DE19828546A1 - Image taking unit for measuring purposes with at least one optical system - Google Patents

Abstract

The unit has at least one optical arrangement (1,1), which is fitted in the front of an image taking camera (1,2). The optical arrangement optically alters sectionwise the resolution of the entire unit. The image taking camera may be a linear CCD arrangement.

Description

The invention relates to an image recording device for Measuring purposes.

Image acquisition devices are used in a wide variety Facilities used. It's always about that incoming beam of rays through optical elements on it map, then the requirements for an image recording. Ultimately, there is an image device made of photosensitive elements, which by the beam of rays falling on them can be changed. This Change can be permanent (e.g. photographic film) or limited in time (electronic tubes, CCD's, etc.).

There is usually an optical one in front of the image recording device Arrangement attached, which the radiance falling on them bundle changed in the desired manner.

An autofocus system is known from US Pat. No. 5,237,167, which has an anamorphic optics. The anamorphic optics shown in FIGS. 6 and 7 reduce the diameter of the beam of rays striking them in one axis by means of a positive and a negative cylindrical lens. The relations within the beam remain in the respective axes.

A sensor is known from US Pat. No. 5,485,277 a negative cylindrical lens arranged in a linear CCD array is. However, this lens is only used for correct relations Illustration of the beam of rays striking them on a linear CCD array.

All of the known arrangements have a constant Resolution in the entire measuring range.

The object of the invention is an image recording device to create one in front of the imaging camera arranged optical arrangement an impinging on it Beams optimized for a measurement task.

This object is achieved through the inventive features of the first Claim resolved.

The image recording device according to the invention is an optical one Arrangement, which the resolution of this from image recording camera and optical arrangement existing overall arrangement changed in some areas.

The image recording device preferably uses a CCD Arrangement (linear or flat) as an image recording camera, since one such an electronic device Editing / storage of the captured images very much simplified. In addition, a CCD arrangement has the advantage that the overall arrangement relative to shocks relative is insensitive. Corresponding CCD arrangements are very easy to get.

If one uses a diode row or a CCD arrangement linear CCD array, so you get a simplified data recording, which also take place at the highest speed can.

The image recording device according to the invention is suitable preferably for use in an autofocus device because it is built very compactly from a few parts.

This is particularly beneficial when you have the auto focus on direction in a surgical microscope, which thereby can be constructed with very small external dimensions and surgeons can quickly take a look to the side of the Surgical microscope.  

The image recording device according to the invention should also Recording a laser beam can be designed as this in the various fields of application are increasingly used becomes. The corresponding design can be selected Corresponding cameras exist or in an additional one homogeneous beam attenuation (e.g. filter).

The optical arrangement of the image recording according to the invention In extreme cases, the device can be made from a single lens exist, but the task of the single lens also through one or more lens assemblies from different optical Components can be met. The single lens can also pass through a mirror acting accordingly.

If you use a single lens, this contributes to the desired one compact design of the image recording device.

The beam of rays striking the optical arrangement can either its beam entry area into the optical arrangement change (movement of the beam in a plane perpendicular to the optical axis) and by hitting different ones Guiding areas or the optical arrangement can (if necessary by a z. B. from a computer controlled regulation) the image recording camera can be moved to the invention To achieve goal.

For most applications, especially when used the image recording device in an autofocus device it is advantageous that the optical arrangement be either one on it striking parallel beam inside and / or outside of the central area of the image recording device to to increase the resolution.

The invention is based on execution examples, with reference to the accompanying figures, explained in more detail, the following examples none have final character for the invention and others includes advantageous embodiments of the invention.  

Show it

Fig. 1 shows a first image pickup device according to the invention;

Fig. 2 is a second image pickup device according to the invention;

Fig. 3 shows a third image pickup device according to the invention;

FIG. 4 shows an image recording device according to the invention with a lens according to FIG. 1, focusing input beam;

FIG. 5 shows an image recording device according to the invention with a lens according to FIG. 1, entrance beam bundles slightly defocused;

FIG. 6 shows an image recording device according to the invention with a lens according to FIG. 1, the input beam is strongly defocused and

Fig. 7 shows a fourth image pickup device according to the invention.

In the variants of the image recording device according to the invention shown in FIGS. 1-3, a single lens ( 1.1 , 2.1 , 3.1 ) is located in front of a CCD arrangement ( 1.2 , 2.2 , 3.2 ) as an optical arrangement ( 1.1 , 2.1 , 3.1 ), the optical arrangement ( 1.1 , 2.1 , 3.1 ) each being at a certain distance from the CCD line array ( 1.2 , 2.2 , 3.2 ).

