JP2002281530A - Image pickup method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup method and an image pickup device, by which a picked-up image free from noise can be speedily obtained by displaying and picking up a reference image on a display screen at good timing. SOLUTION: The reference image is displayed and the exposure of the reference image is started on the basis of the vertical synchronizing signal of a display screen detected just after an image pickup start switch 103 is turned on. Then, the read of the exposed reference image signal out of an imaging device 102 is started on the basis of the vertical synchronizing signal of the display screen detected after the reference image is displayed for one vertical synchronizing period at least.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus for picking up an image displayed on a display screen, and more particularly, to an image pickup apparatus used for performing posture detection and position detection based on a displayed / imaged reference image. The present invention relates to an imaging device.

[0002]

2. Description of the Related Art Recently, many methods for detecting a position on a display using a camera have been proposed. One of them is a position detecting device that displays a reference image on a display, captures the reference image with a camera, and detects a camera position or a mark position. For example, JP-A-6-35607
JP, JP-A-7-112293, JP-A-11-112
No. 319316. Japanese Patent Application Laid-Open No. 7-12129, which is a typical example, proposes a controller that captures a marker displayed on a screen at the time of operation, extracts the captured marker, and detects a position based on the marker coordinates. .

On the other hand, conventionally, a reference image from a CRT tube surface or a projector is picked up using a video camera such as a CCD, and based on the picked-up image, inspections such as display performance, luminance measurement, and setup adjustment of a display device are performed. ing. Usually, when a reference image displayed on a display is captured by a camera, horizontal timing and flickering occur because the timing of imaging by the camera and the timing of a display image cycle do not match. That is, a problem caused by a difference between the vertical scanning frequency of the video camera and the vertical frequency of the display. Many solutions have been proposed in the past, for example, as disclosed in Japanese Patent Application Laid-Open Nos.
317432, JP-A-11-184445 and the like. JP-A-11-18444 which is a representative example
Japanese Patent Application Laid-Open No. 5 (1999) -2005 discloses a method of generating an imaging control signal in accordance with a vertical synchronization signal of a display and controlling the imaging timing with the control signal.

[0004]

In a conventional apparatus for detecting a position based on a reference image, there is no disclosure about the timing of displaying and imaging the reference image at present. When the display image signal and the imaging drive signal are asynchronous,
If the vertical scanning period at the time of imaging is longer than the vertical scanning period of the displayed image, there are problems such as longer image processing time and uneven brightness (flicker) on the captured screen. In addition, if the vertical scanning period from the start of reading to the end of reading from the image sensor at the time of imaging is shorter than the vertical scanning period of the display image, there is a problem that the image is captured without ending the display of one screen.

Further, when a reference image is extracted, difference image processing is performed. However, two reference images having different luminances are sequentially displayed, and each of the reference images must be accurately imaged and image processing must be performed quickly. No. However, at present, there is no such technology disclosed.

In the case where an image that is constantly displayed is taken by a video camera as disclosed in Japanese Patent Application Laid-Open No. 11-184445, noise (flicker or the like) is obtained simply by taking an image based on a vertical synchronization signal of a display device. Although it is possible to obtain a captured image without the parentheses, there is no disclosure of a process of performing an operation of displaying a reference image and an operation of capturing the reference image.

An object of the present invention is to provide an image pickup method and an image pickup apparatus capable of promptly obtaining a noise-free picked-up image by displaying and picking up a reference image on a display screen with good timing. is there.

[0008]

[Means for Solving the Problems] To solve the above problems, according to the first aspect of the present invention, a predetermined reference image is displayed on a display screen, and a display screen on which the reference image is displayed is displayed. An image capturing method for capturing a reference image based on a vertical synchronization signal of a display screen detected immediately after an imaging start switch is turned on and starting exposure of the reference image, and The reading of the reference image signal exposed from the image sensor based on the vertical synchronization signal of the display screen detected after displaying at least one vertical synchronization period is started.

According to a second aspect of the present invention, predetermined first and second reference images are displayed in chronological order on a display screen, and the first and second reference images are displayed. An image capturing method for sequentially capturing a display screen, comprising: displaying a first reference image based on a vertical synchronization signal of the display screen detected immediately after an imaging start switch is turned on; Exposure is started, a second reference image is displayed based on a vertical synchronization signal of a display screen detected immediately after reading of the exposed first reference image signal from the image sensor is completed, and the second reference image is displayed. The exposure of the reference image is started.

