Lasers have biological effects.
Light is a very special thing. All high school students know that this thing has wave-particle duality.
Fluctuate and give 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 includes 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.
However, the corresponding laser wavelengths are different.
With the instrument in hand, Lu Chuan quickly completed the collection of fingerprint information on the envelope.
But that's not all.
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 finally came 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, basically I have 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.
Moreover, many of the thirty-nine fingerprints collected were superimposed.
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 fingerprints.
For fingerprint comparison, the prerequisite is that fingerprint preprocessing must be in place.
It's like foreplay, without sufficient preparation, it will be dry and uncomfortable.
Fingerprint preprocessing includes many steps, and different fingerprint preprocessing requirements are different.
Just like different people like different methods of foreplay, ranging from rough to gentle.
Generally speaking, 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 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 has an irregular shape of an oblong oval.
Preprocessing 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 fingerprint identification and comparison.
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.
Junior fingerprint identification and analysis skills made Lu Chuan very handy in preprocessing fingerprints.
Compared with 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 was just the opposite. All the experience instilled in Lu Chuan in the primary fingerprint identification and analysis skills was completed through the image processing software that comes with the fingerprint comparison system.
In this way, there is an advantage, which is that the legitimacy of the results is higher.
This involves a question of the degree of fingerprint preprocessing.
Processing the fingerprint shape 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 used the drawing software that comes with the fingerprint comparison system to have a greater chance of successfully passing the review.
Because the system itself limits the degree of deformation of fingerprints.
In front of the computer, Lu Chuan's eyes widened and he 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 were severely overlaid and had too many breakpoints. With Lu Chuan's current strength, there was no way to perform valuable preprocessing.
However, twenty-seven fingerprints...
That's enough.
It was already past four o'clock in the afternoon when the fingerprint preprocessing 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 automatic fingerprint comparison system compares 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 and is just a comparison of data.
The so-called feature point does not mean marking a point, just drawing a circle.
Instead, it requires certain calculations to display the angle and coordinate data of each feature point in the form of coordinate axes.
Then the comparison is done 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.
Letting the system run for comparison, Lu Chuan turned on his phone.
I looked at WeChat and saw 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 was at work, Lu Chuan no longer dared to mention what he wanted 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?
hehe.
Most of the remaining information belongs to a few classmates.
What caught Lu Chuan's attention was a message from three minutes ago.
