JPH0332948B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for reading color images using a line-type photo sensor, and in particular a method for reading light source lamps corresponding to separated light of a plurality of specific colors in a time-sharing manner sequentially and periodically. The present invention relates to a method for correcting image data when each of the above-mentioned separated lights is photoelectrically converted by one line-type photo sensor.

(Prior Art) In recent years, with the increase in the density of line-type photo sensors (for example, CCD photo sensors), it has become possible to obtain highly accurate two-dimensional image data. The basic method is to image the light transmitted through the original 1 or the light reflected by the original 1 onto the light-receiving surface of the line-type photo sensor 2 using the lens 3, as shown in FIG. By sequentially changing the relative position of the document and the document in the sub-scanning direction perpendicular to the longitudinal direction (main-scanning direction) of the photo sensor,
Images of required portions of the document are sequentially scanned by the photo sensor and photoelectrically converted.

By the way, when trying to duplicate a color image,
Basically, it is necessary to obtain separated color light of R (red), G (green), and B (blue) from the original, and one way to do this is to use specific multiple color lights placed on the back of the original as shown in Figure 6. Decomposed light (basically, the above
Multiple light source lamps 6R, 6 corresponding to RGB colors)
G and 6B are blinked in a time-sharing manner and periodically, and further synchronized with the blinking of the light source lamp to determine the light reception timing and time (if the line-type photo sensor is a CCD array, the integration period) of the line-type photo sensor 2. There is a method of obtaining separated signals of each RGB color from one main scanning line in a time-divisional manner by controlling (for example, Japanese Patent Laid-Open No. 58-212255). In this case, when a CCD sensor array is used as a line-type photo sensor, two or more separated color lights are mixed together during the integration period of the CCD sensor array.
It is necessary to prevent it from entering the array. Therefore, as shown in Figure 7a, the integration period for each color signal is
Each light source lamp 6R, 6G, 6B in T _R , T _G , T _B
One possible method is to turn the lights on and off, and also to prevent the afterglow after the lights are turned off from occurring during the next integration period.Another method is to change the integration periods T _R , T _G , A sacrificial time Te is provided between T _{and B} , and each light source lamp is lit before the start time t _0R , t _0G , t _0B of each integration period, and at the end of the integration period t _1R , t _1G , t _1B
Even if the light is turned off after that and photoelectric conversion is performed at the waste time Te,
Methods have been devised to prevent the data from being used (for example, Japanese Patent Application Laid-open No. 58-212255).

Using any of the above methods, it is possible to extract signals of multiple fixed colors using a single CCD sensor array without causing a delay greater than that of the scanning line.

(Problems to be Solved by the Invention) However, in the above method, there is a difference in emission intensity between the RGB light source lamps 6R, 6G, and 6B, and even if they are the same light source lamp (for example, 6R), Fluctuations in luminous intensity occur each time the lamp is lit due to external factors such as voltage and internal factors such as lighting time. Therefore, in the conventional method, which assumes that the light emission time of the light source and the light reception time of the line type sensor 2 are constant, when the above-mentioned fluctuation occurs, the level of the obtained image data becomes uneven, and the duplicated image This was causing a decline in the quality of the products.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and an object of the present invention is to ensure that the amount of light emitted from each light source lamp used for each photoelectric conversion is constant.

(Means for solving the problems) In order to achieve the above object, the present invention employs the following means. That is, the line-type photo sensor and the original are sub-scanned relatively and intermittently in the sub-scanning direction perpendicular to the main-scanning direction of the photo sensor, and while the sub-scanning is stopped, R (red), G
(Green) and B (Blue) light source lamps are sequentially blinked, and while these light source lamps are on, the colored light from the light source lamps obtained through the original is photoelectrically converted by the line type photo sensor. In addition to extracting image data, a control photo sensor directly receives colored light from the lit light source lamp to detect the amount of light emitted from the light source lamp itself, and the amount of light emitted reaches a predetermined detection level. Then, the lit light source lamp is turned off or light reception by the line type photo sensor is stopped, and each of the light source lamps is sequentially blinked and the image data is extracted for one main scanning line while each light source lamp is lit. When the sub-scanning is completed, the sub-scanning feed is executed for a sub-scanning width of one main-scanning line, and image data extraction for the next main-scanning line is started.

Note that it is desirable to use a control photo sensor whose spectral sensitivity characteristics are as close as possible to those of a line-type photo sensor. Furthermore, when a CCD sensor array is used as a line-type photo sensor, the light reception time is limited by the integration period of the CCD.

