JPH0411451A - Picture reader - Google Patents

Abstract

PURPOSE:To control luminous quantity of a light source properly by controlling a Lighting time of the light source based on an overflow detection output at A/D conversion. CONSTITUTION:A read timing control circuit 9 and a memory control circuit 10 are controlled by a system control circuit 21 including a function of an overflow detection means and a data and a control signal are sent and received between the system control circuit 21 and a CPU 22. A light source switching timing control signal from the read timing control circuit 9 is fed to a light source changeover circuit 70 to apply lighting changeover control of light sources 3R, 3G, 3B. Thus, the dynamic range of an A/D converter 6 is utilized at a maximum and feedback is applied so that a change in the range at the lighting time control of the light source is a small value from a large value.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image reading device that outputs image data read by an image reading means as a display signal to a CRT (cathode ray tube) display means or the like. .

[Summary of the Invention] The present invention reads an image using the light reflected from the image document of the light source, and the lighting time of the light source is determined based on the overflow detection output during A/D conversion of the image reading output. By controlling the amount of light from the light source, it is possible to appropriately control the amount of light from the light source, and by applying feedback so that the amount of change when controlling the lighting time of the light source is from large to small. The present invention provides an image reading device that can control the light amount of a light source at high speed.

[Prior Art] As a conventional image reading device, there is a known scanner device that reads an image document using an image sensor such as a CCD and outputs the obtained digital image data through a digital interface such as CPIB. However, in order to output the read image in a visual form (printout, display on a monitor, etc.), it is necessary to intervene with a computer device, which makes the system large-scale. In addition, since signal processing requires time, responsiveness is relatively poor. For this reason, conventional image reading devices such as scanner devices are unsuitable for use in presentations at exhibitions, lectures, etc., for example.

Therefore, the applicant of this application reads an image original, stores it in an image memory, and repeatedly reads it from the image memory in synchronization with the horizontal scanning signal and vertical scanning signal of the video signal, thereby outputting it as a video signal for displaying a still image. Such an image reading device is proposed in the specifications and drawings of Japanese Patent Application No. 1-83330, Japanese Patent Application No. 1-83696, and Japanese Patent Application No. 183697. According to this image reading device, an original image can be visualized and displayed with good responsiveness in a short time.

[Problems to be Solved by the Invention] Incidentally, the above-mentioned image reading device uses a light source such as a fluorescent lamp, a light emitting diode (ED), or the like. For example, when reading a two-dimensional image original as a color image, for example, while reading one line of the image original, three of the so-called three primary colors R, G, and B are
A color image is obtained by sequentially switching over and turning on two light sources and reading the reflection of these lights from the image document with a line sensor.

Here, the signal from the line sensor is converted into a digital signal by an A/D converter or the like. However, the individual characteristics of each light source mentioned above (e.g. light intensity,
Temperature characteristics, etc.) are generally not constant and vary, so for example, the amount of light may vary for each light source, or the amount of light from each light source may change due to temperature changes.

In this case, "Guinaminoclen 7 of the A/D converter;
There is a risk that you will not be able to use it as effectively as possible. That is,
For example, if the amount of light becomes too large, the signal from the line sensor may exceed the dynamic range of the A/D converter (overflow).
If the A/D converter causes an overflow in this way, it becomes impossible to obtain normal data from the A/D converter. Also, for example, if the light weight is too low, the signal level from the line sensor will also be low, so the A/D converter will only be used to a point that is much lower than the upper limit of input. As a result, the effective number of bits of the A/D converter cannot be fully utilized.

For this reason, in the past, for example, vision correction was performed in advance for each light source, or, for example, a temperature detection means was provided in the device, and power control (current or voltage control) was carried out based on the output of this temperature detection means. etc.) to stabilize the amount of light from the light source.

However, since the above-described light amount correction and light amount control based on temperature detection are performed in an analog manner, a circuit with a complicated configuration is required.

The present invention has been made in view of the above points, and has the following features:
An object of the present invention is to provide an image reading device that can obtain an appropriate amount of light that can utilize the dynamic range of a /D converter to the maximum extent possible with a simple configuration and at high speed, and that can obtain good read images. It is something to do.

[Means to solve the problem]

An image reading device according to the present invention includes a light source, an image reading means for reading an image using light reflected from the image document of the light source, and an A/D conversion means for A/D converting the output of the image reading means. and an overflow detection means for detecting an overflow of the A/D conversion means, and a lighting time control means for controlling the lighting time of the light source 7,
The lighting time control means is controlled based on the detection output of the overflow detection means, and the lighting time control means is configured to control the lighting time of the light source so that the amount of change when controlling the lighting time of the light source is from large to small. By applying a feed bank, the above-mentioned problem is solved.

