BenQ Th681 Digital Projector User Manual

							Introduction 11
Remote control
1. POWER
Toggles the projector between standby 
mode and on.
2. Info
Shows the status information of the 
projector.
3. MENU/EXIT
Turns on the On-Screen Display (OSD) 
menu. Goes back to previous OSD menu, 
exits and saves menu settings.
4. Left
5. MODE/ENTER
Selects an available picture setup mode.
Activates the selected On-Screen Display 
(OSD) menu item.
6. ECO BLANK
Used to hide the screen picture.
7. Keystone/Arrow keys ( / Up,  /
Down)
Manually corrects distorted images 
resulting from an angled projection.
8. SmartEco
Displays the lamp mode selection bar. 
9. Aspect
Selects the display aspect ratio.10. Page Up/Page Down
Operate your display software program (on 
a connected PC) which responds to page up/
down commands (like Microsoft 
PowerPoint).
11. Digital Zoom (+, -)
Magnifies or reduces the projected picture 
size.
12. Timer On
Activates or displays an on-screen timer 
based on your own timer setting.
13. Timer Set up
Enters presentation timer setting directly.
14. 3D settings
Enters 3D settings directly.
15. AUTO
Automatically determines the best picture 
timings for the displayed image.
16. Right
When the On-Screen Display (OSD) menu 
is activated, the #4, #7, and #16 keys are 
used as directional arrows to select the 
desired menu items and to make 
adjustments.
17. SOURCE
Displays the source selection bar.
18. Volume +/-
Adjusts the sound level.
19. Mute
Toggles projector audio between on and off.
20. Freeze
Freezes the projected image.
21. Quick Install
Quickly selects several functions to adjust 
the projected image and displays the test 
pattern.
22. CC
Displays the video term description on 
screen which is provided for hard-of-hearing 
viewers.
23. Teaching template
Enters Teaching template setting directly.
2
3
4
8
9
11
1213
15
17
1920
21
2322
16
14
10
65
77
1
18
18 
						

							Introduction 12
Remote control effective range
The remote control must be held at an angle within 30 degrees perpendicular to the 
projectors IR remote control sensor(s) to function correctly. The distance between the 
remote control and the sensor(s) should not exceed 8 meters (~ 26 feet).
Make sure that there are no obstacles between the remote control and the IR sensor(s) on 
the projector that might obstruct the infra-red beam.
Replacing the remote control batteries
1. To open the battery cover, turn the remote control over to view its back, push on 
the finger grip on the cover and slide it up in the direction of the arrow as illustrated. 
The cover will slide off.
2. Remove any existing batteries (if necessary) and install two AAA batteries observing 
the battery polarities as indicated in the base of the battery compartment. Positive 
(+) goes to positive and negative (-) goes to negative.
3. Refit the cover by aligning it with the base and sliding it back down into position. Stop 
when it clicks into place.
•  Avoid leaving the remote control and batteries in an excessive heat or humid environment like the 
kitchen, bathroom, sauna, sunroom or in a closed car.
•  Replace only with the same or equivalent type recommended by the battery manufacturer.
•  Dispose of the used batteries according to the manufacturers instructions and local environment 
regulations for your region.
•  Never throw the batteries into a fire. There may be danger of an explosion.
•  If the batteries are dead or if you will not be using the remote control for an extended period of time, 
remove the batteries to avoid damage to the remote control from possible battery leakage.
•  Operating the projector from the front
Ap
p
rox.
 +
30
º
•  Operating the projector from the top
Ap
pr
ox. +30
º 
						

