JP4469956B2 - Multifocal imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly to a multifocal imaging apparatus that can acquire images focused on a plurality of perspective positions on a subject by a single imaging operation.

  Currently, imaging devices are used in combination with image recognition devices, including manufacturing industries such as product inspection, quality control, manufacturing process management, image acquisition for information presentation, building It is used in various forms such as management.

  For example, in products used in the manufacturing process, products generally have a three-dimensional shape, but when performing inspection of minute parts, in order to perform more accurate inspection, an image pickup lens having a high NA is used. It has become like this. By using an imaging lens with a high NA, a large amount of light is captured, and the situation of minute parts becomes clearer. On the other hand, the depth of field is shallow, and the focus of the subject is far away. The position is blurred. Therefore, if you want to see not only a specific perspective position of the part but also the overall situation, it is necessary to refocus on another perspective position. It is difficult to do exactly.

  In order to obtain a stereoscopic image with a microscope, it is necessary to combine images at a plurality of focal positions. This means that images at different focal positions are acquired and combined in several steps. Such an image cannot be acquired. There is also a technique that uses deconvolution by image processing. However, it is necessary to obtain a point response function, which results in a complicated image processing process and a long processing time. Therefore, a three-dimensional image can be easily obtained. It does n’t mean you can.

Multifocal image formation is disclosed in the following documents.
JP-A-6-70212 JP-A-4-329775 JP 11-311832 A Japanese Patent Laid-Open No. 10-254055 JP-A-10-260471

  Patent Document 1 detects the amount of change in image data for each pixel or region for a plurality of original images with different focus positions within the same image frame, and determines the image data in focus based on this amount of change. The present invention relates to an image processing apparatus that selects and generates a focused composite image as a whole screen using the image data. However, it does not specifically disclose how to acquire a plurality of images with different focus positions as an imaging device, and as a general imaging means, imaging is performed a plurality of times. This is an image processing method based on the above, and does not give a new feature as an imaging device for acquiring a plurality of multi-focus images.

  In Patent Document 2, light from the same subject is guided through an optical system, the light is split into a plurality of light by a spectroscopic means, and photographing conditions such as an exposure amount and a focus position are made different from each other. The present invention relates to a solid-state imaging device that simultaneously captures and stores an image obtained by a solid-state imaging device arranged in each spectral path and combines a plurality of images according to a photographing condition. However, among these photographing conditions, although the exposure amount is different for each spectral path and imaging can be performed simultaneously, the same optical system (objective lens) is used. Regarding the simultaneous imaging of multiple images with different positions, a specific method is not disclosed. If a general imaging method is used, the objective lens is adjusted for each focal position, etc. In this case, imaging must be performed a plurality of times.

  Furthermore, as multifocal imaging devices for acquiring images focused on a plurality of perspective positions, there are those disclosed in Patent Documents 3 to 5, but in order to obtain images of different perspective positions, A plurality of objective lenses are provided, and imaging is performed by changing the focal position for each imaging lens. Any one of the plurality of objective lenses is selected, and imaging with a desired objective lens is performed. Therefore, the imaging apparatus is configured to include a plurality of objective lenses, and does not simultaneously capture images at different perspective positions.

  As described above, a conventional imaging apparatus or image forming apparatus that acquires images at different perspective positions uses a normal imaging apparatus, performs imaging multiple times at different perspective positions, and synthesizes images based on the imaging. One that performs image processing such as performing, or having a plurality of objective lenses for obtaining images at different perspective positions in one imaging device, and obtaining an image at a desired perspective position by selectively using the imaging lens There were things.

  In the case of image processing, in addition to taking time and manpower to obtain images at a plurality of perspective positions, such as performing image processing after performing multiple imaging, hardware for image processing and It is necessary to provide software means.

  As in Patent Documents 3 to 5, a device having a plurality of objective lenses in one image pickup device is substantially similar to a combination of a plurality of image pickup devices, and the device becomes large-scale and perspective. In order to obtain a plurality of images having different positions, it was necessary to perform imaging a plurality of times.

