CH620297A5 - Method for the optical analysis of a sample in a double-resolution apparatus, and apparatus for implementation thereof - Google Patents

Description

The present invention relates to a method for the optical analysis of a sample in a two-resolution apparatus and an apparatus for its implementation.

In many areas where particles have to be analyzed, such as for example in the analysis of blood cells or rubbed, the particles of interest are dispersed in a field where they are surrounded by particles of no interest. For example, leukocytes can be surrounded by hundreds of red blood cells, while cancer cells or dysplastic cervical cells can be surrounded by tens and thousands of normal cervical cells and waste products.

It is however desirable to analyze in detail only the particles of interest located in the field of vision of the analysis apparatus. This can be achieved by performing a detailed analysis of all objects so that we can exclude those that are devoid of interest. However, such a technique is very long and therefore relatively without commercial value. You can also use a single detector to carry out an initial analysis of all the particles, this at low resolution, then switch the detector to a higher resolution to carry out a more detailed analysis when you have found an interesting particle in the sample. However, this method requires a mechanical or electrical switching of the resolving power with the drawback that there is only one analysis mode available at a given time.

The use of simultaneous analyzes at different resolutions makes it possible to avoid the drawbacks of known analysis methods. Exploration devices with two resolving powers have already been used. Aldrich and his associates described in the invention disclosure of U.S. Patent No. 3,448,271 an

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device of exploration with two powers of resolution which centers on and pursues the celestial bodies. In this device, two coaxial and enlarged images are used differently to obtain and track the stars or the solar disk. The output signal resulting from the scanning by a single detector is used as a signal indicating the centering, this in a feedback loop, for centering the image of the star on the optical axis. No analysis of the image of the celestial bodies is carried out or represented. In fact, the images superimposed on the single detector make it impossible to analyze the output signal of the exploration device.

Similarly, Ward described in the invention disclosure of US Patent No. 3,614,449 a two-resolution scanning device for detecting and tracking a distant light source (the target). Ward describes the same type of device with two coaxial resolutions, in which the two images are projected on the same detector. In addition, a second detector is provided which is sensitive to a telemetry source constituted by light with a narrow spectral band which is emitted by the device and reflected by the target. Although the telemetry device operates independently of the dual resolution centering and tracking device, it is housed in the same assembly to ensure the small footprint required for NASA applications. Here too, no analysis of the image has been described or represented by the tracking and tracking system or by the telemetry system.

Other uses of exploration at two resolutions have been described, for example by Gard in the disclosure of US Patent No. 3,804,967, which uses the explored images for display. However, these presentations do not describe or represent an image analysis.

Adkins described, in the invention disclosure of US Patent No. 3,864,564, a two-resolution scanning device, a low-resolution, one-dimensional scanning being used to find and determine the position of a cell and a two-dimensional, high-resolution scan being used to analyze the cell. The high resolution detector consists of a vidicon television camera which is well suited for the analysis of the centered blood cell. On the other hand, the low resolution detector consists of a simple photodetector. The image is scanned through the photodetector using a rotating mirror, thereby producing one-dimensional linear scanning. The low resolution signal is only used to detect and center the cell so that it can be analyzed by the high resolution detector. Analysis using the low resolution part of the device is neither described nor shown. In fact, any analysis using the one-dimensional information provided by the linear scanner can only be difficult and limited.

A device such as that described by Adkins has various drawbacks. In the case of the blood cell for example, if there are different classes of cells detected by the acquisition and centering device at low resolution, and if one wishes to perform a detailed analysis only of a sub- together of these cells, it is necessary to locate and center all the cells detected and to analyze them all in detail using the Adkins device. Thus, it is necessary to make an unnecessary extra effort. In the case of rubbings where there may be thousands of normal cells for each cancer cell, the extra work required to perform a detailed analysis of each normal cell to find a single cancer cell makes commercial application impossible.

In different cases, it is possible to obtain enough information from a low resolution preliminary analysis to know if a detected particle deserves a more detailed further analysis. In the case of the blood cells mentioned above, particles such as dirt or large stained crystals can and should even appear in blood smears. A simple preliminary measurement of the particle size is usually sufficient to exclude these particles from detailed high resolution analysis. A more complicated low resolution analysis can be used if desired.

Thus, the general object of the invention is the establishment of a method and an apparatus which avoid the drawbacks of the known devices.

