Merge

Merge Settings

Finger Lakes Instrumentation
200 Tech Park Drive
Rochester NY 14623 USA

Phone: 585-624-3760
Email: sales@flicamera.com
Web: https://flicamera.com

Note: Changing Black Level Adjust settings, under the Sensor tab, will impact the merged image. It is recommended that if you modify the Black Level Adjust that you then rerun the Merge Calculate to get new Merge Variables.

The high dynamic range (HDR) image is created by

combining the low gain and high gain images. Both images

are the same, but read out of the sensor at two different gain

settings.

FLI Pilot creates the HDR image by combining these two

Low and High gain images into one. The high gain images

allow for improved resolution in the darker regions of the

image, while the low gain provides better resolution in your

bright areas. The resulting HDR image is 16 bits/pixel

instead of the 12 bits/pixel that the low and high gain images

contain. The user interface provides the ability to input a

variety of Merge Variables to modify how the image is

merged. Please see below for more information on the

Merge Variables. The user interface may also display the

default values calculated by the program if the user does not

wish to provide custom data.

Generally, the best merged image results when the exposure

is adjusted such that the low gain image has pixel values

spanning the range of values from 0 to 4095. Under these

conditions, the high gain image will be saturated in most

image areas.

Automatic vs Fixed Merge Calculation (Override)

Automatic: To use automatic merge calculations uncheck

the Override box.

The automatic merge calculates new variables for each

image that is captured. This means that each merge

image may have different parameters on how it was

created. If the camera is not able to determine new

variables for an image due to a lack of useable pixel

values it will use the last calculated merge variables. It is

recommended that you use the fixed merge calculation. If

you are operating the camera in an unusual manner

please see Merge Calculate to automatically have the

camera determine the optimum merge variables for your

settings.

Fixed: To use fixed merge calculations check the Override box.

The fixed merge uses the Merge Variables set in the variable boxes to merge each image. This

standardizes each merge image if you are capturing multiple images. Many cameras will already have

Factory Default Merge Variables for the default Gain Pair and Black Level settings. These were calculated

for each camera to deliver the best merged images for the default settings. If you are operating outside of

the default parameters you can run Merge Calculate, in the Tester Routines tab, to have the camera

determine the optimum Merge Variables for your settings.

Merge Variables

Temperature

By providing sensor temperature values at three points, as well as Line Offset values at the corresponding

temperatures, FLI Pilot can calculate an effective Line Offset value for each image at various temperatures,

using linear interpolation. If you operate the camera at a different temperature and would like more direct

control, that temperature can be used instead of the defaults (KL4040 -10, 5, 20 or KL400 -20, 0, 20). Please

see Merge Calculate for determining the best settings at your unique settings.

Line Offset

The Line Offset value is used to ensure there is a smooth transition for pixels around the threshold value. This

ensures that the last pixel used from the high gain image and the first pixel from the low gain image will have

the same pixel value, ensuring that there is not gap in pixel values in your image.

Gain Ratio

The Gain Ratio is used to ensure that the low gain and high gain pixels mapped to the merged image have an

equivalent photon response, which unless otherwise changed is 1 ADU/electron. A higher Gain Ratio will

increase the Low Gain photon response compared to that of the High Gain, conversely a lower Gain Ration

will decrease the Low Gain photon response compared to that of the High Gain.

ADU/Electrons

On some Low/High gain pair choices it is possible that the combined image calculation may result in pixel

values greater than can be expressed in 16bits. These pixels will result in saturated pixels (value of 65535).

Exposure time could be reduced to correct for this, however a new image capture would be required. An

alternative is to modify this parameter and apply it to update the merged image, using the Merge Frames

Tester Routine. This parameter adjusts the photon response slope of the merged image. This can be used to

avoid saturation of pixels in the merged image, or to express all images at a certain photon response (1:1, 2:1

etc.).

Threshold

The threshold value is used to determine whether a pixel in the merged HDR image is taken from the high

gain image or the low gain image. When a pixel has a high gain value less than or equal to the threshold value,

then the high gain pixel value is used in the HDR merged image. Otherwise, the modified low gain image pixel

is used. The threshold value is set based on the sensors characteristics from the sensor manufacturer and

thus should not need to be modified from its factory default.

Custom Merge Variables

Custom Merge Variables may be used by overwriting the individual boxes and clicking the Apply Button.

User/Factory Saved Settings

Merge Variables may be saved and recalled by the user at any time. For the default Gain Pair, the factory

default Merge Variables may be recalled by pressing the Restore Merge Settings from Factory Defaults

button. If custom settings are preferred, the user may save one set of Merge Variables for each Gain Pair by

pressing the Save button. Similarly, to recall the user saved Merge Variables for the selected Gain Pair press

the Read button, this will recall the User saved Merge Variables. It is possible to store around 40 Merge

Variable sets. After you have reached maximum capacity the Pilot will not allow you to save any more sets

without first deleting existing sets. If you would like to delete one set of Merge Variables pick the Gain pair

you no longer use and press the Delete button. If you would like to delete ALL user saved Merge Variable

sets press the Clear All button.

Capture and Replace Merge Settings

The Capture and Replace Merge Settings enables you to save and retrieve Merge Settings from a .csv format

file that can be saved on the users computer.

To save the current Merge Settings please click the browse button next to the Output Path: and enter the

location that you would like to save the file. Once the Output Path has been specified you may click the

Retreive Camera Settings button to save the .csv.

To retrieve Merge Settings, click the browse button next to the Settings File: and select the appropriate .csv

file containing the Merge Settings you would like to load. Once the Settings File has been selected click on

the Write File to Camera button.