Whatever happened to pico projectors embedding in phones?

iPad smBack around 2007 when I was at Syndiant we started looking at the pico projector market, we talked to many of the major cell phone as well as a number of PC companies and almost everyone had at least an R&D program working on pico projectors.  Additionally there were market forecasts for rapid growth of embedded pico projectors in 2009 and beyond.  This convinced us to develop small liquid crystal on silicon (LCOS) microdisplay for embedded pico projectors.  With so many companies saying they needed pico projectors, it seemed like a good idea at the time.  How could so many people be wrong?

Here we are 6 years later and there are almost no pico projectors embedded in cell phones or much else for that matter.   So what happened?   Well, just about the same time we started working on pico projectors, Apple introduced their first iPhone.    The iPhone overnight roughly tripled the size of the display screen of a smartphone such as a Blackberry.  Furthermore Apple introduced ways to control the screen (pinch/zoom, double clicking to zoom in on a column, etc.) to make better use of what was still a pretty small display.   Then to make matter much worse, Apple introduce the iPad and tablet market took off almost instantaneously.    Today we have larger phones, so called “phablets,” and small tablets filling in just about every size in between.

Additionally I have written about before, the use model for a cell phone pico projector shooting on a wall doesn’t work.   There is very rarely if ever a dark enough place with something that will work well for a screen in a place that is convenient.

I found that to use a pico projector I had to carry a screen (at least a white piece of paper mounted on a stiff board in a plastic sleeve to keep clean and flat) with me.   Then you have the issue of holding the screen up so you can project on it and then find a dark enough place that the image looks good.    By the time you carry a pico projector and screen with you, a thin iPad/tablet works better, you can carry it around the room with ease, and you don’t have to have very dark environment.

The above is the subjective analysis, and the rest of this article will give some more quantitative numbers.

The fundamental problem with a front projector is that it has to compete with ambient light whereas flat panels have screens that absorb generally 91% to 96% of the ambient light (thus they look dark when off).     While display makers market contrast number, these very high contrast numbers assume a totally dark environment, in the real world what counts is the net contrast, that is the contrast factoring in ambient light.

Displaymate has an excellent set of articles (including SmartPhone Brightness Shootout, Mobile Brightness Shootout 2, and Smartphone Shootout 2) on the subject of what they call “Contrast Rating for High Ambient Light” (CRHAL)  which they define as the display brightness per unit area (in candela’s per meter squared, also known as “nits”) of the display divide by the reflectivity of ambient light in percent by the display.

Displaymate’s CRHAL is not a “contrast ratio,” but it gives a good way to compare displays when in reasonable ambient light.  Also important, is that for a front projector it does not take much ambient light to end up dominating the contrast.  For a front projector even dim room light is “high ambient light.”

The total light projected out of a projector is given in lumens so to compare it to a cell phone or tablet we have to know how big the projected image will be and the type of screen.   We can then compute the reflected light in “nits”  which is calculated by the following formula Candelas/meter2 = nits = Gn x (lumens/m2)/PI (where Gn is the gain of the screen and PI = ~3.1416).   If we assume a piece of white paper with a gain of 1 (about right for a piece of good printer paper) then all we have to do is calculate the screen area in meters-square, multiply by the lumens and divide by PI.

A pico projector projecting a 16:9 (HDTV aspect ratio) on a white sheet of notebook paper (with a gain of say 1) results in 8.8-inch by 5-inch image with an area of 0.028 m2 (about the same area as an iPad2 which I will use for comparison).    Plugging a 20 lumen projector in to the equation above with a screen of 0.028 m2 and a gain of 1.0 we get 227 nits.  The problem is that same screen/paper will reflected (diffusing it) about 100% of the ambient light.   Using Displaymate’s CRHAL we get 227/100 = 2.27.

