GB2161639A

GB2161639A - Method and apparatus for superimposing two images

Info

Publication number: GB2161639A
Application number: GB08516030A
Authority: GB
Inventors: Arthur Richard Berrill
Original assignee: Wild Heerbrugg AG
Current assignee: Leica Geosystems AG
Priority date: 1984-06-27
Filing date: 1985-06-25
Publication date: 1986-01-15
Also published as: DE3521902A1; GB8516030D0

Abstract

An apparatus for superimposing two images having a transparent liquid crystal display 20, 21 and an image processor 10, 11 connected thereto. On one side of the display is provided a device for reading in the first image, and on the other side thereof is provided an image writing means, with the two being controlled to operate on a common coordinate system. In use of the apparatus as an evaluation tool in stereophotogrammetry, the first image is a stereo map or aerial photo, and the other side of the LCD receives manually selectable images of designs or characters as an overlay. <IMAGE>

Description

SPECIFICATION Method and apparatus for superimposing two images The present invention relates to method and apparatus for superimposing two images to produce stereo images. Apparatuses for superimposing digitally represented images particularly for use in stereophotogrammetry are known. An example thereof is in the field of aerial photographs which are taken quickly one after another at the same altitude and which are projected as right-hand and lefthand images resulting in a stereo image.

When observing these images, an operator seeks common points or objects and attempts to make them coincide. Common coinciding points are, for example, joined by contours. In order to facilitate the operator's work, a further image with auxiliary representations or marks is superimposed by projection on at least one of the two images making up the stereo image.

For example, this occurs in EP 0,035,067 using optical deflecting and beam guidance means, but this approach involves considerable constructional expenditure. According to the aforementioned publication, the additional image is obtained with the aid of a television camera, which is located on a drawing or visual display means and which must be constantly moved therewith. Thus, the camera is an impediment when observing the image.

The installation of the camera and the need to insure completely satisfactory iilumination are also difficult. Finally, when working with the equipment for prolonged periods, the problem of interline flicker which is inherent in connection with television pictures is a disadvantage.

It is also not possible to superimpose digital auxiliary data onto the image in this system.

According to a further proposal for the use of an apparatus for superimposing images in photogrammetry (WO-83/01305), the additional image, which is varied in an image processing device with the aid of inputs from the operator, is also fed into the optical path of one of the stereo images for superimposition with the normal image. In the case of this device, once again considerable effort and expenditure are involved in superimposing the additional image. The relatively poor image quality also has a disadvantageous effect when working for long periods with this apparatus.

According to the present invention, there is provided an apparatus for superimposing two images, the apparatus comprising transparent liquid crystal display (LCD) means, image processor means, means interconnecting said image processor means and said display means, means to read in a first image onto said LCD means from said image processor means positioned at one side of said LCD means, means to read in a second image onto said LCD means positioned at the other side of said LCD means, and means to interface said image processor and means to read in a second image so that they operate on a common coordinate system with respect to said LCD means.

As will become apparent from the following description, the invention can improve known image superimposing means so that they have a simpler construction, permit simple and reliable operation and lead to a marked improvement in operation when used in photogrammetric image processing.

The easy manipulation of the indicating or display device while it simultaneously acts as a storage plate in accordance with the invention is particularly advantageous. Particularly when used in stereophotogrammetry, considerable simplification results from the omission of additional constructional devices and their corresponding expenditure in connection with image superimposing, such as beam deflecting means or television cameras. There is also a marked improvement in the representation provided to the operator for further processing.

It is also possible to produce copies of the processed images in a simple manner.

An additional advantage is the possibility of being able to remove the image storage medium from the apparatus whereby the image information can be stored for long periods. At a different location and/or at a later time, the stored image carrier can again be inserted in a corresponding apparatus and undergo further processing, without loss of image information.

In the same way, image information from spatially separated image detection means, e.g. radars, or image processing equipment can be kept for a certain time in stored form on the image storage medium and can be transported to another processing location.

The invention is described in greater detail below relative to non-limitative embodiments and the attached drawings, wherein: Figure 1 is an overall schematic view of a preferred embodiment of the invention; Figure 2 is a view of the image display according to the preferred embodiment; and Figure 3 is a block diagram of the image processor thereof.

A preferred embodiment of the invention, for use in the field of stereophotogrammetry, is shown in the drawings and is described below, by way of example.

