JP3155607B2 - Screen position measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen position measuring apparatus for automatically measuring the screen position of an underscan character display device at high speed and with high accuracy.

[0002]

2. Description of the Related Art In an underscan character display device using a CRT (cathode ray tube), a rectangular screen is displayed on the CRT in an outer frame in front of the character display device. The screen must be set so that the positions of the four sides of the raster edge, up, down, left and right, are equidistant from the ridge line where the CRT and the outer frame are in contact (hereinafter referred to as the ridge line of the outer frame). It is required that such a distance be reduced to zero as much as possible. For this purpose, the character display device is provided with a screen position adjusting mechanism, whereby the position of the display screen can be adjusted vertically and horizontally.

Conventionally, for such display screen position adjustment,
A method for automatically measuring the position of the display screen is known. Examples thereof are disclosed in Japanese Patent Application Laid-Open Nos.
-99376.

[0004] In the former example, two ITs are arranged at the top, bottom, left and right.
A V-camera (hereinafter, referred to as a camera) is arranged, and the upper and lower cameras are, respectively, the upper part of the projection area of the display screen and a part of the upper part of the outer frame on the CRT screen, and the lower part of the projection area of the display screen. And the lower part of the outer frame as an imaging area, and the left and right cameras are a left part of the projection area of the display screen, a part of an upper part of the left part of the outer frame, and a right part of the projection area of the display screen, respectively. Each part of the right side of the outer frame is taken as an imaging area, and each imaging area is imaged. Then, for each of these cameras, a raster is displayed on the entire tube surface in the outer frame to emit light, and in this state, a first mode for imaging each imaging region and a display screen is projected on the tube surface. In this state, it is possible to set a second mode for imaging each imaging region, detect the position of the ridge line of the outer frame from the image information obtained by the imaging in the first mode, and in the second mode Then, the position of the side of the display screen is detected from the image information obtained by the above imaging, and the position of the display screen within the outer frame is detected from the position information.

In the latter example, a camera having an imaging area including an outer frame in front of a CRT display device and one illumination means for illuminating the entire imaging area of the camera from the front are provided. A first mode in which a display screen is projected on a screen of a CRT to capture an image, and a second mode in which the display screen is illuminated by an illuminating unit without being projected and the image is captured, can be set. The position of the edge of the outer frame is detected from the image information obtained by the imaging in the second mode, the position of the side of the display screen is detected from the image information obtained by the imaging in the second mode, and The position of the display screen within the frame is detected. As such an illuminating means, a method of illuminating with a circle spot using a halogen lamp has been standard.

[0006]

However, in the former case, even if a raster is displayed on the entire tube surface in the outer frame to emit light, the contrast between the outer frame and the tube surface depends on the brightness and color of the outer frame. In some cases, the ridgeline of the outer frame is not clear, and in such a case, the ridgeline position of the outer frame cannot be accurately detected. The measured C
The RT display device also requires special deflection means for raster-displaying the entire outer frame.

In the latter case, since the illumination means illuminates from the front, the contrast between the outer frame and the tube surface may not be sufficient due to the brightness and color of the outer frame, and the ridgeline of the outer frame may not be clear. In addition, there is a problem in that the irradiation time is required to turn on and off the halogen lamp, which is an obstacle, and the measurement time becomes longer than 20 seconds.

An object of the present invention is to provide a screen position measuring apparatus which can solve such a problem and can measure accurately in a short time.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a display screen including a ridge line of an outer frame which is a boundary with a cathode ray tube and projected on the tube surface. At least four image pickup units each having an image pickup region on the left side, right side, upper side, and lower side of the output region; and a plurality of strobe lights arranged diagonally forward of the tube surface and corresponding to the respective image pickup units. And performing an imaging operation for each of the imaging means.
Next, corresponding to the imaging unit that performs the imaging operation for each imaging operation.
Control for selectively setting a first mode in which the strobe light is selectively turned on and a second mode in which the display screen of a uniform high-intensity raster is projected on the tube surface and the imaging means performs an imaging operation. Means for processing the output information of the imaging means in the first mode and the output information of the imaging means in the second mode to create position information of the display screen in an outer frame Means , the control means selecting in the first mode.
The strobe light to be turned on is the imaging means for performing an imaging operation.
Creating a shadow on the ridge line of the case frame within the imaging region of
The strobe light.

