DE4035799A1 - Confocal scanning microscope with computer control - has illumination raster corresponding to raster of CCD sensor receiving image of scanned object - Google Patents

Abstract

The confocal scanning microscope has a light source (11) and confocal optical elements (13o, 13u, 13t) providing an image of the illumination plane (11b) at a focal plane (13f) containing the object (14). An illumination raster (12) is contained in the illumination plane (11b), corresponding to the raster of the photosensitive area of the CCD sensor (17) located at a stop plane (17b) receiving an image of the focal plane (13f). Pref. the illumination raster (12) is provided by holes (12l) in an opaque layer (12s) illuminated by the light source (11). The CCD sensor (17) is coupled to a computer controlling the relative movement of the scanning microscope. USE - For evaluating surface profile of scanned object.

Description

The present invention relates to a device for three-dimensional examination of an object with a Light source, a receiver and optical elements for a confocal beam path in which an illumination plane is depicted in a focal plane that is on or in the object lies, and in which the focal plane in an aperture plane is shown.

Such a device in the form of a confocal scanning Microscope is in a publication by D. K. Hamilton e.a. (Appl. Phys. B 27, 211 (1982)). Scanning Microscopes with a confocal beam path, in which a so-called Point light source in a plane of the object and this plane of the object to a so-called point receiver or a Pinhole, behind which a receiver sits, is shown, have the property of being very height selective, d. H. Planes that are a short distance apart, optically separate. In the publication cited above this property is used to create a surface profile to record a semiconductor device. For this, for everyone x-y position of the light point the object in the z direction (direction the optical axis) and the intensity curve measured. Since this has a pronounced maximum, if that Image of the point of light lies exactly on the surface for each point in the x-y plane the height of the surface in z-direction can be determined and in this way temporally successively the entire surface profile of the object be included.

A disadvantage of this known device is that the  Recording a surface profile, a relatively long time required.

The present invention has for its object a To create device with in a relatively short time Surface profiles can be recorded.

The object is achieved according to the invention in that that a lighting grid in the lighting plane is arranged that a CCD receiver in the aperture plane is arranged and that the lighting grid on the CCD receiver is shown with a grid dimension that the Grid dimension of the light-sensitive areas of the CCD receiver is approximately the same or larger.

The use of a CCD receiver and one two-dimensional arrays of holes in an illuminated Layer is for a scanning microscope from US-PS 48 06 004 known. However, it only states that the object in different layer levels can be observed. Especially the aperture effect of the CCD receiver is not there exploited, d. H. the fact that he is out of grid arranged photosensitive areas, whose Dimensions are significantly smaller than their distances from each other.

In the above-referenced U.S. patent is the confocal Rather, the beam path only with a reflected light microscope realized in which those going to the object Beams of rays go through the same hole array as that of the Object reflected beam of rays. Therefore, it is necessary through an optical element called an eyepiece Map holes array into a plane in which it is observed or is recorded. For the latter case, among other things specified a video camera with a CCD receiver, whose Images can be saved and evaluated.  

In contrast, in the present invention, one is always CCD receiver used and its generally disadvantageous Property exploited that only a small proportion of the Receiver surface consists of light-sensitive areas.

Compared to the publication of Hamilton not only has the solution according to the invention Advantage that the inclusion of a surface profile as a result of the lighting grid goes much faster, but that a height-selective view is also possible is because the intensity of the Radiations reflected from the individual object locations directly from the heights of the relevant points of the Depends on the object, so that each raster element contains information about the height of the surface in the place belonging to it of the object and thus the intensity distribution the surface immediately gives an overview of the Height distribution of the object surface there. In particular can be done if the object is relative to the beam path is moved in the direction of the optical axis, very simply the Identify areas with the same height of the surface.

For objects with reflective areas in or under there is a transparent layer for the dependent intensity of the height in the object reflection profiles with a small maximum for the surface of the transparen th layer and a large maximum for the reflective Area. Therefore, it is with the device according to the invention possible not only to examine surface profiles, but also structures inside or under transparent layers.

