SCIENCE & TECHNOLOGY

Technology of 3D cinema
Cinema — the biggest entertainment system in the world, has already been through two major revolutions. First revolution was the transition from silent to talkie, and the second was from black and white to colour. Cinema is now ready for the next major revolution: 3D (three-dimensional), i.e. movies with depth perception.

The red and blue glasses in the goggle allow only one of the projected image to enter each eye.The polarised filters allow only one of the images formed by the corresponding polarisation axis into each eye.
The red and blue glasses in the goggle
allow only one of the projected image
to enter each eye. (Image courtesy:
www.howstuffworks.com)
The polarised filters allow only one of the images formed by the corresponding polarisation axis into each eye. (Image courtesy: www.howstuffworks.com)

Anorexia changes bone structure
A new study presented at the annual meeting of the Radiological Society of North America (RSNA) showed that children and teenagers with even mild cases of anorexia, an eating disorder, exhibit abnormal bone structure.

Prof Yash Pal

Prof Yash Pal

This Universe
Prof Yash Pal
If we start an engine it can run a machine and can simultaneously generate electricity through a generator to charge batteries, which can further be utilised to run a machine and that machine can again generate electricity and so on. Can this chain power generation and utilisation go on for an unlimited period and a generation house can be built?
 


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Technology of 3D cinema
D. S. Chhabra

Cinema — the biggest entertainment system in the world, has already been through two major revolutions. First revolution was the transition from silent to talkie, and the second was from black and white to colour. Cinema is now ready for the next major revolution: 3D (three-dimensional), i.e. movies with depth perception.

The depth perception in a photograph, movie, or any other two-dimensional scene is created by presenting to each eye an image of a scene shot at slightly different angles, similar to the perspectives that both eyes naturally receive from an object (stereoscopic vision).

The stereoscopic vision system relies on the fact that the pupils of our eyes are spaced about 6.5 centimeters apart.

Therefore, each eye sees the object from a slightly different perspective, and our brain fuses the two images into one, creating depth perception.

Apart from providing entertainment experience, 3D technology can be used for training pilots, doctors, technicians, and soldiers.

The first generation 3D technology in which viewer has to wear special type of goggle to see the characters popping out of the screen, was invented decades ago.

Such 3D movie shows are available in a few theatres and science centres abroad as well as in some science centres in our country. Pushpa Gujral Science City (PGSC), Kapurthala is the nearest science centre to Chandigarh which projects 3D cinema shows to the public, making them aware of the technology.

The latest technology in which the viewers are not required to wear any goggle has been developed for 3D gaming on PC monitors. However, the commercialisation of this technology will take place in due course of time after receiving the positive market feedbacks.

The following are the technologies for creating and viewing 3D effects:

1. Coloured glasses

The goggle fitted with red and blue/green glasses was used in many older 3D movies.

In this system, two images are projected on the screen, one in red and the other in blue or green colour. The colored glasses in the goggle allow only one image to enter each eye, and the brain does the rest.

However, this type of goggle can not really be used for a colour movie because colors are used to provide separation between two images. So the image quality is not nearly as good as in other technology which uses goggle fitted with polarised sheet glasses.

2. Polarised glasses

The preferred method for viewing a 3D movie uses polarised filter sheet in the goggle because they allow viewing coloured movies with improved picture quality. In this technique, two synchronised projectors throw images each with orthogonally aligned polarisation axis, onto a silver screen. Silver screen is preferred so that polarisation is preserved.

The projectors receive their outputs from a computer with a dual-head graphics card. Since the filters in the goggle also have their polarisation axis orthogonally aligned, only one of the image is allowed to enter into each eye.

If the linearly polarised filter sheets are used, the viewer is required to keep his head at one level because tilting of the viewing filters will cause the images of the left and right channels to bleed over to the opposite channel thereby diluting the 3D effect. Therefore, to enhance the effect, circularly polarising filters of opposite handedness are used to project and view the images.

The viewer wears goggles containing a pair of circularly polarising filters of opposite handedness. Light that is left-circularly polarised is extinguished by the right-handed polariser; while right-circularly polarised light is extinguished by the left-handed polariser.

3. LCD shutter glasses

These goggles are used to view 3D visuals displayed on a compatible LCD or CRT monitor, or HDTV capable of delivering 3D visuals. The goggle consists of a pair of special glasses with lenses that are capable of opening and closing rapidly. Its wireless IR base plugs into an USB port. The IR base sends the required signals to the lenses to flicker on and off.

4. Latest Technology - No glasses required

This technology does not forces the user to wear any kind of glasses. Using this technology, last year Philips has launched 3D television in UK which sends two images of the same scene shot at slightly different angles to each eye using lenticular lenses (array of micro-magnifying glasses) embedded in the screen. This tricks one’s brain into seeing images floating in front of the screen.