The incident beam ( 1.3 , 2.3 , 3.3 ) is smaller than the CCD arrangement ( 1.2 , 2.2 , 3.2 ) and than the optical arrangement ( 1.1 , 2.1 , 3.1 ) and therefore only falls on a sub-area of the CCD arrangement ( 1.2 , 2.2 , 3.2 ) and the optical arrangement ( 1.1 , 2.1 , 3.1 ).

Would you be an autofocus device for surgical microscopes according to the state of the art, the would for detection  the diode line used a reproducible uniform resolution or a setting of the overall system allow from 0.5 to 1 mm, the limiting element of The pixel spacing in the central area of the CCD line is approx. 14 µm.

In contrast, the image recording device according to the invention with its optical arrangement ( 1.1 , 2.1 , 3.1 ) ensures that the laser beam to be detected ( 1.3 , 2.3 , 3.3 ) is spread by it and thus more diodes on the CCD line ( 1.2 , 2.2 , 3.2 ) be illuminated. However, this increases the resolution. This spreading differs, however, depending on where the laser beam ( 1.3 , 2.3 , 3.3 ) impinges on the optical arrangement ( 1.1 , 2.1 , 3.1 ), whereby the resolution of the overall arrangement differs in some areas.

The lens ( 1.1 , 2.1 , 3.1 ) arranged directly in front of the CCD line ( 1.2 , 2.2 , 3.2 ) in the imaging beam path of the autofocus in an operating microscope is essentially a diverging lens, but some (especially in the edge area) also have a collecting effect can. The area of the lens ( 1.1 , 2.1 , 3.1 ) with a scattering effect causes a spreading of neighboring (almost parallel) autofocus beams ( 1.3 , 2.3 , 3.3 ) on the CCD line ( 1.2 , 2.2 , 3.2 ) and the area with a collecting effect one Upsetting. However, the resolution is higher in a particularly interesting area than in a less interesting area, which ultimately also makes it possible to enlarge the measuring range (depending on the specific design of the optical arrangement).

The image recording device according to the invention thus enables the resolution of a system to be controlled in areas in which the position of an object (for example a line mark) imaged on a CCD arrangement ( 1.2 , 2.2 , 3.2 ) on the CCD arrangement ( 1.2 , 2.2 , 3.2 ) should be recorded.

The shape of the lens (or lenses) ( 1.1 , 2.1 , 3.1 ), which represents the optical arrangement, can vary depending on the application. The material should be selected depending on the radiation ( 1.3 , 2.3 , 3.3 ) to be detected, preferably glass or plastic (in particular CR 39 molded part or molded part) being used.

The lens ( 1.1 ) shown in FIG. 1 is essentially a diverging lens, the side ( 1.1 b) facing the linear CCD array ( 1.2 ) being flat. The side ( 1.1 a) facing the incident beam ( 1.3 ) has a radius which gives the lens ( 1.1 ) an overall dispersing effect. Characterized the light incident on the lens (1.1) beams (1.3) is expanded when passing through the lens (1.1) and covers more diodes of the subsequent CCD array, as is the case (1.2) without the upstream optical arrangement (1.1). However, this also increases the achievable resolution, since a vertical movement of the beam ( 1.3 ) must be smaller in order to be detected. This means that with smaller focus deviations, a larger beam deflection or beam widening is obtained.

The curvature of the lens surface ( 1.1 a) can differ in some areas (general asphere), so that the catch area of the arrangement ( 1.1 , 1.2 ) need not be less than without a lens ( 1.1 ). Yes, it can even be larger, as shown in FIG. 2.

In this lens ( 2.1 ), only the central area (B2) has a distracting effect on the incident rays ( 2.3 ). In the edge area (A2, C2) the lens ( 2.1 ) has a collecting effect, so that with such a lens ( 2.1 ) on the one hand an increase in resolution can be realized in the central area (B2) and in the edge area (A2, C2) an increase in Catch area. The transitions from the scattering area (B2) to the collecting areas (A2, C2) are continuous in this example. In the individual areas (A2, B2, C2) the lens radius can change constantly, so that around the lens center (B2) one has a stronger distracting effect than in the border area of the scattering area next to the edge areas (A2, C2). A movement of the incident beam ( 2.3 ) around the optical axis is thus detected much sooner than in the edge area.

