Chapter 47 Fingerprints on the Envelope (Additional Update for 20230305143137924 Silver)
Laser has a biological effect.
Light is a very special thing. High school students all know that this thing has wave-particle duality.
Volatilize, giving it energy.
Particles, giving them impact.
Laser of a specific wavelength can react with biological proteins. This is the principle of laser development of fingerprints.
Lu Chuan's intermediate fingerprint collection skill card contains an analysis of the effects of lasers of different wavelengths on fingerprint collection.
A laser light source with an output wavelength of 445±5 nanometers and an output power greater than 13 watts can develop fingerprints on paper without loss.
Of course, fingerprints on leather and clothing can also be developed using this method.
It’s just that the corresponding laser wavelengths are different.
With the instrument in hand, Lu Chuan quickly completed the collection of fingerprint information on the envelope.
But this is not the end.
What the economic investigation side needs is the fingerprint comparison results.
Lu Chuan was in a rather excited mood.
Because, the primary fingerprint identification and analysis skills rewarded by the system have finally come in handy.
Before this, whether it was the arson case in the southern suburbs or the corpse sinking case in the reservoir, Lu Chuan had made great contributions in collecting fingerprints.
But in terms of comparative analysis, I have basically never participated.
This time is different. From collecting fingerprints to analyzing and identifying fingerprints, Lu Chuan will do it all.
"Ding"
"Basic task: complete an excellent fingerprint identification analysis and determine the identity of the fingerprint owner."
Although the fingerprints on the envelope were collected with the help of a variable frequency laser spectrum analyzer, the fingerprints were developed, but the integrity was not high.
And many of the thirty-nine fingerprints collected were superimposed on each other.
What Lu Chuan needs to do now is to compare and analyze all the fingerprints and try to find their owners as much as possible.
The first step is to preprocess the fingerprint.
For fingerprint comparison, the prerequisite is that fingerprint preprocessing must be in place
Fingerprint preprocessing includes many steps, and different fingerprint preprocessing requirements are different.
Broadly speaking, fingerprint preprocessing can be divided into two categories.
The first is to adjust the shape of the fingerprint, and the second is to mark the fingerprint feature points.
The shape is adjusted because the fingerprints extracted from different carriers are different in shape from the fingerprints collected normally.
For example, the fingerprint left by the same person's index finger on a flat surface is round and regular in shape because it has not been interfered by the outside world.
But if your finger is held on the water glass, the fingerprint will be affected by friction and deform slightly. In addition, the water glass is cylindrical, and the fingerprint will extend along the shape of the water glass.
The fingerprint collected in this way is an irregular shape of an oblong oval.
Pre-processing is to try to eliminate the effects of strength and carrier shape on fingerprints, thereby increasing the success rate for later fingerprint comparisons.
Marking feature points is for identifying and comparing fingerprints.
Any collected fingerprint can mark end points, bifurcation points, divergence points and other characteristic points on the lines.
Fingerprint recognition uses these points to determine the similarities and differences of fingerprints.
Basic fingerprint identification and analysis skills made Lu Chuan very handy in fingerprint preprocessing.
Compared with the previous fingerprint preprocessing, Lu Chuan felt it was smooth.
In front of the computer screen, a fingerprint was enlarged in front of Lu Chuan's eyes.
Lu Chuan did not use complex drawing software to adjust the fingerprint. Instead, he used the fingerprint adjustment software in the fingerprint automatic comparison system to adjust the shape.
In fact, many criminal police officers responsible for fingerprint comparison are unwilling to use the software that comes with the system.
Because the image adjustment software in the fingerprint automatic comparison system has a single function and can only make limited adjustments to fingerprints.
And the scope of adjustment is limited.
But Lu Chuan is just the opposite. All the experience instilled in Lu Chuan in the primary fingerprint identification analysis skills is completed through the image processing software that comes with the fingerprint comparison system.
In this way, one advantage is that the result is more legitimate.
This involves a question of the degree of fingerprint preprocessing.
Processing the shape of the fingerprint actually changes the size of the fingerprint and the gaps between the lines. This is equivalent to changing the characteristic points of the fingerprint in disguised form.
This is also the reason why some people can successfully compare the same fingerprint after processing, while others cannot successfully compare after processing.
Ordinary image processing software has no restrictions. During pre-processing, fingerprints can be adjusted without restrictions.
Therefore, many fingerprint comparisons need to be re-checked by two or even three people to confirm whether the identification is successful.
This review is actually to judge the degree of preprocessing deformation of the fingerprint.
Lu Chuan directly uses the drawing software that comes with the fingerprint comparison system, and the probability of successfully passing the review will be greater.
Because the system itself limits the degree of deformation of fingerprints.
In front of the computer, Lu Chuan widened his eyes and looked excited.
Processing fingerprints is different from what most people think. It does not mean that after entering the fingerprint image into the system, it can be compared.
This is a job that requires a very high level of detail.
Boring, boring, even torturous.
Of the thirty-nine fingerprints, Lu Chuan successfully completed twenty-seven.
The remaining twelve fingerprints have serious overlapping and too many breakpoints. With Lu Chuan's current strength, there is no way to perform valuable preprocessing.
However, twenty-seven fingerprints...
is enough.
It was already past four o'clock in the afternoon when the pre-processing of fingerprints was completed.
The rest of the work is much simpler.
Just input the twenty-seven fingerprints into the system for automatic comparison.
Of course, this does not mean that the system comparison is successful and the fingerprint identification analysis is successful.
In other words, if the system comparison fails, the fingerprint identification analysis will fail.
In the current criminal investigation system, the fingerprint automatic comparison system will compare the similarities and differences of fingerprints based on their characteristic points.
Completely different fingerprints will be eliminated at the first opportunity, which is the so-called fool comparison.
This is actually very fast, it is just a comparison of data.
The so-called feature point does not mean marking a point, just drawing a circle.
But after certain calculations, the angle and coordinate data of each feature point are displayed in the form of coordinate axes.
Then the comparison is performed within the system.
In these data, there must be certain characteristic points of certain fingerprints that are the same.
The system will automatically list these fingerprints.
And sort them from high to bottom according to the number of identical data.
If the data of all feature points are the same, it means that the fingerprint comparison is successful.
While the system was running for comparison, Lu Chuan turned on his phone.
Looking at WeChat, there are more than a dozen unread messages.
Mom: "Your dad and I will go out to play during the National Day holiday. You can work overtime."
Ever since he entered college, Lu Chuan suddenly felt as if he was really paying for his phone bills.
When I was in high school, I should say, I ate whatever I wanted.
After going to college, I can eat whatever I want.
Now that he is at work, Lu Chuan no longer dares to mention what he wants to eat.
Dad: "Your mother wants to go out to play during the National Day holiday. Do you want to accompany her?"
Lu Chuan grinned and decisively deleted Comrade Lu's information.
Shall I accompany you?
Haha.
Most of the remaining information is from a few classmates.
What caught Lu Chuan's attention was a message from three minutes ago.
Thank you 20230305143137924 Silver Boss for the reward. I wish you good luck and longevity, and be the groom every day and the bride every night!
(End of this chapter)