xiaolabaDIY 的部落格

.



initial test, a better understanding if the resolution is capable to do the job.
640x480, interpolated by software.

352x288, actual output by image sensor, target is 12" 1024x768 LCD screen.
LCD screen, 248mm / 1024 pixel / 3 = 0.08mm each dot
image, 26 RGB columns = 26x3 = 78 dots
resolution = 352 / (78 * 0,08)= 56 pixel / mm = 18um / pixel

0mm extension

1.5mm extension, it is possible achieve 9um / pixel with handy focus adjustment

Note :

modification to have a smaller aperture (F number is bigger) is a must, in order to improve the Depth Of View (DOV) or Depth Of Field (DOF), or the image is not given fineness without useful view. Open the housing of the webcam and remove the lens off from the assembly, cut a piece of used carrier tape salvaged by remove the IC component inside (if you want this, send me email, I have couple 1000 of this pieces), the small hole as a 2mm diameter, it is perfect for the purpose without detail of calculation for F value.

and you can search the GOOGLE for "aperture DOV 光圈 景深"....ect.

Light source is a must and the color temperature (K value) is not important, however, color scheme must be calibrated before a usful color determination, or just look at the image itself without caution to the color mapping correspondence. LED with white or red color is able to do this job very well, the webcam itself is a 5V device connected to USB and the power is capable to drive more couple LED for this lighting purpose.


Resolution & scale improvement -

a) the Quickcam express is equipped with a Agilent CMOS image sensor HDCS-1020, an overall for low-end application with limited 352x288 pixels (RGB), however, color mapping of these RGB cells, they are one layer configuration and if the individual color cell for one pixel could be used as a 3-pixel readout, the resolution will be able to increased.

b) to include an extension tube as a common from the commercial
microscope, only drawback is the image intensity could be affected and
the magnification is limited.

c) buy another webcam with higher pixel number today, ie. 130M pixel / 500M pixel, it will be simply given the ultimate resolution and so on, the drawback is possible a lack of development software package.




The Imaging Signal Processors is STV0602, however no data sheet is avaialble from the STMicroelectronics website, perhaps a OEM model or obsolete product. STV0676, a latest model is available.

TO DO,

a) to develop an overlay of the scale image to a display;
b) to fix the light and stand for the complete assembly as a commercial microscope;
c) to extends the switch for image capture to outside a foot paddle, it will be easier for operation;

...
...
...
...


Enquiry of a want to know what it does of the Quickcam express, here your are.