According to a third aspect of the present invention, predetermined first and second reference images are displayed in time series on a display screen, and the first and second reference images are displayed. An image capturing method for sequentially capturing a display screen, comprising: displaying a first reference image based on a vertical synchronization signal of the display screen detected immediately after an imaging start switch is turned on; Starting exposure, and exposing said first
Based on the vertical synchronization signal of the display screen detected immediately after the reading of the reference image signal from the image sensor is completed.
And exposing the second reference image is started.

According to a fourth aspect of the present invention, there is provided a display screen in which predetermined first and second reference images are displayed in a time series on a display screen, and the first and second reference images are displayed. And an imaging start switch for inputting an imaging start signal for starting imaging of the first and second reference images, and detecting a vertical synchronization signal from a display image signal on the display screen. A vertical synchronizing signal detecting unit, which starts displaying the first reference image based on a vertical synchronizing signal detected by the vertical synchronizing signal detecting unit immediately after being output from the imaging start signal, and The exposure of the reference image is started, and based on the vertical synchronization signal of the display screen detected by the vertical synchronization detection means immediately after the reading of the exposed first reference image signal from the imaging device is completed. And displaying the second reference image and starting exposure of the second reference image.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an image capturing apparatus according to the present embodiment. FIG.
1 is a schematic configuration perspective view of an image capturing apparatus according to an embodiment.

In FIG. 2, reference numeral 100 denotes a main body of the image pickup apparatus which allows an operator to perform a position detection operation at hand. Reference numeral 120 denotes a personal computer that generates an original image, and 130 denotes a projector that enlarges and projects the original image of the personal computer on the screen 110. In the image 111 projected in the figure, four marks are superimposed and displayed as one reference image. In the figure, the position of the center of gravity of the four marks characterizing the rectangular shape is indicated by the characteristic point Q1,
These are shown as Q2, Q3 and Q4. Note that the reference image may be any geometric shape that can be extracted after imaging.

Next, a configuration related to image capture of the image capturing apparatus will be described in detail with reference to FIG. The image pickup apparatus main body 100 displays an image pickup lens 101 for taking in a display image, an image pickup device 102 such as a CCD (represented as CCD in the following description), and a reference image including the marker at hand by an operator. And an A / D converter 10 for converting an output signal from the CCD 101 into a digital signal.
4. A timing generator 105 for generating various clocks necessary for the CCD 102 to capture signals, a synchronization signal detection means 106 for detecting only a vertical synchronization signal among video signals output to the display means, and a personal computer 120 and a predetermined signal. And an interface means 107 for performing the operation. Of course, this image pickup device body 100
Requires a power supply unit, etc., but is omitted here because it is not directly necessary for the explanation of the operation.

A captured image signal captured by the image capturing apparatus main body 100 is input to the interface means 121 of the personal computer 120 via the interface means 107. The output form from the interface means 107 is USB, IEEE1394, IrDA, BL
Various methods of wired or wireless connection such as uetooth can be appropriately adopted. If a video board is already provided in the personal computer, an analog output from the CCD 101 can be directly input to the personal computer because the A / D converter is already installed.

The personal computer 120 includes a display timing generator 123 for synchronizing with a video signal and a display control means 124 for controlling and displaying a video video signal.
An image processing unit 50 and the like are provided. Image processing means 50
Then, predetermined image processing is performed according to a preset program. The image processing means of this embodiment performs operations such as mark extraction processing for position detection processing and position calculation processing.

The operation of the display control means 124 is to output a video image signal to the display means in the same cycle as the vertical synchronizing signal generated from the display timing generator 123. In the present embodiment, the synchronization signal detection means is provided on the main body of the image capturing apparatus, but may be provided on the personal computer.

Further, in the present embodiment, the display means 130 is a projector, and the image is projected on the screen 110. However, a display device combined with the screen unit, for example, a CRT display device or a liquid crystal display device may be used. First, a basic operation for detecting a position using the image capturing apparatus according to the present embodiment will be described.

FIG. 3 is a basic operation flow for performing position detection based on a mark image as a reference image. The reference image used in the present embodiment is a first reference image in which four G (green) marks are arranged and four B (black) marks in the first.
And the second reference image arranged at a position corresponding to the position of the G mark of the reference image of the second type.

