JPH0623096Y2 - Electronic blackboard - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electronic blackboard used for meetings, meetings and the like.

[Prior Art] FIG. 6 shows an outline of a conventional roll-up type electronic blackboard. A screen 3 is arranged in an expanded state in an opening 2 formed in the front surface of a frame 1, and the screen 3
Is configured to be movable in the left-right direction by being wound by the left and right take-up rolls 4 and 5 arranged in the frame 1 via the rolls 6 and 7. In addition, the image on the screen 3 is the area A between the winding rolls 4 and 6 in the frame 1.
By passing through the point, the light beam from the fluorescent lamp 8 is reflected by the mirror 9, passes through the lens 10, and reaches the light receiving element (CCD) 11 to become image information. Reference numeral 12 is a reflection type sensor for detecting the page of the screen 3. The image information from the light receiving element 11 is processed as image data and stored in a D-RAM (Direct Random Access Memory) 13 shown in FIG. 7, and then sent to a thermal head 14 for thermal sensitivity. It is output as an image on paper.

FIG. 7 is an overall circuit diagram, and 15 is a CPU, 16 is a DMA (direct memory access) for controlling the transmission of image data from the light receiving element 11 to the D-RAM 13 and from the D-RAM 13 to the thermal head 14. Controller), 17 is a ROM for storing programs, and 18 is a RAM. Further, 19 is a timer for making timings such as pulses of the left and right take-up roll driving stepping motors 21 and 22 and the copy sheet conveying stepping motor 23, 24 is an I / O, 25 is an operating section, and 26 is a driving of the stepping motor. Reference numeral 27 is a sensor switch, 28 is a light receiving element controller, 29 is a thermal head controller which is a print timing generation circuit, and 30 is a thermistor. Reference numeral 31 is a shading correction plate, 32 is an inverting amplifier, and 33 is a selector.

In the electronic blackboard having such a structure, conventionally, no auto shading is performed, or a shading correction is performed by setting a reference white level reading position on a part of the screen 3.

However, it is difficult to surely obtain the reference white level waveform because the screen 3 may be easily soiled and letters or the like may be written. Therefore, the shading correction function does not operate normally, and side effects may adversely affect image output.

That is, in the case of the electronic blackboard of the type that reads the image information formed on the light receiving element 11 using the lens 10, (i) the fluorescent lamp 8 has a bright light source center and dark ends.

(ii) Fluorescent lamps change over time, increasing non-uniformity.

(iii) Due to design problems and manufacturing problems of the light receiving element, variations in sensitivity occur between bits.

(iv) Due to the characteristic of the image illuminance of the lens 10 (aperture ratio COS ⁴ θ rule, etc.), there is a difference in the amount of light between the central portion and the peripheral portion of the lens 10.

(v) Distortion occurs in the frame 1 and the optical system when the entire blackboard is moved or due to impact or the like.

Problems such as the above are caused.

Therefore, it is necessary to correct the white level by the shading correction mechanism in order to solve the problem caused by the distortion and variation of the white level (video formation).

Therefore, the present invention is intended to provide an electronic blackboard having a shading correction mechanism that can solve the above problems.

[Structure] In order to achieve the above object, the present invention provides a roll-up type electronic blackboard having a shading correction mechanism, in which a take-up roll is displayed in front of one page of the screen and with one page of the screen being displayed. A structure for setting a reference white level position at a position wound by the device and recognizing one page of the screen, and reading the reference white level at the reference white level position after recognizing one page And

Therefore, once the screen moves backward from the first page toward the 0th page, the reference white level provided at the position where the screen is wound by the take-up roll is displayed at the reading position. After appearing and reading the reference white level, the screen is advanced. The brightness of the read white level and the brightness of the screen on and after the first page are calculated to obtain a correction value.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a state in which the screen 3 of the electronic blackboard shown in FIG. 6 is developed. In this embodiment, the screen 3 has a total of 5 pages, of which 1 to 4 pages can be copied. This is because the fifth page cannot move to point A in FIG. Further, marks 34 for identifying the pages by the sensor 12 are provided at predetermined intervals on the screen 3, and only the mark of the first page is for searching the first page when the power is turned on and the other pages. The home position mark 35 having a long length is provided so as to be able to identify and the screen is not advanced any further.