Now compare the pico projector numbers to an iPad2 of the same display area which according to Displaymate has 410 nits and only reflects 8.7% of the ambient light.   The CRHAL for the iPad2 is 410/8.7  = 47.   What really crushes the pico projector by about 20 to 1 with CRHAL metric is that the flat panel display reflects less than 10th of the ambient light where the pico projector’s image has to fight with 100% the ambient light.

In terms of contrast,to get a barely “readable” B&W image, you need at least 1.5:1 contrast (the “white” needs to be 1.5 brighter than the black) and preferably more than 2:1.   To have moderately good (but not great) colors you need 10:1 contrast.

A well lit room has about 100 to 500 lux (see Table 1 at the bottom of this article) and a bright “task area” up to 1500 lux.   If we take 350 lux as a “typical” room then for the sheet of paper screen there are about 10 lumens of ambient light in our 0.028 m2 image from used above.   Thus our 20 lumen projector on top of the 10 lumens of ambient has a contrast ratio of 30/10 or about 3 to 1 which means the colors will be pretty washed out but black on white text will be readable.  To get reasonably good (but not great) colors with a contrast ratio of 10:1 we would need about 80 lumens.   By the same measure, the iPad2 in the same lighting would have a contrast ratio of about 40:1 or over 10x the contrast of a 20 lumen pico projector.   And the brighter the lighting environment the worse the pico projector will compare.    Even if we double or triple the lumens, the pico projector can’t compete.

With the information above, you can plug in whatever numbers you want for brightness and screen size and no matter was reasonable numbers you plug in, you will find that a pico projector can’t compete with a tablet even in moderate lighting conditions.

And all this is before considering the power consumption and space a pico projector would take.   After working on the problem for a number of years it became clear that rather than adding a pico projector with its added battery, they would be better off to just make the display bigger (ala the Galaxy S3 and S4 or even the Note).   The microdisplay devices created would have to look for other markets such as near eye (for example, Google Glass) and automotive Heads Up Display (HUD).

Table 1.  Typical Ambient Lighting Levels (from Displaymate)

Brightness Range

Description

0 lux  –

100 lux  –

500 lux  –

1,000 lux  –

3,000 lux  –

10,000 lux  –

20,000 lux  –

50,000 lux  –

100,000 lux  –

100 lux

500 lux

1,500 lux

5,000 lux

10,000 lux

25,000 lux

50,000 lux

75,000 lux

    120,000 lux

Pitch black to dim interior lightingResidential indoor lighting

Bright indoor lighting:  kitchens, offices, stores

Outdoor lighting in shade or an overcast sky

Shadow cast by a person in direct sunlight

Full daylight not in direct sunlight

Indoor sunlight falling on a desk near a window

Indoor direct sunlight through a window

Outdoor direct sunlight

10 comments

  1. Ian says:

    Having developed a picoprojector and bought and used several others I have to say I agree with everything here. Of course, to use a tablet you need to carry an extra (quite large) device. I can also see a possible application for a stand alone 200 lumen projector to connect to, and be recharged by, a laptop for projection of TV-sized images for small meeting presentations. Meeting rooms can be dimmed.

    • admin says:

      Ian,

      Thanks for the feedback.

      There certainly is a market but it is relatively small for “traveling professionals.” The problem is that when you are traveling and you don’t know if a projector or TV is going to be available, you usually also don’t know if the lighting conditions and/or room arrangement are going to be conducive to using a projector while you know for sure your laptop screen or tablet will at least work in any indoor environment. Yes, usually meeting rooms can be dimmed (although I have been in a few where they can’t), but I have been in meeting rooms where curtains can’t be drawn and the room is too bright.

      If there are only a few people in the meeting then a laptop or tablet will work. If the room is larger, then it will usually already have a projector or large TV screen in it and/or the room it not conducive (lighting and/or a good place to project to) for using a 200 or so lumen projector.

