Tuesday, June 3, 2014

Scribble Pen, a real Color Picker Pen?

I wrote a blog post a while ago called "Color Picker Pen". This pen had a color sensor and could change the color of the ink to match. There weren't a lot of technical details available on the pen, but what I read was enough to convince me that this pen is fiction. I recently found out about another pen that's under development which just might be real. I could find nothing suspicious in their press release and emails, and it seems like the miniaturization technology might just be available today.

Meet the Scribble. Ok,.. cute name, but is this one real?  The website says that they will be having a Kickstarter campaign. I sent an email to their "info" email address, and I got a human-generated reply. So far, so good. 

The Scribble pen

The website and email provided some technical details. The pen uses an ARM 9 processor, has a rechargeable 325 maH lithium battery, 1 Gb of memory, and communicates through Bluetooth or micro USB. At the very least, this shows that they have actually through through some of the details.

Unlike the Color Picker Pen, they also demonstrate some knowledge of basic color science. The Scribblers had the foresight to include a white LED as part of the sensor. They use cyan, magenta, yellow, and black inks instead of the RGB inks in the Color Picker. And another detail shows that they have (at the very least) thought through some details here is that they also mention the use of white ink.

Why white ink?

Why do they add white ink, you may ask? My desktop printer doesn't use white. The printing press that printed my copy of the Edmund Optics Swimsuit Issue used CMYK inks, but no white. Why would this fabulous pen need white?

There are two reasons why white is used when mixing stuff to get colors. White flood-coat is often used on clear packaging to back up the standard inks. This provides opacity that is not found in the substrate or the inks. Much like writing with a red pen on black paper, the ink wouldn't show up without a base of white. But, I suspect that this isn't the reason that the engineers of the Scribble Pen added the complexity of white ink.

If I want to print a pink highlight with an ink jet printer or on a web offset press, the approach is pretty simple. Don't put much ink down. Just a dribble of magenta ink, or just a sprinkling of tiny halftone dots. But if you are searching for that same color to paint your wall, you need a different solution. You need the same volume of paint, just less color. When mixing up a can of paint, the paint mixologist first reaches for a can of white base. 

You see something similar when you can look at the Pantone fan deck, which includes the recipe for each of the thousand-plus colors of ink. Pantone 217, for example, calls for 1 part of rubine red ink and 31 parts of something called "transparent white". Transparent white is unpigmented ink, and would look transparent (not actually white) if printed by itself.

The Scribblers may actually be using ink that contains white pigment (titanium dioxide or zinc oxide, maybe). But I think it's more likely that it is more likely that they use a transparent white ink. It would be neat to write on black paper with a pen, but I would guess that it is nearly impossible to get any sort of decent opacity with the amount of ink dispensed with a pen. Think about how much "ink" that a WhiteOut dispenser spits out.

Color sensor

I was told a tiny bit about the sensor in my email from Scribble. It is an RGBC sensor. This means they collect light through a red, green, and blue filter, like practically every digital camera in the world. But they add a "C" filter, which mean "clear". That is, the fourth channel measures all the light together: red, green, and blue.

Why RGBC, you might ask? Digital cameras with this fourth channel are a relatively new development. Here is an article about the RGBC imager in Google's Moto X cell phone. The big selling point for the extra channel is that you get better sensitivity when the light is low, since the C channel sees about three times more light. 

This is a trick that the human eye plays. There are actually four light sensors in the eye. We have the equivalent of red, green, and blue sensors (the rods) that we use when the lights are bright. When the lights get low and the mood romantic, we make use of our rods, which are more sensitive to light. It's a cool design, but it does mean that we can't see color very well at night. 

Just like black and white TV, the rods can't distinguish color. The Moody Blues lamented this at the end of Nights in White Satin:

Cold hearted orb that rules the night,
Removes the colors from our sight,
Red is gray and yellow, white,
And who decides which is right,
And which is ... an illusion.

A legendary album about color perception

Which makes me wonder why they chose that sensor rather than a straight RGB sensor. I mean, they want to measure color, right? I have a few thoughts, but obviously I can't speak for the designers.

The whole "better performance at low lighting levels" thing might have been the motivator, but I'm not sure that's such a big deal. If I am taking pictures of my buddies getting drunk at the bar, I want high sensitivity to low levels of light because the lighting in the bar is low. But the Scribble pen has a white LED, so they should theoretically have enough light. If the sensor picks up a low light level, then it's likely to be a dark object. 

Then again, maybe dark objects are where the four channel can really help?

