"Camera Calibration" is the process of measuring a camera's lens curvature and plate. This process is essential for accurate scoring, without it images will be distorted and unsuitable for scoring. All NC models are calibrated at the factory before being shipped to consumers. Camera Calibration is generally not needed unless a camera had to be replaced or recommended by Athena's support team.

Process Overview

Camera Calibration is done by taking a series of photographs, from different angles and locations, of a "calibration board." About 20 photographs of the calibration board are needed for a good calibration. After the photographs are taken and internal process measures the distortion of the lens and records these values.

When taking the calibration photographs it is important to move the calibration board around the field of view of the camera, and angle the board. This more angles and locations you can give the calibration process the better the results. If instead you keep the board at a static location for all photos, the calibration will not be as good and may result in image distortion.

Calibration Board Size

The calibration board looks like a cheeseboard and is generally printed on an aluminum plate. The size of the squares on the board are precisely known.

Scopos offers two sizes of calibration boards "small" and "large". The small calibration board is used for calibration Athena's NC models, and is 140mm x 140mm in size. It will be labeled as either "7 x 6" (more common) or "6 x 6." The large calibration board is 8.5in x 11in and should not be used with Athena's NC models.

Setting the Expected Calibration Board Size

To change the expected size of the board. In Orion:

1.Open the Athena Unit Maintenance form. From the menu bar click on Athena -> Athena Unit Maintenance.

2.Select which target you wish to change (it is OK to select all the targets).

3.Click on Miscellaneous -> Set Calibration Board Size -> Your calibration board size.

Physical Access to the Target

To take calibration photos you will need physical access to the NC model target; no one should be shooting while you are performing these steps.

It is best if you have a good view of Orion or the paired Monitor, this way you can see the calibration Images the target is taking.

Be sure to know how to flip the camera arm up, pointing the camera away from the aiming bull. On older NC models, with a curved camera arm the camera arm rotates at a 45 degree angle (towards 10:30). On newer NC models with a squared camera arm, the camera arm rotates up (towards 12:00).

Calibrating

Read through all of these instructions before starting.

Step 1: Starting Calibration

There are two ways to start the calibration process, either from the Target's paired Monitor, or from Orion. Once the calibration process starts, it can not be stopped.

Option 1: Starting Calibration from Orion (recommended)

1.Open the Athena Unit Maintenance form. From the menu bar click on Athena -> Athena Unit Maintenance.

2.Select which target you wish to calibrate.

3.Click on Maintenance -> Live Camera and Calibration. The Athena Live Camera View form will open, displaying the live target image.

4.Click the Start Camera Calibration button.

Option 2: Starting Calibration from the Target's paired Monitor

1.Put the firing point into practice mode if it not already. Starting Calibration is not possible in competition mode.

2.Click on Menu -> Advanced -> Calibrate. The Calibration form will open. Click on Start Calibration.

The Target's Red X and Green O will light up for four seconds, indicating calibration is about to begin.

Step 2: Flip the Camera Arm Up

Flip the camera arm up, so it is pointing away from the aiming bull. See "Physical Access to the Target" to learn how.

NOTE: It is OK if the Red X flashes a few times while you flipping the camera arm up.

Step 3: Take Calibration Images

Using the Calibration Board hold the board 20 to 25cm away from the camera. Hold the board so the top of the board (with the QR Code) is at the top of the taken images. You may view the images in Orion or the Monitor to verify.

Hold the Calibration Board still until a photo is taken. When a photo is taken either the Green O will flash, indicating a good calibration image was taken, or the Red X will flash, indicating a bad calibration image was taken. Athena needs about 20 good photos to have a successful calibration.

After each image is taken, move the board around the field of view, and or change it's angle slightly.

When calibration is complete the Green O will flash radpidly multiple times, indicating Calibration was successful. Or, the Red X will flash rapidly multiple times, indicating calibration was not successful.