The method according to the invention is defined in claim 1.

The apparatus for carrying out the method is defined in claim 5.

The drawing represents, by way of example, two embodiments of the apparatus according to the invention:

Fig. 1 is a schematic perspective view of an analysis device with two resolving powers;

fig. 2 is a block diagram of the electrical circuit used for the low resolution analysis of a large area in order to determine the presence of an interesting object and these coordinates;

fig. 3 is a detailed flow diagram illustrating the transmission of data in a characteristic analysis at low resolution;

fig. 4A to 4D illustrate different relationships between the fields of vision of low resolution and high resolution detectors; and fig. 5 is the diagram of another embodiment of the apparatus.

Fig. 1 is a schematic perspective view of an analysis device with two resolutions. It includes a sample holder 1 which can be moved in both directions X and Y using drive motors 2 and 3, and which carries a sample 4 comprising several interesting particles 5a, 5b and 5c. In the case of blood analysis, the sample holder 1 normally comprises a glass plate on which the blood sample 4 is placed in a known manner. Note that the blood sample will contain many red blood cells and a number of leukocytes 5a, 5b and 5c etc. dispersed among these red cells and constituting the particles of interest, groups of leukocytes, other groups of particles and impurities such as dust particles and colored precipitates.

A first objective 6, constituted for example by a microscope objective forms an image of a certain zone 7 of the sample. This image is sent using a blade with parallel faces 6b and a low resolution optics 8 on a low resolution detector 9. It is illustrated at 10. A smaller area 11 of the sample gives, through the first objective 6 and a second high resolution optic 12, an image on a high resolution detector 13. The high resolution image formed on the detector 13 is shown at 14. A high resolution analyzer has the reference number 37. Box 38 represents a calculator of the coordinates of an object detected by the low resolution sensor 9, to bring its image into the high resolution sensor 13.

Conventional optoelectric image exploration devices can be used to form the low and high resolution detectors 9 and 11. For example, the opto-electric detectors may include a television camera, an image dissector and an array of photo-diodes or the like. Opto-electric detectors convert the corresponding images into electrical signals of a well-known material.

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In this embodiment, the low resolution signal appearing at the output of the detector 9 is applied to the line 14b and is used to analyze the area 7 and determine whether an interesting particle (leukocyte) such as 5a, 5b and 5c is present and if so to determine its position in said area 7 so as to form signals to bring the particle of interest into the field of vision of the high resolution detector so that it can be subjected to a more detailed analysis. In the embodiment illustrated in FIG. 1, the particle of interest is brought into the field of vision of the high resolution detector by moving the sample holder in the X and Y directions using the drive motors 2 and 3. It is necessary to note that the same relative movement can be obtained by moving the optical system and holding the sample holder in place. Such a device is illustrated in FIG. 4 and will be described later.

A circuit allowing the analysis of the area 7 in order to discover there a new interesting particle, the calculation of its coordinates and producing output signals to activate the motors 2 and 3 so that they bring the interesting particle in the field of vision of the high resolution detector is illustrated in the block diagram of fig. 2. The output signal from the low resolution detector, which is applied to line 15, is introduced into a low resolution analyzer 16.

In this example, the densities of the particles of interest are higher than those of the surrounding sample. Thus, the threshold is fixed so that when the low resolution output signal from the detector 9 exceeds this threshold, the two resolution exploration device is supposed to have encountered an interesting particle. This condition is indicated by a signal appearing on the output line 17 of the comparator.

Different analyzers can be used to perform the low resolution analysis, depending on the characteristics of the particular sample to be analyzed. Such an analyzer is described in the disclosure of the invention of US Patent No. 3,851,156. This analyzer will be used in the case where an intensive analysis must be carried out at low resolution.

If a simple low resolution analysis is desired, an analyzer can be used which discriminates by indicating whether the size of the particle is less than or greater than a determined value or if its length is less than or greater than a determined value. This can be done by a particle analyzer such as the zi MC image analyzer from Bosch & Lomb Corp. or the Quantimet image analyzer available from Imanco Corp. The use of a relatively simple or relatively complex low resolution image analyzer does not matter and does not change anything as to the principle of the invention. The low resolution image analyzer is chosen based on the particular application to be performed.

