Machine visionlenses

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There are three general classifications for lenses related to the image field of view. A lens with a focal length close to the diagonal length of the sensor format produces an image with a near-human field of view and is considered a "normal" lens for that sensor format. A wide-angle lens has a focal length shorter than normal, which produces a wider field of view but has a tendency to exhibit barrel distortion effects towards the edge of the image. Finally, a lens with a focal length longer than normal is known as a telephoto lens, which has a smaller field of view and a greater magnification of objects in the image.

C-Mount Lens

CroppingWhen the lens format is larger than the camera format, the effect on the resultant image is known as cropping. In this case, a full image is produced but at a smaller size (i.e. cropped) because the sensor is only capturing a fraction of the complete image. A crop factor or focal length multiplier quantifies the amount of cropping and is defined as the ratio of the diagonal length of the lens' design format divided by the diagonal length of the sensor format. The crop factor for all possible 1/3", 1/2.9", 1/2", 1/1.8", 2/3", 1", and 4/3" format lens/sensor combinations are shown in the table to the right.

An image that is cropped appears as if it was taken with a lens of higher focal length (i.e. a smaller field of view), but does not magnify the image. The cropping effect can be quantified using an adjusted focal length (defined as the crop factor multiplied by the lens focal length). For example, an image taken using a 1" format, 50 mm focal length lens with a 1/2" format sensor will produce an image with an adjusted focal length of 100 mm. While the field of view is reduced as if using a 100 mm lens, objects in the image will remain at the same size. The table to the right lists all of the lenses offered on this page with the adjusted focal length for different sensor formats.

Opto Engineering lens

The focal length (FL) is roughly defined as the distance from principal plane to the focal plane. For a camera lens, the focal length determines the field of view of the camera system; the longer the focal length, the smaller the field of view. As a general guideline, a 50 mm focal length lens and 35 mm format camera combination produces roughly the same field of view as the human eye (~53° diagonal). The table below lists the focal lengths needed to achieve the same field of view as the human eye for different sensor formats.

The MVL7002 lens comes with lens caps for both ends. Due to the weight of the MVL7002, we do not suggest using it with cameras with plastic lens mounts unless the lens is supported by additional hardware.

Specifically, f-number is defined as:where f/# is the f-number, f is the focal length and d is the entrance pupil diameter.

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Camera lenses that can collect a lot of light (i.e., a low f-number) are known as fast lenses as they can be used with shorter exposure times and are ideal for low-light conditions. For example, a 50 mm focal length lens with a f/1.4 aperture has a bigger aperture and is therefore faster than a lens at the same focal length with a f/2.5 aperture. While using larger apertures increases light collection, doing so reduces the axial in-focus region of the image, known as the depth of field. To illustrate the effect of different aperture sizes visually, the table below shows a sequence of images taken with the same lens (MVL12M43 on a DCU224C 1/2" format camera) for increasing f-numbers. Because the images were taken at constant exposure, for each f/# increase (by a factor of ~1.4) the amount of light collected by the lens is reduced by half.

The MVL7002 macro lens features a removable close-up lens for imaging between 5.00" (127.0 mm) and 12.00" (304.8 mm). When removed, the MVL7002 can be used for imaging objects at distances from 19.70 inches" (500.4 mm) to infinity. The lens focus, iris, and zoom are each manually adjustable and lockable.

The aperture of the lens controls the amount of light that a lens can collect; the more light a lens collects, the brighter the image. Because of this, the aperture size affects the exposure time and therefore the speed of the camera. Thorlabs provides the maximum aperture size in the tables below for each lens in terms of the f-number, which is expressed using the symbol f/# (e.g., f/1.4). As the f-number increases, the aperture opening becomes smaller and less light is collected by the lens.

