Method for calculating focal length and object distance of video monitoring system
When the distance between the object and the lens is very far, the lens's amplification factor equals to focal length/object distance. Using this formula, one could calculate another quantity when two of the quantities were known. For example, if one knew the focal length and the object distance of the lens, one could calculate the focal length, or if one knew the focal length and the focal length, one could calculate the object distance, etc. In addition, in a conventional camera lens, if you want to calculate the focal length, you can also calculate it according to Formula 1: F = wD / W or Formula 2: F = hD / H. Here, F is the focal length of the lens, W is the width of the image (the width of the image of the object on the LCD target), W is the width of the object, D is the distance from the object to the lens, and h is the height of the image (the height of the object on the LCD target). And the relevant parameters needed to be determined according to the different specifications of the LCD target surface (such as 1/3": 4.8×3.6mm;1/2": 6.4×4.8mm;2/3": 8.8×6.6mm;1": 12.7×9.6mm, etc.). Read more exciting novels for free
Distance and the focal length of glasses
The relationship between the distance and the power of the glasses was: the power of the glasses = 10000/distance (in centimeters). As for glasses for short-sightedness, the focal length corresponding to the degree was related to the distance of the far point. The degree of short-sightedness could be seen as a concave lens of the same degree in the eye. The far point was the focal length of the concave lens, and the focal length of the concave lens was the inverse of the focal length, that is, focal length x focal length = 1. For example, if you have 50 degrees of nearsightedness, the focal length can be calculated to be 2 meters according to the relationship between focal power and focal length. This is also the distance of the far point when you have 50 degrees of nearsightedness. The distance between the far point of the myope and the front of the eyeball is equal to the focal length of the concave lens needed to correct the myope. For example, the far point of-2.0D myope is 50cm in front of the eye, and the far point of-4.0D is 25cm in front of the eye. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Method for adjusting focal length of laser processing machine
There are the following methods to adjust the focal length of the laser cutting machine: The first method: Since the spot of light at the focal point of the laser cutting machine is the smallest, press the "burst" button to determine the focal length according to the size of the spot. The specific operation was to place an object under the laser head, adjust the height of the laser head, and when the laser head was at different heights, press the "Burst" button to observe the size of the light spot. First, adjust the position of the laser head to a large extent, find the height area of the laser head with a small light spot, and then adjust the height of the laser head in this area. When the light spot is the smallest, it can be considered the best height of the laser head when cutting objects. The second method was to determine the focal position of the laser cutting machine based on the depth of the laser on the object during the self-test. Put an object under the laser head and adjust the height of the laser head. When the laser head is at different heights, press the "locate" button for more than 3 seconds. When the depth of the drawing is the deepest, it can be considered as the best height of the laser head. The method to adjust the focal length of the laser marking machine is as follows: First of all, the length from the center of the concave lens to the point where the light converged was the focal length. The laser could only achieve the maximum power and effect when it was at the focal point. The concave lens of the laser marking machine was combined into a field lens and installed on the vibrating mirror. The focal length could be adjusted by lifting the workbench. The mechanical principle was that the four corners of the workbench were supported by four light circles, and there was a screw rod in the middle. There were four guide sleeves on the base of the workbench, and a set of nut mechanism in the middle. The nut was transmitted by a pair of conical gears turning 90 degrees. There was a handle rotating in front of the workbench to adjust the height of the workbench. After that, he used the laser software to create any text and checked the continuous marking. Then, he pressed the start marking button. During the laser work, he adjusted the height of the scanner to make the laser reach its strongest state (the strongest state was the dazzling blue-white light emitted by the laser, accompanied by a loud buzzing sound). After finding the focal length, he could use a ruler to measure the distance between the scanner and the surface of the object. This distance would be used as a fixed value. The next time he changed the object, the height of the scanner would reach this value again. For items with different levels, the focal length can be quickly determined by adding an external light source. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Method for converting lens glass radius and focal length