The low resolution image analyzer 16 applies a charge signal to line 17 when it recognizes a particle deserving of more detailed analysis. Assuming that the low resolution scanning device scans a frame of 64 X 64 elements, its position can be recorded using X and Y coordinate counters, 19 and 20 respectively, of 6 bits each. These counters are reset using a line 21 before the start of each exploration. During the exploration, the clock line 18 increments the counter 19 each time the exploration device detects a mark on a horizontal line. At the end of each horizontal line, the X coordinate counter is saturated and an overshoot signal, sent on a line 22, is used to increment the Y coordinate counter 20.

Registrers 23 and 24 cooperate with counters 19 and 20 respectively. The X coordinate register 23 is linked to the X coordinate counter and the register 24 is linked to the Y coordinate counter, so that when a load signal occurs on line 17, the content of the X coordinate counter is transferred to the X coordinate register and the content of the Y coordinate counter is transferred to the Y coordinate register. Thus when an interesting particle is detected by the low resolution analyzer 16, its position in the area 7 is recorded in the registers 23 and 24.

The output signals from the X and Y coordinate registers are applied to output buses 25 and 26. These supply subtractor adders 27 and 28 in which the position of zone 11 relative to zone 7 is subtracted (or added depending on the case) so as to generate displacement control signals in X and Y, on the output lines 29 and 30. The motor control circuits 31 and 32 transform the displacement control signals into electrical control signals motors so that they print the displacements represented by said control signals.

It should be noted that at the end of an exploration, the circuit, according to fig. 2, will have recorded the position of the last particle in zone 7. It will however be noted that it is possible to block the charge signals after the first particle of interest encountered so that it is its position which is recorded instead of that of the last particle. The overshoot of the Y coordinate counter 20 is used to stop the movements of the motors by means of an “end of frame” circuit 34, this until the last change of the content of the registers 23 and 24.

If a more complex low resolution analyzer is used, such as that described in the disclosure of the US patent 3,851,156 mentioned above and shown in the flow diagram of FIG. 3, the position signals according to the X and Y coordinates are obtained by taking account of the characteristics of the cells which have been recorded. This is shown in fig. 3 by the outputs corresponding to the positions in X and Y, where

39 = calculation of the partial characteristics for the cell segment,

40 = assignment of a number from the region segment and

41 = calculation of complete characteristics from partial characteristics.

The position information is obtained from the low resolution detector and is delayed or not in the same way as for the data relating to the cell. The overshoot signal at y is replaced by an end of analysis signal intended to trigger the movement.

The short description above of a relatively complex low resolution analyzer concerns the processing of information relating to a single interesting individual. It is clear that several interesting particles can be treated if one has the appropriate storage and processing capacities.

It should be noted that when the particle of interest detected by the low resolution analyzer was moved into the field of vision of the high resolution detector, this movement also brought a new range in the field of vision of the detector at low resolution. Although the particle is being explored and analyzed by the high resolution detector and by high resolution analysis means, the new range 7 can be explored and analyzed by the low resolution detector and the analyzer at low resolution to see if there is another interesting particle in this new range 7. Thus, when the detailed exploration of the particle located in the field of vision of the high resolution detector is complete, registers 23 and 24 of the coordinates X and Y contain the coordinates of a new interesting particle if one of them is actually in the new

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velie plage 7. This characteristic which allows the simultaneous or almost simultaneous analysis of the sample with different resolutions results in a considerable increase in its working speed compared to a device which must perform these operations sequentially. s

It should also be noted that the position of the field of vision of the high resolution detector relative to the field of vision of the low resolution detector as shown in FIG. 1 can only be one of a determined number of positions. Fig. 4 illustrates some of the relative positions of the two fields of vision. In fig. 4A the field 1 lb of vision of the detector with higher resolution is represented in the center of the field 7b of vision of the detector with low resolution. Other locations within the field of view of the low resolution detector can be used as shown in fig. 4B. The field of vision of the high resolution detector can also be situated astride the limit of the field of vision of the low resolution detector as shown in FIG. 4C or even be located entirely outside of it as shown in FIG. 4D. These four provisions are not exhaustive but represent only examples of a large number of possibilities.