[0010]

With the respective image pickup means, the upper and lower sides of the display screen projected on the surface of the cathode ray tube, the four sides of the left and right sides, the upper and lower sides of the outer frame,
The position of the display screen is detected from the difference between the position of the edge in the same direction and the position of the four left and right ridge lines. Therefore, the side of the side clearly appears in the output of the imaging means, and the accurate side position can be detected. In the measurement of the ridge of the outer frame, the ridge of the outer frame is measured by the illumination of the strobe light. This ridge line portion clearly appears in the output of the imaging means, and accurate ridge line position detection becomes possible. In addition, since a strobe light capable of sufficiently illuminating at high speed ON and OFF is used as the illumination means, the imaging means is sufficient to image one screen, and high-speed measurement is possible.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a screen position measuring device according to the present invention, wherein 1 is a CRT display device, 2 is an outer frame,
3 is CRT, 4 is display screen, 5a, 5b, 5c is ITV
Camera, 6 an image processing unit, 7 a monitor, 8a, 8b strobe lights, 9, 9a, 9b, 9c imaging areas, 10
Denotes a CPU (Central Processing Unit).

Referring to FIG. 1, a CTR display device 1 displays a raster display screen 4 on the front of a CRT 3, and this display screen 4 is positioned within an outer frame 2.
Further, in order to image the CRT 1 and the outer frame 2 including the CRT 1 at a relatively high resolution, three CCD ITV cameras (hereinafter, referred to as “hereafter”) arranged in the raster direction (lateral direction) of the display screen 4.
5a, 5b, and 5c are provided, and strobe lights 8a and 8b are arranged on both front sides of the CRT display device 1, respectively. As such a camera, for example, an ITV monochrome CCD camera XC-57 having a 25 mm lens B2518 manufactured by Sony Corporation and having 510 × 492 pixels is used. Further, as the strobe lights 8a and 8b, for example, strobes (SM-334H, SH-321 Joules) manufactured by Sovic can be used.

Under the control of the CPU 10, cameras 5a, 5b and 5c are arranged in a horizontal direction from left to right on the drawing.
Captures an image of the imaging area 9 including a part of the tube surface of the CRT 2 and the left and right sides of the outer frame 2 including the tube surface as a whole. For example, in the case of the above-mentioned CCD ITV monochrome camera, these three cameras 5a, 5b, and 5c allow about 540m.
An image is taken in a field of view of 150 × 112 mm from a position m m away.
This field of view is the imaging area 9. And these cameras 5
a, 5b, and 5c share imaging of the imaging region 9. That is, the left camera 5a displays the left imaging region 9a, the center camera 5b displays the center imaging region 9b, and the right camera 5c displays the left imaging region 9b.
Captures the right imaging region 9c, respectively. Here, the imaging region 9a of the camera 5a and the imaging region 9b of the camera 5b partially overlap, and the imaging region 9b of the camera 5b and the imaging region 9c of the camera 5c also partially overlap. The video output of these cameras 5a, 5b, 5c
, And supplied to the monitor 7, and the three cameras 5a,
The images of the imaging area 9 are displayed by 5b and 5c.

The strobe lights 8a and 8b are used to irradiate an area including the positions of the four sides of the display area 4 formed by rasters and the positions of the ridges of the outer frame 2.

Actually, a total of nine cameras are used in three rows and three columns, and a total of four strobe lights are used in two columns and two rows. For convenience of explanation, the three cameras in the center row are used. , And only two strobe lights are shown.

FIG. 2 is a block diagram of the embodiment of FIG. 1 showing the image processing section more specifically, 11 is a test signal generator, 12 is a power supply drive section, 13 is a camera selector, and 14 is a video frame. A memory, 15 is a parallel output interface, 16 is a bus, 17 is a RAM (random access memory), and parts corresponding to those in FIG.

