Linux – cmake error : opencv2/opencv.hpp：opencv2/opencv.hpp：No such file or directory

I am compiling opencv programs with cmake.
The code is as follows:

DisplayImage.cpp:

#include <stdio.h>
#include <opencv2/opencv.hpp>
using namespace cv;
int main(int argc, char** argv )
{
    if ( argc != 2 )
    {
        printf("usage: DisplayImage.out <Image_Path>\n");
        return -1;
    }

    Mat image;
    image = imread( argv[1], 1 );

    if ( !image.data )
    {
        printf("No image data \n");
        return -1;
    }
    namedWindow("Display Image", WINDOW_AUTOSIZE );
    imshow("Display Image", image);

    waitKey(0);

    return 0;
}

CMakeLists.txt:

cmake_minimum_required(VERSION 2.8)

project( DisplayImage )

set(OpenCV_DIR /home/lmk/opencv-3.1.0/release)

include_directories( ${OpenCV_INCLUDE_DIRS} )

add_executable( DisplayImage DisplayImage.cpp )

target_link_libraries( DisplayImage ${OpenCV_LIBS} )

I put the DisplayImage.cpp and CMakeLists.txt in the folder called test in my personal home folder, namely /home/lmk/test/.
Then I use command lines :

lmk@lmk-virtual-machine:~/test$ mkdir build
lmk@lmk-virtual-machine:~/test$ cd build
lmk@lmk-virtual-machine:~/test/build$ cmake ..

Which give me:

— The C compiler identification is GNU 5.3.0
— The CXX compiler identification is GNU 5.3.0
— Check for working C compiler: /usr/bin/cc
— Check for working C compiler: /usr/bin/cc — works
— Detecting C compiler ABI info
— Detecting C compiler ABI info – done

— Check for working CXX compiler: /usr/bin/c++
— Check for working CXX compiler: /usr/bin/c++ — works
— Detecting CXX compiler ABI info
— Detecting CXX compiler ABI info – done
— Configuring done
— Generating done
— Build files have been written to: /home/lmk/test/build

But when I use:

Scanning dependencies of target DisplayImage
[100%] Building CXX object CMakeFiles/DisplayImage.dir/DisplayImage.cpp.o
/home/lmk/test/DisplayImage.cpp:2:30: fatal eror：opencv2/opencv.hpp：No such file or directory
compilation terminated.
make[2]: * [CMakeFiles/DisplayImage.dir/DisplayImage.cpp.o] Error 1
make[1]: * [CMakeFiles/DisplayImage.dir/all] Error 2
make: *** [all] Error 1

Do you konw why?
I am using opencv 3.1.0 and cmake 2.8.12.2 in the terminal of ubuntu 14.04 in VM!