DLP Projector

Sequential Imaging

In a projector with only one chip, each colour has to be projected in turn, Sequentially, one after the other.

Sequential Imaging

Wheel Speed, Segments

The first generation DLP projectors, incorporated a colour wheel that rotated sixty times per second (60Hz or 3600 RPM). With one red, green and blue segments in the wheel, updates on each colour happened 60 times per second.

This baseline 60Hz rotation speed in the first generation products is also known as a "1x" speed.

The second generation doubled the rotation speed - referred to as 2x Speed (120Hz, or 7200 RPM).

Today, DLP projectors designed for the home cinema market incorporate a six-segment colour wheel which has two sequences of red, green, and blue. This wheel still spins at 120Hz or 7200 RPM, but because the red, green, and blue is refreshed twice in every rotation rather than once, the industry refers to this as a 4x speed.

The ultimate projection system. The move away from the single chip, removes all the associated issues. Occupying the very high end, Ultra Bright projector category. With a brightness 16,000 and over, suitable for 3D Mapping. Projectisle are the only Australian website authorized to sell high end Barco, Digital Projection, Panasonic 3-chip projectors

Vivid Sydney - 3D mapping

Laser Phosphor Technology based on 1-chip Technology.

Using a single blue laser and one micro-mirror-device engine (DLP chip).

A phosphor wheel and a colour wheel generate the red, green and blue coloured parts of a picture, providing natural colour representation.

• Natural colours and good brightness uniformity
• High brightness
• Excellent white reproduction
• Compact size

Blue Laser phosphor

RB Laser Technology based on 3-chip DLP Technology

3-chip projectors generate the three coloured parts of a picture in parallel. RB laser systems use two blue and a red laser. Green is produced from one dedicated blue laser via a phosphor wheel. Having two blue lasers improves colour representation and brightness uniformity.

• Excellent colours and very good brightness uniformity
• High brightness
• DCI (Digital Cinema Initiative) compliant colour space

3-chip using Red and Blue Lasers

Laser Phosphor Technology based on 3-chip DLP Technology

Primary colours are created from the two blue lasers, Green created with a phosphor wheel. Generates improved colour and brightness uniformity.

• Excellent colours and very good brightness uniformity
• High brightness
• DCI (Digital Cinema Initiative) compliant colour space

3-chip using two blue Lasers

RGB Laser Light Source with 3-chip DLP Technology

RGB laser uses the so-called ‘pure laser’ technology. Red, green and blue lasers are delivered directly to the 3 DLP image chips. The product of this technique creates a light pipe consisting of absolutely pure light that is split into the three RGB components.

The light is emitted in very narrow RGB bands with very distinct spectral frequencies. This technology allows the creation of a large colour space that easily exceeds even that of Adobe-RGB or DCI and can already cover the demanding Rec. 2020 colour space.

• Best colours and brightness uniformity
• Highest brightness
• Adobe-RGB, DCI compliant, Rec. 2020

3-chip using Red, Green and Blue Lasers

Rainbow Effect

Unfortunately, the downside to the single chip system is that a colour wheel projects the primary colours sequentially (one after the other). This means that in any one instant, there is only one colour on the projection screen, unlike 3LCD systems that project all three primary colours in one hit. Single chip DLP relies on the slow response of the human eye to combined the colours to create the full colour image in the viewers mind.

Upon release of the first generation machines, it became apparent that a small but vocal percentage of the population were experiencing headaches from either seeing colour breakup more commonly known as the "Rainbow Effect" or from the sequencing of the colours. One point that must be considered with public projection systems using

Single chip and the possible effect on Epileptics.

Although not always visible to the naked eye. The rapid flashing Due to the sequencing of colours produced by the single chip system, has been noted to make some epileptics feel ill.

The color wheel speed improvements have reduced this considerably.Yet there is still a small fraction of the population who are sensitive to them.

How to see the Rainbows

To see the rainbow artifacts, spread your fingers and wave your hand in front of your face. While watching a DLP image or move your eyes (see diagram 1) quickly from left to right, as if watching a Tennis match. Picture 2 shows a bad case, this is created from the projection of a single white circle and using the eye movement technique. For those of you that don't have the classic white circle DVD, picture 3 shows an example of when the rainbow effect is most visible compared to an LCD projector.

Brightness drop

The introduction of the colour wheel to the light path also reduces the brightness of the projector. This means that more powerful lamps must be used to achieve the same lumens as similar LCD machines. The increased lamp power subsequently produces more heat which is dissipate with faster fans - producing more noise.

If we consider the opration during projection. The light switches on and off between each segment. More segments mean more off time and the percentage of the wheel that is coloured glass is higher. A four segment colour wheel, gives higher brightness than using six segments with the same wattage lamp. In fact a six segment colour wheel can be 75% of the brightness of a 4 segment colour wheel

To reduce the brightness drop a white (clear) segment has been added. This is fine for data presentations, but it creates a disparity between the brightness of colours and the white content of the image. People in the industry often deny this. But it was introduced to boost brightness, QED it is brighter than the existing system.

This disparity can be seen more when the data projector is used for video. DLP home theatre projectors do not have the white segment. Although some cheaper brands are using them in Home theater machines.

If the white segment is passing through the full lumens of the projector the colour segments may only be passing 50% of this. LCD projectors do not have this disparity and subsequently colours look more vibrant.

Dithering Artifacts

The mirrors on the digital micro mirror device have two positions on or off. Unlike LCD which can project shades by varying the light transmission of the LCD panels DLP can not be partially on. In the on position the mirror reflects light. In the off position no light is reflected - black is projected. DLP systems uses Dithering to project Grey. The process involves increasing the DLP mirrors switching speed. So that only a partial amount of light is projected compared to the normal on time. As with the sequential colour projection, your eye is not supposed to perceive this rapid switching and only see the desired grey. The side effect of dithering is that it can produce some visible instability in solid colours especially in darker areas of the image. This instability is commonly referred to as dithering artifacts.