In FIG. 2, only two cameras 5a and 5b are shown here. The test signal generator 11 is connected to the CPU 10 by a control line of a communication circuit RS232C, and receives a control signal from the CPU 10 via the control line to generate a test signal of a white raster signal or a black raster signal. CRT
Supply 3 As a result, the display surface of the CRT 3 shown in FIG.
As shown in the figure, the display screen 4 in raster is displayed.

When an imaging command is output from the CPU 10 via the bus 16 while the display screen 4 is displayed on the CRT 3 as described above, a trigger pulse is output from the parallel output interface 15 and the power supply driving unit 12 operates. Then, the strobe lights 8a and 8b are turned on and the camera 5
a, 5b, etc. start imaging in the imaging region shown in FIG. One of the image outputs of these cameras is selected by the camera selector 13 controlled by the parallel output interface 15, and 512 × 512 addresses vertically and horizontally, and one address 1
The byte is supplied to the high definition video frame memory 14. In the video frame memory 14, the selected image signal is converted into a digital image signal of 256 gradations and 512 × 512 pixels and stored. The video frame memory 14 is accessed from the CPU 10 via the bus 16 and can be through or frozen after A / D conversion. Video frame memory 1
The digital image signal read from 4 is passed through a bus 16, D / A converted by a CPU 10, and supplied to a monitor 7.

FIG. 3 shows the three cameras 5a, 5a and 5a shown in FIG.
It is the figure which showed the imaging area of b, 5c in more detail.

In FIG. 1, an imaging area 9a of the left camera 5a has a height Wh and a width W connecting points A, B, D and C in order.
An Lx rectangular area, and an imaging area 9b of the central camera 5b
Is a rectangular area having a height Wh and a horizontal width WCx connecting points E, F, H, and G in order, and an imaging area 9c of the right camera 5c is a point I, L,
It is a rectangular area having a height Wh and a horizontal width WRx connecting K and J in order. The imaging regions 9a and 9b overlap each other in a region connecting points E, B, D, and G sequentially.
b and 9c overlap in an area connecting points I, F, H and J in sequence. Here, the imaging area 9a is at least CRT3
Including the ridge line of the outer frame 2 that forms a boundary with the tube surface of the imaging region 9
c also includes at least a ridge line of the outer frame 2 that forms a boundary with the tube surface of the CRT 3.

The camera 5a takes an image of the image pickup area 9a and outputs image information. This image information is stored in the video frame memory 14 and used for position measurement of the display screen. 9a, points A, E,
An area having a height Wh and a width Wlx connecting G and C in order is defined as an effective imaging area of the camera 5a, and image information of the effective imaging area is used for position measurement of the display screen. Here, a straight line connecting the points E and G is defined as a vertical reference line SL1 and a straight line connecting the points I and J is defined as a vertical reference line SL2.
Assuming that the ridge line at the boundary of the boundary 3 is FL1 and the ridge line at the boundary between the right outer frame 2 and the CRT 3 is FL2, the tube surface portion of the CRT 3 in the effective imaging area, that is, the ridge line FL1 and the reference line SL1
Is defined as Lex. Similarly, the effective imaging area of the camera 5c is an area of a height Wh and a width Wrx connecting points F, L, K, and H in the imaging area 9c in order, and image information of the effective imaging area is displayed on the display screen. Used for position measurement. Here, the width of the tube surface portion of the CRT 3 in the effective imaging area, that is, the width between the ridge line FL2 and the reference line SL2 is defined as Rex. On the other hand, the effective imaging area of the camera 5b coincides with its own imaging area 9b. Note that the cameras 5a,
The above-mentioned imaging sharing of the imaging region 9 by 5b and 5c is divided by the reference lines SL1 and SL2.

When measuring the position of the display screen 4 projected on the screen of the CRT 3 with respect to the outer frame 2, the position of the ridge line of the outer frame 2 and the position of the side of the display screen 4 are measured, and the distance between these positions is measured. The difference is set as the position of the display screen 4. When the distance differences are equal in all directions, the position of the display screen 4 is determined to be correct, and when they are not equal, position adjustment is performed.

Next, the measurement of the position of the ridge line of the outer frame 2 and the position of the side of the display screen 4 will be described. First, the measurement of the position of the ridge line of the outer frame 2 will be described.