[For production]

According to the present invention, the amount of light from the light source is determined by the lighting time of the light source, and whether or not the amount of light is appropriate is determined by whether or not the A/D conversion means is in overflow mode. There is.

Furthermore, when controlling the lighting time of the light source, the lighting time is first controlled by a large amount of change, and then controlled by a small amount of change, thereby shortening the time until the light amount reaches an appropriate amount.

〔Example〕

FIG. 1 is a functional block diagram for explaining the basic configuration of an image reading device according to the present invention.

The image reading apparatus of this embodiment shown in the functional block diagram of FIG. 1 includes a light source function block 105 having a light source, and an image reading function block 101 that reads an image using the light reflected from the image original from the light source. , an A/D conversion function blank 102 for A/D converting the output of the image reading function block 101, an overflow detection function block 103 for detecting an overflow in the A/D conversion function block 102, and an overflow detection function block 103 for detecting an overflow in the A/D conversion function block 102; The lighting time control function block 104 is controlled based on the detection output of the overflow detection function block 103. block 10
In No. 4, feedback is applied so that the amount of change during the lighting time control of the light source becomes small from large.

The image reading function block 101 is provided with a line sensor in which, for example, a plurality of CCD light receiving cells are arranged in a one-dimensional direction (main scanning direction). It is designed to receive the light reflected by the original. For example, a line sensor (or image original) receives and reads reflected light for one line (main scanning direction) of an image original, and sequentially reads I lines in the sub-scanning direction perpendicular to the nuclear scanning direction.
By moving the images and sequentially reading them, the entire image original is read.

The light source of the light source function block 105 is, for example, a fluorescent lamp,
A light source such as an LED (light emitting diode) is used.

For example, when reading a two-dimensional image original as a color image, for example, while reading one line of the image original, three light sources of the so-called three primary colors R, G, and B are sequentially switched on and turned on. By reading the reflection of these lights from the image original with the line sensor of the image reading function block 101 described above, a color image signal can be obtained.

The lighting time control function block 104 generates a pulse and controls the light source of the light source function block 105 to turn on for a time corresponding to the pulse width (lighting time control).
It is carried out. Here, the amount of light from the light source is determined by the pulse width. In other words, the light source used in a normal image reading device controls the amount of light to increase or decrease by controlling power such as current or voltage, but the amount of light from the light source in this embodiment depends on this pulse width (lighting time).
It is designed to increase or decrease depending on the situation. For example, if the pulse width is long (wide), the image reading function block 10
Since the amount of charge accumulated in the CCD light receiving cell of the first line sensor also increases, the result is equivalent to a large amount of light.

Conversely, if the pulse width is short (narrow), the charge accumulated in the CCD light-receiving cell is not large, so it is equivalent to a small amount of light.

The A/D conversion function block 102 converts the output of the image reading function block 101 into an A/D converter or the like.
/D conversion to digital data is performed.

By the way, in general, when performing A/D conversion processing with an A/D converter, the level of the supplied input signal is
You can make the most effective use of the converter's dynamic range.1. -Bell 1, you need to rub it. That is,
For example, if the input signal level is too large, it will exceed the dynamic range of the A/D converter (overflow).
When such an overflow occurs, normal data cannot be obtained from the A/D converter. Also, for example, if the input signal level is too low, this A/D converter will be used only to a point much lower than the input upper limit, and the number of effective signals of the A/D converter will decrease. It's a shame that I can't use it enough anymore. For this reason, the A/D conversion function block 102
It is also necessary to make maximum use of the dynamic range of the A/D converter.

Here, in order to make the most effective use of the dynamic range of the A/D converter with respect to the output obtained from the image reading function block 101, the amount of change in the light amount control based on the pulse width control must be It is necessary to make it small and control it in small increments. That is, the ratio of the one step width of the light amount change to the dynamic range of the A/D converter is made smaller, and the output of the image reading function block 101 is brought closer to the dynamic range of the A/D converter. By making this possible, the dynamic engine can be used as effectively as possible. In order to make effective use of the dynamic range as described above, controlling the output of the image reading function block 101 (i.e., the amount of light received) in small increments is performed using the lighting time control function block J-2. This can be achieved by controlling the increase/decrease of the pulse width in steps 104.

Furthermore, in order to effectively utilize the dynamic range, the detection output of the overflow detection function block 103 is used to control the pulse width increase/decrease, which is performed by the lighting time control function block 104.

