The invention relates to a method for presenting images that have been recorded by means of a digital surgical microscope. The invention also comprises a digital surgical microscope system in which the method according to the invention is realized.

Digital images that have been recorded by a surgical microscope are usually viewed by a user, for example a doctor carrying out a surgical operation, by means of a display device, for example a monitor, digital binoculars or a head-mounted display. If the display device has a high display resolution, but is too far away from the user, the user cannot make out all of the details of the object presented on the monitor because of his restricted eyesight.

A similar problem is known in the area of digital cameras: Digital cameras generally include an optical zoom function, which enables the user to take photos of objects with a desired magnification. However, the user then possibly cannot make out all of zo the details that are presented on the monitor since the pixel density on the monitor is very high and the user views the monitor from too great a distance to make out all of the details that have been resolved by the optical zoom and the image sensor. For these cases in which the built-in optical zoom in the digital camera is not sufficient to present the object to be photographed in a sufficient size on the monitor, the user is provided with what is known as a digital zoom function, which allows further magnification of the object in the photo. While, however, when using the optical zoom the lenses in the lens system move and change the image angle while utilizing the full format of the camera image sensor, whereby the quality of the image remains at the same high level over the entire optical zoom range, when using the digital zoom the lens system is brought to its maximum telescopic setting and a smaller region of the image sensor is used for recording the image. This image is subsequently converted to the original size (and number of pixels), in order to achieve the same scale of magnification as when using a stronger telephoto lens. The greater the digital zoom setting, the smaller the region of the image sensor that is used, so that the quality of the image keeps decreasing.

Use of a digital zoom does not allow any additional image information, i.e. knowledge of smaller details of the object in the photo, to be obtained. To achieve an image quality that is as high as possible, therefore, first the optical zoom of the camera is brought to the maximum telescopic setting and then—if necessary—the digital zoom is additionally activated.

A similar method is known for the Kodak EasyShare LS633 digital camera: There, a method known as the “Advanced Digital Zoom” is used, a method in which first the optical zoom is set to the maximum magnification and then optionally a digital zoom can be additionally activated by the user if this optical zoom is insufficient.

Many digital cameras therefore have a two-stage zoom method, in which first an internal optical zoom in the camera is set to the maximum magnification and then if need be the image is digitally re-magnified. This gives the user the possibility of using the digital zoom to magnify small details until they are of sufficient size on the monitor for the user to see them. However, it is in this case relatively laborious and difficult for the user to find precisely that overall magnification with which he can make out the details with the optimum magnification. Adjusting the zoom too little means that the user cannot make out the entire detailed information of the object on the monitor even though this information was registered by the digital image recording device. Adjusting the digital zoom into the image too much means however that there is very quickly a noticeable loss of image quality, and the image looks unsharp and blurry.

The object of the present invention is therefore to provide a method and a device that assists the user in setting a suitable overall magnification of a digital microscope system. In particular, the intention is for it to be easily possible to set that overall magnification with which the user can still just visually perceive the smallest object details resolved by the digital image recording unit without a loss of quality already being caused by the digital zoom.

This object is achieved by a method and a device having the features of the independent claims. The subclaims concern advantageous developments and variants of the invention.

A method according to the invention for presenting images that have been recorded by means of a digital surgical microscope system uses situative parameters to present the images with suitable magnification. For this purpose, an image is produced on an image sensor by means of an image recording unit, and this image is reproduced for a user, at least in certain regions, on a display unit. The magnification of the image reproduced is then increased by electronic means, using a limit value of the magnification in the determination of which the aforementioned situative parameters are incorporated. Increasing the magnification of the image reproduced by electronic means is understood as meaning measures with which the magnification of the image on the image sensor does not change, that is to say in particular measures with which there is no optical zoom.

For the purposes of the present invention, situative parameters are parameters that arise from the respective application situation of the surgical microscope.

A distance of a user from the display unit may be used in particular as an example of situative parameters. In this way it can be estimated in advance which magnification of the image is best suited to provide the user with the optimum information about the smallest structures that can be resolved by the digital microscope.

Furthermore, it is useful for example when choosing a suitable magnification to include the vision (i.e. the visual acuity) of the user. If, for example, the user has greatly restricted vision, a presentation of very small details on the display unit cannot be used to its full extent since, with his poor visual acuity, the user cannot resolve the details. In this case, the situative parameters do not just comprise the application situation, independently of the respective user, but also include user-specific parameters—in the example described the visual acuity of the user—in the setting of the limit value.

In an advantageous refinement of the invention, a method in which an optical zoom followed by a digital zoom is carried out is proposed. For this purpose, first the limit value of the magnification is determined and then an optical zoom factor of the image recording unit is increased iteratively until its maximum value is reached. Subsequently, a digital zoom factor is additionally activated and is increased iteratively until the image reproduced on the display unit is presented with an overall magnification that corresponds to the limit value of the magnification.