This tab contains performance plots for the MVL5TM23, MVL25TM23, and MVL50TM23 10 megapixel lenses sold on this page. Shown below are modulation transfer function (MTF) plots for each lens calculated for an infinite object distance. The MTF is calculated at four different full-angle fields of view (FOV) that span the specified FOV of each lens, as well as the diffraction-limited case.

Some lenses are designed for improved aperture or resolution performance. Because of the simplified optical design, some prime lenses are designed as fast lenses with large maximum apertures up to f/0.95 (see the Camera Lens Tutorial tab for details). Thorlabs also offers 2/3" format lenses at 5 mm, 25 mm, and 50 mm fixed focal lengths that feature 200 lp/mm resolution, commonly referred to as 10 megapixel (10 MP) lenses. These lenses are the ideal choice for high-end inspection or high-resolution imaging applications. For more information on these lenses, Modulation Transfer Function (MTF) plots can be found in the 10 MP Lens Data tab above.

Imaging Source lens

Machine Visionmacrolens

Lenses that are equipped with C-Mount (1.00"-32) threads are fully compatible with most of our C-Mount CMOS Cameras and our line of Scientific-Grade Cameras. CS-Mount cameras are compatible with these lenses when using a CML05 CS- to C-Mount adapter.

The images below illustrate this effect visually using two images taken using the same lens with 1/2" and 1/3" format cameras. The image taken using the smaller 1/3" format camera produces an image that is cropped compared to the image taken using the 1/2" format camera. Note, however, that the objects in both images remain at the same magnification.

Selecting an appropriate camera and lens pair can significantly improve image quality. A lens should generally not be used with camera sensors that have a larger format than the lens. While these lenses can be used with a smaller format camera, the resultant image will be cropped (see Camera Lens Tutorial tab for details). See the table below for a list of sensor formats for Thorlabs cameras.

Modern cameras that use CCD or CMOS sensors are specified for a camera sensor format, and similarly, lenses are designed to provide optimal imaging for a specific camera format. This format designation (e.g., 1/2", 2/3", 4/3") is a hold-over convention from when video was recorded using cathode-ray tubes and refers to the outer diameter of the video tube required for a given image size. The diagram to the right illustrates the size difference between several standard camera formats. In the ideal imaging system, a camera and lens would be designed for the same format, however, it is also possible to use camera/lens combinations with different formats. Doing this will have an effect, either vignetting or cropping, on the resulting image.

To illustrate this, the sequence of three images to the right were taken with the same camera with three different lenses. As focal length of the lens increases, magnification of the objects in the photos increases while the field of view decreases. The items in the image are each roughly spaced in 10" (254 mm) increments in the following order: Polaris™ Fixed Monolithic Mirror Mount (10" from camera), Ø1/2" post with KM100 mirror mount (20" from camera), and post-mounted RSP1 rotation mount (30" from camera). The MVL4WA used to shoot the first image is a wide angle lens which clearly distorts the door frame on the left edge of the image.

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The Camera Lenses sold here are specifically designed to be used with 1/2", 2/3", 1", or 4/3" sensor format cameras and are well-suited for machine vision applications. Thorlabs offers lenses with fixed focal length (i.e., prime lenses) that offer superior optical performance at focal lengths from 3.5 mm to 100 mm, as well as a 2/3" format zoom lens with an adjustable focal length of 18 mm to 111 mm. All lens models are equipped with lockable focus and aperture rings.

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VignettingVignetting occurs when the lens format is smaller than the camera format. When this occurs, the area of the sensor is incompletely exposed, causing a dark ring to appear around the borders of the image. The vignetting effect is illustrated in the two images below, which were both captured using the same 4/3" format camera. In the image to the left, using a 12 mm focal length, 4/3" format lens produces a full image with slight dimming around the edges. This minor example of vignetting is due to the lens design which has decreased transmission at the edge of the lens. On the other hand, a 2/3" format lens at the same focal length produces a prominent dark ring around the photo edge. As the latter example is very visually apparent, we do not recommend using lenses with smaller formats than the camera sensor for imaging.