First, in step S11, the center of the visual field of the image pickup device is aimed at the position to be detected on the display image. In step S12, the imaging start switch is turned on. When turned on, the first reference image provided with a plurality of marks is superimposed on the display image on the screen, and is captured by the image pickup device (step S13). A second reference image superimposed and displayed on the display image in time series following the first reference image is captured (step S14). Step S
At 15, difference image processing is performed based on these two captured images, and at step S 16, binarization processing is sequentially performed, and only four marks are extracted as reference images.

The position of the center of gravity of the mark extracted in step S17 is specified as coordinates as a feature point on the captured image.
In step S18, based on these specified coordinates,
The coordinates of the position to be detected as the imaging center on the display image are calculated.

Here, the calculation processing of the detected position will be briefly described. FIG. 4 shows a captured image q obtained by capturing the image from the arbitrary position of the image capturing unit 100 provided on the position detecting device main body toward a predetermined rectangular plane. In the figure, the captured image has a detected position Ps, which is a coordinate position on a plane, matched with a reference position (origin Om of the imaging surface) set on the imaging surface. These four feature points q1, q2, q3, q4 are represented by a plane coordinate system X * -Y in FIG.
* Corresponds to Q1, Q2, Q3, Q4 in the coordinate system.

In the next step, the calculation is sequentially performed, and the coordinates of the detected position on the screen image are calculated. (1) The vanishing point is calculated. Based on the coordinate positions of q1, q2, q3, q4, a straight line formula I1. I2, I3, and I4 are calculated, and vanishing points Q0 and T0 corresponding to a pair of parallel sides of the rectangular display screen are calculated. That is, the vanishing point Q0 is defined as a straight line q1q2 on the imaging surface corresponding to the straight line Q1Q2 and a straight line q3 corresponding to the straight line Q3Q4.
It is the intersection with q4 and q1q4. (2) Calculate vanishing feature points.

A straight line connecting the two vanishing points and the image origin and each straight line I1. Intersections with I2, I3, and I4 (this point is referred to as a vanishing feature point) _qs1 , _qs2 , _qt1 , and _qt2 are calculated. (3) The coordinate system is rotated around the image coordinate system so that the vanishing point S0 coincides with the X axis in the image coordinate system.

In FIG. 4, the XY coordinate system is rotated counterclockwise by an angle β.
Rotate. The coordinate system after the coordinate rotation is an X′-Y ′ coordinate system, and the coordinates of the feature points Q1, S1, S2, T1, and T2 are q ₁ (X ₁ , Y ₁ ) → q ′ ₁ (X ′ ₁ , Y ' ₁ ), q
_s1 ( _Xs1 , _Ys1 ) → _q's1 ( _X's1 , _Y's1 ), q
_s2 ( _Xs2 , _Ys2 ) → _q's2 ( _X's2 , _Y's2 ), q
_t1 ( _Xt1 , _Yt1 ) → _q't1 ( _X't1 , _Y't1 ), q
_t2 ( _Xt2 , _Yt2 ) → _q't2 ( _X't2 , _Y't2 ). (4) One of the elevation angle γ and the depression angle あ る, which are plane attitude parameters of the screen plane with respect to the imaging plane, is calculated by performing a perspective projection calculation based on the coordinate values obtained after the rotation of the coordinate system. In the present embodiment, the depression angle ψ is calculated by the following equation (1).

[0026]

(Equation 1)

(5) Using the posture parameter 姿勢, the coordinates of the position to be detected on the screen image are calculated by the following equation (2).

[0028]

(Equation 2)

Here, the horizontal axis ratio m = | S1Ps | / | S2Ps
|, Vertical axis ratio n = | T1Ps | / | T2Ps |, and focal length f of the imaging lens. In the position detection operation described above, in order to capture a reference image displayed on the display screen with good timing, an operation of displaying two reference images,
The display / imaging operation, which is the operation of imaging each display image, must be performed by a single operation using an imaging start switch provided in the imaging device main body.

Next, the image capturing operation of the image pickup apparatus according to the present embodiment will be specifically described with respect to first to third examples. <First Embodiment> FIG. 5 is a timing chart of the image pickup operation of the image pickup apparatus of the first embodiment. First, the first embodiment will be described based on the timings (a) to (e).

