DLP vs LCD Projectors

I'm using 4 DLP projectors (Dell 5100MP) for my tabletop display system and so far they are giving me a lot of troubles. First, it produces rainbow artifacts when the display is seen through a camera. Now, it produces significant flickering when projecting through an optical shutter. The LCD projector does not produce such artifacts. It seems like we should have gone for the LCD projectors at the very beginning. I think by understanding better how each of them works will allow us to make better decisions in the future and also for the current research.

LCD Projector
LCD (liquid crystal display) projectors contain three separate LCD glass panels, one each for the red, green, and blue components of the video signal. Each LCD panel contains thousands (or millions) of liquid crystals that can be aligned in either open, closed, or partially closed positions to allow light to pass through. The alignment is controlled by the electric field between the two transparent electrodes on the two sides of the liquid crystal molecules. The projector typically sends light through special dichroic filter / reflector assemblies called "dichroic mirror" that separates light to the three LCD panels. Wikipedia has a nice explanation and a diagram on how it works.

DLP Projector
DLP (Digital Light Processing) projectors use a DLP chip with reflective surface made up of millions of tiny mirrors. To define color, a color wheel is used which contains a red, green and blue filter. This wheel spins in the light path between the lamp and the DLP chip and alternates the color of the light hitting the chip. The mirrors tilt away form or into the lens path based upon how much each color is required for each pixel. In the most expensive DLP projectors, there are three separate DLP chips, one each for the red, green and blue channels. They are usually over $10,000 and do not use a color wheel.

Rainbow Artifacts and Flickering
The wheel based DLP projectors produce rainbow artifacts because of the sequential color updating from the wheel. As the color wheel spins, the image on the screen is either red, green or blue at any given instant in time. Since LCD projectors and 3-chip DLP projectors always deliver a constant red, green, and blue image simultaneously, they do not create rainbow artifacts.

Under a switching optical shutter, flickering occurs with the 1-chip DLP projector because the period of the rotating wheel does not match with the period of the optical shutter.

Source: http://www.projectorcentral.com/lcd_dlp_comparison.htm

Notes on David Rose's TED Talk on How to Pitch to VCs

Things to Convey
Integrity, Passion, Experience, Knowledge, Skill, Leadership, Commitment, Vision, Realism, Coachability

Timeline of Your Presentation
The moment you walk into the door, you are going to take the VCs on an emotional ride. The overall arc of your presentation should start like a rocket. Use the first 10 - 30s to grab the attention. And then take them on a solid, steady, upward path right from the beginning to the end. Everything should be reinforcing this and it should get better, better and better. And in the end, boom! You should make them excited, ready to write you a check and throw money on you.

How to do this?

• Logical progression: Don't skip a step and go backwards. First, talk about what the market is? Why are you going to do X, Y, Z? And how are you going to that?
• Thing VCs know or can relate to: relate back to the world.
• Validators: outside references, sales, award, people has done before, beta test is doing well .
• Believable upsides: revenue in 5 years (a million, not a upside; a billion, not believable).
• Avoid downsides: 
• Things VCs know that are not true.
• Things they don't understand: need to make a leap to think about it. This will stop the flow of the presentation.
• Things make them think: need to take them step by step without being patronizing.
• Internal inconsistencies: e.g. numbers in sales.
• Typos, errors, unpreparedness.

What to Include in Your Presentation

• Company logo
• Quick 15-30s intro to grab the attention (a factor, something counterintuitive, a story, an experience)
• Quick business overview: 2 sentences (we built widgets for the X, Y, Z market; we sell service to help someone to do X) to put everything in context.
• Management team: past experience
• Market: size
• Product: what is it? A screenshot of the website or a canned demo (no live demo). Why people would buy it?
• Revenue (business) model: how are you going to make money on a per unit basis? Who are your customers?
• Strategic relationships: distribution, producing partner. This is good for validation. 
• Competition: even it is an old way of doing something. This allows the VCs to judge how you fit in all these and how you are special.
• Barrier to entry
• Financial overview: 1-2 years backwards and 3-5 years forward (5 may be too much, 4 is rational). Translate business model to a company model (how many units you are going to sell?). Give a picture of how the company will perform in the next few years.
• Use of proceeds
• Capital and valuation: who invested; did you invest yourself? your friends, family? What's the capital structure up until this point?
• Conclusion: take back to your logo and wrap up. This the final boom that should send the VCs to the space.

