Noise in laser imaging. Penumbrol imaging is a technique

Chapter 4, Problem 80E

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QUESTION:

Noise in laser imaging. Penumbrol imaging is a technique used by scanning companies for imaging objects (e.g., X-rays and lasers) that emit high-energy photons. In IEICE Transactions on Information & Systems (Apr. 2005), researchers demonstrated that penumbrol images are always degraded by noise, where the number x of noise events occurring in a unit of time follows a Poisson process with mean \(\lambda\). Suppose that \(\lambda =9\) for a particular image.

a. Find and interpret the mean of x.

b. Find the standard deviation of x.

c. The signal-to-noise ratio (SNR) for a penumbrol image is defined as \(SNR=\mu/\sigma\), where \(\mu\) and \(\sigma\) are the mean and standard deviation, respectively, of the noise process. Find the SNR for x.

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QUESTION:

Noise in laser imaging. Penumbrol imaging is a technique used by scanning companies for imaging objects (e.g., X-rays and lasers) that emit high-energy photons. In IEICE Transactions on Information & Systems (Apr. 2005), researchers demonstrated that penumbrol images are always degraded by noise, where the number x of noise events occurring in a unit of time follows a Poisson process with mean \(\lambda\). Suppose that \(\lambda =9\) for a particular image.

a. Find and interpret the mean of x.

b. Find the standard deviation of x.

c. The signal-to-noise ratio (SNR) for a penumbrol image is defined as \(SNR=\mu/\sigma\), where \(\mu\) and \(\sigma\) are the mean and standard deviation, respectively, of the noise process. Find the SNR for x.

ANSWER:

Answer

Step 1 of 3

(a)

Researchers demonstrated that penumbral images are always degraded by noise.

The number  of noise events occurring in a unit of time follows a Poisson process with mean

Suppose that  for a particular image.

We are asked to find and interpret the mean of

A random variable  is said to have a  Poisson probability distribution if and only if

         

…………(1)

A random variable  possessing a  Poisson probability distribution with parameter  then

Since we have given  for a particular image.

Hence we can write the mean of

Hence the mean of  is  in unit of time.

And the meaning of this is that the average of 9 noise events in a unit of time.


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