  2. admin says:

    I received a comment from an anonymous email address which asked some questions but also include some rude comments in it. I have copied the questions below and will follow up with my reply:

    Comparing a projector to an iPad seems like a specious argument to me. I’ll play your game and pose you a question: Can you tell me the CRHAL, weight and/or logistics for carrying an iPad with a 200 inch display on it? How does it compare to a pico projector that can project a 200 inch display?

    Why is it that you are the only person that possess such expert knowledge of the subject while other companies are wasting 100′s of millions developing pico technology FOR mobile devices?

    How is it that OSRAM recently won the “Electronic 2012 PRODUCT of the YEAR” award for their green laser diode where they specifically state, and I quote, “the green laser diodes represent a milestone in the development of miniature projectors for mobile devices such as smartphones and cameras?”

    • admin says:

      Projecting a 200-inch image from a pico projector is a marketing stunt and not a typical or realistic real world use. A 200-in diagonal image in HD aspect ratio has an area of 12 square meters! If we assume a pico projector with 20 lumens (the upper end of what has been embedded in any product) that gives about 1.6 Lux and if projected on a white screen with a gain of 1.0 on a ridiculously small 0.5 nits. Consider that a very dimly lit room as more than 1 LUX of ambient light.

      Unless the room is nearly pitch black the image is going to be totally washed out. SMPTE recomments 48nits for a high quality viewing experience so you need about 100 times the brightness for 2000 lumens.

      As to “Electronic Product Awards,” this is also more of a marketing competition than any measure of commercial viability. If you look at OSRAM’s product offering to date they only support 50mW of green at about 520nm which translates to about a 7 to 8 lumen projector (using LBS or LCOS).

      Even the most optimistic pricing I have hear for the direct green lasers make them ridiculously too expensive for the light they product to be used in a projector. They are apparently finding some market in $260 to $600 gun sights (I estimate in the few 10′s of thousands). A green LED supporting more than 10 lumens is more on the order of $2.

      There are some very large projectors starting to use frequency doubled (IR converted to green) lasers, but the direct green lasers required by pico projectors are not even close to being viable in terms of lumens/Watt of energy or lumens/dollar.

  3. kristie coffey says:

    Have you seen microvision a (available embedded the size of a penny) projector. Less battery consumption and always in focus with red, green and blue laser. 50 lumens? Why aren’t they using this?

    • admin says:

      I’m afraid you are buying into the hype and not looking at the reality of laser beam scanning by Microvision.

      You are not seeing it because it does not exist at a price even close to what somebody is willing to pay. Additionally a 50 lumen laser scanning projector would have serious safety concerns (laser illuminated projectors were the light is spread out over the area of the entire display is a different matter). I don’t think that even Microvision has officially claimed they have a 50 lumen projector only that it would be possible someday.

      First off the the lasers requires are very expensive (many hundreds of dollars to produce a green laser for scanning with enough light output). Microvision’s demonstrated products are extremely power inefficient (look through this blog for my actual measurements of Microvision systems) so that “less battery consumption” is a marketing claim unsubstantiated by facts.

  4. Interesting article.

    Wireless Mobi Solution (WMS) will be launching our Movi 1Q17. It is an Android OS smartphone with an embedded LED HD pico projector.

    http://www.moviphones.com

    • KarlG says:

      I will be interested to see how your product does. The web site only says it is, “DLP High Definition (HD) pico projector”. I’m assuming from this that the projector is a 720p DLP as you would have said it was “Full HD” if it was 1080p. Your site also does not give the lumens.

      When is the product going on sale?

      • Hello Karl.

        Sorry. Yes, you are correct. It is a DLP 720p pico projector. The lumens is 50.

        It was an oversight not to call out the lumens and calling out 720p during the design phase of the website and we have not been able to updated the website to reflect the latest specs. The front facing camera is now 13 MP, which was a new update, too.

        We have a collateral sheet that calls out the lumens, 720P, contrast, aspect ratio, 1280×70 and auto focus. I’d be happy to share with you if you want to email me.

        Please lets stay in touch. I’d like to share with you when our crowdfunding campaign kicks off.

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