Ubuntu brightness can't be changed after upgrading to 13.04

[915086731]

Today I upgrade my ubuntu to version 13.04 from 12.10, however , the brightness can't be adapted. I have tried the previous kernel which worked on version 12.10, brightness can't be changed too. My PC is Acer 4750G.My boot parameter:

RAMDISK$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.8.0-29-generic root=UUID=0f905c49-affc-49b5-809b-4f7eea7dddbf ro quiet splash acpi_backlight=vendor vt.handoff=7

My graphic card details:

RAMDISK$ sudo lspci -vnn | grep -A12 VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
    Subsystem: Acer Incorporated [ALI] Device [1025:0507]
    Flags: bus master, fast devsel, latency 0, IRQ 43
    Memory at f3400000 (64-bit, non-prefetchable) [size=4M]
    Memory at d0000000 (64-bit, prefetchable) [size=256M]
    I/O ports at 3000 [size=64]
    Expansion ROM at <unassigned> [disabled]
    Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
    Capabilities: [d0] Power Management version 2
    Capabilities: [a4] PCI Advanced Features
    Kernel driver in use: i915

00:16.0 Communication controller [0780]: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 [8086:1c3a] (rev 04)
--
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF108M [GeForce GT 540M] [10de:0df4] (rev ff) (prog-if ff)
    !!! Unknown header type 7f

03:00.0 Network controller [0280]: Atheros Communications Inc. AR9287 Wireless Network Adapter (PCI-Express) [168c:002e] (rev 01)
    Subsystem: Foxconn International, Inc. Device [105b:e034]
    Flags: bus master, fast devsel, latency 0, IRQ 17
    Memory at f3900000 (64-bit, non-prefetchable) [size=64K]
    Capabilities: [40] Power Management version 3
    Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit-
    Capabilities: [60] Express Legacy Endpoint, MSI 00
    Capabilities: [100] Advanced Error Reporting
    Capabilities: [140] Virtual Channel
    Capabilities: [160] Device Serial Number 00-15-17-ff-ff-24-14-12
RAMDISK$

My brightness interfaces and their values:

RAMDISK$ for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/max_brightness; done
/sys/class/backlight/acer-wmi
1
15
/sys/class/backlight/intel_backlight
509
976

Thanks