The displays can have multiple viewing zones allowing multiple users to view image at the same time. One can play a variety of video games in full 3D with images appearing to pop out of the computer screen. Home movies are also moving towards 3D. The day is not far when people will be able to enjoy high-fidelity, immersive experiences of 3D movies in their homes.

The writer is former Consultant, PGSC, Chandigarh and Ex- Dy. Director,
CSIO, Chandigarh


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Anorexia changes bone structure
K.S. Parthasarathy

A new study presented at the annual meeting of the Radiological Society of North America (RSNA) showed that children and teenagers with even mild cases of anorexia, an eating disorder, exhibit abnormal bone structure.

Miriam A. Bredella, the lead author of the study and musculoskeletal radiologist at Massachusetts General Hospital (MGH) used high-resolution, flat-panel, volume computed tomography (VCT) to identify differences in bone structure between the anorexic patients and the healthy controls. Radiology published the study in its December issue.

VCT allows the examination of bone at high resolution with relatively low radiation exposure making it a suitable technique to evaluate bone structure in adolescent patients.

The subjects of the study were 10 girls, aged 13 to 18, with mild anorexia and 10 age-matched girls without the disorder. CT exam revealed structural differences between the groups. DXA which uses two x-ray beams of different energies to determine bone density, did not reveal structural differences.

“Adolescence is the most critical period for growth of bone mass, and the onset of anorexia interferes with that process,” Bredella, noted.

The researchers observed that though bone mineral density did not differ significantly between the patients and the control group, there were significant structural differences, indicating that changes in bone structure begin to occur in anorexic patients well before decreases in bone density.

“Impairment of bone development may alter bone structure permanently and increase the risk of fractures and osteoporosis in adult life.” She cautioned.

Anorexic patients suffer many health problems including bone loss. Normally, physicians rely on DXA to test bone mineral density (BMD) in adolescents with anorexia.

Reassuring values of BMD obtained by using DXA may not reflect the true status of bone structure in this under-nourished population. “In patients with anorexia, bone structure should be analyzed to detect abnormal bone health”, Dr. Bredella asserted

“How did you explain the benefit versus risk equation to the volunteers particularly to the control children and their parents?” I asked.

“There are no direct benefits to the participation in the study and the children and their parents were aware of this” she conceded.

“The radiation dose of the VCT of the wrist is very low (0.027 mSv), which is about the same as the dose an average person receives from background radiation in 3 days”, she explained.

To the query “How the results of the investigation will benefit treatment of anorexia?” she replied that treatment of osteoporosis may be initiated earlier. “It will be important to determine whether therapies that increase BMD will concomitantly improve bone structure in this patent population”, Dr Bredella clarified.

All research protocols have to go through the scientific review committee and the Institutional Board. Obtaining informed consent is a must. The MGH team complied with these requirements.

Is the study relevant in India? In Indian Pediatrics (2007), the researchers at the Christian Medical College, Vellore reported that eating disorders are prevalent among children and adolescents in India are similar to that in Western and non Western countries. We must use unique technologies that help to alleviate human suffering.

K.S. Parthasarathy is former Secretary, Atomic Energy Regulatory Board

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This Universe
Prof Yash Pal

If we start an engine it can run a machine and can simultaneously generate electricity through a generator to charge batteries, which can further be utilised to run a machine and that machine can again generate electricity and so on. Can this chain power generation and utilisation go on for an unlimited period and a generation house can be built?

When you use your engine to generate electricity, you can never get all the energy of the engine into electricity. You must have noticed that the engine gets hot. This means that a lot of the energy is being wasted as heat.

There would be other losses due to friction in the bearings, also in the fan used to cool the engine. And do not forget that the engine also produces sound, which is also a form of energy.

Now you use the electricity generated to run a motor. Here also you have to worry about the efficiency of conversion. The power lines would get hot. If you are using alternate current machine the produced current would also radiate some of the energy away. 

Yes, you will be able to generate  fresh electricity  using the secondary motor , but it will be significantly less than that of the first generator.  You will certainly not be able to get the same amount as you did the first time.

This is a general law. You lose some at every step. Therefore it is impossible to make a perpetual motion machine.

Why do we put our hand/fingers on the eye centre when we try to remember something? Is it that it is a memory point in our brain or just an imitation going on from generation to generation?

Putting your hand or finger on your eye when you are trying to remember something might be to stop distraction by visual sensations coming through your eyes.

But every one does not do the same thing. For example I tend to close my eyes and tap on the side of my head. 

We humans develop different habits. I just discovered that sometimes I close my eyes and tap on the forehead!

Readers wanting to ask Prof Yash Pal a question can e-mail him
at palyash.pal@gmail.com.

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