In this case, first, as described above,
For example, the above-mentioned Strobe light 8a manufactured by Sovic is lit for 40 μsec, for example, to illuminate the outer frame 2 and the CRT 3, and a black raster signal is supplied from the test signal generator 11 to the CRT 3 as a test signal. Is displayed on the CRT 3. This increases the contrast between the outer frame 2 and the CRT 3 when illuminated by the strobe light 8a. In addition, since the outer frame 2 and the CRT 3 are illuminated obliquely from the front, shadows are generated at the ridge lines that are the boundaries between the outer frame 2 and the CRT 3, and the ridge lines of the outer frame 2 become clear. In this state, the left camera 5a captures an image of the imaging region 9a. The output image information of the camera 5a is stored in the video frame memory 14 in FIG. 2, read out by the CPU 10 and displayed on the monitor 7, and by using the RAM 17 to perform image processing described below. , The ridge position of the outer frame 2 is detected. This ridge line position is indicated by the reference line S in FIG.
L1 is a reference position, and a distance L from this reference position SL1 is
Detected as ex.

FIG. 4 shows a memory area 14L for storing digital image information for one image from the camera 5a in the video frame memory 14 in FIG. 512 pixels are stored. In this memory area 14L, if the horizontal axis is the i-axis and the vertical axis is the j-axis, the addresses in the i- and j-axis directions are both 51.
There are two.

When measuring the position of the ridge line of the outer frame 2, the address at the center of the j-axis direction, that is, the pixel data at address j = 256 may be used, but here, the surface of the outer frame 2 and the CRT 3 As shown in FIG. 4, pixel data at the address (256 ± 5) on the j-axis is averaged and used in order to eliminate luminance unevenness on the tube surface. That is, if the value of the pixel data at the position (i, j) in the memory area 14L is M (i, j), the average value M of the pixel data at the positions (i, 251) to (i, 261) is obtained. (I) is used in place of the pixel data at the address j = 256. Here, assuming that the number of pixel data to be averaged is N (i) and j ← (j−250), the average value M (i) is expressed by the following equation 1.

[0027]

(Equation 1)

In this case, however, N (i) = 11. FIG. 5A shows the average value M (i) with respect to the address in the i-axis direction of the memory area 14L in FIG. , M3 are the average values M (i) of the outer frames 2 and CRT3 on the tube surface, respectively, and MFL1 is the average value M (i) of the ridge lines that are the boundaries between the outer frames 2 and CRT3. As described above, the shadow caused by the illumination of the strobe light 8a is lower than other portions.

With respect to the average value M (i) thus obtained, next, the absolute value ΔM (i) of the difference between the average values M (i) between the adjacent addresses i and i + 1 is obtained. This is shown in FIG.
As shown in (b), the maximum peak of the absolute value ΔM (i) of this difference occurs at the address iFL1 where the average value M (i) in FIG. 5A is MFL1. Therefore, the reference line SL in FIG.
Assuming that the address for ₁ is i1, the ridge line of the outer frame 2 in FIG.
FL1-i ₁ | the address number obtained (hence, the number of pixels data) will be in the position of the n.

Therefore, assuming that the optical resolution α per pixel is 0.3 mm, the distance Lex [mm] of the ridge line of the outer frame 2 from the reference line SL1 in FIG. It is.

[0031]

(Equation 2)

Although the above is the position of the ridge line of the left outer frame 2 in FIG. 3, the position of the ridge line of the right outer frame 2 can be obtained in the same manner.

That is, in FIG. 3, the strobe light 8b
Is turned on for a period of, for example, 40 μsec, and the outer frame 2 and the CRT are
3 is illuminated, and an imaging area 9c is taken by the right camera 8c.
Is imaged, and an average value M (i) shown in FIG. Then, from this average value M (i),
As described above, the absolute value ΔM of the difference shown in FIG.
Find (i). Maximum peak right indicates the ridge line of the outer frame 2, out of these reference line SL2 from the address i ₂ Metropolitan right for this address iFL2 the reference line SL2 in FIG. 3 of absolute value .DELTA.M (i) of this difference The number m of pixel data up to the ridge line of the frame 2 is obtained. Therefore, since the optical resolution α per pixel is set to 0.3 mm, the distance Rex [mm] of the ridge line of the right outer frame 2 from the reference line SL2 in FIG.
Is represented by

[0034]

(Equation 3)

As described above, the reference lines SL1, SL2
Are obtained as distances Lex and Rex. Such distance data is temporarily stored in the RAM 17 of FIG.