In an advantageous embodiment of the invention Illumination grid on the CCD receiver with a grid dimension mapped, which corresponds to the grid size of the photosensitive Areas of the CCD receiver equal or an integer  Multiples of it is.

In an advantageous, simple embodiment of the Invention is the lighting grid through holes in a Realized layer that is illuminated by a light source becomes. To increase the intensity of the illuminated holes - in Hereinafter also referred to as light points for short can reach a lens in front of the layer with the holes Array are arranged, which ensures that the Radiation from the light source does not make the layer uniform illuminates but is focused on the holes.

Usually the CCD receiver and the lighting grid adjusted to each other so that in the aperture plane illustrated light spots on the light-sensitive areas of the CCD receiver. In this case, the Focus through intensity maxima for those object place their reflective surfaces exactly in the focal plane lie.

However, it is also possible to use the CCD receiver and that Adjust the lighting grid to each other so that the in the Aperture plane depicted light points between the light sensitive areas of the CCD receiver. In this Case arise when focusing through intensity minima those object locations whose reflecting surfaces exactly lie in the focus plane. Through a special training of CCD receiver, e.g. B. by relatively large-area light sensitive areas, this effect can be intensified will.

Finally, an inverse lighting grid is also possible; d. H. that depicted on the object and in the aperture plane Raster does not consist of bright points of light, but of a bright area with a grid arrangement of small dark zones. Such a lighting grid,  which z. B. from an illuminated by the light source Layer with opaque zones a CCD receiver with small light-sensitive areas, on which the dark zones are also mapped Intensity minima for those object locations reflective surfaces lie exactly in the focal plane.

In another advantageous embodiment, the Illumination grid generated by a lens array, which an almost punctiform light source often in grid mapped arrangement in the lighting plane.

In a further advantageous embodiment, the Illumination grid generated by one of the light source illuminated aperture often in a grid Arrangement is shown in the lighting level. Also in in this case, an inverse lighting grid z. B. thereby be realized that the aperture is opaque Center.

In a particularly advantageous embodiment, the Illumination grid generated by a light source array. This can e.g. B. composed of individual LEDs be or be manufactured in integrated technology. In In both cases, it is particularly advantageous to use the arrays and train their power supply so that either each individual light source or certain subsets of the Light sources independent of the other on and can be turned off.

To accommodate the above-mentioned height-selective Overview pictures it is useful to have an adjustment device to provide which allows the focus plane with the images the light points on different layer levels of the object adjust.  

To record complete reflection profiles with good Resolution it is appropriate to use an adjustment device to provide, which allows the lighting grid and the Object relative to each other in planes perpendicular to the optical one Axis to move so that the object with the lighting grid is scanned. The relative movement between light score and object can be adjacent within the distance points of light remain or a multiple thereof be.

In a further advantageous embodiment of the invention the CCD receiver is connected to a computer that Signals from the CCD receiver are evaluated. It is in this case advantageous, the adjustment devices for the relative Movement of light points and object towards each other the optical axis and / or in the planes of the light points or to control the object by the computer.

In a particularly preferred embodiment of the invention the computer also becomes a switching device controlled the different subsets of the light sources of the light source array switches on and off. Here, for. B. the number of light sources switched on by the Results of the evaluation of the computer can be controlled, so that in critical areas of an object the Scattered light by reducing the number of effective light sources can be reduced.

When scanning an object, it can be advantageous Illumination grid and CCD receiver relative to each other in the illumination level or in the aperture level by a Adjustment device, conveniently from the computer is controlled to move. With a powerful Computers can add additional through this shift Information is obtained, which is a more precise evaluation enable. In this case, the grid size of the lighting must  grid should only be approximately the same or larger than that Grid dimension of the light-sensitive areas of the CCD receiver.

For the smallest possible depth of focus of the confocal Figure it is advantageous to replace the usual one circular telecentric aperture an annular aperture to provide. The application of such an aperture is from the EP-A2-02 44 640 known. There are also panels with others Transmission patterns (pattern) described, which also for the present optical imaging system are suitable to the three-dimensional transfer function to previously known Adjust object pattern.

