Scanner glass foggy - HP Scanjet 4070 Flatbed Scanner

The seal on the microwave door glass is compromised and allowing moisture and perhaps the microwaves, to enter between the windows inner and outer.
There is a great potential for leakage here.
I would not continue to operate this oven until I have it fixed.

You will have to take it apart and clean the glass which is not an easy task.

Sounds like moisture built up under the glass. Move the unit to a dry warm place and let sit (with cover open) for a few days. You can also use a hair dryer set on low to speed up the process. This moisture can be caused if the unit was in a cool or cold area then moved into a warmer area.

Got this from Canon.com: The foggy haze on the glass is actually an anti-glare treatment that has been intentionally applied to the underside of the scanner glass. This treatment lessens the glare from the lamp under the glass and provides better image quality. This haze may not appear uniform because of the shape of the scanner base and the components under the glass. However, the anti-glare treatment has been uniformly applied and the haze is as expected.

dear sir good day first flip down the scanner you'll find screws open it and then you'll find a mechanism and then the glass with your hands and use a dry cloth and a glass cleaner to do the work thank you

More than likely on that model, the mirrors as you call it will not get dirty it is sealed.If the glass appears foggy, that does not affect the quality of you scans generally.Alot of the newer scanners create that on the glass.And frequently the new replacemtn scanners have that too.

I made contact with cannon and received this reply. I was satisfied with the answer but the question still remained on how to remove the glass should i wish to do so. Also after there answer... would there then be a problem if i did clean the reverse side. Their answer was initialy this...
The foggy haze on the glass is actually an anti-glare treatment that has
been intentionally applied to the underside of the scanner glass.  This 
treatment lessens the glare from the lamp under the glass and provides 
better image quality.  This haze may not appear uniform because of the 
shape of the scanner base and the components under the glass. However, 
the anti-glare treatment has been uniformly applied and the haze is as 
expected.  The treatment should not affect the scan quality or output of
the 8600F.  

you can use liquid detergent and wipe it with an old news paper. you also need to remove first the glass so u can also clean the other side

No problem.
1st step. Remove the lid. It just pulls out at the hinge end by lifting straight up, horizontal if you like. Where the two lid posts insert in the scanner body you will find 2 screws, undo them, no need to remove at this point, too hard. Rememeber you left them in there though.
2nd step. Around the 4 buttons at the control end is a striped trim panel that is the full width of the scanner. Locate the join between this trim and the light grey underside of the scanner body and just left and right of the COPY & EMAIL buttons, Using your fingernails lift with some gentle force. This edge will pop up. Note, the trim panel has 3 location tabs that insert under the grey border edge around the glass. So pop the front edge first and pull towards yourself.
3rd step. Once this trim is removed you will note 4 little grey plugs equally spaced under this area. remove the plugs and you will find 4 screws. Unscrew them, no need to remove, remember point above.
4th step. Time for CAUTION. You will be able to lift the upper part of the scanner up in which the glass is mounted. ***There is a lead with little play connected to the 4 buttons PCB which is attached to the upper panel. To ensure you don't damage it accidently when cleaning the glass you can remove the 2 screws attaching it to the upper panel.
5th step. See if you can wipe it, with a VERY SOFT LINT FREE cloth, without putting you finger on it somewhere......................
6th step. reassembly is the same in reverse

I would not worry about the underside of the glass unless you are having problems. The focal length of the ccd that captures the image is very specific and probably will not pick up anything under the glass. It is normal for the underside to look foggy but it will not hurt anything.