Further, in the present invention, the white level is corrected by the shading correction mechanism so that the screen 3 itself has a reference white level. In this case, the screen is placed at a position in front of the first page of the screen 3 and at a position where the first page of the screen 3 is wound by the take-up roll 4 even when the first page of the screen 3 is stretched in the opening 2 of the frame 1. The reference white level position 36 is set over the entire surface width of No. 3. That is, not only the first page of the screen 3 but also any other page is displayed in front of the first page of the screen 3 and in the portion wound by the take-up roll 4 with the first page of the screen 3 being displayed. Even in the closed state, since it is taken up by the take-up roll 4, it is difficult for atmospheric dust to adhere due to static electricity and is relatively newer than other parts. Therefore, the reference white level position 36 is set in this part. .

Now, when the power switch is turned on, the sensor 12 detects the home position mark 35 and the screen 3 stands by on the first page. Here, when the print switch is turned on, the screen 3 temporarily retreats from the first page toward the 0th page, and the reference white level 36 wound on the winding roll 4 is moved to point A in FIG. Read the white level. After that, the screen 3 is moved to the page to be copied.

Thus, the white waveform level read at the reference white level position 36 is A / D converted by the A / D converter 37 of the circuit shown in FIG. 2 and stored in the memory 38 for each bit of the light receiving element 11. It
However, this data is variation information on the mechanism. This is S _X. On the other hand, the brightness of a certain bit when a character or the like written on the screen 3 is scanned is D _X. Since a relative brightness in the information of the D _X and S _X (brightness), divided by the divider 39 a D _X with S _X. Thereby, the correction value is obtained. In addition, 40 is a peak hold device.

The method of obtaining the correction value will be specifically described.
The peak value of the reference white waveform (waveform shown in FIG. 3) read at the point is 1, and S _X of a certain bit on the light receiving element 11 is 0.
Suppose it was 8. On the other hand, if D _{X at} a certain bit position when scanning a character or the like on the screen 3 is 0.6 (see FIG. 4), this value of 0.6 is relative to S _X (= 0.8) of the reference white waveform. Since it is a value, the actual brightness on the screen 3 is obtained by 0.6 / 0.8. Ie
0.6 / 0.8 = 0.75 will be corrected, and it can be said that 0.75 should have been read if there was no variation above, but this is the correction value. Therefore, the above-mentioned five problems can be solved by performing the correction for each bit with this correction value.

FIG. 5 shows a flowchart of auto shading. That is, when power is turned on, copy is turned on
At this time, it is determined whether or not the automatic shading should be performed by determining whether or not there is one page when moving the screen.

It should be noted that the present invention is not limited to the above-described embodiment, and it is optional to employ it for a fax machine, a whiteboard, etc., and various modifications can be made without departing from the scope of the present invention. Is.

[Effect] As described above, according to the present invention, the screen itself is provided with the reference white level to perform the auto-shading correction. Therefore, (I) the shading waveform due to the deterioration of the light source (fluorescent lamp, etc.) Can cover changes.

(II) The shading waveform can be adjusted flat,
The reading density can be made uniform, and the reference white level is set at the position where the page is wound up inside by the take-up roll while the page 1 of the screen is displayed. Even if any page is displayed, it is taken up by the take-up roll, so that stains are not easily attached to the reference white level and characters are not written. Then, the screen is once retracted in the direction of the 0th page rather than the 1st page to read the reference white level, so that the reference white level waveform can be reliably obtained.

And so on.

[Brief description of drawings]

FIG. 1 is a partially developed view showing an embodiment of the present invention, FIG. 2 is a circuit diagram for obtaining a correction value, FIG. 3 is an example of a reference white waveform, and FIG. 4 is a video waveform for reading image information. FIG. 5 is a flow chart for auto shading according to the present invention, FIG. 6 is a schematic view of a conventional electronic blackboard, and FIG. 7 is an overall circuit diagram of FIG. 3 ... Screen, 4 ... Winding roll, 8 ... Fluorescent light, 10 ...
Lens, 11 ... Light receiving element, 35 ... Home position mark,
36 ... White reference level position, 37 ... A / D converter, 39 ... Divider.

Claims (1)

[Scope of utility model registration request] 1. A roll-up type electronic blackboard having a shading correction mechanism, wherein a reference white level position is located in front of one page of a screen and at a position where the above-mentioned one page is displayed by a winding roll. And set
An electronic blackboard comprising a device for recognizing one page of a screen, and configured to read the reference white level at the reference white level position after recognizing one page.