FIG. 5A shows an image capture start pulse Sp (START pulse) output when the operator presses the switch 103 of the image capturing apparatus main body. This signal is transmitted to the personal computer 12 via the timing generator 106 and the interface means 107 and 121 described above.
Input to 0. FIG. 5B shows a composite video signal (PJ signal) obtained by adding a synchronization signal to a video signal output from the personal computer 120 to the projector 130. FIG. 5C shows only the vertical synchronizing signal VDp of the composite video signal output from the personal computer. When the above-described start pulse Sp is output, the personal computer 120 immediately follows the vertical synchronization period (t1 to t2:
A video signal for displaying the first reference image at Tv) is output to projector 130.

FIG. 5D shows the timing of the reset pulse signal applied to the CCD. The timing generator 105 generates a reset signal (RST pulse) shown in the figure at time t1 in synchronization with the above-described VDp signal, and applies the signal to the CCD 101. CCD from this point
101 starts imaging exposure of the displayed first reference image. FIG. 5E shows the timing of starting signal reading from the CCD. The aforementioned reset signal (RST
pulse) is applied to the CCD, and at time t2 when a Tv period elapses, the timing generator 105 starts a pulse (RD start puls) for starting signal reading.
e) occurs. This start pulse signal is supplied to the CCD1
A clock for signal reading is generated for 01, and this is applied to the CCD. Here, as shown in FIG. 5F, reading of a signal from the CCD 101 (RD out sig
nal) ends in the Tc period. afterwards,
After generating the first reference image for a convenient 3Tv period, the personal computer 120 switches to the second reference image at time t3, and uses the second reference image as a video image signal to the projector 130 for a 1Tv period until time t4. Output.

On the other hand, as shown in FIG. 5D, the timing generator 103 generates a reset signal for discharging unnecessary charges of the CCD 101 and applies it to the CCD 101 at time t3 when the above-mentioned 3Tv period ends. After that, as shown in FIG. 5E, a signal readout pulse is applied to the CCD 101 by a readout start pulse at a time t4 synchronized with the VDp signal from the timing generator 105 as in the case of the first reference image capture. , T
The image signal is read from the CCD 101 over a period c. Note that the first display screen only needs to be displayed during the first 1 Tv period among the 3 Tv periods described above, and need not be displayed continuously.

FIG. 6 is a flowchart for explaining the operation of the image pickup apparatus according to this embodiment. The timing operation of FIG. 5 will be described in detail with reference to FIG. The capture start switch 103 is pressed, and the start pulse Sp (FIG. 5)
(A)) is the timing generator 105 and the personal computer 1
20 and waits for the start of the vertical synchronization portion of the display image in step S301. If the first vertical synchronization signal of the VDp signal comes at time t1, step S
At 302, the personal computer sends an output signal that changes the display screen to a screen on which the first reference image is superimposed, to the projector 130, and the timing generator 105
Reset pulse RSTp for resetting D101
(FIG. 5D) is generated, and this reset pulse is applied to the CCD 101 in step S303 to discharge unnecessary charges of the CCD 101. In step S304, the imaging exposure of the first reference image is started. In step S305, the exposure is continued until the next vertical synchronization signal comes, and the time t after one Tv period is reached.
Since the display for one screen is completed in step 2, the timing generator 105 generates a read pulse (FIG. 5 (e)),
A pulse for reading out a signal is sent by the CCD 101 according to the pulse.
Is applied. As a result, in step S306, the CCD 10
The reading of the signal charge is started from 1 and the signal is read from the CCD 101 over a period of Tc. Thereafter, when the time t3 of the fourth vertical synchronization signal has come, step S308 is performed.
The personal computer changes the display to a screen on which the second reference image is superimposed, and the timing generator 103 generates a reset pulse (FIG. 5D) and applies it to the CCD 101 in step S309.
01 is started. Thereafter, when the next vertical synchronizing signal arrives at time t4 in step S311, the timing generator 105 generates a read pulse (FIG. 5E) and applies a signal read pulse to the CCD. As a result, the second reference image is read from the CCD in step S312, and after the Tc period, this reading ends, and the image capture ends.

<Second Embodiment> Next, a description will be given of a second embodiment of the image pickup apparatus according to the present invention. The cycle of the video image signal output from a personal computer (also referred to as a display scanning cycle) is about 50 to 80 Hz. On the other hand, if the CCD operates in the same manner as a normal video operation, it is necessary to output a signal for one screen. Takes 1/50 seconds (for PAL) or 1/60 seconds (for NTSC).
Therefore, the display scan cycle of the output signal from the personal computer side is CC
In the case where the period is shorter than the period from the start of signal reading from D to the end of reading, the first signal is read as shown in the first embodiment.
If the period for capturing the reference image is 3Tv, it is possible to start capturing the second reference image in the shortest time. However, there are cases where the display scan cycle of the personal computer is longer than the period from the start to the end of signal readout from the CCD, or the case where the readout from the CCD is completed earlier than the display scan cycle of the personal computer. In that case, the display of the first reference image can be shortened to the 2Tv period instead of the 3Tv period, and the capture of the two types of patterns can be completed in a shorter period. This embodiment makes this possible.