This overflow detection function block 103 is
The input signal supplied to the A/D converter of the /D conversion function block 102 (i.e., the image reading function block lO1
It detects whether the output signal exceeds the dynamic range of the acid A/D converter (is overflowing), and the detection output corresponding to whether or not it is overflowing is the above-mentioned output signal. Lighting time control function block 10
It is now sent to 4. Note that it is also possible to have a configuration in which the overflow detection function block 103 is included in the A/D conversion function block 102.

Therefore, the lighting time control function block lO4 performs control to narrow the pulse width in response to the detection output of the over-half low detecting function block 103, for example, when a signal indicating that the over-half low is being supplied, thereby narrowing the pulse width. When a signal indicating that the pulse width is not being used is supplied, control is performed to widen the pulse width. This pulse width control is performed in small steps as described above, and
The output level of the image reading function block 101 is
When the pulse width reaches approximately the same level as the dynamic range of the A/D converter, the pulse width is held.

These pulse width controls are performed by the light source function block 105.
By performing this for each light source, the light amount of each light source is controlled, and an appropriate amount of light that can effectively utilize the dynamic L-range can be obtained.

Furthermore, in the apparatus according to the embodiment of the present invention, the output level of the image reading function block 101 described in F can be adjusted more quickly.
In order to approach the dynamic range of the /D converter, that is, to control the light amount of each of the light sources at high speed, the lighting time control function block 104 sets the amount of change in the lighting time system of the light sources '< 8 o'clock. Pulse width control is performed such that feedback is applied so that the value decreases from large to small. That is, in the initial stage of pulse width control, the pulse width is largely changed, and as the pulse width approaches the appropriate value (the amount of light from the light source is appropriate), the amount of change in the pulse width is reduced.

FIG. 2 shows a flowchart of a specific example of pulse width feedback control in the lighting time control 1m function block 104, which is performed based on the detection output of the overflow detection function block 103.

First, in step Sl, the lighting time control function block 104 turns on the light source with a predetermined initial pulse width of 4M. The pulse width of this initial value is determined by taking into account the dynamic range of the A/D converter of the A/D conversion function block 102, and is set to a pulse width that provides, for example, the average level of the output of the A/D converter. It is said that Of course, the pulse width of this initial value may be smaller than the pulse width that becomes this average level. In step S2, the light source is turned on with the pulse width of the initial value, and the output obtained from the image reading function block 101 is sent to the overflow detection function block 103 via the A/D conversion function block 102. The overflow detection function block 103 determines whether or not the A/D converter has overflowed. Step S2 is Y
In the case of es, that is, in the case of an overflow, the process advances to step S5. Further, if No in step S2, that is, if there is no overflow, step S2
Proceed to step 3. In this step S3, the lighting time control function block 104 outputs the pulse width of the initial value, for example, 2.
A pulse with twice the width is output. Therefore, the light source is driven to turn on with a pulse having a width twice the initial value.

In step S4, the image reading function bronch 1 is obtained by turning on the light source with a pulse width twice that of this initial value.
Based on the output from 01, it is determined whether or not an overflow occurs again. If the answer in step S4 is NO, the process returns to step S3, in which the pulse width is further doubled, and again in step S4 it is determined whether or not it becomes an overflow. Also, step S4 is Y
In the case of es, the process advances to step S5. In step S5, the lighting time control function block 104 outputs a pulse having a width, for example, 3/4 times the pulse width selected in step S4 in the affirmative. That is, here, the amount of change in the pulse width in step S3 is smaller than the amount of change in the pulse width in step S5. In step S6, this 3/4
Based on the output from the image reading function bronch 101 obtained by turning on the light source with double the pulse width, it is determined whether or not an overflow occurs again. If the result in step S6 is Yes, the process returns to step S5, the pulse width is further increased by 3/4 times in step S6, and it is again determined in step S6 whether or not it becomes an overflow.

Further, step S6 is N.

In this case, the process advances to step S7. In step S7, from the lighting time system a function block 104 to the step S6
A pulse having a width that is, for example, 9/8 times the pulse width selected when "No" is output is output. That is, the amount of change in the pulse width in step S5 is smaller than the amount of change in the pulse width in step S7. In step S8, based on the output of the image reading function block 101 obtained by lighting the light source with a pulse width 9/8 times as large as this width, it is determined whether or not an overflow state has occurred again. If the result in step S8 is No, the process returns to step S7, where the pulse width is further multiplied by 9/8, and it is again determined in step S8 whether or not it becomes an overflow. Further, if the result in step S8 is Yes, the process advances to step S9. In the step S9, a pulse having a width, for example, 15/16 times the pulse width selected by the lighting time control function BRONK 04 to the step S8 with Yes is output. That is, the amount of change in pulse width in step S7 and the amount of change in pulse width in step S9 are different from each other in step S.
The amount of change at 9 is smaller. In step SIO, based on the output of the image reading function block 101 obtained by turning on the light source with a pulse width that is 15/16 times the width, it is determined whether or not an overflow has occurred again.

