JPH0527154A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To make the best use of the high speed and the versatility of a one- dimensional image sensor and a two-dimensional, image sensor to the maximum by properly and selectively using output from the one-dimensional image sensor and the two-dimensional image sensor. CONSTITUTION:When a video signal is not inputted in a video signal input part 35, a control part 34 performs autofocusing based on image information inputted in the one-dimensional image sensor part 31. At such a time, front focus and rear focus images are inputted in the sensor part 31, and dark current noise is cancelled in terms of the output from the image sensor which is photoelectrically converted by a correction circuit 5, and the balance of the output of the front focus image and the rear focus image is adjusted by a variable gain amplifier 6. Meanwhile, in the case that the video signal from the two-dimensional image sensor part 30 is inputted in the input part 35, autofocusing is performed first based on the output from the sensor part 31, and autofocusing is performed based on two-dimensional video information inputted in the input part 35 when focusing is impossible as a result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device for a microscope or the like.

[0002]

2. Description of the Related Art In recent years, in a system mainly composed of a microscope or the like, observation of a microscope image by a TV camera is increasing. The automatic focus adjusting devices in those systems are roughly classified into those using a video signal of a TV camera as a two-dimensional image sensor and those using a dedicated image sensor for focus detection.

As an example of the former system, Japanese Patent Laid-Open No. 64-64-
There is 54408 issue. This is an improvement of the hill-climbing method, and a system mainly composed of a microscope has a configuration as shown in FIG. The latter system has a configuration as shown in FIG. 5, and is a microscope TV camera system including a TV camera and a monitor connected to the TV camera, and an automatic system including an image sensor unit and a control unit. The focus adjusting device is configured as an independent system. Prior art examples of automatic focus adjusting devices for such a system include JP-A-53-50851 and JP-A-55-106421.

[0004]

In the hill-climbing autofocus system using the video signal of the TV camera described above, (1) when the focus degree is detected, the focus position is either on the front pin side or the rear pin side. However, since it cannot be determined from the information obtained at one place and the direction is determined from the focus degree detection values at several places, the time required to detect the focus position is relatively long. (2) The TV camera has an image pickup unit that uses a CCD in order to capture a good image on the monitor, but the TV camera that uses a CCD has the following problems from the viewpoint of autofocusing. have. (A) In some cases, information over all spatial frequencies of a high-definition image of a microscope or the like cannot be sampled.

(B) In the case of autofocusing on a dark object with a low aperture ratio, there are cases where the S / N level of the output signal cannot be sufficiently secured to be used for autofocusing. (C) The frame frequency (field frequency) is constant, which is not suitable for high-speed autofocus.

The system using the dedicated image sensor for focus detection is generally called an optical path difference method, but it is a linear one-dimensional image sensor in view of ease of adjustment and cost. Often sensors are used. However, when using a linear sensor,
(A) When an object is present other than the linear sensor unit, the object image is not formed on the linear sensor, and focusing is impossible. (B) When the object image does not have a spatial frequency component in the pixel array direction of the linear sensor, there is a drawback that focusing becomes impossible.

The automatic focus adjusting device of the present invention has been made in view of such a problem, and its purpose is to appropriately select the output of the one-dimensional image sensor and the output of the two-dimensional image sensor. The purpose of the present invention is to provide an automatic focus adjusting device that can maximize the high speed of a one-dimensional image sensor and the versatility of a two-dimensional image sensor.

[0008]

In order to achieve the above object, an automatic focusing apparatus according to the present invention comprises an image forming optical system and two object images in the vicinity of a planned image forming plane of the image forming optical system. Two one-dimensional image sensors for respectively picking up images, a two-dimensional image sensor for picking up an object image on an image plane, and an optical system for projecting the object image on the one-dimensional and two-dimensional image sensors. A video signal input unit for receiving an output signal from the two-dimensional image sensor, and the two one-dimensional images depending on whether the output signal from the two-dimensional image sensor is supplied to the video signal input unit. A control means for detecting the degree of focus of the imaging optical system and adjusting the focus based on one or both of the output signal from the sensor and the output signal from the two-dimensional image sensor.

[0009]

That is, according to the present invention, the output signals from the two one-dimensional image sensors and the two-dimensional image sensor are determined according to whether the output signals from the two-dimensional image sensors are supplied to the video signal input section. The focus adjustment is performed by detecting the degree of focus of the imaging optical system based on one or both of the output signals from the.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a system configuration diagram when the automatic focusing apparatus of the present invention is applied to a microscope. In the figure, the automatic focus adjustment device of the present invention is a two-dimensional image sensor unit (T
V camera) 30, a one-dimensional image sensor unit 31, a video signal input unit 35, a control unit 34, and a stage vertical drive unit 33. In FIG. 2, the one-dimensional image sensor unit 31 and the control unit 34 are configured separately, but there is no difference even if these are the same unit. Also,
A linear sensor is used as the one-dimensional image sensor unit 31.

