How to adjust the focal length of an old-fashioned camera lens

The focal length of the laser lens was measured as follows: 1. ** Experimental measurement method ** - ** Roughly measure the focal length of the concave lens (uncertainty not calculated)**: clearly image an object in the distance (such as the scenery outside the window or a lit table lamp more than 5 meters away in the room) on the image screen. Move the lens back and forth, and measure the distance between the concave lens and the image screen with a steel ruler. This distance is the focal length of the lens. The reading is accurate to millimeters. It is not estimated below 1 mm. - ** Measuring the focal length of the concave lens by the two-time imaging method (estimated reading: 1/2 mm, uncertainty not calculated)**: Place the object screen and the image screen on the optical bench, so that the distance between the object screen and the image screen is greater than 4 times the focal length of the lens. The distance between the object screen and the image screen was kept constant, and the concave lens was moved. The positions of the concave lens corresponding to the magnified image and the reduced image were recorded clearly on the image screen, and the focal length of the concave lens was calculated after multiple measurements. - ** Measuring the focal length of a concave lens by auto-alignment ** - ** Manual reading (uncertainty limit 0.1mm, estimated reading 1/2 division value (mm))**: Put the light source, object screen, concave lens, and reflective mirror on the optical bench in turn, move the concave lens until a clear image is seen on the object screen (the method to determine that it is a self-aligned image depends on the specific experimental situation), and record the position of the object screen and the concave lens; then rotate the concave lens around the support by 180°, repeat the above measurement, and finally calculate the focal length and uncertainty of the concave lens. - ** Laser ranging (uncertainty limit 0.2mm, minimum indication value 1mm, no estimation)**: Similarly, place the light source, object screen, concave lens, and reflective mirror on the optical bench in order. Move the concave lens until a clear image appears on the object screen. Record the position of the object screen and the concave lens. Then rotate the concave lens 180° around the support and measure again to calculate the focal length. 2. ** Calculating using optical principles **: For an ideal thin lens, the formula can be used according to the curvature radius and refraction index of the lens.(f = \frac{(n -1) \times R}{2}\)(where <f> is the focal length,<n> is the refraction index of the lens material, and <R> is the radius of curvature of the lens). For thick lenses, the thickness of the lens and the curvature radius of the two surfaces need to be considered.(<frac{1}{f} = (n-1) (<frac{1}{R1} -<frac{1}{R2} -<frac{(n - 1)d}{nR1R2})>)>, where <R1> and <R2> are the curvatures of the two surfaces of the lens, and <d> is the thickness of the lens.) 3. ** Determined according to the characteristics of the laser resonant cavity **: In the laser system, the focal length of the laser resonant cavity is related to the mode radius and the optical wavelength of the laser crystal. The focal length of the thermal lens can be determined by measuring the output power of the laser, but this process involves the influence of the thermal effect of the laser on the parameters. 4. ** Use optical design software **: In modern optical design, professional optical design software can be used to help calculate the focal length. These software can simulate the path of light in the lens and accurately calculate the focal length. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

If it is a thin lens, the focal length can be calculated according to the object-image distance formula of the thin lens. The focal length depends on the lens 'geometry (the curvature radius of the two surfaces) and the material (the material's refraction index), but also the refraction index of the medium on both sides. When it is used in air (the refraction index of the medium on both sides is approximately 1), the focal length can be calculated according to the lens manufacturer's formula. If it is a non-thin lens, the thickness of the lens must be considered when calculating the focal length. The focal length formula is different from that of a thin lens. The specific formula is [specific formula]. At the same time, according to the focal point of the lens, a lens with a real focal point (f 'and f> 0) is called a positive lens or a converging lens; a lens with a virtual focal point (f' and f <0) is called a negative lens or a diffusing lens. When the refraction index of the lens material is greater than the refraction index of the medium on both sides, a concave lens is a positive lens, and a concave lens is a negative lens. In addition, the focal length of the concave lens was related to the radius of curvature. The larger the radius of curvature, the larger the focal length, and the smaller the amplification factor. The smaller the radius of curvature, the smaller the focal length, and the larger the amplification factor. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

The focal length of a laser focusing lens could not be determined simply. Many factors needed to be considered. From the scanning range and spot diameter, as the focal length increases, the scanning range and spot diameter will increase correspondingly, but the power density will decrease rapidly, which may be unfavorable for processing. Moreover, in the F-Theta field mirror, as the focal length increased, the difference between the actual theta and tg theta would cause the distortion to increase. In terms of laser cutting, different materials and cutting requirements have different requirements for the focal point position (related to focal length). For example, for a small laser cutting machine, the distance between the focusing lens and the material (basically 50.8MM and 63.5MM, etc.), when cutting carbon steel and stainless steel, according to the thickness of the plate, the focus position (related to the focal length) needs to be adjusted to achieve better cutting quality. When the focus of the fiber laser cutting machine is in the best position, the slit is the smallest and the efficiency is the highest to obtain the best cutting result. In the laser marking machine, the focal length of the focusing lens would also affect the effect after focusing. Under ideal circumstances, the position of the focusing point depended on the focal length and the angle of the lens, and the scanning range of the focusing lens was affected by the focal length. Over-increasing the scanning range may cause problems such as the spot becoming thicker and distorting. Therefore, it is necessary to judge whether the focal length of the laser focusing lens is large or small according to the specific application scenarios (such as cutting, marking, etc.), the processing materials, the requirements for power density and the effect of the spot. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