The invention is explained in more detail below with reference to exemplary embodiments shown in FIGS. 1 to 7. Show:

Wherein the illumination grid is generated by an illuminated layer with holes Fig. 1 shows an embodiment,

Wherein the illumination of the holes is improved ver by an additional lens array Fig. 2 an embodiment,

Wherein the illumination grid is generated by a semiconductor array Fig. 3 shows an embodiment,

Fig. 4 is a glass plate with a pattern of an inverted illumination grid,

Fig. 5 shows an arrangement for generating a lighting grid by multiple imaging of a light source with a lens array,

Fig. 6 shows an arrangement for generating a lighting grid by multiple imaging of an illuminating aperture with a lens array and

FIG. 7 shows an example of the illuminated diaphragm in FIG. 6.

In Fig. 1 with ( 11 ) is a light source, for. B. a halogen lamp, which illuminates holes ( 12 l) in one layer ( 12 s) with the aid of the condenser ( 11 k), possibly via a filter ( 11 f) (for separating out a sufficiently narrow spectral range). Such a layer can in a known manner, for. B. made of chrome on a glass plate ( 12 g). The holes ( 12 l) are arranged in the layer ( 12 s) just like a grid like the light-sensitive areas of the CCD receiver ( 17 ). Is z. B. the receiver uses 1 CX 022 from Sony, then the layer contains 512 × 512 holes with a distance of 11 microns in the directions of the grid and with a hole size of z. B. 2 µm × 2 µm. The size of the holes is therefore considerably smaller than their distance. The distance between the holes or areas from center to center is called the grid dimension.

The illumination grid generated by the illuminated holes ( 12 l) in the layer ( 12 s) lies in the illumination plane ( 11 b). This is imaged by the lenses ( 13 o, 13 u) in the focal plane ( 13 f), so that in the latter the object ( 14 ) is illuminated with light points arranged in a grid. With non-transparent objects, only the surface ( 14 o) can be illuminated, while with transparent objects, layers ( 14 s) inside can also be illuminated with the light points. The light beams reflected by the object in the focal plane ( 13 f) are focused by the lenses ( 13 u, 13 o) via a beam splitter ( 16 ) in the diaphragm plane ( 17 b). The diaphragms necessary for a confocal arrangement are realized in the diaphragm plane ( 17 b) by the light-sensitive areas of the CCD receiver ( 17 ), which are separated from one another by relatively large spaces.

A so-called telecentric diaphragm ( 13 t) is usually arranged between the lenses ( 13 o, 13 u), which ensures that the center beam ( 13 m) strikes the object ( 14 ) parallel to the optical axis ( 10 ), so that the position of the light spots on the object does not change when the object ( 14 ) is moved in the direction of the optical axis ( 10 ).

The object ( 14 ) can be moved in all 3 spatial directions by an adjusting device ( 15 ) so that different layers ( 14 s) of the object ( 14 ) can be scanned. The movement in the x and y directions can be chosen to be smaller than the grid dimension of the light points ( 12 ) or the CCD receiver ( 17 ). Of course, the movement of the object ( 14 ) in the z direction can also be achieved by shifting the lenses ( 13 o, 13 u) in the direction of the optical axis ( 10 ) and likewise instead of moving the object in the x and y directions the layer ( 12 s) with the holes ( 12 l) and CCD receiver ( 17 ) can be moved accordingly.

The signals of the CCD receiver ( 17 ) are transmitted via the connecting line ( 17 v) to a computer ( 18 ), which takes over the evaluation in a known manner and on a screen ( 18 b) the results of the evaluation z. B. in the form of graphical representations. The computer ( 18 ) can also control the shift of the focal plane ( 13 f) in the object and the scanning in the x and y directions via the connecting line ( 18 v). This control can be present in the computer as a fixed program or can take place depending on the results of the evaluation.