Based on context alone For a thin lens, there is a certain relationship between the focal length (f) of the lens and the radius of curvature (R) of the lens surface. This relationship can be expressed by the lens maker's formula: For a bicive-concave or bicive-concave lens,<<</>>(<</><<</><<</><</>>>/>></>>>,<<</>>/>If it is a plano-concave lens or a plano-concave lens, one of the curvatures has an infinite radius. If the refraction index of the lens is known, as well as the curvature radius of the lens, the focal length of the lens can be calculated by the above formula. However, it should be noted that this formula was based on the thin lens. In practical applications, for thick lenses, a more complicated optical model was needed to accurately describe the relationship between focal length and radius of curvature. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
I want to know the relationship between shooting distance and focal length
There was a certain relationship between the shooting distance and the focal length. First of all, the shorter the focal length, the larger the shooting range, and the smaller the subject in the picture. For example, in a surveillance lens, a 12mm lens is more suitable to see people at 10m. Different lenses have corresponding field of view. According to the field of view, the distance between the camera and the object or the width of the object to be seen, the installation distance or the viewing range can be calculated. From the perspective of the viewing range, the focal length of the lens determined the viewing range of the camera, and the focal length was inverse to the angle of view (short focal length, large angle of view; long focal length, small angle of view), and the shooting distance was one of the elements that determined the scene. In photography, these factors influenced each other. For example, a short focal length could capture a larger range of objects even if the shooting distance was relatively close, while a long focal length could capture a larger image ratio when the shooting distance was far. In addition, the focal length and depth of field were also inverse (short focal length, large depth of field; long focal length, small depth of field), and the shooting distance would indirectly affect the depth of field effect. Under different shooting distances, in order to achieve the ideal depth of field effect, it might be necessary to adjust the focal length. In terms of perspective, the perspective of the image was only related to the shooting distance, not the focal length. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
objective focal length
The focal length of an objective lens is an important factor in an optical system. There were many methods to measure the focal length of an objective lens. The fixed-focal length collimator method had a large measurement range and high accuracy. The relative error was generally less than 1%. It was a commonly used measurement method. In a telescope, the multiplying power was equal to the focal length of the objective lens divided by the focal length of the eyepieces. In terms of aperture, the F value was the ratio of the focal length of the objective lens (f) to the perimeter of the entrance pupil (D). Different types of telescopes or instruments had different focal length values of the objective lens. For example, the focal length of an astronomical telescope was 400mm, and the focal length of the objective lens of the ZWJ - 851 Collimator was 200mm. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
On the application of focal length
In the field of photography, focal length was widely used. When shooting portraits, different focal lengths would produce different effects. For example, a focal length of 85mm was a better choice for close-up portraits, which could show a more natural facial features ratio. When shooting close-up portraits with a focal length of 17mm (a wide-angle focal length), the parts close to the lens such as the mouth, nose, and arms would be magnified, easily deformed, and the ratio of the character to the background would be exaggerated. As the focal length increased, the ratio of the character to the background would become more natural, the distance between the five facial features would be shortened, and the face would become flatter. The hairstyle would look thicker, and the face would not be so sharp. For the lens label, if the focal length label on the lens had two numbers (such as 17 - 40mm), it meant that it was a zoom lens, covering the focal length from 17mm to 40mm; if there was only one number (such as 50mm), it was a fixed-focus lens. The smaller the number, the shorter the focal length, the wider the angle of view, and the wider the viewing range. The picture could accommodate more elements but the proportion of each element was small. The larger the number, the longer the focal length, the narrower the angle of view, and the narrower the viewing range. The picture could accommodate fewer elements but the proportion of each element was larger. In some simple self-made microscopes (such as the glue stick microscope with an adjusted focal length), the focal length needed to be adjusted to observe the object (such as garlic film). <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Calculating the length of retirement