The following aspects could be considered when selecting the monitoring focal length: * * 1. Choose according to the monitoring range ** 1. * * Small monitoring range and large viewing angle **: For example, in a family living room or small shops, you can choose a surveillance camera with a smaller focal length. For example, a camera with a focal length of 3.6mm or 4mm can have a viewing angle of 75 °-90 °, an effective monitoring distance of more than 5 meters, and can cover a space of 40 - 80 square meters. 2. * * Large monitoring range (10m * 10m or more)**: You need to choose a surveillance camera with a larger focal length, but a larger focal length will reduce the monitoring angle. To achieve complete monitoring, you can consider using a cloud platform ball machine or installing multiple surveillance cameras. 3. * * Surveillance range is fixed and very far away (such as monitoring a parking lot 30 meters away)**: You need to choose a camera with a larger focal length, such as a surveillance camera with a 12mm or higher. * * 2. Choose based on the usage scenario ** 1. * * Narrow space (such as garage, storage room, etc.)**: It is recommended to choose 2.8mm focal length, and the best monitoring distance is within 3 meters. 2. * * Home or small shop environment **: It is recommended to choose 4 mm focal length, and the best monitoring distance is 3 - 5 m. 3. * * Family courtyard, balcony, doorway, etc. **: 6mm focal length is recommended. 4. * * A wide outdoor area without high requirements for details **: A camera with a 4mm focal length is more suitable. 5. * * Need to capture detailed information from a distance (such as license plate number or facial features)**: A camera with an 8mm focal length is more suitable. In addition, the field of view of the surveillance camera is determined by the width, height, and distance from the surveillance camera. Once the scene to be monitored is determined, the correct choice of the focal length of the lens is also affected by the size of the scene to be monitored, the distance between the camera and the scene, and the size of the camera imagers (such as 1/3 ", 1/2", 2/3 "or 1 "). The calculation method is: f = vD/V or f = hD/H (where, f represents the focal length. When f = vD/V, v represents the vertical height of the CCD-target surface, D represents the distance from the lens to the scene, and V represents the height of the object being observed; when f = hD/H, h represents the horizontal width of the CCD-target surface, D represents the distance from the lens to the scene, and H represents the width of the object being observed). After calculating the focal length value, if there was no corresponding focal length lens, one could choose a similar model according to the product catalog. Generally, one would choose a smaller lens than the calculated value, so that the viewing angle would be larger. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

When choosing the focal length of the home surveillance camera, you can refer to the following points: 1. ** Surveillance Scene * - ** Narrow space (such as garage, storage room, etc., the best monitoring distance is within 3 meters)**: You can choose 2.8mm focal length to obtain a larger field of view and a larger monitoring range. - ** Home or small shop (optimal monitoring distance 3 - 5m)**: 4mm focal length is more suitable, wider field of view, can capture a large range of scenery, can meet the basic monitoring needs, but the picture clarity and detail display ability is average, may need a higher resolution to make up for. - ** Family courtyard, balcony, door (optimal monitoring distance 5 - 10m)**: It is recommended to choose a 6mm focal length. Its field of view and clarity are more balanced. It can provide a relatively wide field of view, and can ensure the clarity and details of the picture. The resolution requirement is also relatively moderate. - ** Open areas (such as parking lots, playgrounds, etc.)**: 4mm focal length can be used to monitor large areas, but it may not be enough in terms of image clarity and details. If you need to cover a wider area (such as parking lots, factory workshops, etc.), a 6 - 8mm focal length lens is also a good choice. If you want to monitor a very long distance (such as a parking space 30 meters away), you may need a camera with a focal length of more than 12 mm. 2. ** budget and technical requirements **: The price of high-resolution cameras is higher, and the requirements for storage and processing equipment are also higher. If the budget is limited or the technical conditions do not allow it, comprehensive consideration should be taken when selecting the focal length. For example, you cannot choose a focal length that requires too much resolution and cannot be met by your own equipment. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

Different focal lengths had different effects and uses when shooting models on the street. The 35mm and 50mm focal lengths were suitable for full-body shots, which could better interpret the background. The 50mm focal length was close to the human eye's vision and had the characteristic of " what you see is what you get ". The 85mm focal length was called the " Portrait Mirror Emperor ". The blurring effect outside the focal length was soft and beautiful, which was suitable for shooting half-body close-ups. The 105mm and 135mm focal lengths were also good choices for street portraits because of their longer focal lengths, but the long focal length would make the photographer and model far away, making communication inconvenient. The 70 - 200mm medium telephoto lens was the most commonly used lens for street shooting. Under the same aperture, the longer the focal length, the better the blurring effect. In addition, the focal length of a portrait was usually set between 50mm and 85mm because the 85mm lens basically did not distort the face and the image compression was strong. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

Old fashioned camera cartoons often have a retro look with simple lines and less detailed shading. They might focus on classic camera designs and capture a nostalgic feel.

Well, these cameras usually have a classic look, maybe with mechanical dials and a vintage color scheme. The image quality could have a certain charm, like soft focus or a bit of graininess that adds to the old-timey effect.

An old fashioned cartoon camera might have simple mechanics and a basic design. Maybe it doesn't have all the fancy digital features of modern cameras.

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>