If the step SIO is Yes, the process returns to step S9, in which the pulse width is further multiplied by 15/16 times, and it is again determined in step 510 whether or not it becomes an overflow. If the step SIO is No, the pulse width control process ends.

That is, in flowchart 1 of FIG. 2,
The pulse width in step S3 is 2 times, the buffless width in step S5 is 3/4 times, and the pulse width in step S7 is 9 times.
Pulse width control is performed such that feedback is applied such that the amount of change in pulse width increases from large to small, such as increasing the pulse width by /8 times and increasing the pulse width at step S9 by 15/16 times. Here, for example, if step S2 is Yes and the overflow judgment in each step 56S8 S10 is completed only once, the pulse width control is performed in the least 3
With this control, a pulse width that is 15/16 times the final pulse width can be obtained. By driving the light source to turn on with a pulse of width 15/16 times, the output from the image reading function block 101 is at least 15/16=9 of the dynamic range of the A/D converter.
3.75% can now be used, and for example, if it is determined Yes in step S10 and it is repeatedly multiplied by 15/16 in step S9, more than 93.75% can also be used.

As described above, in the image reading apparatus of this embodiment, the above-described detection is performed based on the over-half flow detection output by the over-half flow detection function block 103 during A/D conversion of the image reading output of the image reading function block 101. By controlling the lighting time of each light source of the light a function block 105 by the lighting time control function block 104, the light amount of the light source can be controlled to an appropriate light amount that can effectively utilize the above dynamic range. In addition, when controlling the lighting time of the light source, feedback is applied to change the amount of pulse width from large to small, making it possible to quickly control the light intensity of the light source until the appropriate light intensity is achieved. It becomes like this. In other words, by performing such light intensity control every time reading starts, for example, it is possible to eliminate variations caused by devices such as each light source (including various lenses and other components described below), and changes in light intensity caused by temperature changes. etc. can be absorbed.

FIG. 3 shows the physical configuration of an image reading device according to an embodiment of the present invention.

That is, in the image reading apparatus of this specific example shown in FIG. 3, the image reading head 2 that reads the image original GD placed on the original platen 1 made of transparent glass or the like has three primary colors. The three lights #3R36, 3B of the above light source that emit certain R, G, and B lights (in the illustrated example, R and G
light sources 3R and 3c.

are shown as one for simplicity. , light g 3 x=
For 36! A light lens (rod lens) 80, a multi-lens array 4, and a CCD line sensor LS as the image reading means are provided, and the three light sources 3. ．． 3. ．．
311 are sequentially switched by the light source switching circuit 70 to illuminate the image original GD, and the reflected light from the image original GD is received by the line sensor LS via the multi-lens array 4. Further, the light source 3B is
It is a blue (B) fluorescent lamp (fluorescent tube), and the light di3*, 3c is transmitted across the multi-lens array 4.
It is located opposite to the Above line sensor L
S is composed of, for example, 1728 CCD light-receiving cells arranged in a straight line along the main scanning direction. 3 light sources 3R3c, L is color - 3 primary colors R
, G, and B, image signals of the three primary colors can be obtained line-sequentially (line-sequentially). The output from the line sensor LS of the image reading head 2 is amplified by the amplifier 5 and
It is sent to the A/D converter 6, which is a /D conversion means, and converted into digital image data, and the timing is adjusted by a line buffer 7 such as a so-called FIFO.
The image is stored in an image memory 8 such as AM (random access memory) or dual port memory. Before starting to read the image original CD, color correction is generally performed using R, G, and B reflected light from a white standard board, etc., and uneven light emission of each light source is performed. Alternatively, so-called shading caused by variations in the light intensity distribution of the multi-lens array 4 is removed.