A two-dimensional image attached to the microscope 32.
The output signal of the image sensor unit 30 is input to the video signal input unit 35, and at the same time, the monitor 36 also receives the video signal input unit 35.
Is output via. In FIG. 2, the stage vertical drive unit 33 moves the stage up and down to change the relative distance between the imaging optical system of the microscope 32 and the object. However, the imaging optical system of the microscope 32, or a part thereof. There is no difference even if you drive up and down. Hereinafter, the detailed configuration of the automatic focus adjusting device according to the first embodiment of the present invention will be described with reference to FIG.

Reference numeral 1 is an image forming optical system, and 31 is a one-dimensional image sensor for picking up two object images in the vicinity of the planned image forming surface. The projection optical systems 4a and 4b receive light rays from an object and project two object images on the one-dimensional image sensor unit 31, and are configured by a half mirror and a mirror, a prism, or the like. The correction circuit 5 is a circuit that corrects fixed pattern noise, dark current component, and the like for the output of the one-dimensional image sensor unit 31, and synchronizes each pixel with the clock signal from the first timing controller 10. Make a correction. The variable gain amplifier 6 controls the gain by the control signal from the first timing controller 10. The first A / D converter 7 performs A / D conversion in synchronization with the clock signal from the first timing controller 10. The driver 8 receives the clock signal from the first timing controller 10, converts the one-dimensional image sensor unit 31 into a drivable signal, and supplies it to the one-dimensional image sensor unit 31.

The memory circuit 9 temporarily stores a video signal read at high speed. The accumulation operation is performed in synchronization with the clock signal from the first timing controller 10.

The projection optical system 4c splits the light beam from the object and projects it on the two-dimensional image sensor unit 30. The video signal from the two-dimensional image sensor unit 30 is a video signal input unit 35.
And the following processing is performed. That is, this video signal is input to the gate circuit 16 and the sync separation circuit 14. The gate circuit is for determining the focus area evaluation sampling area in the image pickup surface of the TV camera. Then, the video signal in the sampling area becomes only the high frequency component by the HPF 17, and the amplitude is detected by the next detection circuit 18. The amplitude-detected signal is A / D converted by the second A / D converter 19, and the data latch integration circuit 20 generates a focus evaluation value for one field.

The second timing controller 15 receives data for setting a sampling area from the control unit 34 and, at the same time, receives a horizontal / vertical sync signal from the sync separation circuit 14 to generate a gate control signal for setting a sampling area and gate the gate. Send to circuit 16. At the same time, the second A
A timing signal is sent to the / D converter 19, the data latch integration circuit 20, and the driver-21 for driving the two-dimensional image sensor unit 30. When the focus evaluation value for one field is generated, the second timing controller 15 outputs an interrupt signal to the control unit 34.

The control unit 34 controls the first and second timing controllers 10 and 15, reads image data from the memory circuit 9 and performs focus evaluation calculation, and inputs data from the data latch integration circuit 20 to a TV camera. The focus evaluation value is read, a control signal is sent to the motor driver 12, and the focus is adjusted by the motor 13.

That is, the control unit 34 controls the video signal input unit 3
If there is no video signal at 5, automatic focus adjustment is performed based on the image information input to the one-dimensional image sensor unit 31. At this time, the front pin image and the rear pin image are input to the one-dimensional image sensor unit 31, the dark current noise and the like are canceled by the correction circuit 5 in the photoelectrically converted image sensor output, and the front pin image is output by the variable gain amplifier 6. Adjust the balance between image output and rear pin image output. Using the signals thus preprocessed, a focus evaluation value such as the sum of adjacent pixel differences is obtained from each of the front-focused and rear-focused signals, and automatic focus adjustment is performed based on the difference.

On the other hand, a two-dimensional image is input to the video signal input section 35.
When the video signal from the digital sensor (TV camera) 30 is input, the video signal input unit 3 is used as the first step.
Similarly to the case where the video signal does not come to 5, automatic focus adjustment is performed by the output of the one-dimensional image sensor unit 31. Then, as a result, if the focusing becomes impossible, as the second step, the automatic focus adjustment is performed using the two-dimensional image information input to the image signal input unit 35. As a result, when the automatic focusing adjustment is completed in the first step, the focusing operation can be completed at the highest speed, and when the target object does not form an image on the one-dimensional image sensor unit 31 or the one-dimensional image. Even if the information of the target object on the sensor unit 31 is very small, the automatic focusing can be performed by executing the second step.

In the above embodiment, the defocus direction may be judged by the evaluation value from the one-dimensional image sensor, and the defocus amount may be judged by the two-dimensional image sensor. FIG. 3 is a configuration diagram of the second embodiment of the present invention, in which the configuration of the video signal input section is digitized to have a high function.