On the left-hand side of Fig. 1 is shown a stereo viewer 2 and two symbols L and R indicating the left and right eyes of a human observer. The right-hand side of Fig. 1 shows an associated image processor 1. Processor 1 includes an image store means 10, in which can be stored, for example, a series of aerial photographs, from whose information maps are produced, existing maps are revised, and which can also be provided with contours or symbols. The desired images are supplied by means of an image converter 11 in the form of left and right partial images to the stereo viewer 2. Image processor 1 also contains a character storage means 12, which is connected to a processor 1 3 .As a result of manual input, processor 1 3 makes it possible to read-back a graphic symbol or a particular character from character storage means 1 2 and supply it to a graphics read-out or output unit 14. From the latter, the characters are supplied as overlays or second image information to the stereo viewer 2. In addition, said information can be read out on a plotter 15, e.g. in superimposed form with respect to the first image already in the viewer and is simultaneously drawn by the plotter 1 5 as a photograph or map.

The viewer contains both a left-hand display 20 and a right-hand display 21, which are in the form of transparent liquid crystal displays and whose construction and operation will be explained hereinafter relative to Fig. 2. Both displays 20, 21 receive at least the two left and right partial images L1 and R1 from image converter 11. The resulting images or pictures are stored on each of the displays.

Moreover, by means of suitable viewers not shown in the drawing, they are also visible to the eyes L and R of the observer.

On at least one of these displays 20, 21 is superimposed a second image L2 or R2 from the opposite surface thereof, as described below in regard to Figure 2. These corresponding signals L2 and R2 are the output signals of the graphic output device 1 4. This image is on the one hand stored in the particular display 20 or 21 and on the other facing the observer's eyes. The first partial image and the additional image appear to the observer there in superimposed form. By means of the superimposed images and with the aid of the manual inputs acting on the processor 13, the operator has great flexibility, e.g. he can carry out image displacements or insert symbols at particular points on the first partial images, and the like.

An interface 51 and the corresponding element 51A of Fig. 3, interconnects many parts of the respective apparatuses including image converter 11 and the overlay processor 1 3 to assure that the coordinate drives of the upper and lower image producing means described below in conjunction with Fig. 2 produce images which are in registry, i.e., that the coordinates correspond between the two images. This operates the entire system for both input and output on a common coordinate system.

With the aid of Fig. 2, a more detailed description will now be given of the construction and operation of display 20 forming part of viewer 2. A liquid crystal display (LCD) 30 is embedded in a frame 31, which simultaneously acts as a guide for coordinate guidance on both the top and the bottom of the arrangement.

On the bottom surface of the transparent LCD display 30 is diagrammatically shown in dash lines and by arrows the XY-guide of a carriage which is not further represented and on which is provided a device for representing the partial image supplied by line L1 onto the display 20. Display 20 also contains scanning optics 32, as well as an illumination system 33, which form part of a conventional viewer.

The carriage carrying optics 32 receives control signals for the displacement of its position along the X and Y coordinates.

On the top surface of display 20, there is a second carriage 34, which is also controllable along the X and Y coordinates and to which is fitted a laser diode 35 controllable from the image processor 1. In accordance with the information received from image processor 1, image or character contents from the top surface are written on the LCD 30 and simultaneously this image information is stored therein. Carriage 34 can also carry means not shown for scanning the image information of the LCD for retransmission back to image processor 1.

The liquid crystal display 30 is preferably removable and interchangeably arranged in frame 31. The image content, which will remain unchanged for long periods of time without any additional aids, can at a subsequent time be further processed on the same or a different but similar apparatus without difficulty. Thus, data from external or spatially remote image data detection means can initially be stored in a display 30 and then further processed on other means, at the same or at different locations.

A particularly advantageous embodiment is described below and is shown in Fig. 3. Of course, as is clear, and which is also true of Fig. 2, only one display 30 is shown by way of example, another similar one will be provided for stereo use, as shown in Fig. 1. The overlays can be on one or on both LCDs 30.

The Fig. 3 embodiment comprises a display means 30 with interconnected auxiliary devices, the means being connected via a first bus 40 to an image representation means 41, e.g. a plotter. The lower part of Fig. 3 essentially shows the image processor 1 according to Fig. 1. The latter has a second bus 50, which is connected to the first bus via the corresponding interface 51.