							Positioning your projector 13
Positioning your projector
Choosing a location
Your projector is designed to be installed in one of four possible installation locations: 
Your room layout or personal preference will dictate which installation location you select. 
Take into consideration the size and position of your screen, the location of a suitable 
power outlet, as well as the location and distance between the projector and the rest of 
your equipment.1. Front Table
Select this location with the projector 
placed on the table in front of the screen. 
This is the most common way to position 
the projector for quick setup and 
portability.
2. Front Ceiling
Select this location with the projector 
suspended upside-down from the ceiling in 
front of the screen.
Purchase the BenQ Projector Ceiling 
Mount Kit from your dealer to mount your 
projector on the ceiling.
Set Front Ceiling in the SYSTEM 
SETUP: Basic > Projector Installation 
menu after you turn the projector on.3. Rear Ceiling
Select this location with the projector 
suspended upside-down from the ceiling 
behind the screen.
Note that a special rear projection screen 
and the BenQ Projector Ceiling Mount Kit 
are required for this installation location.
Set Rear Ceiling in the SYSTEM 
SETUP: Basic > Projector Installation 
menu after you turn the projector on.
4. Rear Table
Select this location with the projector 
placed on the table behind the screen.
Note that a special rear projection screen 
is required.
Set Rear Table in the SYSTEM SETUP: 
Basic > Projector Installation menu 
after you turn the projector on. 
						

							Positioning your projector 14
Obtaining a preferred projected image size
The distance from the projector lens to the screen, the zoom setting, and the video format 
each factors in the projected image size.
Projection dimensions 
Installation for a 16:9 ratio screen
 The screen aspect ratio is 16:9 and the projected picture is in a 16:9 aspect ratio




Floor Installation
: Screen             : Center of lens
 
 

Ceiling Installation
: Screen             : Center of lens
Screen dimensionsProjection distance  [mm]Lowest/
Highest lens 
position  
[mm] Diagonal

[inch (mm)]Height 

[mm]Width

[mm]Min 
distance 
(with max 
zoom)AverageMax 
distance 
(with min 
zoom)
40 (1016) 498 886 1013 1165 1316 25
50 (1270) 623 1107 1266 1456 1646 31
60 (1524) 747 1328 1519 1747 1975 37 
70 (1778) 872 1550 1772 2038 2304 44 
80 (2032) 996 1771 2025 2329 2633 50 
90 (2286) 1121 1992 2278 2620 2962 56 
100 (2540) 1245 2214 2532 2911 3291 62 
110 (2794) 1370 2435 2785 3203 3620 68 
120 (3048) 1494 2657 3038 3494 3949 75 
130 (3302) 1619 2878 3291 3785 4278 81 
140 (3556) 1743 3099 3544 4076 4608 87 
150 (3810) 1868 3321 3797 4367 4937 93 
160 (4064) 1992 3542 4051 4658 5266 100 
170 (4318) 2117 3763 4304 4949 5595 106 
180 (4572) 2241 3985 4557 5241 5924 112 
190 (4826) 2366 4206 4810 5532 6253 118 
200 (5080) 2491 4428 5063 5823 6582 125 
235 (5969) 2926 5202 5949 6842 7734 146  
						

							Positioning your projector 15
Installation for a 4:3 ratio screen
The illustrations and table below are provided for those users who already have 4:3 aspect 
ratio screens or intend to purchase 4:3 aspect ratio screens to view 16:9 ratio projected 
images.
 The screen aspect ratio is 4:3 and the projected picture is in a 16:9 aspect ratio
All measurements are approximate and may vary from the actual sizes. 
BenQ recommends that if you intend to permanently install the projector, you should physically test the 
projection size and distance using the actual projector in situ before you permanently install it, so as to make 
allowance for this projectors optical characteristics. This will help you determine the exact mounting position 
so that it best suits your installation location.






