I also have an avision-based scanner (Xerox DocuMate 510), and encountered the reported issue with the version of sane-utils in wheezy.
I downloaded the later version of the package source from unstable, built the package, and verified it resolved the problem.
kbare@musicality:~$ scanimage -L
device `v4l:/dev/video0' is a Noname BT878 video (Hauppauge (bt878)) virtual device
device `avision:libusb:002:012' is a Xerox DocuMate510-G flatbed scanner
kbare@musicality:~$ scanimage -d avision --help
Usage: scanimage [OPTION]...
Start image acquisition on a scanner device and write image data to
Parameters are separated by a blank from single-character options (e.g.
-d epson) and by a "=" from multi-character options (e.g. --device-name=epson).
-d, --device-name=DEVICE use a given scanner device (e.g. hp:/dev/scanner)
--format=pnm|tiff file format of output file
-i, --icc-profile="" include this ICC profile into TIFF file
-L, --list-devices show available scanner devices
-f, --formatted-device-list=FORMAT similar to -L, but the FORMAT of the output
can be specified: %d (device name), %v (vendor),
%m (model), %t (type), %i (index number), and
-b, --batch[=FORMAT] working in batch mode, FORMAT is `out%d.pnm' or
`out%d.tif' by default depending on --format
--batch-start=# page number to start naming files with
--batch-count=# how many pages to scan in batch mode
--batch-increment=# increase page number in filename by #
--batch-double increment page number by two, same as
--batch-prompt ask for pressing a key before scanning a page
--accept-md5-only only accept authorization requests using md5
-p, --progress print progress messages
-n, --dont-scan only set options, don't actually scan
-T, --test test backend thoroughly
-A, --all-options list all available backend options
-h, --help display this help message and exit
-v, --verbose give even more status messages
-B, --buffer-size=# change input buffer size (in kB, default 32)
-V, --version print version information
Options specific to device `avision':
--mode Lineart|Dithered|Gray|Color [Color]
Selects the scan mode (e.g., lineart, monochrome, or color).
--resolution 75..600dpi (in steps of 1) 
Sets the resolution of the scanned image.
--speed 0..4 (in steps of 1) 
Determines the speed at which the scan proceeds.
Request a preview-quality scan.
--source Normal|ADF Front [Normal]
Selects the scan source (such as a document-feeder).
-l 0..216mm 
Top-left x position of scan area.
-t 0..297mm 
Top-left y position of scan area.
-x 0..216mm 
Width of scan-area.
-y 0..297mm 
Height of scan-area.
--overscan-top 0..4mm [inactive]
The top overscan controls the additional area to scan before the paper
--overscan-bottom 0..4mm [inactive]
The bottom overscan controls the additional area to scan after the
paper end is detected.
--background-lines 0..50pel [inactive]
The background raster controls the additional background lines to scan
before the paper is feed through the scanner.
--brightness -100..100% (in steps of 1) 
Controls the brightness of the acquired image.
--contrast -100..100% (in steps of 1) 
Controls the contrast of the acquired image.
Turn on quality scanning (slower but better).
Do a quality white-calibration
--gamma-table 0..255,... [inactive]
Gamma-correction table. In color mode this option equally affects the
red, green, and blue channels simultaneously (i.e., it is an intensity
Gamma-correction table for the red band.
Gamma-correction table for the green band.
Gamma-correction table for the blue band.
--exposure 0..1000% (in steps of 1) [inactive]
Manual exposure adjustment.
Enable infra-red scan mode.
Enable multi-sample scan mode.
--frame 0..0 [inactive]
Selects the number of the frame to scan
--power-save-time <int> 
Allows control of the scanner's power save timer, dimming or turning
off the light.
Newer scanners can utilize this paper length to detect double feeds.
However some others (DM152) can get confused during media flush if it
Tells page-flipping document scanners to flip the paper back to its
original orientation before dropping it in the output tray. Turning
this off might make scanning a little faster if you don't care about
manually flipping the pages afterwards.
Type ``scanimage --help -d DEVICE'' to get list of all options for DEVICE.
List of available devices:
kbare@musicality:~$ dpkg -l sane-utils
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
ii sane-utils 1.0.23-3 amd64 API library for scanners -- utili