Display 30 contains a first servo-amplifier 36 for controlling carriage 34, and a second servo-amplifier 37 for controlling the lower carriage, which carries both the reading optics 32 and the other means connected thereto.

Both amplifiers 36 and 37 are guided on the first bus 40 and are connected via the same with a positioning processor 38. A control device 39 connected to the first bus serves to support plotter 41. Device 39 can be provided with means for accepting manual instructions.

Image processor 1A contains a data input station 52, the aforementioned connecting interface 51, a computer 53, a graphics means 54 and, if required, a storage medium 55, a station 56 for producing safety copies, and a connection 57 to other data networks.

While the invention has been described in detail above, it is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the scope of the invention as defined in the following claims.

Claims

1. An apparatus for superimposing two images, the apparatus comprising transparent liquid crystal display (LCD) means, image processor means, means interconnecting said image processor means and said display means, means to read in a first image onto said LCD means from said image processor means positioned at one side of said LCD means, means to read in a second image onto said LCD means positioned at the other side of said LCD means, and means to interface said image processor and means to read in a second image so that they operate on a common coordinate system with respect to said LCD means.

2. Apparatus according to claim 1, said means to read in a second image comprising a laser diode.

3. Apparatus according to claim 1 or 2, wherein said image processor means converts an optical image into digitally coded image information to be read onto said LCD means.

4. Apparatus according to claim 1,2 or 3 and including means to read-out information stored in said LCD means, and means to cause said read-out means to also operate on said common coordinate system.

5. Apparatus according to any one of the preceding claims, wherein said LCD means is removable from the apparatus and said LCD means comprising means to retain images thereon for prolonged periods of time both when in place in and removed from said apparatus to thereby act as an interchangeable image storage means.

6. Apparatus according to any one of the preceding claims, wherein said apparatus is used as an evaluation means in stereophotogrammetry, and said LCD means and said image processor means both being of suitable dual construction to thereby provide a stereo image.

7. Apparatus according to claim 6, wherein said means to read in a second image comprises means to overlay on at least one of the dual images in said stereo image representations of at least one of a plurality of designs and characters to be overlaid on said stereo image.

8. Apparatus according to claim 7, and including stereo viewer means, and means to position said dual LCD means in said stereo viewer means for viewing of said stereo images with said overlays thereon by a human observer.

9. Apparatus according to claim 8, wherein said stereo images are presented on the side of said LCD means furthest from said observer and said designs and characters are presented on the side of said LCD means closest to said observer.

10. Apparatus according to claim 7,8 or 9, said stereo images comprising one of maps and photographs.

11. A method for superimposing two images, comprising the steps of providing transparent liquid crystal display (LCD) means and image processor means, interconnecting said image processor means and said LCD means, reading in a first image onto said LCD means from said image processor means from one side of said LCD means, reading in a second image onto said LCD means from the other side of said LCD means, and performing said two steps of reading in a first and a second image using a commmon coordinate system with respect to said LCD means.

12. The method of claim 11, including using a laser diode in said step of reading in a second image.

13. The method of claim 11 or 12 and including using said image processor means to convert an optical image into digitally coded image information to be read onto said LCD means.

14. The method of claim 11,12 or 1 3 and including the step of reading out information stored in said LCD means, and performing said reading out step also on said common coordinate system.

1 5. The method of any one of claims 11 to 14 and including the step of removing said LCD means from the apparatus and retaining images on said LCD means for prolonged periods of time both when in place in and removed from said apparatus to thereby cause said LCD means to act as an interchangeable image storage means.

16. The method of any one of claims 11 to 1 5 and including the step of using said method as an evaluation means in stereophotogrammetry, and causing said LCD means and said image processor means to both be of suitable dual construction to thereby provide a stereo image.

17. The method of claim 16, said step of reading in a second image also performing the step of overlaying on at least one of the dual images in said stereo image representations of at least one of a plurality of designs and characters.

1 8. The method of claim 1 7 and including the step of providing stereo viewer means, and positioning said dual LCD means in said stereo viewer means for viewing of said stereo images with said overlays thereon by a human observer.

1 9. The method of claim 18 and including the step of presenting said stereo images on the side of said LCD means furthest from said observer and presenting said designs and characters on the side of said LCD means closest to said observer.

20. The method of claim 1 7 or 18 wherein said stereo images are one of maps and photographs.

21. Apparatus for superimposing two images, such apparatus being constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

22. A method of superimposing two images substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.