In Fig. 2, a lens array ( 22 a) is arranged between the condenser ( 11 k) or the filter ( 11 f) and the layer ( 12 s) with the holes ( 12 l), which also has as many small lenses ( 22 l) contains how the layer ( 12 s) has holes ( 12 l). The lenses ( 22 l) have the task of imaging images of the filament of the light source ( 11 ) into the holes and thus giving the light points a greater intensity.

The lens array ( 22 a) and the layer ( 12 s) with the holes ( 12 l) can - as shown - be combined in a common part ( 22 g). The production of suitable lens arrays is e.g. B. from a publication by K. Koizumi (SPIE Vol. 1128, 74 (1989)) known.

A particularly advantageous implementation of the lighting grid is shown in Fig. 3. There ( 31 ) denotes a light source array which, for. B. from Lumines zenzdioden (LEDs) ( 31 l). Such an array with a size of z. B. 10 × 10 diodes z. B. from commercially available mini diodes LSU260-EO from Siemens with a pitch of 2.5 mm and therefore has a total size of 2.5 cm × 2.5 cm. It is imaged on a scale of approx. 1: 5 into the illumination plane ( 11 b) through the lens ( 31 o) in such a way that it has approximately the size of the entire photosensitive surface of the CCD receiver of 5 mm × 5 mm. In this case, only 100 light-sensitive areas with a grid size of approx. 0.5 mm × 0.5 mm are used by the CCD receiver ( 17 ). Nevertheless, the 100 light points result in considerable time savings compared to scanning with just one light point.

In this case, too, it can be advantageous to arrange a layer ( 32 s) with holes ( 32 l) in the lighting plane ( 11 b) so that the light spots have sufficiently small dimensions. In addition to the objective ( 31 o) for the reduced image, a field lens ( 31 f) is useful for further imaging in the confocal beam path.

It is much more advantageous to use integrated LED arrays for the lighting grid, as z. B. are described in a publication by JP Donnelly (SPIE 1043, 92 (1989)). LED arrays of this type, like the assembled array of mini diodes, also have the advantage that defined subsets of the LEDs can be switched on and off. In both cases, the switching on and off can be controlled by the computer ( 18 ) via the switching device ( 19 ).

The confocal beam path shown in FIGS. 1 to 3 between the illumination plane ( 11 b), focal plane ( 13 f) and diaphragm plane ( 17 b) is only a special embodiment of several known confocal beam paths, in which the invention in immediately for the expert recognizable way can be applied. In addition, a mapping of the illumination plane ( 11 b) into the focal plane ( 13 f) on a scale of 1: 1 is by no means necessary in the beam path shown. Rather, not only - as is known from microscopes - a downsizing but also an enlargement is possible, which is why the term microscope was not used in the heading.

In FIG. 4, a glass plate (41) is shown for an inverted illumination grid. Here, the opaque layer applied to the glass plate consists only of small zones ( 42 ), which are separated from one another by relatively wide, translucent areas.

In Fig. 5, the illumination grid is generated by a lens array ( 53 ), which produces sufficiently small light spots ( 54 ) in the illumination plane ( 11 b) by sufficiently good imaging properties from an almost punctiform light source ( 51 ). The condenser lens ( 52 ) causes the lens array ( 53 ) to be penetrated by a parallel bundle, so that each individual lens ( 53 l) is used optimally.

Fig. 6 shows an arrangement in which a diaphragm (61) is frequently displayed in the illumination plane (11 b) by a lens array (53). This diaphragm is illuminated via the condenser ( 62 ) and the lens ( 63 ) from the light source ( 11 ). A wide variety of embodiments are possible as an aperture. As an example, FIG. 7 shows an aperture ( 61 ) with a square boundary of the translucent area ( 71 ) and an opaque center ( 72 ) for an inverse illumination grid. Of course, panels for a lighting grid made of light points etc. are also possible.

