Size of scanner CCD, in number of elements

[Steven Ruttenberg]

Epson V700 CCD board rear view, I was unable to identify anything as to give a clue of which sensor the V700 actually uses.

Ahh, ok

[Ted Baker]

Epson V700 CCD board rear view, I was unable to identify anything as to give a clue of which sensor the V700 actually uses.

The sensor on the Epson are supposed to use pixel shift, with two rows of sensors ofset half a pixel wide.

[Steven Ruttenberg]

That is interesting. I had not heard that. Wonder what happens on the V850.

[Ted Baker]

That is interesting. I had not heard that. Wonder what happens on the V850.

I think they all have it, that why it's a 6 line ccd instead of 3. Also pixel shift does not quite work as well the marketing would have it. This seems to tally with performance.

[coisasdavida]

The sensor on the Epson are supposed to use pixel shift, with two rows of sensors ofset half a pixel wide.

A lot o people replicate this idea, but I have not found an actual source/confirmation of this info.
Back in 2008, a user of this forum even explained the math behind the 4800 dpi, 2 lines of 20400 pixels, offset half a pixel.

[coisasdavida]

This seems to tally with performance.

So it is a 2400/3200 dpi scanner, depending on the lens used.

[Pere Casals]

The sensor on the Epson are supposed to use pixel shift, with two rows of sensors ofset half a pixel wide.

The Epson V700-850 may include a sensor similar to the TCD2964BFG

In page 3 of the TCD2964BFG datasheet https://www.glynshop.com/erp/owweb/D...TCD2964BFG.pdf shows the pixel alignment



It looks that the second row has shifted half a pixel, but I guess that the effective separation is close to a full pixel, because the sensitive area of the photosite is smaller than the theoric surface in the arrangement:



In that image we see an area sensor (not linear) including microlenses on the photosites to use a larger effective surface.

Well, it's clear that in that kind of arrangement the information from a row 4um row it is completed after the sensor has advanced 64+64+6 = 134um.

So the a row of the film it is not scanned in one shot, it will take dozens of steps to allow to pass all sensor rows over the film row, so some dozens of film rows are being scanned in course at the same time.

[Pere Casals]

So it is a 2400/3200 dpi scanner, depending on the lens used.

No, it's a true 6400 dpi hardware scanner for a 5.9" wide scan, and true 4800 dpi hardware for a full bed scan. As manufacturer specifies.

There are 6 rows in the sensor: 2 green, 2 red and 2 blue, this is two RGB sets: a half of the rows are shifted to take the (inter-pixel) space that was not scanned by the "first" set of rows. ("first" because in fact both sets are interlaced, as the image shows in previous post)

Because of the opto-mechanical design (mirrors, lenses, vibrations) this delivers 2000 to 2800 dpi optical neat perfomance, depending on the scanning settings and the axis.

All scanners deliver less optical performance that hardware dpi... In the case of the Epson V7/8 there is a lower than usual yield because the targeted manufacturing cost. They distributed the manufacturing budget in the way they could obtain best performance at the intended cost. This is mass production mentality.

A winner mentality, because today they own a market niche.

[Ted Baker]

A lot o people replicate this idea, but I have not found an actual source/confirmation of this info.
Back in 2008, a user of this forum even explained the math behind the 4800 dpi, 2 lines of 20400 pixels, offset half a pixel.

It in the marketing documentation, they refer to it as ... Epson Double CCD technology

http://content.epson.it/maco/technol...anners/ccd.htm

But there is no information on how it's implemented, when my scanner breaks I will pull it apart and find out for sure. I would also like to understand in more technical details on the scanner. For example what is the spectral sensitivity of the sensor etc.

So it is a 2400/3200 dpi scanner, depending on the lens used.

More or less but with added modest improvement that pixel shifting allows.

The Epson V700-850 may include a sensor similar to the TCD2964BFG

...

In that image we see an area sensor (not linear) including microlenses on the photosites to use a larger effective surface.

Well, it's clear that in that kind of arrangement the information from a row 4um row it is completed after the sensor has advanced 64+64+6 = 134um.

So the a row of the film it is not scanned in one shot, it will take dozens of steps to allow to pass all sensor rows over the film row, so some dozens of film rows are being scanned in course at the same time.

This is pixel shift, what not clear is how the algorithm in this particular scanner is working, for example how does it work when the stepper motor is driven at much greater steps. When you scan at say 1200dpi what happens? How is X pixel data merged with Y pixel data?

[Pere Casals]

More or less but with added modest improvement that pixel shifting allows.

Ted, I disagree. It is a 200% real improvement. Of course the lens has to match that performance to get the real improvement in the result.

If you review how linear sensors have evolutioned you will find that the pixel in the middle (of the second set) effectively takes just the area that was not covered by the first set.

It can be said that shift is half a pixel... but in fact is a full photosite shift, in terms of sensitive area, and this physically multiplies hardware dpi density by 2.

Look, the modesty of the improvement comes from optical limitations of the rest of the system. In fact a 6 rows arrangement has clear advantages over having the same pixel count in 3 rows, and is the preferred arrangement, single problem is that 6 rows instead 3 is a more expensive part, I think that this is well known.