Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-05-13
2001-11-20
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231180
Reexamination Certificate
active
06320185
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image detection apparatus for use in observing or measuring a minute structure or a three-dimensional structure of a sample.
A Nipkow type confocal microscope, which uses a so-called Nipkow disk having many pinholes arranged in a spiral with an equal pitch, is well known as a confocal microscope which is a type of an image detection apparatus.
The confocal microscope obtains a confocal image of a sample by optically scanning the sample, while rotating the Nipkow disk by means of a motor. Accordingly, if a confocal image of the sample is picked up by a CCD camera, etc., a brightness/darkness fringe may occur in a picked-up image due to non-uniform scanning unless the scan cycle of the disk is synchronized with the image pick-up cycle of the CCD camera.
To solve this problem, Jpn. Pat. Appln. KOKAI Publication No. 9-297267, for example, discloses a motor control apparatus for a confocal microscope.
FIG. 1
shows a schematic structure of the motor control apparatus. A vertical sync signal extraction circuit
2
extracts a vertical sync signal from an NTSC (National Television System Committee) type signal output from a CCD camera
1
. A frequency multiplier circuit
3
multiplies the vertical sync signal and produces a control signal for a motor drive circuit
4
. The motor drive circuit
4
drives a motor
5
at a speed corresponding to the control signal. Thereby, the disk speed for scanning the surface of the sample is synchronized with the image pick-up cycle of the CCD camera
1
.
Since this motor control apparatus can control the rotation of the motor
5
with use of the NTSC signal from the CCD camera
1
, even if the NTSC signal fluctuates, the rotation of the motor
5
can be synchronized in accordance with NTSC signal.
Jpn. Pat. Appln. KOKAI Publication No. 9-80315 discloses another apparatus for solving the problem due to non-uniform scanning. In this apparatus, scan start detection pinholes are provided at beginning points of scan tracks on the disk. A photodetector photo-electrically converts light, which has passed through the scan start detection pinhole, and synchronizing means produces a trigger signal for an image pick-up apparatus. Thereby, the scan cycle is synchronized with the image pick-up cycle to solve the problem of non-uniform scanning.
FIG. 2
shows a schematic structure of this apparatus. A scan disk (Nipkow disk in this example)
7
, as shown in
FIG. 3
, has scan tracks
13
(indicated by hatching) provided with many pinholes like a conventional Nipkow disk, and scan start detection pinholes
14
arranged on a circumferential area of the scan tracks
13
at scan beginning points. A photodiode
8
serving as a photodetector is disposed at such a position as to receive light passing through the scan start detection pinholes
14
. A current/voltage converter circuit
9
converts a current produced by the photodiode
8
to a voltage. A voltage comparison circuit
10
compares a signal from the current/voltage converter circuit
9
with a reference voltage
11
and digitizes the magnitude of the signal voltage. The resultant digital signal is output to an externally connected image pick-up apparatus
12
as an imaging sync signal (a trigger signal).
In the above structure, incident light
6
is radiated on the surface of the Nipkow disk
7
. In this case, a diameter r of a beam of incident light
6
is set such that the light
6
can illuminate both the scan tracks
13
and scan start detection pinhole
14
. In this state, the Nipkow disk
7
is rotated, and the incident light which has passed through the scan track
13
scans the sample in a multi-point scanning manner. On the other hand, the incident light which has passed through the scan start point detection pinhole
14
is received by the photodiode
8
each time the scan start detection pinhole
14
passes over the photodiode
8
.
In this case, an output current from the photodiode
8
varies in a pulsating manner. The variation in current is converted to a voltage in the current/voltage converter circuit
9
. A voltage signal from the converter circuit
9
is input to the voltage comparison circuit
10
and compared with a predetermined reference voltage
11
. Thus, a signal of a voltage pulse sequence having the cycle synchronous with the scan cycle is output. This pulse-sequence signal is output to the external image pick-up apparatus
12
as a trigger signal. Thereby, the rotational cycle of the Nipkow disk
7
can be synchronized with the imaging cycle of the image pick-up apparatus
12
.
In the structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-297267, the vertical sync signal is extracted from the NTSC signal output from the CCD camera
1
which images the surface of the sample, the extracted vertical sync signal is multiple, and the multiplied signal is output to the motor drive circuit
4
as the motor control signal. Since the signal flows in one direction in the respective components, a fluctuation in the rotation of the disk, which may occur due to eccentricity of the disk or friction of the motor shaft, cannot be fed back. Even if the frequency multiplier circuit
3
and motor drive circuit
4
perform the control based on the NTSC signal from the CCD camera
1
, once a fluctuation occurs in the rotation of the disk due to the eccentricity of the disk or friction of the motor shaft, the scan cycle of the disk becomes asynchronous with the imaging cycle of the CCD camera
1
and a brightness/darkness fringe may occur in the screen image.
Besides, in the structure disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-80315, the scan start detection pinholes
14
are formed at the beginning points of the scan tracks on the Nipkow disk
7
. The light which has passed through the scan start detection pinhole
14
is detected to produce the trigger signal for the image pick-up apparatus
12
. On the basis of the trigger signal, the imaging timing of the image pick-up apparatus
12
is controlled and the vertical sync signal of the image signal is reset. In this case, however, if a fluctuation occurs in the rotation of the disk due to eccentricity of the disk or friction of the motor shaft, the scan start detection pinhole
14
cannot pass, at regular cycles, over the photoelectric converter
8
for generating the trigger signal. Because of this, the cycle of the trigger signals applied to the image pick-up apparatus
12
becomes irregular and also the cycle of the vertical sync signals of image signals output from the image pick-up apparatus
12
varies. Consequently, images on the TV monitor are flickering and the observation of the sample cannot be performed.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an image detection apparatus capable of obtaining a screen image free from problems of non-uniform disk scanning and occurrence of a brightness/darkness fringe.
Another object of the invention is to provide an image detection apparatus capable of obtaining a bright image of a sample even if the brightness of the sample is low.
Still another object of the invention is to provide an image detection apparatus capable of obtaining an image with high efficiency of use of light.
According to a first aspect of the invention, in order to achieve the above objects, there is provided an image detection apparatus comprising:
a rotary member having a light-transmission pattern;
a rotary drive unit for driving the rotary member;
an imaging unit for detecting an image which has passed through the light-transmission pattern of the rotary member, and outputs an image signal representing the detected image;
a sync signal generator for generating a sync signal at a predetermined cycle;
a rotational state sensing unit for sensing the rotational state of the rotary member and outputs a sensor signal; and
a control circuit for comparing the sensor signal and the sync signal and controlling the rotary drive unit such that the sensor signal is synchronized with the sync signal.
According to a second
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Lee John R.
Olympus Optical Co,. Ltd.
Pyo Kevin
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