Another possibility... RGB sensors aren't good at measuring color. Yes, really. They're not. I have a whole bunch of technical papers on the topic, including this one Why Do Color Transforms Work?  Having a fourth channel might help a tiny bit, but probably not much.

Here's another thought. Years ago before computers were ubiquitous, color separation was done as an integral part of scanning. The image through a red filter would determine how much cyan was needed, the image through a green filter would determine magenta, and the image through a blue filter would determine the yellow. Black ink was determined by using no filter.

I'm thinking that might not be the reason that the Scribblengineers decided on an RBGC sensor, though. My explanation is pretty arcane, and since they have a computer in this device, they could come up with way much more better algorithms.

So, I don't know why they chose this sensor. I'm not saying it's a bad idea. It might be slightly advantageous. Or maybe it's cost effective. I dunno. 

How about the ink mixing?

One thing that puzzled me was how the ink was mixed. The email I got from Scribble was intentionally mute on how they do this part, due to patent stuff. But, it seems like a lot of mechanics to be stuffed into such a little package. I am not an expert here, but I wondered whether it is even possible.

So I did a little patent searching. I found an interesting patent, that is, if patents can be called "interesting".  I have no information about whether the good folks at Scribbler do anything like this particular patent. I have no idea of whether they know of this patent. It's from a little company called HP and is titled a "Writing instrument with user-controlled ink color". Ink jet heads from at least three inks (CMY) feed into a tiny mixing chamber, where it is transferred to the roller ball. 

Pen from US patent #6,749,355 

This patent was filed back in 2002, so evidently twelve years ago someone in HP felt that such a thing could be built. Funny thing about patents, BTW. To get a patent, it must be "reduced to practice". Contrary to what you would normally think, this isn't a requirement that you actually build and test your invention. You can "reduce an invention to practice" just by describing it. Writing the patent application in enough detail is a way of reducing the invention to practice. Go figger. So, I don't know whether this HP invention was ever built. HP did eventually abandon the patent, which usually means that they decided it wasn't worth paying the maintenance fees.

Another feature of the HP invention is that one embodiment includes a color sensor. I quote from the patent: 

The embodiment of FIG. 4 incorporates a scanner (151). This scanner (151) is preferably a three element Charge Coupled Device (CCD) array. Each of the three elements detects photons of a particular wavelength, i.e., color. 

Thus, when the scanner (151) scans a color, the three elements of the CCD array will output signals indicative of the ratio of each of the three primary colors in the scanned color. Consequently, the pen (100b) can be programmed to duplicate those ratios of the three colored inks in the cartridge (102) to reproduce the color scanned by the scanner (151). 

Consequently, the user can sample a color with the scanner (151) from any object at hand. The pen (100b) will then write in that sampled color.

This appears to describe many of the features of the Scribble pen. Uh-oh. Does that mean that the Scribble pen would infringe? That's a deceptively simple question. First, you need to look at the claims to determine infringement. Disclaimer: I am not a patent attorney, and I haven't spent the time to do a thorough analysis, but I did notice one thing in the first claim. In order to infringe this claim, the pen must have a button for every color of ink. So, it looks like the Scribble pen as described would not infringe on claim 1 of this patent. But as for claim 2, who knows? I will leave that up to someone else to decipher. 

But, to do a complete "freedom to operate", one would have to do a thorough patent search, and then do this sort of analysis for every claim in every relevant patent that turns up. In doing so, one would probably stumble upon US patent #8,292,527, which lists a fellow by the name of Kia Silverbrook as one of the inventors. I have heard this name before. As of March 26, 2014, Silverbrook has 246 times more US patents than I do. I guess that's sorta impressive. He's got more patents than God, Thomas Edison, and Shaquille O'Neal put together; 4,665 and counting.

I did not spend a lot of time digging up prior art. I would do this if I were to be submitting a patent application (just to make sure the claims were reasonable) and also to get a sense of what can be built without infringing. My meager prior art search turned up quite a few other patents that could be interesting, so I am going to take a wild guess that deciding on freedom to operate might get a bit involved.

There are a few conclusions here. First, it would appear that the technology to do the Scribble pen exists today or will exist soon. This bodes well for the Scribble folks. Second, it appears that the patentscape might perhaps be a bit rough. Without further investigation, it's hard to say whether this will be an issue for them.

Output colors

Ok... now it's time for me to vent. And scratch to scratch my head. Their press release states that the "innovative pen ... can reproduce over 16 million unique colors." Come on. Really? Where does this number come from?  