Fig. 3 shows that the transition between the regions does not have to be continuous . Here peaks occur in the transitions between the regions (A3, B3.1, B3.2, C3). The number of areas (A3, B3.1, B3.2, C3) is only an example here and can be much larger in the specific lens design. Nevertheless, you get the desired effect of a different resolution of the overall arrangement depending on the area.

All of the lenses ( 1.1 , 2.1 , 3.1 ) shown in FIGS. 1-3 can develop their optical effect either in only one axis perpendicular to the optical axis (cylindrical lenses) or in the two axes perpendicular to the optical axis (circular lens). The lens surface can have a uniform radius or a general aspherical shape, depending on the optimization goal of the application in question.

The image recording device shown in FIGS. 4-6 has a collecting entrance lens ( 4 ), which the ray bundle ( 5 ) imaged by it via a deflecting mirror ( 6 ) on the additional lens ( 1.1 ) shown in FIG. 1 for accuracy increase with minimal Maps focus difference. A CCD chip ( 7 ) is arranged behind the additional lens ( 1.1 ). If the bundle of rays ( 5 ) is precisely in focus, the bundle of rays ( 5 ) also falls exactly on one (or on a previously determined number) detector element on the CCD chip ( 7 ) (see FIG. 4).

If, on the other hand, the beam ( 5 ) is slightly defocused, the additional lens ( 1.1 ) ensures that the deposit on the CCD chip ( 7 ) increases (see FIG. 5). With "stronger" defocusing, the beam ( 5 ) is then directed onto the

the last detector elements of the CCD chip ( 7 ) are shown (see FIG. 6).

FIG. 7 shows the optical arrangement from FIGS . 4-6 with defocusing, but the additional lens ( 1.1 from FIGS . 1, 4-6) has been replaced by another additional lens ( 1.4 ).

The additional lenses ( 1.1 , 1.2 , 1.3 , 1.4 ) can be selected depending on the measurement problem and allow the sensitivity of the detection to be adjusted in the event of defocusing, without the image recording device ( 1.2 , 2.2 , 3.2 , 7 ) having to be replaced (and thus the control electronics used ). Only with the evaluation software in the evaluation computer (not shown in the figure), to which the signal of the image recording device ( 1.2 , 2.2 , 3.2 , 7 ) is fed, must the lens currently used be taken into account.

This enables the use of essentially the same Defocus detectors (with the correspondingly selected Additional lens) for different measuring purposes.

Claims (10)

1. Image recording device for measuring purposes, in which at least one optical arrangement ( 1.1 , 2.1 , 3.1 ) which changes the resolution of the overall arrangement in some areas is mounted in front of an image recording camera ( 1.2 , 2.2 , 3.2 ). 2. Image recording device according to claim 1, characterized in that the image recording camera ( 1.2 , 2.2 , 3.2 ) is a CCD arrangement. 3. Image recording device according to claim 2, characterized in that the CCD arrangement ( 1.2 , 2.2 , 3.1 ) is line-shaped. 4. Image recording device according to claims 1, 2 or 3, characterized in that the image recording device in an autofocus device is installed. 5. Image recording device according to claim 4, characterized characterized in that the autofocus device in one Surgical microscope is installed. 6. Image recording device according to one of claims 1-5, characterized in that the image recording device is designed to receive a laser beam ( 1.3 , 2.3 , 3.3 ). 7. Image recording device according to one of claims 1-6, characterized in that the optical arrangement ( 1.1 , 2.1 , 3.1 ) is constructed from at least 2 lenses. 8. Image recording device according to one of claims 1-7, characterized in that the optical arrangement ( 1.1 , 2.1 , 3.1 ) at least one beam incident on it ( 1.3 , 2.3 , 3.3 ) in the central region (B, B2, B3.1, B3.2) of the image recording camera ( 1.2 , 2.2 , 3.2 ). 9. Image recording device according to one of claims 1-7, characterized in that the optical arrangement ( 1.1 , 2.1 , 3.1 ) at least one incident on it rays ( 1.3 , 2.3 , 3.3 ) outside the central area (B, B2, B3.1 , B3.2) of the image recording camera ( 1.2 , 2.2 , 3.2 ). 10. Image recording device according to one of claims 1-9, characterized in that the CCD arrangement ( 1.2 , 2.2 , 3.2 ) is a CCD chip.