  As in Patent Document 2, even in the case of splitting light from one objective lens, if there is only one objective lens, it is necessary to perform imaging a plurality of times in order to select images at different perspective positions. It was.

  As described above, the conventional method and apparatus for obtaining a multifocal image cannot obtain images at different perspective positions by one imaging, and the scale of the imaging apparatus and the image processing apparatus is increased. Therefore, there has been a demand for providing an imaging apparatus that can obtain a plurality of images at different perspective positions by one imaging operation, and that can be reduced in cost with a simple configuration.

The present invention has been made to solve the above-described problems, and a multifocal imaging device according to the present invention includes a single objective lens and light from an imaging target guided by the objective lens in a plurality of optical paths. a beam splitter for splitting the light, the beam light dispersed by splitter so as to form an image on the imaging plane, respectively, so that the optical path lengths are different from each other in the optical path from the objective lens to each of the imaging plane In the multifocal imaging apparatus provided with the optical path length changing means for making the in -focus image portions on the respective imaging planes different from each other , the optical path length changing means comprises: A plurality of mirrors each disposed in one or more of a plurality of optical paths from the objective lens to each of the imaging planes to change the optical path length ; Is designed to be adjustable.

  In the multifocal imaging device of the present invention, by providing optical path length changing means for making optical path lengths different from each other in a plurality of optical paths dispersed by the beam splitter, a plurality of different perspective positions can be obtained by one imaging operation. The image can be obtained, and the cost is low with a simple configuration.

  FIG. 1 shows a basic form of a multifocal imaging device according to the present invention. In the multifocal imaging device A, light from an imaging target B taken in from an objective lens 1 is beam splitters 2a, 2b, The light that is divided into three optical paths by the mirror 3 and travels straight through the beam splitter 2a forms an image on the image plane 10a through the filter 5a, is reflected by the beam splitter 2a, and is further reflected by the beam splitter 2b. Is imaged on the imaging surface 10b through the filter 5b, and the light passing through the beam splitter 2b and reflected by the mirror 3 is imaged on the imaging surface 10c through the filter 5c.

  The spectral sensitivity of the filters 5a, 5b and 5c is as shown in FIG. The light transmitted through the beam splitter 2a passes through the filter 5a that transmits the R band, the R band light forms an image on the imaging plane 10a, and the light reflected by the beam splitter 2b passes through the G band. The light in the G band is imaged on the imaging plane 10b, and the light reflected by the mirror 3 passes through the filter that transmits the B band and the light in the B band is imaged on the imaging plane 10c.

  As shown in FIG. 1, when the imaging surfaces 10a, 10b, and 10c are on the same plane, the optical path lengths reaching the imaging surfaces 10a, 10b, and 10c from the objective lens 1 are different, and the distance between the beam splitters 2a and 2b. There is a difference in the distance between the beam splitter 2b and the mirror 3. Therefore, due to the difference in optical path length, the position P3 of the image pickup object B is focused on the imaging plane 10a, and the position P2 of the image pickup body B is focused on the imaging plane 10b. The portion of the image pickup object B at the position P1 is focused on the image plane 10c.

  In other words, in order to form an image in a state where the different perspective positions P3, P2, and P1 of the imaging target B are focused on the imaging surfaces 10a, 10b, and 10c, respectively, as shown in FIG. What is necessary is just to set the mutual space | interval of the beam splitters 2a and 2b and the mirror 3 so that the optical path length for that may be given. When it is necessary to make the perspective positions P1, P2, and P3 of the imaging target B variable, in the imaging apparatus A, for example, a pinion-gear mechanism using the beam splitter (or mirror), filter, and imaging plane as a unit. For example, the optical path length may be adjusted by adjusting the distance between them by an external operation.

  In the configuration of the image pickup apparatus A in FIG. 1, R, G, and B band images focused on the positions A1, A2, and A3 of the imaging target are formed on the imaging surfaces 10a, 10b, and 10c, respectively. To do. If an image sensor is arranged on each imaging plane, R, G, and B images at respective perspective positions can be obtained. The R, G, and B color component images are also obtained for the time being, but the color component image signal may be converted into a monochrome image signal to obtain a monochrome image. The image pickup apparatus shown in FIG. 1 can obtain images at different perspective positions by placing a photosensitive film on the image plane and exposing it. If it is a color film, a color component image is obtained, and if it is a black and white film, a black and white image is obtained.