The operation of the line sensor LS and the line sensor 7 is controlled by an image reading timing control signal from the reading timing control circuit 9, which is the lighting time control means, and the image memory 8 is controlled by a control signal from the memory control circuit IO. Write/read is controlled. The image reading head 2 also operates a motor drive circuit 26 in response to a motor drive timing control signal from the read timing control circuit 9.
By rotationally driving the head feed motor 27, the movement is controlled in the sub-scanning direction (the direction perpendicular to the main-scanning direction, which is the direction in which the line sensors are arranged). Further, the light source switching timing control signal from the reading timing control circuit 9 is supplied to the light source switching circuit 70. That is, the light source switching timing control signal is a switching pulse for switching the light source in the light source switching circuit 70, and the light source switching circuit 70 turns on the three light sources 3z, 3c, and 3m according to this light source switching timing control signal. The switching operation is performed. Furthermore, the read timing control circuit 9 also outputs a sample timing control signal for A/D conversion processing in the A/D converter 6. This sample timing control signal is a sampling pulse for sampling in the A/D converter 6, and is sent to the A/D converter 6.

Each primary color image data corresponding to the colors R, G, and B is read out from the image memory 8 and sent to the D/A converter 11.
, B image symbol and sent to the superimposition circuit 12. This superimposition circuit 12 is supplied with a character display signal for displaying, for example, a pointer mark, and this character display signal is superimposed on the image signal and output. The R, G, and B image symbols from the superimposing circuit 12 are taken out via output terminals 13R, 113G, and 13B, and sent to a display device such as a color CRT (cathode ray tube) monitor 14 or the like. The R, G, and B signals from the superimposing circuit 12 are sent to a Y (luminance) signal matrix circuit 15 and a C (chroma) signal matrix circuit 15.
The Y and C signals from these matrix circuits 15 and 16 are respectively sent to the signal matrix circuit 16.
They are taken out via output terminals 13Y and 13C, respectively. Further, these Y signal and C signal are mixed by a mixing circuit 17 to form a so-called composite video signal Sv, which is taken out via an output terminal 13V.

Next, the read timing control circuit 9 and the memory control circuit 10 are a system control circuit (so-called system controller) that also includes the function of the overflow detection means.
This system control circuit 21
Data and control signals are exchanged with the CPU 22. The system control circuit 21 and the CPU 22 may have an integrated configuration. In addition, from the key human power device 23,
For example, key human input signals are supplied to the CPU 22 for scrolling the contents of the displayed image, displaying a pointer mark to point to an arbitrary location within the displayed image, and determining the image reading range. There is.

Character generation circuit (or CRT controller) 2
Reference numeral 5 is provided to display functions related to various operations of the image reading device, and is equipped with a character pattern ROM etc. in which alphabetic character patterns, numeric patterns, symbol patterns, etc. are stored. As part of this character, a pattern for displaying a pointer mark and a trimming frame is provided.

Note that the system control circuit 21 outputs a horizontal synchronization signal HD.
, vertical synchronization signal VD, and a composite synchronization signal 5YNC that is a mixture of these signals are output from output terminals 18H118, respectively.
V, +83.

[Effects of the Invention] According to the image reading device of the present invention, based on the overflow detection output during A/D conversion of the image reading output,
By controlling the lighting time of the light source, it becomes possible to perform appropriate light amount control that can utilize the dynamic range of the A/D converter to the maximum extent possible. Also,
By applying a feed hack so that the amount of change when controlling the lighting time of the light source is small compared to humans, it becomes possible to appropriately and quickly control the light amount of the light source with a simple configuration. Therefore, it becomes possible to obtain a good read image.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram for explaining the basic configuration of an image reading device according to the present invention, FIG. 2 is a flowchart for explaining a specific example of lighting time feedback control, and FIG. 3 is a functional block diagram for explaining the basic configuration of an image reading device according to the present invention. FIG. 2 is a block diagram illustrating a specific example. 101... Image reading function block 102...
- A/D conversion function block 103... Overflow detection function block 104... Lighting time control function block 105... Light source function block... Document placement table 2... ...Image reading head 3R, 3G, 3
B...Light source 8...Image memory 9...Reading timing control circuit 10.
. . . Memory control circuit 12 . . . Superimposition circuit 14.0. ,,,CRT (cathode ray tube) monitor 21...
...System control circuit 22 ...CPU 23 ... Key human power device 25 ... Character generation circuit 70 ... Light source switching circuit 71 ... ...Switching pulse generation circuit 72...Sampling pulse generation circuit GD...
...Image original L S...Line sensor

Claims (2)

[Claims] (1) a light source, an image reading means for reading an image by light reflected from the image document of the light source, an A/D conversion means for A/D converting the output of the image reading means, and the A/D conversion. It has overflow detection means for detecting an overflow of the means, and lighting time control means for controlling the lighting time of the light source, and the lighting time control means is controlled based on the detection output of the overflow detection means. An image reading device characterized by: (2) The image reading device according to claim 1, wherein the lighting time control means applies feedback so that the amount of change when controlling the lighting time of the light source is from large to small.