Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

Chapter 47 Fingerprints on the Envelope (Addition for 20230305143137924 Silver)

Lasers have biological effects.

Just a very special thing, high school students all know that this thing has wave-particle duality.

Fluctuate to give it energy.

Particles to give it impact.

Lasers with specific wavelengths can react with biological proteins, which is the principle of laser development of fingerprints.

In Lu Chuan's intermediate fingerprint collection skill card, there is an analysis of the effect of different wavelength lasers on fingerprint collection.

However, 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 damage.

Of course, fingerprints on leather and clothing can also be developed using this method.

However, the corresponding laser wavelengths are different.

With the instrument, Lu Chuan quickly completed the collection of fingerprint information on the envelope.

However, this is not the end.

What the economic investigation side needs is the result of fingerprint comparison.

Lu Chuan was more excited.

Because, the basic fingerprint identification and analysis skills rewarded by the system finally came in handy.

Prior to this, whether it was the arson case in the southern suburbs or the sinking corpse case in the reservoir, although Lu Chuan had made great contributions to fingerprint collection.

But in terms of comparative analysis, it has basically never been involved.

This time is different, Lu Chuan will complete from collecting fingerprints to analyzing and identifying fingerprints.

"Ding"

"Basic task: Complete an excellent fingerprint identification analysis to determine the identity of the fingerprint owner."

For the fingerprint collection on the envelope, although with the help of frequency conversion laser spectrum analyzer, the fingerprint was developed, but the integrity is not high.

Moreover, many of the 39 fingerprints collected were superimposed together.

What Lu Chuan has to do now is to compare and analyze all the fingerprints and find their owners as much as possible.

The first step is to preprocess the fingerprint.

For the comparison of fingerprints, the prerequisite is that the preprocessing of fingerprints should be in place
Fingerprint preprocessing includes many steps, and different fingerprint preprocessing requirements are different.

In general, fingerprint preprocessing can be divided into two categories.

One is to adjust the shape of the fingerprint, and the other is to mark the fingerprint feature points.

The shape is adjusted because the fingerprints extracted on different carriers have different shapes from the fingerprints collected normally.

For example, the index finger of the same person leaves fingerprints on a flat surface, because they are not disturbed by the outside world, the fingerprints are round and regular in shape.

However, if the finger is held on the water glass, the fingerprint will be affected by the friction force and will be slightly deformed. 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 a long ellipse.

Preprocessing is to eliminate the influence of strength and carrier shape on fingerprints as much as possible, so as to increase the success rate of fingerprint comparison in the later stage.

The purpose of marking feature points is to identify and compare fingerprints.

Any collected fingerprint can mark characteristic points such as end points, bifurcation points, and bifurcation points on the lines.

Fingerprint identification is to use these points to judge the similarities and differences of fingerprints.

Basic fingerprint identification and analysis skills make Lu Chuan handy in fingerprint preprocessing.

Compared with the previous fingerprint pretreatment, Lu Chuan feels smoother.

In front of the computer screen, a fingerprint was zooming in front of Lu Chuan's eyes.

Lu Chuan did not use complex drawing software to adjust the fingerprints, but used the fingerprint adjustment software in the fingerprint automatic comparison system to adjust the shape.

In fact, many criminal police who are in charge of 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, it can only perform limited adjustments to the fingerprint.

And the adjustment range is limited.

But Lu Chuan is just the opposite. All the experience instilled in Lu Chuan in the basic fingerprint identification and analysis skills is completed through the image processing software that comes with the fingerprint comparison system.

In this way, there is an advantage that the legitimacy of the comparison result is higher.

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 gap between the lines.

This is equivalent to changing the feature points of the fingerprint in a disguised form.

This is also the reason why some people can successfully compare the same fingerprint after processing, while others fail to compare after processing.

Ordinary image processing software, without any restrictions, can make unlimited adjustments to fingerprints during preprocessing.

Therefore, many fingerprint comparisons need to be re-checked by two or even three people to confirm whether the identification is successful.

And 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 processing of fingerprints.

In front of the computer, Lu Chuan's eyes widened with excitement.

Processing fingerprints is different from what most people imagine. 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 tormenting.

Of the 39 fingerprints preprocessed, Lu Chuan successfully completed 27.

The remaining [-] fingerprints, because of serious superimposition and too many breakpoints, with Lu Chuan's current strength, there is no way to perform valuable preprocessing.

However, 27 fingerprints...

That's enough.

The preprocessing of the fingerprints was over, and it was already past four o'clock in the afternoon.

The rest of the work is much simpler.

Just input 27 fingerprints into the system for automatic comparison.

Of course, it does not mean that the system comparison is successful and the fingerprint identification analysis is successful.

In other words, if the system comparison is unsuccessful, the identification and analysis of the fingerprint will fail.

In the current criminal investigation system, the automatic fingerprint comparison system will compare fingerprints with similarities and similarities according to the characteristic points of fingerprints.

Completely different fingerprints will be excluded immediately, which is the so-called fool comparison.

This is actually very fast, just a comparison of data.

The so-called feature point does not mean marking a point and just drawing a circle.

Instead, after certain calculations, the angle and coordinate data of each feature point are displayed in the form of coordinate axes.

Only then are the comparisons performed within the system.

Among these data, the data of some feature points of some fingerprints must be the same.

These fingerprints are automatically listed.

And according to the same number of data, sort from high to low.

The data of all the feature points are all the same, which means that the fingerprint comparison is successful.

After the system was running on its own for comparison, Lu Chuan turned on the phone.

Checking WeChat, there are more than a dozen unread messages.

Mom: "I'll go out with your dad during the eleventh holiday, so you should work overtime."

Ever since he went to college, Lu Chuan suddenly had the feeling that he was really paying for his phone bill.

When I was in high school, it should be said that 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 eleventh holiday, do you want to accompany her?"

Lu Chuan grinned, and decisively deleted old Comrade Lu's information.

I go with you?
Ha ha.

Most of the remaining information belonged to a few classmates.

What caught Lu Chuan's attention was a message from 3 minutes ago.

　Thanks for the reward 20230305143137924, big brother Baiyin, I wish you good luck like Donghai Shoubi Nanshan, be a bridegroom every day and a bride every night!
　　
　
(End of this chapter)