FIG. 7 is a timing chart of the image pickup operation of the image pickup apparatus according to the second embodiment. FIG.
(F) is the same timing as in FIGS. 5 (a) to 5 (f),
Further, FIG. 5 (g) for generating a signal reading end pulse
Has been added. In this embodiment, it is a signal RDend indicating that the capture of the signal from the CCD generated from the timing generator 105 at time t5 has been completed. Further, based on FIG. 7 (g), the personal computer 120 changes the display to the second reference image in synchronization with the VDp vertical synchronization signal immediately thereafter. In the timing of FIG.
Since the capture period from 101 is longer than the display scan cycle of the personal computer, the period until the capture is completed is the same as in the first embodiment. However, when the relationship between the periods is reversed, the time required for capturing 1Tv period is reduced.

As can be seen from the above description, in the second embodiment, it is necessary to output an extra control signal cable from the image pickup apparatus main body 100 to the personal computer 120. If this seems to be difficult due to limitations on the number of pins of the connector, etc.
If the display period can be set on the personal computer side so that it can be changed to the 2Tv period or the like in accordance with the frequency of the output signal of the personal computer used instead of displaying the pattern of the two types of images, the two types of images can always be obtained in the shortest time. Signals can be captured.

FIG. 8 is a flowchart for explaining the fetch operation of the image pickup apparatus according to the second embodiment.
8, steps S401 to S406 for reading out the first reference image signal from the CCD 101 are the same as steps S301 to S306 in FIG.
In the next step S407, signal reading from the CCD 101 is started, and at time t5 after the Tc period, the timing generator 105 outputs a reading end pulse (FIG.
(G)) and the timing generator 105 and I
The data is sent to the personal computer having display means via the / F units 107 and 121. PC 1 that received this read end pulse
At 20, the display is switched to the second reference image (step S409) in synchronization with the next vertical synchronizing pulse at time t3 (step S408), and step S41 is performed.
At 0, the timing generator 103 generates a reset pulse (FIG. 7D) and applies it to the CCD 101, and exposure of the CCD 101 is started at step S411. Thereafter, in step S412, the display for one screen is completed at time t4, so in the next step S413, the timing generator 103 generates a read pulse (FIG. 7 (e)) and applies a signal reading clock to the CCD. As a result, the second reference image is read from the CCD in step S312, and after the Tc period, this reading ends, and the image capture ends. <Third Embodiment> In the first and second embodiments, the CCD 1
Although the exposure period of 01 has been described as a 1Tv period as shown in FIGS. 5 and 7, a sufficient output level cannot be obtained with an exposure period of only 1Tv period when the CCD 101 having low sensitivity is used. The third embodiment described here corresponds to such a case.

FIG. 9 is a timing chart for explaining the image capturing operation of the image capturing apparatus according to the third embodiment. FIGS. 9A to 9F are basically the same operations as FIGS. 6A to 6F. Reset pulse (Fig. 9 (c))
A read pulse (see FIG. 9)
The period until the application of (d)) may be multiplied by a plurality of periods in units of one vertical synchronization period (FIG. 9 shows an example in which the period is twice). As a result, it is possible to increase the luminance level of the captured signal without causing flicker, and to minimize the period until the completion of capturing the two reference images. Although the reference image used in the present embodiment is four mark images characterizing a rectangle whose position can be detected, it may be a geometric shape pattern adapted to the purpose of image processing after imaging. Further, the two reference images need not be geometric patterns having different luminance states, but may be two screens having different contrasts.

When the position is detected by using the image pickup apparatus main body, the position detection apparatus has a high degree of freedom with respect to the display screen. For example, when capturing a large display screen such as a projected image, a case may occur in which a part of the display screen or the reverse thereof is also captured including the periphery of the display screen. Even in such a case, since display and exposure are always performed in synchronization with one vertical synchronization period of the display screen as a unit, it is possible to obtain a captured image free from flickering of the captured screen, and to quickly perform position detection. Becomes possible.

