Steven Zhu - 2021-12-31T13:57:19+00:00
Question: Why am I unable to use the auto-focus command to focus my DCAM
Why am I unable to use the auto-focus command to focus my DCAM camera in Image Acquisition Toolbox 2.1(R2007a)? I am using the Image Acquisition Toolbox with the WINVIDEO adaptor in order to connect to my DCAM camera. The camera works fine in AMCap, and is in-focus when I first open a PREVIEW window in MATLAB. However, it goes out of focus, as though it were trying to focus on a point far in the distance. In addition, if I send it an auto-focus command, the camera goes into focus, but then again goes out of focus when I execute the START or PREVIEW commands in MATLAB. My camera connects to MATLAB via both a firewire cable, and through a separate cable to the serial port. The camera's "auto-focus" command is sent through the serial port.
Expert Answer
Kshitij Singh answered .
2025-11-20
This is the expected functionality. Whenever a device is started, via START, GETSNAPSHOT, or PREVIEW, the toolbox reads the current values for all of the properties on the source object and sends them to the device. In this case, a default value of 10 for the focus property is sent to the device every time one of the aforementioned commands is issued. This will cause the camera to revert back to the farthest focus setting available. The behavior is different from what AMCap does. However this is not a bug in Image Acquisition Toolbox. It is necessary to allow certain functionality in the toolbox that is not present in AMCap.
The following code should allow the use of the auto-focus command to focus the camera:
% Create the videoinput object:
vid = videoinput('winvideo',1,'Y800_320x240');
triggerconfig(vid, 'manual');
% Start the acquisition
start(vid)
% Open the preview window (this step can be transposed with the start
command
preview(vid);
% Focus the camera using the SERIAL command
port = 'COM8';
baud = 19200;
databits = 8;
parity = 'none';
stopbits = 1;
terminator = 'CR';
flowcntrl = 'none';
FLIRSerialPortObject = serial(port, 'BAUD', baud, 'DataBits', databits, ...
'Parity', parity, 'FlowControl', flowcntrl, 'StopBits', stopbits, ...
'Terminator', terminator);
fopen(FLIRSerialPortObject);
fprintf(FLIRSerialPortObject, 'autofocus now');
pause(2);
fclose(FLIRSerialPortObject);
% Start an acquisition
trigger(vid);
data = getdata(vid);
Note that the next call to START will cause the camera to go out of focus again because the default value of 10 for the focus property will be sent to the camera. The options at this point are to refocus the camera, get the autofocus value and set the focus property, or set the TriggerRepeat property to Inf and call TRIGGER multiple times while only calling START once. The last option will only send the property values to the hardware a single time so the camera should not de-focus again. Also, TriggerRepeat does not have to be set to Inf, it is just a convenient number.
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