(Example) and (effect) A more detailed explanation will be given below with reference to the drawings.

FIG. 1 is a block circuit diagram of an apparatus implementing the present invention when a CCD is used as a line photo sensor. The original table 11 is connected to the sub-scanning motor 1
The sub-scanning motor 12 is controlled by a sub-scanning control circuit 16 described below. On the back of the original table 11, as explained in FIG.
B Three light source lamps 6R that emit separated light of three colors,
6G, 6B are arranged, and the light sources 6R, 6G, 6B
The light is transmitted through the original 1 and formed into an image on the light-receiving surface of the line-type CCD photo sensor 2 via an optical device 30 such as a lens. This light source 6
R, 6G, 6B are, for example, R→G→
The light source control circuit 18 controls the lights to turn on and off periodically in the order of B.

By turning on the light sources 6R, 6G, and 6B, the image data accumulated in the photo sensor 2 is sequentially input by the CCD drive circuit 17 to a preprocessing circuit 19 having an AD conversion function.

Incidentally, necessary timing pulses are input from the timing control circuit 15 to the sub-scanning control circuit 16, the CCD drive circuit 17, and the light source control circuit 18.

A control photo sensor 7 that directly receives the light from the light source lamps 6R, 6G, and 6B is provided in front of the light source lamps 6R, 6G, and 6B, and the output of the control photo sensor 7 is input to a light amount monitor circuit 31. Ru. The light amount monitor circuit 31 checks that the effective amount of light received by the control photo sensor 7 is always constant, and notifies the timing control circuit 15 of the result of the check. This device basically operates as follows.

First, the document table 11 is stopped, and when the light source lamp 6R is turned on, the image data accumulated in the photo sensor 2 while the light source lamp 6R is turned on is
It is read out from the CCD photo sensor 2 under the control of the CCD drive circuit 17, and the A/
The signal is converted into D and stored in the delay buffer memory 20R. Next, while the original table 11 remains in the same position and the light source lamp 6G is turned on, the G color image data accumulated in the photo sensor 2 is stored in the delay buffer memory 20G as described above. Furthermore, B color image data is similarly stored in the delay buffer memory 20B. In this way, manuscript 1
When the RGB three-color image data of the above specific line is read out from the photo sensor 2, the sub-scanning control circuit 16 causes the document table 11 to advance by one pixel (one main-scanning line width) in the sub-scanning direction and turn on the light source lamp 6R again. Repeat the above process by turning on the light.

On the other hand, the image data stored in the three delay buffer memories 20R, 20G, and 20B as described above are then sequentially and synchronously read out and input to the image processing circuit 21. The timing of lighting and extinguishing the light source lamps 6R, 6G, and 6B in this device is as shown in Fig. 7a and b above, and Fig. 2 shows two control examples shown in Fig. 7a and b. This is an embodiment in which the present invention is applied. Figure 2a,
The shaded area b indicates the effective amount of light received by the control photo sensor 7.

First, FIG. 2 a shows the light source lamps 6R, 6G, 6.
12 is a timing chart showing an example of blinking control of B. First, each light source lamp 6R, 6G, 6B is
As shown in Figure a, the light is turned on during the integration period of the line type photo sensor 2. Then, the effective amount of light emitted by each light source lamp, that is, the effective amount of light received by the control photo sensor 7 (the area of the shaded part in FIG. 2) is calculated for each integration period T _R ,
When T _G and T _B become equal to predetermined values (detection levels) for each required RGB, the timing of turning off the light sources 6R, 6G, and 6B is controlled based on this value.

On the other hand, FIG. 2b shows a method of adjusting the integration period when the discard time Te is provided as shown in FIG. 7b. That is, the light source lamps 6R, 6
The integration period itself is adjusted so that the effective amount of light received by the photo sensor 7 (hatched in FIG. 2) becomes equal to a certain reference amount during the light reception period that starts after lights G and 6B are turned on. In this case, the interval Ti between the beginnings of each effective light reception period is kept constant, and at the end of the integration period
It is preferable to control by adjusting t _1R , t _1G , and t _1B .

The above operation will be further explained based on the timing charts shown in FIGS. 4a and 4b. Note that FIG. 3 is a block diagram showing an example of the circuit of the light amount monitor circuit 31, and the operation of this light amount monitor circuit 31 will be included in the following description. Also, in Figure 4a ()
The CCD analog output signal is a serial representation of each RGB signal shown in FIG. 2a, and the same signal in FIG. 4b is a serial representation of each RGB signal shown in FIG. 2b.