Floor Installation
: Screen             : Center of lens

 


Ceiling Installation
: Screen             : Center of lens
Screen dimensionsProjection distance  
[mm]Lowest/
Highest 
lens 
position 

[mm]
Image 
height 

[mm] Diagonal

[inch (mm)]Height

[mm]Width

[mm]Min 
distance 
(with 
max 
zoom)AverageMax 
distance 
(with 
min 
zoom)
40 (1016) 610 813 929 1069 1208 23 457
50 (1270) 762 1016 1162 1336 1510 29 572
60 (1524) 914 1219 1394 1603 1813 34 686
70 (1778) 1067 1422 1627 1871 2115 40 800 
80 (2032) 1219 1626 1859 2138 2417 46 914 
90 (2286) 1372 1829 2091 2405 2719 51 1029 
100 (2540) 1524 2032 2324 2672 3021 57 1143 
110 (2794) 1676 2235 2556 2940 3323 63 1257 
120 (3048) 1829 2438 2788 3207 3625 69 1372 
130 (3302) 1981 2642 3021 3474 3927 74 1486 
140 (3556) 2134 2845 3253 3741 4229 80 1600 
150 (3810) 2286 3048 3486 4008 4531 86 1715 
160 (4064) 2438 3251 3718 4276 4833 91 1829 
170 (4318) 2591 3454 3950 4543 5135 97 1943 
180 (4572) 2743 3658 4183 4810 5438 103 2057 
190 (4826) 2896 3861 4415 5077 5740 109 2172 
200 (5080) 3048 4064 4647 5345 6042 114 2286  
						

							Connection 16
Connection
When connecting a signal source to the projector, be sure to:
1. Turn all equipment off before making any connections.
2. Use the correct signal cables for each source.
3. Ensure the cables are firmly inserted.
•  In the connections shown below, some cables may not be included with the projector (see Shipping 
contents on page 8). They are commercially available from electronics stores.
•  The connection illustrations below are for reference only. The rear connecting jacks available on the 
projector vary with each projector model.
•  Many notebooks do not turn on their external video ports when connected to a projector. Usually a key 
combo like FN + F3 or CRT/LCD key turns the external display on/off. Locate a function key labeled CRT/
LCD or a function key with a monitor symbol on the notebook. Press FN and the labeled function key 
simultaneously. Refer to your notebooks documentation to find your notebooks key combination.
•  The D-Sub output only works when an appropriate D-Sub input is made to the COMPUTER 1 jack.
1. VGA cable
2. VGA to DVI-A cable
3. USB cable
4. Component Video to VGA (D-Sub) 
adapter cable5. S-Video cable
6. Video cable
7. Audio L/R cable
8. Audio cable
9. HDMI cable
787841216359
Notebook or desktop computer
Speakers A/V device
Monitor
(DVI)
(VGA)
oror 
						

							Connection 17
•  If you wish to use this connection method when the projector is in standby mode, make sure the 
Monitor Out function is turned on in the SYSTEM SETUP: Advanced menu. See Standby Settings 
on page 45 for details.
Connecting video source devices
You need only connect the projector to a video source device using just one of the 
connecting methods, however each provides a different level of video quality. The method 
you choose will most likely depend upon the availability of matching terminals on both the 
projector and the video source device as described below:
Connecting audio
The projector has built-in mono speaker(s) which are designed to provide basic audio 
functionality accompanying data presentations for business purposes only. They are not 
designed for, nor intended for stereo audio reproduction use as might be expected in 
home theater or home cinema applications. Any stereo audio input (if provided), is mixed 
into a common mono audio output through the projector speaker(s).
The built-in speaker(s) will be muted when the AUDIO OUT jack is connected.
•  The projector is only capable of playing mixed mono audio, even if a stereo audio input is connected. See 
Connecting audio on page 17 for details.
•  If the selected video image is not displayed after the projector is turned on and the correct video source 
has been selected, check that the video source device is turned on and operating correctly. Also check 
that the signal cables have been connected correctly.
Te r m i n a l  n a m eTerminal appearancePicture quality
HDMI
Best
Component Video
Better
S-Video
Good
Video
Normal 
						

