JPS595214A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To enable the exact matching of a focus by making a lens movable to the position where the focus matches on an image pickup plane by the output from an arithmetic processing means. CONSTITUTION:The 1st photoelectric detector 6 disposed in the 1st optical path having the optical path length equal to the optical path length from a lens 2 movable on the optical path to an image pickup plane, the 2nd photoelectric detector 7 disposed in the 2nd optical path having the optical path length shorter than said optical path length and the 3rd photoelectric transducer 8 disposed in the 3rd optical path having the optical path length longer than the 1st optical path length are provided. The 1st, the 2nd, the 3rd arithmetic means 9, 10, 11 which calculate the evaluation of focus matching from the respective output values of the detectors 6, 7, 8, and an arithmetic processing means 12 which is inputted with the outputs of the means 9, 10, 11 and calculates the direction and extent of movement of the lens 2 are provided. The lens 2 is made movable to the position where the focus matches on the image pickup plane by the output from the means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an automatic focus adjustment device required for processing various optical images in the medical field, pattern recognition field, etc.

[Technical background of the invention and its problems]

In recent years, in the medical field, optical images of chromosomes or cells obtained using a microscope are not directly observed with the naked eye, but are converted into electrical signals and then introduced into an image processing device. The image is displayed on an appropriate display device, or the image data is subjected to analysis processing such as contour extraction and image enhancement using a computer, and then the image is displayed on an appropriate display device for observation. It's starting to look like this.

In this case, in order to display the image clearly and perform various types of accurate analysis processing, it is necessary to achieve accurate focus, as misfocusing when receiving the optical image becomes a problem. Benevolence is important.

This importance is not limited to various medical diagnostic devices related to medical images, but also applies to image processing devices such as various pattern recognition devices.

By the way, conventional automatic focus adjustment devices that automatically adjust the focus when receiving an optical AT image employ a so-called high frequency range method that detects the point where the high frequency component of the image is maximum and adjusts the lens position to that point. , or USP4,22
As disclosed in No. 0,850, the difference between the outputs of two optical sensors placed before and after the focal plane, and the difference between the outputs of the lens and the lens? Determine the driving direction (front or rear of the focal point), move the lens one step in the determined direction, again calculate the difference between the outputs of the two optical units, and determine in the same way as before. Some systems employ a method in which the lens is moved by one step in the specified driving direction, and the same operation is repeated until the sign of the difference between the outputs of the two optical sensors changes. Both methods have the disadvantage that focus adjustment takes time. In addition, especially in the latter method, since the focus is adjusted stepwise, there is a drawback that when the focus position is between the step distances, it is not possible to accurately focus the focus.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an automatic focus adjustment device that enables accurate focusing by determining both the direction and amount of movement of the lens. It is something.

[Embodiments of the invention]

The drawing is a schematic block diagram showing one embodiment of the present invention.

In the figure, reference numeral 1 indicates a subject, for example, cells applied to a preparation in a cytodiagnostic apparatus. 2 is a lens, and light source 1 is used for object 1.
6, and the lens drive mechanism 14
O4 is configured to be movable along an optical path from the light source 16 to an imaging surface (not shown) in the image processing unit 15.
A first No.-7 mirror with a transmittance of 50 cm is shown in FIG. photoelectric detector 6
The 10th photoelectric detector 6 detects the light distributed by the 10th 1-7 mirror 4, and sends an electric signal corresponding to the amount of light to a first calculating means, for example, which will be described later. The length of the optical path (first optical path) from the charging converter circuit output to the first difference summation circuit 9 and the object 1 to the tenth photoelectric detector 6 via the first half mirror 4 is as follows. The photoelectric detector 6 is arranged at the end of the first optical path so that the optical path length from the subject 1 to the imaging plane in the image processing unit 15 is equal to the optical path length. Reference numeral 6 indicates a second half mirror 2 with a transmittance of 50 cm, which is placed on the optical path between the first half mirror 4 and the lens 2, and which transmits the light passing through the lens 2 in two directions. (One direction is toward the first half mirror 4). A sixth half mirror 5 is disposed on the path of the light distributed in the other direction by the second half mirror 6, and the third half mirror 5 directs the light to the second half mirror. The elements distributed at step 6 are further distributed to a second photoelectric detector 7 and a sixth photoelectric detector 8.

Each of the second photoelectric detector 7 and the 60th photoelectric detector 8 is a photoelectric converter similar to the photoelectric detector 6 of Ml, and the electric signals outputted respectively are sent to the second difference sum circuit 10 and the 5th photoelectric detector 8. It is designed to be input to a difference sum circuit 11.

Moreover, the length of the optical path (second optical path) from the subject 1 to the second photoelectric detector 7 via the second half mirror 6 and the sixth half mirror 5 is , is arranged in the second optical path so that the optical path length from the subject 1 to the imaging surface in the image processing unit 15 is shorter, and
The sixth photoelectric detector 8 has a length of the optical path (sixth optical path) from the subject 1 to the third photoelectric detector 8 via the second half mirror 6 and the sixth half mirror 5. The first, second, and third calculation means arranged in the fifth optical path so as to be longer than the optical path length from the subject 1 to the imaging plane in the image processing unit 15 evaluate focus accuracy. It is a circuit that calculates, for example, the differential value at the image boundary is focused correctly.
This is a difference sum circuit that performs calculations based on the so-called difference sum method, which takes advantage of the fact that the value within the image boundary is small and does not change that much, whereas the value increases by 1, and the amount Ff given by the following equation (1) The first, second, and sixth difference sum circuits send the calculation results to the arithmetic processing means 12, which will be described later.
It is configured to output a digital signal indicating Fz p's.