Next, the case where the position of the side of the "display screen on the CRT 3" is determined will be described. In this case, the test signal generator 1 is controlled by the CPU 10 in FIG.
1 generates a white raster signal as a test signal;
Supply to RT3. As a result, a display screen of a white raster is displayed on the screen of the CRT 3. At this time, neither strobe light 8a, 8b is turned on. For this reason, the luminance of the display screen 4 is much higher than other parts (the part other than the display screen 4 on the display screen of the CRT 3 and the outer frame 2).

FIG. 7 shows such a display state on the CRT device 1. 4L and 4R are the left side and the right side of the display screen 4, respectively, and the portions corresponding to the above-mentioned drawings are denoted by the same reference numerals. . Further, circles in the display screen 4 indicate pixels.

In the display state shown in FIG.
When the position of the left side 4L is detected, the left camera 5a is detected in the same manner as when the ridge position of the left outer frame 2 is measured.
(FIG. 1) captures an image of the image capturing area 9a, and the CPU 10 captures the output image information via the video frame memory 14 of FIG. In the CPU 10, in the same manner as the method described with reference to FIG. 4 and FIG.

[0039]

(Equation 4)

Here, M (i, j) ′ is the value of the pixel data at the position (i, j) similar to the case of the above equation (1). Also, N
With (i) = 11, the average value M (i) ′ of the pixel data values as shown in FIG. 8 is obtained, and as shown in FIG. 8, the difference between the adjacent addresses of the average value M (i) ′ is obtained. Absolute value of Δ
M (i) ′ is obtained.

Since the display screen 4 is based on a white raster, the average value M (i) 'greatly changes at the position of the left side 4L of the display screen 4, as shown in FIG. A maximum peak occurs at the value ΔM (i) ′. Therefore,
If the number of addresses between the address of the position of the reference line SL1 and the address of the position of the maximum peak, that is, the number of pixel data is n ′, the optical resolution α per pixel is 0.3 mm. The distance Lex ′ from the reference line SL1 in FIG. 7 to the display screen 4L is obtained from the following Expression 5.

[0042]

(Equation 5)

Similarly, the display screen 4 composed of a white raster is displayed on the CRT 3, and the right camera captures the image of the image pickup area 9c to obtain image information, thereby obtaining the average value M (i) as shown in FIG. And the absolute value ΔM (i) ′, obtain the number m ′ of pixel data from the reference line SL2 of FIG. 7 to the right side 4R of the display screen 4, and use this to calculate the following equation 6. From these reference lines SL2, the right side 4 of the display screen 4
The distance Rex 'to R is obtained.

[0044]

(Equation 6)

The distances Lex ', R obtained as described above
The data of ex ′ is temporarily stored in the RAM 17. Thereafter, the distance Lex from the reference line SL1 to the ridge line of the left outer frame 2
The distance ΔL between the ridge line of the left outer frame 2 and the left side of the display screen 4 is obtained from the following Expression 7 based on the distance Lex ′ to the left side of the display screen 4.

[0046]

(Equation 7)

Similarly, from the reference line SL2 to the right outer frame 2
Distance Rex to the ridge line and distance R to the right side of the display screen 4
The distance ΔR between the ridge line of the right outer frame 2 and the right side of the display screen 4 is calculated from the following equation (8) using ex ′.

[0048]

(Equation 8)

Then, the obtained intervals ΔL and ΔR are compared, and when ΔL = ΔR, it is determined that the position of the display screen 4 in the left-right direction with respect to the outer frame 2 is symmetric. When ΔL ≠ ΔR, the position of the display screen 4 in the left-right direction may be adjusted by means such as a conventional screen position adjustment mechanism.

The detection of the side position of the display screen and the detection of the ridge position of the outer frame 2 may be performed first.

The position measurement in the horizontal direction of the display screen 4 has been described above. However, the position measurement in the vertical direction can be similarly performed by using a camera arranged in the vertical direction.