  FIG. 3 shows an example of an image pickup apparatus A that uses a beam splitter 2 of another form. Light that has passed through the objective lens 1 by the beam splitter 2 is transmitted through the beam splitter 2. And the light reflected by the mirror 3a and reflected by the mirror 3a onto the imaging surface 10a via the filter 5a, and the light transmitted through the beam splitter 2 onto the imaging surface 10b via the filter 5b. The light reflected by the mirror 3b forms an image on the image plane 10c through the filter 5c. If the optical path lengths from the spectral plane of the beam splitter 2 to the imaging planes 10a, 10b, and 10c are made uniform, images at the same perspective position of the imaging target are formed on the imaging planes. It will be.

In order to form images of different perspective positions of the imaging target, for example, the optical path length changing optical element 4b is provided in the optical path to the imaging surface 10b, and the optical path length is provided in the optical path to the imaging surface 10c. The changing optical element 4c is arranged. The optical elements 4b and 4c for changing the optical path length are made of a transparent plate-like member having a large refractive index. When the thicknesses are d ₁ and d ₂ and the refractive indices are n ₁ and n ₂ , the optical path length is changed. Are n ₁ d ₁ and n ₂ d ₂ (n ₁ d ₁ <n ₂ d ₂ ), respectively. By disposing such an optical path length changing optical element, the position P3 portion of the imaging target B is focused on the imaging surface 10a without the optical path length changing optical element, and the imaging surface 10b. On the upper side, the portion at the position P2 of the imaging target B is focused and focused by the light passing through the optical path length changing optical element 4b, and the light passing through the optical path length changing optical element 4c is focused on the imaging surface 10c. A portion at the position P1 of the imaging target is focused and imaged.

  FIG. 4 shows an example of an image pickup apparatus A provided with an optical path length changing unit according to another embodiment, and shows that the light is divided into two as a beam splitter. The light that has passed through the objective lens 1 is divided into two by the beam splitter 2, and the light to the left in the figure is sequentially reflected by the mirrors 3a, 3b, and 3c and forms an image on the image plane 10a through the filter. The light to the right is sequentially reflected by the mirrors 3d, 3e, and 3f, and forms an image on the image plane 10b through the filter. The light is reflected at right angles by the reflecting surfaces 3a to 3f. Here, the mirrors 3a and 3b are integrally attached to the base, and the mirrors 3d and 3e are integrally attached to the base. The mirrors 3a and 3b are integrally attached to the base, and can be moved by a rack-pinion mechanism or the like. , So that the pair of mirrors 3a and 3b and the mirrors 3d and 3e can be adjusted separately in the horizontal direction in the figure. The optical path length from the beam splitter to each imaging plane can be adjusted by such a displacement of the set of mirrors in the left-right direction. According to such an optical path length changing means, by adjusting the optical path length by an external operation in each optical path, the perspective position of the part to be imaged of the imaging target can be variably adjusted as necessary. Although FIG. 4 shows an example in which the optical path is divided into two by the beam splitter, the same configuration can be made even when the optical path is divided into three. However, the set of mirrors is not in the same plane as shown in FIG.

  In each of the examples shown in FIGS. 1, 3 and 4, the filters are provided for extracting color component light from the respective lights dispersed by the beam splitters 2a and 2b (the beam splitter 2 in FIGS. 3 and 4). . Obtaining images at different perspective positions can be achieved by changing the optical path lengths of the light beams separated by the beam splitters 2a and 2b. In that respect, the filter is not necessarily an indispensable element. It is provided.

