Recently, when purchasing projectors, we often see a parameter “display chip size”, such as the data of 0.47dmd and 0.33dmd. What does this parameter mean and what should we pay attention to in the process of purchasing?

DLP imaging technology

At present, the mainstream projectors on the market use 3lcd and DLP technology. DLP technology has become the first choice for smart projectors of Jimi, ottocode, BenQ and other manufacturers because of its excellent brightness, realistic and natural image and high reliability.

DLP is the abbreviation of “digital light processing”, that is, digital light processing, that is, this technology needs to digitally process the image signal first, and then project the light.

It is a technology to complete visual digital information display based on the digital micromirror device DMD (digital micromirror device) developed by Ti (Texas Instruments). Specifically, DLP projection technology uses digital micromirror chip (DMD) as the main key processing element to realize the digital optical processing process.

The DMD chip works by controlling the reflection direction of light by many micro mirrors. The larger the deflection angle of the micro mirror, the higher the contrast of the image, the faster the deflection speed and the lower the delay of the image. After passing through the condenser lens and color filter system, the light from the projection lamp is directly irradiated on the DMD. When the lens is in the open position, they pass through the projection lens Reflect the light on the screen to form a digital square pixel projection image. When the DMD base plate, projection lamp, color wheel and projection lens work together, these flipped mirrors can reflect the image on the demonstration wall, film screen or TV screen together.

The technology of DLP projector is reflective projection technology. With the application of reflective DMD devices, DLP projector has the advantages of reflection, excellent contrast and uniformity, high image definition, uniform picture, sharp color, disappearance of image noise, stable picture quality, and accurate digital images can be continuously reproduced and renewed for a long time.

DMD chip size

Explanation in official documents of Texas Instruments (Ti, Texas Instruments):

– A DMD is an optical micro-electrical-mechanical system (MEMS) that contains an array of highly reflective aluminum micromirrors

-DMD is an optical micro electro mechanical system (MEMS) containing a set of high reflection aluminum micro mirrors.

In the official DMD specification manual, the chip is divided into two versions: DLP Pico chipsets and DLP standard chipsets: designed for small-size, low-power portable models and high brightness and large screen models.

(small DMD chipset)

(standard DMD chipset)

DMD chip has 500000-400000 micro lenses gathered on CMOS silicon substrate. There are two mainstream sizes in the market. 0.33 inch DMD chip has 920000 micro mirrors, which can throw 1280 x 720 pixels; 0.47 inch DMD chip has 2070000 micro mirrors, which can throw 1920 x 1080 pixels.

Then why can the 0.33 inch chip in the above table also display the resolution of 1080p and the 0.47 inch chip can display the resolution of 4K? Many businesses have nominal 1080p Full HD and 4K ultra-clear in the product details page because TSP optical module is added to the chip to make one micro mirror form two pixels by dithering the micro mirror at high speed, and make use of the retention effect of human eyes to make one virtual and one real The superposition of pixels doubles the visual resolution, so that the jitter of models with only 720p and 1080p physical resolution can reach 1080p and 2160p. Theoretically, the larger the size of DMD chip, the better its imaging quality and higher light utilization.

Upstream DMD chip price and corresponding models

(comparison of low-power versions)

Among the low-energy version chips, the prices of the two 1080p chips, dlp3310 and dlp4710, are $73.49 and $148.00 respectively, with a price difference of more than double, equivalent to 478 yuan. Therefore, most 1080p models with a price of 3000 yuan on the market use 0.33 inch chips, while most models with 0.47 inch chips cost more than 4000 yuan.

(standard chip comparison)

If you compare the same size low-power chip with the standard chip, the prices of the low-power dlp4710 and the standard dlp470te are $148.00 and $227.37 respectively, and the price also differs by more than 500 yuan, which means that there are cost differences between different models using the same size chip on the market. When purchasing projection, you might as well find out when you are tangled about the price of the same size chip For the chip model corresponding to this model, if it is the same model, select the one with lower price and the one with better performance within a reasonable price range.

Ranking of common chip ladder for household projection

DMD as the “heart” of a projector “, the core components of optical and mechanical parts are an important part of the cost in both the production process and the maintenance process. However, some manufacturers do not clearly mark the specific size and model of the chip in the parameter page, confusing consumers with exaggerated and untrue product descriptions, which aggravates the screening difficulty of consumers in the purchase process to a certain extent. When purchasing a good projector, the first concern should be DMD. The larger the size of the chip, the higher the brightness and the clearer the display effect. In the environment of mostly relying on the upstream supply chain Texas Instruments, with the gradual rise of domestic brands and breaking the monopoly market of imported projectors, it is hoped that more domestic leading manufacturers will move towards the direction of self-developed optical machine chips.

How DMD can crush people to death? Take 3000 yuan gear chip as an example

At present, the projection of 3000 yuan gear on the market mainly uses dlp230np of 0.23dmd and dlp3310 of 0.33dmd. Among them, 510000 micro mirrors of 0.23 DMD are combined in the form of ⽅ dimensional array. Each micro mirror represents ⼀ pixels on the screen, 1.05 million of ⽽ 0.33dmd and ⽐ times of ⽐ 0.23dmd.

Both chips can achieve 1080p resolution through micro mirror jitter, but the methods to realize 1080p are not the same. The original resolution of 0.33dmd is 1368 * 768, which is the same as 960 * 540 of 0.23dmd, so the resolution of the core is naturally stronger, and 1080p resolution can be realized only by single axis galvanometer. ⽽ 0.23dmd can realize 1080p display with the help of double axis galvanometer.

The number of micro mirrors under 1mm2 is about 7560 at 0.33dmd and 5212 at 0.23dmd. There is a very obvious difference in the fineness and sharpness of the edge picture display. You can obviously feel it when playing dense text images. For example, if you are watching a hero League game, the ID of the player displayed on both sides of the picture may not be recognized by the naked eye because of insufficient sharpness 。

Due to the size, the projection peak brightness of 0.33dmd is higher than that of 0.23dmd. Therefore, if the nominal brightness of some projections using 0.23dmd is very high, there may be false labeling; when the minimum brightness is the same, the contrast of 0.33dmd is relatively higher and the light and dark details are richer. In some cinematography with rich details In the visual scene, the larger chip can retain the restoration degree of the scene to the greatest extent – the bright place is bright and the dark place is dark.

As mentioned above, the cost price of the chip is US $73.49 for the 0.33dmd chip and US $42.98 for the 0.23dmd chip, nearly doubling the cost, which makes many 2000 projections adopt 0.23dmd. In this price range, major manufacturers introduce their products as 1080p, and the definition is no problem. Through the residual micro mirror jitter, it can indeed reach 1920 * 1080 Resolution, but even so, there will be specific effect differences, resulting in misunderstandings in the selection process of purchase. In conclusion, in the price range of 2000-3000 yuan, 0.33dmd chip projection is a more worthy choice.