Parentheses

Use parentheses ( ) to include material that you want to de-emphasize or that wouldn't normally fit into the flow of your text but you want to include nonetheless.

If the material within parentheses appears within a sentence, do not use a capital letter or period to punctuate that material, even if the material is itself a complete sentence. (A question mark or exclamation mark, however, might be appropriate and necessary.) If the material within your parentheses is written as a separate sentence (not included within another sentence), punctuate it as if it were a separate sentence.

Examples:
Forty-three years after his death, Robert Frost (we remember him at Kennedy’s inauguration) remains America’s favorite poet.
Forty-three years after his death, Robert Frost (do you remember him?) remains America’s favorite poet.
Forty-three years after his death, Robert Frost remains America’s favorite poet. (We remember him at Kennedy’s inauguration.)

Source: http://www.nationalpunctuationday.com/parentheses.html

Understanding Certificates

Digital Signature

A digital signature scheme typically consists of three algorithms:

• A key generation algorithm that selects a private key uniformly at random from a set of possible private keys. The algorithm outputs the private key and a corresponding public key.
• A signing algorithm that, given a message and a private key, produces a signature.
• A signature verifying algorithm that, given a message, public key and a signature, either accepts or rejects the message's claim to authenticity.

Keyboard Shortcuts

Clear browser cache with refresh
Firefox MacOS: Cmd+Shift+R
Safari: Alt-Cmd-E

Home
Firefox Windows: Alt + Home

Eclipse shortcuts

Action	Shortcut
1. Go to the next highlighted word	Ctrl + K
2. Go to the next/previous error	Ctrl + , / Ctrl + .
3. Expand / collapse	Ctrl + Numpad + / Ctrl + Numpad -

ActiveRecord

Associations
Auto-generated methods

Singular associations (one-to-one)
                  |            |  belongs_to  |
generated methods | belongs_to | :polymorphic | has_one
------------------+------------+--------------+---------
#other            |     X      |      X       |    X
#other=(other)    |     X      |      X       |    X
#build_other()    |     X      |              |    X
#create_other()   |     X      |              |    X
#other.create!()  |            |              |    X
#other.nil?       |     X      |      X       |

Collection associations (one-to-many / many-to-many)

                              |       |          | has_many
generated methods             | habtm | has_many | :through
------------------------------+-------+----------+----------
#others                       |   X   |    X     |    X
#others=(other,other,...)     |   X   |    X     |    X
#other_ids                    |   X   |    X     |    X
#other_ids=(id,id,...)        |   X   |    X     |    X
#others<<                     |   X   |    X     |    X
#others.push                  |   X   |    X     |    X
#others.concat                |   X   |    X     |    X
#others.build(attributes={})  |   X   |    X     |    X
#others.create(attributes={}) |   X   |    X     |    X
#others.create!(attributes={})|   X   |    X     |    X
#others.size                  |   X   |    X     |    X
#others.length                |   X   |    X     |    X
#others.count                 |   X   |    X     |    X
#others.sum(args*,&block)     |   X   |    X     |    X
#others.empty?                |   X   |    X     |    X
#others.clear                 |   X   |    X     |    X
#others.delete(other,other,..)|   X   |    X     |    X
#others.delete_all            |   X   |    X     |
#others.destroy_all           |   X   |    X     |    X
#others.find(*args)           |   X   |    X     |    X
#others.find_first            |   X   |          |
#others.uniq                  |   X   |    X     |    X
#others.reset                 |   X   |    X     |    X

Explanations of some methods:

others.build(attributes = {}, …): Returns one or more new objects of the collection type that have been instantiated with attributes and linked to this object through a foreign key, but have not yet been saved.


attr_protected
Attributes named in this macro are protected from mass-assignment, such as new(attributes), update_attributes(attributes), or attributes=(attributes).

Mass-assignment to these attributes will simply be ignored, to assign to them you can use direct writer methods. This is meant to protect sensitive attributes from being overwritten by malicious users tampering with URLs or forms.