[0041]

According to the above-described embodiment, the reference image is displayed at a desired timing, and the reference image can be quickly and accurately taken. Therefore,
A captured image free of noise such as flicker can be obtained.

Further, even when the designated position on the display screen is detected based on the captured reference image, a quick position detecting operation can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an image pickup apparatus according to the present invention.

FIG. 2 is a configuration perspective view of an image pickup device according to the present invention.

FIG. 3 is a flowchart illustrating a basic operation when the image capturing apparatus according to the present invention is used for position detection.

FIG. 4 is an example of a captured image for describing a position detection method using the captured image device according to the present embodiment.

FIG. 5 is a timing chart illustrating screen display and capturing of an image pickup signal according to the first embodiment.

FIG. 6 is a flowchart illustrating the operation of the first embodiment.

FIG. 7 is a timing chart illustrating screen display and capturing of an image pickup signal according to the second embodiment.

FIG. 8 is a flowchart illustrating the operation of the second embodiment.

FIG. 9 is a timing chart illustrating screen display and capturing of an image pickup signal according to the third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 imaging apparatus main body 101 imaging lens 102 imaging element 103 imaging start switch 104 A / D converter 105 timing generator 106 vertical synchronization detection means 107, 121 interface 120 personal computer 130 display means (projector)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N5 / 335 H04N5 / 335Z (72) Inventor Yukinobu Ishino 1-325 Futaba, Shinagawa-ku, Tokyo No. F-term in Nikon Technical Studio Co., Ltd. (reference) 5B047 AA30 BB04 BC06 BC16 BC23 CA07 CA23 CB16 CB17 DC07 5B057 AA20 BA02 BA19 BA26 DA07 DB02 DC05 DC06 DC33 5C022 AA01 AB51 AB64 AB65 AC01 AC42 CA02 CA07 5C024 BX03X06 BX03 BX03 BX03 JX46 5C061 BB03 BB15 CC05 EE05 EE09 EE11

Claims (4)

[Claims] 1. An image capturing method for displaying a predetermined reference image on a display screen and capturing the display screen on which the reference image is displayed, wherein the detection is performed immediately after an imaging start switch is turned on. A reference image is displayed based on a vertical synchronization signal of the display screen, and exposure of the reference image is started, and exposure is performed based on a vertical synchronization signal of the display screen detected after displaying the reference image for at least one vertical synchronization period. And starting reading the reference image signal from the image sensor. 2. An image pickup method for displaying predetermined first and second reference images on a display screen in a time-series manner, and sequentially capturing the display screen on which the first and second reference images are displayed. A method of displaying a first reference image based on a vertical synchronization signal of a display screen detected immediately after an imaging start switch is turned on, and starting exposure of the first reference image. The second reference image is displayed based on the vertical synchronization signal of the display screen detected immediately after the reading of the first reference image signal from the image sensor is completed, and the exposure of the second reference image is started. An image capturing method characterized by the above-mentioned. 3. An image capturing apparatus for displaying a predetermined reference image on a display screen and capturing an image of the display screen on which the reference image is displayed, wherein an image capturing start signal for starting capturing the reference image is provided. An imaging start switch to be input, and a vertical synchronization signal detection means for detecting a vertical synchronization signal from a display image signal on the display screen, wherein the vertical synchronization signal is detected by the vertical synchronization signal detection means immediately after the imaging start signal is input. The display of the reference image is started based on a vertical synchronization signal and the exposure of the reference image is started, and after displaying the reference image for at least one vertical synchronization period, the vertical position of the display screen detected by the vertical synchronization signal detection unit is displayed. An image pickup apparatus, wherein reading of the reference image signal exposed based on a synchronization signal is started. 4. An image pickup apparatus for displaying predetermined first and second reference images on a display screen in chronological order, and sequentially capturing the display screen on which the first and second reference images are displayed. An imaging start switch for inputting an imaging start signal for starting imaging of the first and second reference images, and a vertical synchronization signal detecting means for detecting a vertical synchronization signal from a display image signal on the display screen. And starting the display of the first reference image based on a vertical synchronization signal of the display screen detected by the vertical synchronization signal detection means immediately after the input of the imaging start signal, and the first reference image Starting the exposure of the second reference image based on the vertical synchronization signal of the display screen detected by the vertical synchronization detection means immediately after the reading of the exposed first reference image signal from the image sensor is completed. To An image pickup apparatus for displaying and starting exposure of the second reference image.