请帮我写一段用matlab 调用usb摄像头的代码

Sure, I can help with that! Here's a sample code in MATLAB for accessing a USB camera:

% Initialize the camera
cam = webcam;

% Set the resolution of the camera
cam.Resolution = '640x480';

% Preview the camera stream
preview(cam);

% Capture and save images from the camera
for i = 1:10
    img = snapshot(cam);
    filename = sprintf('image%d.jpg',i);
    imwrite(img,filename);
end

% Close the camera
clear('cam');

This code will allow you to access and capture images from a connected USB camera. Remember to replace the resolution value and file names according to your needs. Let me know if you have any other questions!