First, I'm gonna say straight out that the number did not come from a color scientist. I wrote a very entertaining blog about how many colors there are, and then another where I gave the definitive answer: 346,005. I'm sorry. There aren't 16 million colors in the universe, so you can't produce that many colors. That is, if you define "color" to mean "a unique visual sensation". The image below shows nine "unique" shades of pink. If you can see a difference between them, then perhaps you are able to sense 16 million colors.

Nine of the 16 million purported colors

Of course, I'm just being persnickety about the definition of the word "color", but still, it's a BS number. It's likely that the sensor has three outputs which are each eight bits. That would give 16 million possible inputs to the software. That's not the question though. The question is how many distinct outputs there are. How many distinct levels are there for each of the six inks?

That's the end of my rant on 16 million. Now for the head scratching part. Assuming that they computed the 16 million based on 256 levels for each of three channels R, G, and B... What happened to the C channel? Remember? The sensor is an RGBC sensor. Four channels of eight bits would give 4.3 billion colors. 

Or maybe they are talking about the total number of distinct ink mixtures that they can make? That's an interesting combinatorial problem that I don't want to get into right here.

Ok, so the 16 million number is probably marketing hype. Certainly not any sort of proof that the whole idea is bogus.


In the Color Picker Pen post, I came to the conclusion that the pen that was portrayed was not anything real. In the case of the Scribbler pen, I didn't find any red flags. As far as I can tell, they know what they are doing. It  isn't a final product - I mean, they are doing a Kickstarter to fund the product development. But from the limited information that has been made available, it all looks legit.

But, all the usual disclaimers hold. I am not a patent attorney, and I am not an investment counselor. For that matter, my wife would probably tell you that I can be an idiot at times. My personal liability in your investment in the Kickstarter campaign is limited to the amount of money that you paid me for the opinion. So far, I think that's zero.


  1. I am still skeptical about this. So they have already all the details (down to the weight of 39 grams) but no demostration video? Not even for a clumsy prototype? And what's this Capacity value - "1 Gb or 100,000 colors", so they require 10Kb to store a single color value?

    I also wonder how this will work in practice when you change colors - since there is probably still the previous color in the mixing tank, would I have to scribble on some draft paper until the new color replaces the old one?

    I suspect that what they really have working is that digital pen. But since that kind of technology is not really new anymore and wouldn't create enough press for their Kickstarter campaign they manage to create some buzz with this design study, But hey I'd love to be proven differenty.

  2. The 100,000 Color limitation doesn't necessarily mean that each color takes 10KB, considering that we know that the pen will contain some kind of software considering that it contains a full SoC and logical operations even if limited in scope.

    Further, said swatches can be named and have a timestamp added to them, so additional space would be added that way, even if it is a trivial increase.

    Still, considering that Scribble's Blog states that their sensor is only 16-bit (and confirmed multiple times, including in their Kickstarter campaign with phrases like "You can progamatically add more colors via our mobile app without worrying about what is captured in the Pen sensor."), the ability to store 100,000 colors is frankly pretty arbitrary.

    Still, there is certainly a use-case for storing two "named colors" that by pure happenstance are the exact same, however unlikely that may be.

    My larger concern is Scribble's dogmatic insistence that they use dyes rather than pigments, and their claims of being able to write or draw in any color on any writing surface, including over existing writing using any color you desire, including white. Using a pigment, yes, that is certainly a possibility, but with a dye... not so much.

  3. Hi Guys, i just came across this blog today and just discovered the existence of the scribble pen, but i nowhere found a possibility to order one. Did the company go bust, or ? Pleased to hear if you know where i could order sucu gadget pen. Cheers, R

  4. The kickstarter program for the Scribble Pen was cancelled by the administrators of the program as the Scribble people could not provide them with enough documentation. Then Scribble developers had a try at doing it on a fund raising program called Tilt. Despite quickly reaching the funding goal it too was cancelled by the program administrators at Tilt because Scribble could not produce convincing documentation that it was anything beyond a scam. If you go to the official website put up by Scribble and use
    firefox to attempt to open their blog to read what is currently happening you will get a warning from Firefox telling you the site will steal your information. If you go to the official scribble pen website it will always show that you have only 1 day left to order. So basically it seems to have been set up as a scam from the very beginning and now several years after the announcement it continues to lure people into the scam.

  5. Available pigments don't fully absorb light (preventing reflected color wavelengths), so we have to add a fourth pigment to compensate for this limitation.