Speccy #06 31 августа 1996

Железо

Iron - scanning device for the ZX Spectrum.

    SCANNING DEVICE


 Velichutin NV


 I think that it is not necessary to convince
all that make a decent picture in a graphics editor is much 
more complicated than the same thing to portray on paper. A

if you want these figures is not
one and not two, but dozens?

 My proposed device
help those who wish to diversify its program of beautiful
computer graphics with minimal time.

 You probably noticed that in
Journal SPECCY lot
drawings and photographs. Part
pictures transferred from your computer
IBM, the other part was obtained by
using the scanner.

 Can I make myself a
device? The answer is very simple -
require your desire and perseverance you have nastoychivost.Esli
is, and the desire to appear, then
then proceed.

 Designs scanners an enormous set. We
Naturally, we choose a design
combines the marginal
simplicity and good technical
indicators.

 On the next page you'll be able to estimate the output of the 
device. The figure shows part of the magazine pages scanned 
with a resolution of 50 dpi. For view Use

cursor either O P Q A. Exiting
viewing mode, "gap", Enter
Edit.
8
 To transmit the image in
computer it is necessary to "expand". Scan pictures
in the chosen scheme of the scanner
lower case, ie image sequence of individual points, line by 
line goes in the computer.


 To understand how
scan pictures, imagine lathe, the chuck
which is set blank.
When grinding parts cutter
ostyavlyaet on the details should be in the form
helix. If the item
Place the sheet and after the passage of
Cutter expand this list, we
see the lines that are always
will begin at one end
sheet and end in another.

 Subsequently, we detail
dwell on how and what
make the mechanical part of the scanner, and in this issue of 
the journal very detail on

optical head (incisors).

 To begin construction
optical head, in the first
place where necessary - something
to get a lens, and buy
photodiode FD 1927, producing
our domestic industry.

 All dimensions of the optical head
will depend on what
lens you can buy.
Here is the simplest method
calculation of the geometry of the head.

 In the calculations, apply the following
notation:

 s1 - the distance from the lens to
 sheet with the image;
 s2 - the distance from the lens to
 diaphragm;
 f - focal length;
 dp - the pixel size on the sheet
 paper;
 ds - diameter of the diaphragm.

 Applying the expression of geometrical optics for the lens:


         1 1 1

         - + - = - (1)

         s1 s2 f

 find


              s2 ∙ f

      s1 = (2)

              s2 - f

 Since


         dp s1

             = (3)

         ds s2

 , Then

             dp ∙ s2

      s1 = (4)

                ds
 Equating expressions (2) and (4)
find


          f (dp + ds)

   s2 = (5)

               dp

 Based on the geometric dimensions of the photodiode diameter 
holes diaphragm must be taken in

Within ds = 2 - 2,5 mm. Size
pixel is taken depending on the
what kind of resolution you want
get. At a resolution of 25
dpi dp = 1 mm at 50
dpi dp = 0,5 mm and so on.
 In subsequent calculations underlying
Scan Resolution, will be applied 50 dpi, the focal length lens 
will take equal to 10 mm. 

         10 (0.5 + 2.5)

   s2 = = 60 mm

               0,5


           60 ∙ 10

   s1 = = 12 mm

           60 - 10

 For the manufacture of optical
pick up a metal head
tube with an inner diameter
several large lenses. One of the
edges of the tube (where there will be
set the lens) can be
zavaltsevat or zapresovat
ring with an inner diameter
slightly smaller diameter
lenses.

 On the other side of the tube is better
only threaded for
install plugs that can be
manufacture of conventional bolt
He sawed off the threaded part and
propyl making a screwdriver.
 Mount lenses made
using the remote handset.
This tube can be made from the shell use black
flamastera. To
get rid of the glare, the internal
surface of the tube should be matovoy.Matovuyu surface
can be obtained if the process
the inner surface of the tube
coarse-grained sandpaper. This operation should be
be taken seriously,
as if the tube is "blikovat" you never get
good image.
 The diaphragm also can be made of any - anything black
plastic. Hole in the diaphragm
best done in a small
cone extending in the direction of the photodiode.
e Lighting sheet of paper should be
two incandescent bulbs from
flashlight. To increase the illumination area scanned surface, 
installed the reflectors. Material for the manufacture of 
reflectors can be polished sheet aluminum, tin, or stainless 
steel. 

 When installing the optical head should be possible to move it 
and fixing in the axial direction. Such movement is necessary 
to focus the image in the plane diaphragm.

 In the next figure shows
one way of mounting the optical head, bulbs
and reflectors.


n In the next issue of the journal, which will be released in 
about two month, will be described in detail

mechanism of image scanning.
I think that anyone who is interested
in the manufacture of the scanner for this
time be able to make optical
part. Well, who would overcome all
difficulties associated with the mechanics,
that can consider itself owner
scanner as electronic part,
with such a powerful army radio, do not be a problem. The 
magazine will also be published and Support Program scanning 
device for receiving information via Kempston joystick. 


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