There were several ways to calculate the length of retirement: 1. ** Continuous calculation method (continuous calculation of working age)**: For example, if an employee is transferred from Unit A to Unit B, his working time in Unit A and Unit B shall be counted as continuous working age. If an employee is wrongly dealt with and is later reexamined and rehabilitated, the time of the wrong treatment can be counted as continuous service years with the time of continuous service years before the wrong treatment and the working time after rehabilitation. 2. ** Consolidated calculation method (combining the consecutive years of service)**: It refers to the employee's work experience. If there is a break for a period of time that is generally not due to the subjective reasons of the employee, the time of this break will be deducted. The two working hours before and after the break will be combined for calculation. For example, the continuous working hours of retired workers and staff before retirement and after rejoining the work can be combined. 3. ** Working Age Conversion Method **: For workers who are engaged in special types of work and work in special working environments, their continuous working age can be converted. For example, miners working underground or workers who work in low-temperature workplace below 32 degrees Celsius or high-temperature workplace above 100 degrees Celsius, when calculating their continuous service years, each year of work in such places can be counted as one year and three months. In the industries of refining or manufacturing lead, mercury, arsenite, phosphorous, acid, chemistry, military and other industries, the employees who are directly engaged in work that is harmful to their health will be counted as one year and six months for each year they are engaged in such work. In addition, the calculation method of military service was that the year of enlistment was counted as one year of military service regardless of the month of enlistment. The year of retirement was also counted as one year of military service regardless of the month of retirement. However, social security was calculated based on the month of actual enlistment to the month of actual retirement. At the same time, the retirement salary was related to the number of years of contribution, the base of contribution, the retirement age, when to participate in the insurance, when to retire, where to retire and other factors. The calculation method of retirement salary was the total number of years of contribution (commonly known as the length of service) ×3, among which, if it was more than 7 months but less than 12 months, it was calculated as 1 year. It should also be noted that the length of service was generally divided into the number of years of actual payment of pension insurance, as well as those who seemed to have "missed" but could actually "make up" the number of years of payment. The identification of the number of years of payment required the corresponding supporting materials. The novel "Ten Years of Death" is equally exciting. Everyone is welcome to click and read it!
Normal focal length of glasses
Normal glasses included short-sighted glasses and far-sighted glasses (presbyopic glasses). The focal length was related to the degree of the glasses. For short-sighted glasses, the degree and focal length were in an inverse relationship, that is, the shorter the focal length, the higher the degree. For long-sighted glasses (presbyopic glasses), the degree of the concave lens (far-sighted lens) was positive, and there was a similar relationship between the degree and focal length. To be specific, the power of the lens was equal to 100 divided by the focal length (in meters). For example, a 100-degree spectacles would have a focal length of 1 meter. However, it was not clear whether "normal glasses" were short-sighted or farsighted, so it was impossible to determine a specific focal length value. This was because different degrees of glasses had different focal lengths. From correcting mild vision problems to high vision problems, the focal length would vary greatly. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Staircase camera focal length
For a relatively narrow environment such as stairs, a 2.8mm focal length camera could generally be used. Its field of view was larger and the range that could be seen was the largest. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
The focal length of the surveillance camera
In an optical system, the focal length of the surveillance camera was the distance from the optical center point of the lens to the camera's CCD-based/CMOS-based sensor. It can also be understood as the distance from the center of the lens to the focal point of the light when parallel light is incident. The size of the focal length determined the image size, field of view, and depth of field of the surveillance image. Generally speaking, the larger the focal length, the farther the view, and the smaller the field of view. The smaller the focal length, the closer the view, and the larger the field of view. The focal length of mainstream surveillance cameras was generally 2.8mm, 3.6mm/4mm, 6mm, 8mm, 12mm, 16mm, etc. Some even had a zooming function. Cameras with different focal lengths are suitable for different monitoring ranges. For example, for situations where the monitoring range is small and the viewing angle is large, such as a family living room, small shops, etc., you can choose a surveillance camera with a smaller focal length.(For example, a 3.6mm or 4mm focal length camera can have a viewing angle of 75°-90 °, an effective monitoring distance of more than 5 meters, and can cover 40 - 80 degrees of space); for a larger monitoring range (such as a space of 10m * 10m), you need to choose a surveillance camera with a larger focal length. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>