Here, in Equation (1), Vh is the video signal in time (F), Vh + Δ is the video signal delayed by Δ in time, and U is the unit function of noise. It is inserted to prevent the influence, and rh is a threshold value. Further, F calculated according to equation (1) is the cumulative sum of squares of differences in video signals between two points separated by Δ in the horizontal direction (horizontal direction, A direction) on one screen.

Note that the first, second and third difference sum circuits 9, 10.1
The calculation in 1 can be changed as appropriate depending on the configuration of the first, second, and third photoelectric detectors 6, 7, 8. For example, if the photoelectric detectors are arranged one-dimensionally, If so, the above equation (1) can be replaced with the following equation (2).

F = 5 (Vh-Vh+1 light IVh-Vh+AI-T
h) dh... (2) Fl, F! output from the first, second, and third difference sum circuits 9, 10, and 11, respectively. The arithmetic processing means 12 inputting the digital signals of , F, calculates the moving direction of the lens 2 and the moving scene, converts the calculated results into analog values by the VA converter 13, and then converts the calculated results to analog values by the lens drive mechanism 14. 2t-drive to perform proper focusing. The direction and amount of movement of the lens 2 are calculated as follows. That is, if the output F1 of the first difference summation circuit 9 is a quantity representing the degree of fit (evaluation) of the focus stopper at the lens position Z, f: then the first photoelectric detector 6 is also placed in front of it. 20th to live
The output F of the second difference summation circuit 10 connected to the photoelectric detector 7 is a quantity representing the degree of alignment of the focal spot at the lens position Z0α, and is also the same as that of the first photoelectric detector 6. The output Fs of the third difference summation circuit 11 connected to the sixth photoelectric detector 8, which will be disposed later, has an amount representing the degree of correct focusing at the lens position Z+β.

Here, a and β are constants determined by the difference in optical path loss between the second optical path and the Wc6 optical path. Incidentally, it is known that F and 2 in equation (1) have a quadratic functional relationship as shown in equation (3).

F=-α(Z-b) ” +c ・・・・・・・・・
... (3) (However, α#'i' is the subject,
This is a constant determined by the photoelectric detector. ) So, first. Second and third difference sum circuits 9°10.
11 Yoshi (Fl, Z) - (7' goose, Z + α).

Since the information of (Fs, Z+h) can be obtained simultaneously, the arithmetic processing means 12 calculates the maximum value of F, that is, the focal spot position, according to equation (3). The amount of movement of the lens 2 can be determined based on the absolute value of the moving direction '1-1h of the lens 2 according to the sign of b, and as a result, the output of the arithmetic processing means 12 causes the lens 2 to be in focus. The lens 2 will be driven 〇 Arithmetic processing means 12 that performs the above calculation
Since the automatic focus adjustment device is configured as 0 or more, which can use a microcomputer, for example, light t1 reaches the imaging surface in the image processing unit 15 from the subject through the lens. ．． M2. The 1st, 2nd, . From the amount of light detected by the third photoelectric detector 6.7.8, the first. Second.
The third difference sum circuit performs all evaluations of focus accuracy, and determines the amount and direction of movement of the lens from six types of data regarding focus accuracy, allowing for fast and accurate automatic focus adjustment. can be done.

Although one embodiment of the present invention has been described in detail above, this invention is not limited to the above-mentioned embodiment, and can be implemented with appropriate modifications within the scope of not changing the gist of the invention. For example, the film surface (imaging surface) of a camera attached to the JNC microscope may be used instead of the imaging surface of the image processing section 15.

〔Effect of the invention〕

According to this invention, it is possible to simultaneously determine the amount and direction of movement of the lens by using a simple table configuration with six photoelectric detectors on the optical path, and to quickly, accurately and automatically achieve full focus. can.

[Brief explanation of the drawing]

The drawing is a schematic block diagram showing one embodiment of the present invention. 2...Lens, 6...Ml photoelectric detector, 7
... second photoelectric detector, 8... third photoelectric detector, 9... first calculation means (difference sum circuit), 10.
... second calculation means (difference sum circuit), 11 ... sixth calculation means (difference sum circuit), 12 ... calculation processing means.

Claims (1)

[Claims] a tenth photoelectric detector disposed in a first optical path having an optical path length equal to the optical path length from a lens movable on the optical path to the imaging surface; a tenth photoelectric detector disposed in a second optical path having an optical path length shorter than the optical path length; and a 30th photoelectric detector disposed in the sixth optical path having a longer optical path length than the optical path length, and the output values of each of the first, second, and sixth photoelectric detectors. first, second, and sixth calculation means for calculating the evaluation of focus accuracy; and inputting each output of the first, second, and sixth calculation means to calculate the moving direction and amount of movement of the lens. and an arithmetic processing means, and the lens is moved to a position where the focal point is aligned with the imaging surface by the output of the arithmetic processing means.
An automatic focus adjustment device characterized by being movable.