As described above, according to this embodiment, as the illuminating means, a strobe light which can be turned on / off in a very short time and which can provide sufficient illumination in a short irradiation time is used. In order to measure the position of each side and the position of each ridge line of the outer frame 2, it is sufficient to take an image of at least one screen, so that the screen position can be measured at high speed. The speed can be improved by a factor of 40 or more as compared with the prior art. In addition, each side of the display screen 4 is configured such that the brightness of a white raster is high in the display screen 4,
It becomes very clear, and the ridge line of the outer frame 2 becomes very clear as a shadow when illuminated from the front with a strobe light. The position of the ridge line can be detected with high accuracy, and the position of the display screen 4 can be measured with high accuracy.

It should be noted that the numerical values shown in the description of the above embodiments are merely examples, and the present invention is not limited to such numerical values.

In FIG. 4, the pixel data actually used among the pixel data stored in the video frame memory 14 is the pixel data processed by the above equations (1) and (4). Need only have a capacity capable of storing such pixel data. The pixel data of such an area can be easily determined from the scanning position of the camera or the like.

[0055]

As described above, according to the present invention,
The positional relationship with respect to the outer frame of the display screen projected on the CRT tube surface can be measured at high speed and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a screen position measuring device according to the present invention.

FIG. 2 is a diagram showing a more specific configuration of the embodiment shown in FIG. 1;

FIG. 3 is a diagram for explaining details of an image pickup area of each camera in FIG. 1 and an algorithm for detecting a position of a ridgeline of an outer frame.

FIG. 4 is a diagram showing an area of pixel data used for detecting a ridge position of a left outer frame of image information obtained by imaging the left imaging area in FIG. 3;

5 is a diagram showing information data for detecting a ridge line position of a left outer frame obtained by processing pixel data from the region shown in FIG. 4;

FIG. 6 is a diagram showing information data for detecting a ridge line position of a right outer frame.

FIG. 7 is a diagram for explaining a position detection algorithm of a side of a display screen in the embodiment shown in FIG. 1;

FIG. 8 is a diagram showing information data for detecting the position of the left side of the display screen.

FIG. 9 is a diagram showing information data for detecting the position of the right side of the display screen.

[Explanation of symbols]

 Reference Signs List 1 CRT display device 2 Outer frame 3 CRT 4 Display screen 5a, 5b, 5c Camera 6 Image processing unit 7 Monitor 8a, 8b Strobe light 9, 9a, 9b, 9c Imaging area 10 CPU 11 Test signal generator 12 Power supply device 13 Camera selector 14 Video frame memory

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Maki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Yokohama Plant (56) References JP-A-3-99376 (JP, A) JP-A Heisei 3-123292 (JP, A) JP-A-4-23692 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 17/00-17/06

Claims (3)

(57) [Claims] 1. A screen position measuring device for a cathode ray tube display device for measuring a position of a display screen projected on a tube surface of a cathode ray tube in a case frame, wherein each of the case frames is a boundary with the tube surface. Including the ridgeline of
Left portion of the movies out area of the display screen, a plurality of image pickup means to the right side portion, upper portion, lower portion respectively imaging region is disposed obliquely forward of the tube surface, corresponding respectively to each of said image pickup means
A plurality of strobe lights were, causes image sensing is performed for each imaging means, the imaging operation
The strobe light corresponding to the imaging means that performs an imaging operation every time
Control means for selectively setting a first mode for selectively turning on and off the display unit, and a second mode for displaying the display screen of a uniform high-intensity raster on the screen and performing an image pickup operation of the image pickup means. A process of processing output information of the imaging unit in the first mode and output information of the imaging unit in the second mode to create position information of the display screen in the case frame; and means, strobe the control means for selectively lit in the mode of the first
The light is provided within the imaging region of the imaging unit that performs the imaging operation.
With the strobe light that creates a shadow on the edge of the case frame
Screen position measuring device, characterized in that there. 2. The display device according to claim 1, wherein in the first mode, the display screen is a black screen.
Screen position measuring device, characterized in that consist of a motor. 3. A screen position measuring apparatus according to claim 1, wherein said imaging means is a CCD camera, and said processing means includes a high-precision video frame memory .