First, when the reset signal is at the "H" level in FIG. W becomes zero level. Next, when the reset signal r becomes "L" level, the analog switch 33
The contact contacts the terminal on the level detection circuit 34 side,
A state is created in which the amount of light received by the control photo sensor 7 can be stored in the capacitor 32 as an amount of charge. Further, the light source 6R is turned on after a certain period of time from the rise (or fall) of the reset signal r.

By lighting the light source 6R, the control photo sensor 7
When the amount of received light increases, the level of the integrated light amount signal W increases, and the level of the signal W reaches the detection level Vd, the level detection circuit 34 detects the amount of light detection signal.
Output Pd and turn off light source 6R.

After that, the reset signal is sent to analog switch 3 again.
4, and the same processing as above is repeated, but since the CCD drive signal Cd is also output in synchronization with the reset signal, the optical signal from the light source 6R is transmitted during the period _TR. This means that the image is accumulated in the photo sensor 2.

Next, in FIG. 4b, after the light source 6R is turned on, the capacitor 32 is turned on by the reset signal r.
is discharged to bring the light amount integral signal W to zero level. When the reset signal r goes to the "L" level, the amount of light received by the control photo sensor 7 is obtained from the capacitor 32 as the integrated light amount signal W, as in the case of FIG. 4a. The light amount integral signal W increases and the detection level
When the voltage reaches Vd, the level detection circuit 34 generates a light amount detection signal Pd, and the light source 6R turns off. Then, in both a and b of FIG. 4, by the A/D drive signal Ck until the next integral drive signal Cd is generated,
Through the preprocessing circuit 19, the buffer memory 20R
The image data captured during the period T _R is stored sequentially.

At the timing shown in Figure 2b, the signal between the CCD drive signal Cd and the A/D is not used.
Drive signal Ck is not generated.

Although the timing of lighting the light source 6R has been described, the same applies to the lighting of the light sources 6G and 6B.

Needless to say, the timing control circuit 15 performs control in consideration of the characteristics of the control photo sensor 7 so as to obtain the white balance of the output signals of each RGB color.

(Effects of the Invention) As explained above, the present invention detects the amount of light emitted from the light source lamp, and adjusts the lighting period of the light source lamp itself or the light receiving period of the line-type photo sensor based on the amount of light emitted. The effective amount of light emitted by the line type photo sensor can be made to be a constant amount during each effective light reception period of the line type photo sensor, and uniform image data can be obtained even when the amount of light varies.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an apparatus for carrying out the present invention, Fig. 2 is a diagram of an embodiment in which the invention is carried out using the apparatus shown in Fig. 1, and Fig. 3 is a diagram showing the operating principle of the light amount monitor circuit. , FIG. 4 is a diagram explaining the timing. Fig. 5 is a schematic diagram of obtaining two-dimensional image data using a line-type photo sensor, Fig. 6 is a schematic diagram of an apparatus for obtaining two-dimensional color image data using a line-type photo sensor, and Fig. 7 is a schematic diagram of a device that obtains two-dimensional color image data using a line-type photo sensor. This is a timing chart when obtaining RGB separated color optical signals using the apparatus shown in . 1... Original, 2... Line type photo sensor, 6
...Light source lamp, 7...Control photo sensor, 1
5... Timing control circuit, 17... CCD drive circuit, 18... Light source control circuit, 30... Optical equipment, 31... Light amount monitor circuit.

Claims (1)

[Scope of Claims] 1. A line type photo sensor and a document are sub-scanned relatively and intermittently in a sub-scanning direction perpendicular to the main-scanning direction of the photo sensor, and while the sub-scanning is stopped, R (red), G (green), B
(Blue) Each light source lamp is blinked in sequence, and while each light source lamp is on, the colored light from the light source lamp obtained through the document is photoelectrically converted by the line photo sensor to extract image data. At the same time, a control photo sensor directly receives the colored light from the lit light source lamp to detect the amount of light emitted from the light source lamp itself, and when the amount of light emitted reaches a predetermined detection level,
When the lit light source lamp is turned off or light reception by the line type photo sensor is stopped, and the sequential blinking of each light source lamp and the extraction of the image data while each light source lamp is lit are completed for one main scanning line. . An image reading correction method characterized in that the sub-scanning feed is performed by a sub-scanning width of one main scanning line, and then the process moves to image data extraction for the next main scanning line.