Ubuntu – HDMI connection not recognized on Laptop with Ubuntu 14.04

On a Lenovo Laptop with Ubuntu 14.04 I am not able to display the current screen's stuff on a Monitor connected with HDMI. The HDMI cables are both plugged in to the laptop and the monitor, and the monitor is switched on.

Going to

Systems Settings -> Displays

and clicking on 'Detect Displays' only the standard laptop screen is shown. The external monitor is not shown.

How can I fix this problem in order to see the current screen on both, the laptop screen and on the monitor screen?

Also, it is unimportant if the screen can play the laptop's sound. I only want the visible screen output shown on the external monitor as well, which works fine when starting the laptop with the Windows OS (without any change to hardware and/or cables)…

Additional information:

• xrandr only shows the standard monitor; the full output of xrandr is

  xrandr: Failed to get size of gamma for output default
  Screen 0: minimum 1600 x 900, current 1600 x 900, maximum 1600 x 900
  default connected primary 1600x900+0+0 0mm x 0mm
     1600x900       77.0* 
  

• The HDMI connection works flawless when running the laptop with Windows (dual-boot)

• Output of line of lspci:

  00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09) (prog-if 00 [VGA controller])
  Subsystem: Lenovo Device 3977
  Flags: bus master, fast devsel, latency 0, IRQ 7
  Memory at c0000000 (64-bit, non-prefetchable) [size=4M]
  Memory at b0000000 (64-bit, prefetchable) [size=256M]
  I/O ports at 3000 [size=64]
  Expansion ROM at <unassigned> [disabled]
  Capabilities: <access denied>
  

• Output of sudo lshw -C display:

  *-display UNCLAIMED     
     description: VGA compatible controller
     product: 3rd Gen Core processor Graphics Controller
     vendor: Intel Corporation
     physical id: 2
     bus info: pci@0000:00:02.0
     version: 09
     width: 64 bits
     clock: 33MHz
     capabilities: msi pm vga_controller bus_master cap_list
     configuration: latency=0
     resources: memory:c0000000-c03fffff memory:b0000000-bfffffff ioport:3000(size=64)
  

• I also tried to remove and re-install the package xserver-xorg-video-intel – but it did not change anything (after reboot).

• I followed the steps given here for a Samsung LS22B150NS monitor with a resolution of 1920 x 1080 pixels. But I got an error xrandr: cannot find output "VGA1":

  alex:~$ cvt 1920 1080
  # 1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
  Modeline "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
  alex:~$ xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
  xrandr: Failed to get size of gamma for output default
  alex:~$ xrandr --addmode VGA1  1920x1080_60.00
  xrandr: Failed to get size of gamma for output default
  xrandr: cannot find output "VGA1"