Claims (16)

1. Device for three-dimensional optical examination of an object ( 14 ) with a light source ( 11 ), a receiver ( 17 ) and optical elements ( 13 o, 13 u, 13 t) for a confocal beam path, in which a lighting plane ( 11 b ) is depicted in a focal plane ( 13 f), which lies on or in the object ( 14 ), and in which the focal plane ( 13 f) is depicted in a diaphragm plane ( 17 b), characterized in that an illumination grid ( 12 , 22 , 32 ) is arranged in the illumination plane ( 11 b), that a CCD receiver ( 17 ) is arranged in the diaphragm plane ( 17 b) and that the illumination grid ( 12 , 22 , 32 ) on the CCD receiver ( 17 ) with a grid dimension is shown, which is the grid dimension of the light-sensitive areas of the CCD receiver ( 17 ) approximately the same or larger. 2. Device according to claim 1, characterized in that the illumination grid ( 12 , 22 , 32 ) on the CCD receiver ( 17 ) is mapped with a grid dimension which is the same as or a grid dimension of the light-sensitive areas of the CCD receiver ( 17 ) is an integer multiple of it. 3. Apparatus according to claim 1 or 2, characterized in that the lighting grid ( 12 ) from the light source ( 11 ) illuminated holes ( 12 l) in one layer ( 12 s). 4. The device according to claim 3, characterized in that a lens array ( 22 a) is provided for the illumination of the holes ( 12 l). 5. The device according to claim 1 or 2, characterized in that the lighting grid consists of a light source ( 11 ) illuminated layer with opaque zones ( 42 ). 6. The device according to claim 1 or 2, characterized in that the illumination grid is generated by a lens array ( 53 ), which the light source ( 51 ) often in a grid arrangement in the illumination plane ( 11 b). 7. The device according to claim 1 or 2, characterized in that the illumination grid by a lens array ( 53 ), which from a light source ( 11 ) illuminated aperture ( 61 ) often in a grid arrangement in the illumination plane ( 11 b) , is generated. 8. The device according to claim 7, characterized in that the diaphragm ( 61 ) has an opaque center ( 72 ). 9. Apparatus according to claim 1 or 2, characterized in that the lighting grid ( 32 ) consists of a light source array ( 32 a). 10. The device according to claim 9, characterized in that the light sources ( 32 l) of the light source array ( 32 a) can be switched on and off individually or in subsets. 11. The device according to one of claims 1 to 10, characterized in that the focusing plane ( 13 f) on different layers ( 14 s) of the object ( 14 ) is adjustable by an adjusting device ( 15 ) and / or the lighting grid ( 12 , 22 , 32 ) and the object ( 14 ) can be moved relative to one another in planes perpendicular to the optical axis ( 10 ). 12. Device according to one of claims 1 to 11, characterized in that the CCD receiver ( 17 ) is connected to a computer ( 18 ) in which the signals of the CCD receiver ( 17 ) are evaluated. 13. The apparatus according to claim 12, characterized in that the computer ( 18 ) is connected to an adjusting device ( 15 ) through which the adjustment of the focal plane ( 13 f) to different layers ( 14 s) of the object ( 14 ) and / or the movement of lighting grid ( 12 , 22 , 32 ) and object ( 14 ) relative to each other can be controlled by the computer ( 18 ). 14. The apparatus of claim 10 or 13, characterized in that the computer ( 18 ) is connected to a switching device ( 19 ) through which the light sources ( 32 l) of the light source array ( 32 a) individually or in subsets depending on the results of the evaluation of the computer by the computer ( 18 ) can be switched on and off. 15. Device according to one of claims 12 to 14, characterized in that the computer ( 18 ) with an adjusting device ( 15 v) is connected, through which the lighting grid ( 12 , 22 , 32 ) and the CCD receiver ( 17 ) are displaceable relative to one another in the illumination plane ( 11 b) or in the diaphragm plane ( 17 b). 16. The device according to one of claims 1 to 15, characterized in that a telecentric diaphragm ( 13 t) is provided in the confocal beam path, which is ring-shaped and / or has a transmission pattern.