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Thank you for helping me to solve this problem! Here is my code for 16-Bit Look up table based reduction. hope this might be useful for someone!

main()
{
    Size Img_Size(320,240);
    Mat Img_Source_16(Size(320,240),CV_16UC1,Scalar::all(0));
    Mat Img_Destination_16(Size(320,240),CV_16UC1,Scalar::all(0));

    unsigned short LookupTable[4096];
    for (int i = 0; i < 4096; i++)
    {
        LookupTable[i]= 4096-i;
    }

    int i=0;
    for (int Row = 0; Row < Img_Size.height; Row++)
    {
        for (int Col = 0; Col < Img_Size.width; Col++)
        {
            Img_Source_16.at<short>(Row,Col)= i;
            i++;
            if(i>=4095)
                i=0;
        }
    }

    imshow("Img_Source",Img_Source_16);

    t1.start();
    Img_Destination_16= ScanImageAndReduceC_16UC1(Img_Source_16.clone(),LookupTable);

    imshow("Img_Destination",Img_Destination_16);
    t1.stop();
}

Mat& ScanImageAndReduceC_16UC1(Mat& I, const unsigned short* const table)
{
    // accept only char type matrices
    CV_Assert(I.depth() != sizeof(uchar));

    int channels = I.channels();

    int nRows = I.rows;
    int nCols = I.cols * channels;

    if (I.isContinuous())
    {
        nCols *= nRows;
        nRows = 1;
    }

    int i,j;
    unsigned short* p = (unsigned short*)I.data;
    for( unsigned int i =0; i < nCols*nRows; ++i)
        *p++ = table[*p];

    return I;
}