In FIG. 3, a gate circuit 1 similar to that in FIG.
The video signal in the sampling area that has passed 6 is A / D converted by the second A / D converter 19 in response to the timing signal from the second timing controller 15, and is stored in the DSP memory 24 as image data. The DSP (digital signal processor) 22 recognizes the accumulation of the image data in response to the timing signal from the second timing controller 15, and the DSP memory 2
The data is loaded from No. 4, and the evaluation value of the focus degree is calculated.

The control unit 34 includes a dual port RAM 23.
The focus degree evaluation value calculated by the DSP 22 is loaded via. Unlike the first embodiment, the two-dimensional image data is D
Since it is stored in the SP memory 24, it is possible to evaluate the contrast and the like not only in the scanning direction of the video signal but also in the spatial frequency components of the image in the vertical, horizontal, and diagonal directions.

As a result, when the focusing operation is performed by the two-step method of the first embodiment, at the second step, even if the object image has no spatial frequency component and is difficult to focus with the linear sensor, the object is focused. It becomes possible to focus. This is because in the first embodiment, the scanning direction of the two-dimensional image sensor (TV camera) 30 and the pitch direction of the one-dimensional image sensor (line sensor) 31 are substantially the same.

The third embodiment of the present invention will be described below.
The third embodiment is an application example in the case where the objective magnification of the microscope is changed or the microscope method is changed, and the configuration thereof is the same as that in the first embodiment.

When the objective magnification of the microscope can be changed from low magnification to high magnification, it is difficult to deal with the difference in the optical path between the sensors for the front pin and the rear pin with one kind, and for the low to medium magnification, the optical path is different. Setting a difference and performing a hill-climbing search method at high magnification is considered to be one solution for expanding the range of application of autofocus. Therefore, it is effective to perform the focusing operation accurately based on the output signal of the TV camera on the image plane at high magnification and to use the output of the image sensor at low to medium magnification. In addition, there are some characteristics of the sample distribution that are remarkable by the microscopic method. For example, when the sample distribution is very rough with a fluorescence microscope, the first and When the two-step method of the second embodiment is used, it is possible to reduce the loss time due to the inability to focus in the first step.

As is apparent from the above description, according to the embodiment of the present invention, the video signal can be input to the optical path difference type automatic focus adjusting device, and the following effects can be obtained.

(1) In the optical path difference method, a linear sensor is often used as a sensor. For example, a) it becomes impossible to focus without an object image on the linear sensor, or b).
It is possible to solve the conventional problem that the object image cannot be focused when the object image has no spatial frequency component in the pixel array direction of the linear sensor.

(2) Generally, a linear sensor or the like mainly receives visible light, and therefore, when receiving a wavelength outside the visible range, stable operation of the sensor cannot be expected. However, if the output of the TV camera system that visualizes the invisible image is input to the video signal input of the present apparatus, the focusing operation can be performed on the invisible image due to infrared rays or ultraviolet rays.

[0028]

As described above in detail, according to the present invention, 1
By appropriately and selectively using the output of the two-dimensional image sensor and the output of the two-dimensional image sensor, the high speed of the one-dimensional image sensor and the versatility of the two-dimensional image sensor can be maximized. It is possible to provide an automatic focus adjustment device that can be used.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an automatic focus adjustment device according to a first embodiment of the present invention.

FIG. 2 is a system configuration diagram when the automatic focusing device of the present invention is applied to a microscope.

FIG. 3 is a configuration diagram of an automatic focus adjustment device according to a second embodiment of the present invention.

FIG. 4 is a system configuration diagram when a conventional automatic focus adjustment device is applied.

FIG. 5 is a system configuration diagram when a conventional automatic focus adjustment device is applied.

[Explanation of symbols]

30 ... Two-dimensional image sensor section (TV camera section), 31
1-dimensional image sensor section, 32 microscope, 33 stage up / down drive section, 34 control section, 35 video signal input section, 36 monitor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H04N 5/232 Z 9187-5C 7811-2K G02B 7/11 D

Claims (2)

[Claims] 1. An imaging optical system, two one-dimensional image sensors for respectively capturing two object images near a planned imaging surface of the imaging optical system, and an object image on the imaging surface. A two-dimensional image sensor, an optical system for projecting an object image on the one-dimensional and two-dimensional image sensors, a video signal input unit for receiving an output signal from the two-dimensional image sensor, and the video signal input Based on one or both of the output signals from the two one-dimensional image sensors and the output signals from the two-dimensional image sensors, depending on whether the output signal from the two-dimensional image sensor is supplied to the unit. And a control means for performing focus adjustment by detecting a focus degree of the imaging optical system. 2. The automatic focus adjusting device according to claim 1, wherein the light receiving portions of the two one-dimensional image sensors are formed on the same semiconductor substrate.