  FIG. 5 shows a form of a multifocal imaging apparatus configured using one imaging element. In this imaging apparatus A, the light from the imaging target B guided by the imaging lens 1 is split into three by the beam splitters 2a and 2b, and the three lights pass through filters 5a, 5b and 5c, respectively, and R and G , B component light and then synthesized light by the mirror 3 and the beam splitters 2c and 2d, and forms an image on one imaging element 7 disposed on the imaging plane. Although the optical path lengths of the respective lights dispersed in such an imaging optical system are essentially the same, as shown in the figure, an optical element 4b for changing the optical path length is disposed in the optical path of the light reflected by the beam splitter 2b. In addition, an optical path length changing optical element 4c is disposed in the optical path of the light reflected by the mirror 3, so that the optical path length of the dispersed light is made different. The positions P1, P2, and P3 are set so that focused imaging is performed on the image sensor 7 on the imaging plane.

  In this way, an image obtained by synthesizing images of component light of R, G, and B in which the portions of the perspective positions P1, P2, and P3 of the imaging target B are focused by the imaging element 7 is obtained. If this combined image is decomposed into R, G, and B component light images by the image decomposition device 8, the portions of the perspective positions P1, P2, and P3 of the imaging target B are combined with the monitors 9a, 9b, and 9c, respectively. A focused image is displayed. The decomposed image may be displayed with component light, but may be displayed after being converted into black and white.

  In the example shown in FIG. 5, the image sensor 7 is a color image sensor, and has a form in which light from the object to be imaged illuminated by external light is simultaneously dispersed and imaged, but the object to be imaged is illuminated with a time difference. By doing so, it can also be implemented as a form of imaging using a monochrome imaging device. For this purpose, the imaging device 7 in FIG. 5 is a monochrome imaging device, and further includes illumination means for an imaging target that emits R, G, and B pulses with a time difference (not shown), and the imaging device 7 is an R of the illumination means. , G, and B are further synchronized with the pulsed emission, and a means for synthesizing the obtained images is further provided, and the image decomposition means 8 displays on the monitors 9a, 9b, and 9c black and white images that are in focus. To be able to.

  Here, by illuminating the imaging target with a time difference with pulsed light of R, G, and B, the light from the imaging target due to illumination with the pulsed light of each color is split by the beam splitters 2a and 2b. The image of the perspective position of the object to be imaged corresponding to the optical path length of the optical path is synchronized and captured by the monochrome image element 7 so that the image at which perspective position is obtained. Can be determined. In this way, a multi-focus image can be obtained even with a black and white image sensor by illuminating the imaging subject with color component pulsed light in time division and imaging synchronized therewith.

  Further, a multifocal image can be obtained by using pulsed light and a polarizing filter whose polarization directions are perpendicular to each other instead of the pulsed light and the color filter of each color.

  Although typical embodiments have been described here, the present invention is not limited to these embodiments, and various embodiments can be implemented based on the gist of the present invention.

It is a figure which shows the basic form of the multifocal imaging device by this invention. It is a figure which shows the spectral sensitivity of the beam splitter used in a multifocal imaging device. It is a figure which shows the example of the multifocal imaging device by this invention using the beam splitter of another form. It is a figure which shows the example of the multifocal imaging device by this invention provided with the optical path length change means by another form. It is a figure which shows the example of the multifocal imaging device by this invention comprised using one imaging element.

Explanation of symbols

1 ... Objective lens
2 (2a, 2b) ... Beam splitter 3 (3a to 3f) ... Mirrors 4a and 4b ... Optical elements 5a to 5c for changing the optical path length ... Filters 6 and 6 '... Screw 7 ... Imaging element 8 ... Image decomposition devices 9a and 9b , C ... monitors 10a to 10c ... imaging plane A ... imaging device B ... imaging object P1, P2, P3 ... perspective position

Claims (1)

One objective lens, a beam splitter that splits the light from the imaging target guided by the objective lens into light of a plurality of optical paths, and the light split by the beam splitter forms an image on the imaging plane, respectively. to the comprises an optical path length changing means for optical path length is different from each other in the optical path from the objective lens to each of the image plane, the different perspective positions of the imaged subject in each imaging plane whereby each part in the multifocal imaging apparatus adapted to focus Aseyui images respectively, to one or more optical path of the plurality of optical path from the optical path length changing means the objective lens to each of the imaging plane arranged to be a plurality of mirrors for changing the optical path length, multifocal imaging device you wherein the several mirrors plurality is adjustable.

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