angle is zero degrees

which results in a zero side spin and the ball shot is a straight push right

3. Fade

If club path is 0 degrees and face angle is 5 degrees open, then relative club face angle is +5 degrees

which results in a positive side spin and the ball shot is a curve to the right after starting out straight

3. Push Fade

If club path is 10 degrees in-to-out and face angle is 15 degrees open, then relative club face angle is +5 degrees

which results in a positive side spin and the ball shot is a curve to the right after starting out right

---

VisTrak EVi / LX2

Ball Spin Detection from the Side camera

Note that no additional lighting is required with the LX2 and EVi (near) systems as the light source is very close to the ball

The default camera exposure time for the LX2 Vcam is just 50 micro seconds

New spin detection method for side mounted camera systems (i.e. EV and LX)

The method consists of rotating ball spin frame 1 in single degree steps and comparing it to the ball spin image 2.

A best match test is performed which returns the amount of rotation between the two frames.

Knowing the amount of rotation and the time taken, accurate ball spin can be calculated.

Note that any ball markings can be used.

Ball spin for Putts

Measured ball spin when putting is done without the requirement to use ball markings.

 

---

Spin Dot / Ball Logo Detection issues

In order to detect the spin dots on the ball or ball logos, the images should be sharp and clear.

In order to achieve this, the camera exposure time has to be fast (i.e. around 150 us) with bright lighting.

If the exposure time is too long (i.e. 300 us plus) then image blur will occur and the dots or markings

on the ball will appear faint or washed out.

Click above to read more about ball spin detectionn theory...