							Operation 18
Operation
Starting up the projector
1. Plug the power cord into the projector and into a 
power outlet. Turn on the power outlet switch 
(where fitted). Check that the POWER indicator 
light on the projector lights orange after power 
has been applied.
Please use the original accessories (e.g. power cord) only with the 
device to avoid possible dangers such as electric shock and fire.
2. Press  POWER to start the projector. As soon as the lamp lights up, a Pow e r  
On Ring Tone will be heard. The POWER indicator light flashes green and 
stays green when the projector is on.
The start up procedure takes about 30 seconds. In the later stage of start up, a 
startup logo is projected.
(If necessary) Rotate the focus ring to adjust the image clearness.
To turn off the ring tone, see Turning off the Power On/Off Ring Tone on page 33 
for details.
If the projector is still hot from previous activity, it will run the cooling fan for approximately 90 seconds 
before energizing the lamp.
3. If the projector is activated for the first 
time, select your OSD language following 
the on-screen instructions.
4. If you are prompted for a password, press 
the arrow keys to enter a six-digit 
password. See Utilizing the password 
function on page 22 for details.
5. Switch all of the connected equipment on.
6. The projector will start to search for input 
signals. The current input signal being 
scanned appears in the upper left corner of 
the screen. If the projector doesnt detect 
a valid signal, the message “No Signal” will 
continue displaying until an input signal is 
found.
You can also press SOURCE on the 
projector or remote control to select your 
desired input signal. See Switching input 
signal on page 24 for details.
•  If the frequency/resolution of the input signal exceeds the projectors operating range, you will see the 
message “Out of Range” displayed on the background screen. Please change to an input signal which is 
compatible with the projectors resolution or set the input signal to a lower setting. See Timing chart on 
page 56 for details.
•  If no signal is detected for 3 minutes, the projector automatically enters ECO BLANK mode. 
						

							Operation 19
Adjusting the projected image
Adjusting the projection angle
The projector is equipped with 1 quick-release adjuster foot and 1 rear adjuster foot. 
These adjusters change the image height and projection angle. To adjust the projector:
1. Press the quick-release button and lift the 
front of the projector. Once the image is 
positioned where you want it, release the 
quick-release button to lock the foot in 
position.
2. Screw the rear adjuster foot to fine-tune the 
horizontal angle.
To retract the foot, hold up the projector while 
pressing the quick-release button, then slowly lower 
the projector. Screw the rear adjuster foot in a 
reverse direction.
If the projector is not placed on a flat surface or the 
screen and the projector are not perpendicular to 
each other, the projected image becomes 
trapezoidal. To correct this situation, see 
Correcting keystone on page 20 for details.
Auto-adjusting the image
In some cases, you may need to optimize the picture quality. To do this, press AUTO on 
the projector or remote control. Within 3 seconds, the built-in Intelligent Auto 
Adjustment function will re-adjust the values of Frequency and Clock to provide the best 
picture quality. 
The current source information will be displayed in the corner of the screen for 3 seconds.
This function is only available when PC signal (analog RGB) is selected.
Fine-tuning the image size and clarity
21
Do not look into the lens while the 
lamp is on. The strong light from the 
lamp may cause damage to your eyes.
Be careful when you press the quick-
release button as it is close to the 
exhaust vent where hot air comes 
from.
1. Adjust the projected image to the 
size that you need using the zoom 
ring. 2. Sharpen the image by rotating the 
focus ring. 
						

							Operation 20
Correcting keystone
Keystoning refers to the situation where the projected image is noticeably wider at either 
the top or bottom. It occurs when the projector is not perpendicular to the screen. 
To correct this, you will need to manually correct it following ONE of these steps.
•  Press  /  on the projector or remote 
control to display the Keystone correction page. 
Press   to correct keystoning at the top of 
the image. Press   to correct keystoning at 
the bottom of the image.
•  Using the OSD menu
1. Press MENU/EXIT and then press  /  until the DISPLAY menu is highlighted.
2. Press  to highlight Keystone and press MODE/ENTER. The Keystone 
correction page appears.
3. Press   to correct keystoning at the top of the image. Press   to correct 
keystoning at the bottom of the image.
Press/.Press /.