It was mentioned above that it is not necessary to physically move the sample holder 1 to bring the particle of interest into the field of vision of the detector at 2s high resolution. Fig. 5 shows the sample holder in lb and the sample in 4b. Motors 2b and 3b are used to move movable mirrors 33 and 34, which modifies the area of the sample 4b explored by the high and low resolution detectors, without physical movement of the sample. In general, this arrangement is only practical if the working distance of the first objective 6b is sufficient to allow convenient positioning of the mirrors between it and the sample while maintaining a relatively uniform focus.

It will be noted that the relative movement of the field of vision of the high resolution detector with respect to the particle of interest can be carried out with or without corresponding relative movement of the field of vision of the detector at low resolution. In the preferred embodiment, the two fields of vision of the low and high resolution detectors are both moved relative to the particle of interest to bring it into the field of vision of the high resolution detector. However, in this preferred embodiment there is no relative movement between the two fields of vision during the relative movement of the particle of interest towards the field of vision of the high resolution detector.

The output signal from the high-resolution detector 13 is applied to an appropriate analyzer 37. Such an analyzer is described in the description of US Patent No. 3,851,156 relating to an analysis method and to an apparatus using an algebra of colors and image processing methods.

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Claims (17)

620,297 2 1. Method for the optical analysis of a sample in a two-resolution apparatus, characterized in that the sample is examined in a first field of the apparatus at a low resolution to detect an object therein, that the object detected is analyzed to determine whether it belongs to a determined category and that, if so, it is analyzed in a second field at a higher resolution while continuing to examine the sample at a low resolution to detect another object. 2. Method according to claim 1, characterized in that the continuous examination at low resolution is carried out without moving the sample relative to at least one of the fields of the apparatus. 3. Method according to claim 2, characterized in that the second field is moved relative to the sample to bring each of the objects detected in said second field. 4. Method according to claim 1, characterized in that one moves and the first field and the second field relative to the sample while maintaining their relative position. 5. Apparatus for implementing the method according to claim 1, characterized in that it comprises means of search at low resolution, determining the first field, for detecting an object, first means for analyzing the object in order to determining whether it is an object of said determined category, second means, determining the second field, for analyzing the object of said category at a higher resolution, and means controlled by said first analysis means of the detected object to start the analysis of the object of said category by said second higher resolution analysis means, while said low resolution search means continue the search in the sample in order to 'detect another object. 6. Apparatus according to claim 5, characterized in that it comprises means for positioning the sample, and in that it is arranged so that the continuous examination at low resolution is carried out without moving the sample relative to at least one of said fields. 7. Apparatus according to claim 6, characterized in that it is arranged so that the field relative to which the sample is not moved is the first field. 8. Apparatus according to claim 6, characterized in that it is arranged so that the field relative to which the sample is not moved is the second field. 9. Apparatus according to claim 6, characterized in that it is arranged so that the continuous examination at low resolution is carried out without moving the sample relative to the two fields. 10. Apparatus according to claim 5, characterized in that it comprises means for positioning the sample, in that the search means comprise first opto-electric means for exploring an image to produce an output signal when an object is encountered in said image and first optical means for forming on these first opto-electric means an image of low resolution of the portion of the sample falling in the first field, and in that the second means analysis include second opto-electric means for exploring an image to produce output signals representing the explored image and second optical means for forming on these second opto-electric means an image of higher resolution of the portion of the sample falling into the second field, the first analysis means receiving the output signal produced by said first opto-electric means for analyzing said output signal so to determine if the object encountered belongs to said category and, if so, to produce a signal indicating the presence of an object of said category, and said means controlled by said first analysis means being arranged to bring the object encountered in the second field as a function of the signal produced by said first analysis means. 11. Apparatus according to claim 10, characterized in that said first and second optical means have a common part. 12. Apparatus according to claim 10, characterized in that said means for positioning the sample comprise a sample support which can be moved along the coordinates X and Y and in that said controlled means comprise drive means according to X and Y coordinates to move said sample holder. 13. Apparatus according to claim 10, characterized in that said controlled means are arranged to move the two fields relative to the sample. 14. Apparatus according to claim 13, characterized in that said controlled means are arranged to move the two fields without altering the relative position of these two fields relative to each other. 15. Apparatus according to claim 14, characterized in that the search means and the second analysis means are arranged so that the second field is inside the first field. 16. Apparatus according to claim 14, characterized in that the search means and the second analysis means are arranged so that the first and the second fields partially overlap. 17. Apparatus according to claim 14, characterized in that the search means and the second analysis means are arranged so that the second field is outside the first field.