Automated image analysis employing automatic focussing

Claim 2

In a method of analysing a specimen which iNvolves the steps of forming an image of each of a plurality of small areas of the specimen, scanning each of a succession of images to produce a video signal the amplitude excursions of which are analysed to perform said analysis and deriving an electrical signal indicating the focus of the image for controlling the operation of an automatic focussing system for focussing the image, the improvement comprising: enabling the automatic focussing system only prior to the analysis of the first small area and each nth small area thereafter (n being greater than one), maintaining the focus settings achieved for said first small area and for each nth small area while the intervening small areas are analysed, and; selecting the desired value of n.

Claim 3

The method as set forth in claim 1 further comprising the step of moving the specimen relative to the optical system forming the image in a series of steps along parallel lines to obtain the said succession of small areas.

Claim 4

The method as set forth in claim 2 further comprising the step of enabling the automatic focussing system prior to the analysis of the first small area at the beginning of each new line so that an automatic focussing step is performed at the beginning of each new line.

Claim 5

The method as set forth in claim 3 further comprising the additional steps of storing information relating to the focus setting for the first small area of each of line for the duration of the line and returning the focussing system to this setting before the automatic focussing system is enabled at the beginning of the next line.

Claim 6

The method as set forth in claim 1 further comprising the steps of generating an electrical pulse each time a small area is analysed, counting successive electrical pusles by means of a pulse counter having a capacity of n, and generating an electrical command signal to stop the further analysis of small areas and initiate an automatic focussing step when the counter overflows.

Claim 7

The method as set forth in claim 5 further comprising the step of adjusting the capacity of the pulse counter to vary the value of n.

Claim 8

The method as set forth in claim 1 further comprising the step of generating a frame blanking signal for releasing the video signal only during every nth frame scan of an image of a small area, to allow settlement of the specimen to occur before measurement is made on the video signal.

Claim 9

The method as set forth in claim 1 further comprising the step of generating a rotation producing electric current for an electric motor drive in response to an adverse focus indicating signal, movement of the drive producing movement of the specimen in a direction to improve the focus of the image of the area thereof which is being scanned to produce the said video signal.

Claim 10

The method as set forth in claim 8 wherein the net movement of the motor from a rotation producing current pulse is always k* from its last position either in one direction or the other, depending on the polarity of the pulse.

Claim 11

The method as set forth in claim 9 further comprising the step of selecting one direction of rotation of the motor as the preferred direction of rotation and selecting the corresponding current pulse polarity as the preferred polarity, modifying each pulse of opposite polarity so as to produce a motor movement of (p X k)* (where p>1) and generating immediately after the modified pulse a correction pulse of preferred polarity and magnitude (or duration) to produce a preferred rotation of ((p -1) X k)*.

Claim 12

Apparatus whereby a specimen can be analysed for optical characteristics comprising, means for mounting and illuminating a specimen, optical focussing means for producing an image of an area of the specimen on a photosensitive surface, means for moving the specimen in a series of steps to present a succession of different areas thereof to the optical focussing means, means for scannIng the photosensitive surface to generate a video signal of each imaged area, means responsive to the video signal for making measurements thereon to perform said analysis, circuit means also responsive to the video signal to derive from the amplitude excursions thereof an electrical signal indicative of the focus of the image and automatic focussing means responsive to a focus indicating signal for adjusting the optical focussing means to alter the focus of the image, further comprising circuit means for deriving the focus indicating signal from the video signal, a gate for inhibiting the passage of video signal to the circuit means, a first control circuit for generating a signal for opening the gate, a second control circuit for generating a signal (INF) for indicating when the image is correctly focussed which signal serves to terminate an opening signal from the first control circuit, a counter for counting the number of consecutive areas of the specimen which are analysed after an (INF) signal is generated, the counter being of the type which produces an overflow signal when n steps have been counted and a third control circuit responsive to an overflow signal to generate a further signal to cancel the last generated (INF) signal and initiate a new focussing sequence of the automatic focussing means.

Claim 13

Apparatus whereby a specimen can be analysed for optical characteristics comprising, means for mounting and illuminating a specimen, optical focussing means for producing an image of an area of the specimen on a photosensitive surface, means for moving the specimen in a series of steps to present a succession of different areas thereof to the optical focussing means, means for scannIng the photosensitive surface to generate a video signal of each imaged area, means responsive to the video signal for making measurements thereon to perform said analysis, circuit means also responsive to the video signal to derive from the amplitude excursions thereof an electrical signal indicative of the focus of the image and automatic focussing means responsive to a focus indicating signal for adjusting the optical focussing means to alter the focus of the image, further comprising circuit means for deriving the focus indicating signal from the video signal, a gate for inhibiting the passage of video signal to the circuit means, a first control circuit for generating a signal for opening the gate, a second control circuit for generating a signal (INF) for indicating when the image is correctly focussed which signal serves to terminate an opening signal from the first control circuit, a counter for counting the number of consecutive areas of the specimen which are analysed after an (INF) signal is generated, the counter being of the type which produces an overflow signal when n steps have been counted and a third control circuit responsive to an overflow signal to generate a further signal to cancel the last generated (INF) signal and initiate a new focussing sequence of the automatic focussing means.

Claim 14

Apparatus as set forth in claim 11 further comprising means for adjusting the count capacity of n of the counter.

Claim 15

Apparatus as set forth in claim 11 further comprising a second counter for counting the number of successive steps of specimen movement in one direction, the second counter being of the type which produces an overflow signal when the number of steps counted (m) is equal to the number of steps in the said one direction which are made before flyback of the specimen occurs in the opposite direction, a fourth control circuit responsive to an overflow signal from the second counter for generating an (EOL) signal indicating the end of a line of analysed areas and therefore the specimen flyback condition, said first control circuit also being responsive to an (EOL) signal to also terminate the open signal for the said gate and to initiate a further automatic focussing sequence.