JPS6364936B2 - - Google Patents

Description

[Detailed description of the invention] An accumulation type line image sensor (hereinafter sometimes referred to as an image sensor) that performs main scanning
In a device that obtains image information of the original and an image signal corresponding to the original by moving the original and the original relatively in the sub-scanning direction to perform the required main scanning and sub-scanning, the image of the original is In order to reproduce information as a reproduced image (recorded image) without image distortion or resolution unevenness, first, when reading the image information of a document, the scanning speed in the main scanning direction and the scanning speed in the sub-scanning direction must be adjusted. The speed is
Although it is necessary to always maintain a predetermined value in each applied system, manual sub-scanning type readers in which sub-scanning is performed manually (for example, special (Refer to the specification of Japanese Patent Application No. 15349/1983), the scanning speed in the sub-scanning direction varies widely.

Since fluctuations in the scanning speed in the sub-scanning direction appear as fluctuations in the scanning line interval, this results in uneven resolution in the sub-scanning direction of the recorded image, which is one factor that deteriorates the quality of the recorded image.

Therefore, as a means to always keep the interval between successive scanning positions (scanning line interval) in the sub-scanning direction of the document constant even if there are speed fluctuations in the sub-scanning direction, reading the image signal with an image sensor is recommended. It has been proposed that the operation be started every time the relative moving distance between the document and the image sensor in the sub-scanning direction reaches a predetermined distance. In this existing proposal, a signal can be generated every time the relative moving distance between the document and the image sensor in the sub-scanning direction reaches a predetermined distance (predetermined scanning line interval) predetermined in the system. The above-mentioned problem was solved by starting the readout operation of the image signal in the image sensor by the signal generated by the position detection circuit (movement detection circuit). In the means, instead of making the interval between successive reading positions in the sub-scanning direction of the document by the image sensor constant,
The time interval between the start of successive readout operations in the image sensor (this is the exposure time for the photoelectric conversion part of the image sensor) varies, and the amount of time accumulated in the photoelectric conversion part of the image sensor changes accordingly. Since the amount of charge fluctuates in accordance with the above-mentioned time intervals, the signal level of the image signal read out from the image sensor also fluctuates in accordance with the above-mentioned time intervals. The resulting recorded image has a marked deterioration in image quality due to striped density unevenness.

Deterioration in the quality of the recorded image due to fluctuations in the signal level of the image signal due to the causes described above can be resolved by converting the image signal into a binary signal using a threshold voltage created based on the white peak value in the image signal. , this is a particular problem when a recorded image is obtained using the binarized signal, so research has been carried out on a binarized signal generation circuit that can obtain a binarized signal that does not cause the above-mentioned problem. As a result, the applicant company proposed a binary signal generation circuit as shown in FIG.

FIG. 1 is a block diagram showing a schematic configuration of an image signal generation device equipped with a binarized signal generation circuit already proposed by the above-mentioned applicant company.
In the figure, IS is an accumulation type line image sensor, DC is a drive circuit that supplies drive pulses to the image sensor IS, A is a readout amplifier that amplifies the image signal output from the image sensor IS, PH is a peak hold circuit, and VR is a peak hold circuit
It is a resistor network that creates a threshold voltage Vs by dividing the peak value of the image signal held by PH.
In the illustrated example, a variable resistor VR is used as the voltage dividing circuit. Also, COMP is a comparator,
This comparator COMP uses the image signal output from the readout amplifier A and the threshold voltage Vs set by adjusting the slider of the variable resistor VR mentioned above.
The threshold voltage in the image signal is compared with
The signal part with a voltage value higher than Vs is used as a white signal,
Further, it outputs a binary signal in which a signal portion having a voltage value lower than the threshold voltage Vs is a black signal.

The TPG also includes a drive circuit DC that supplies drive pulses to the image sensor IS, and a peak hold circuit PH that holds the peak value of the image signal.
DS is a timing pulse generator that provides a signal at the required timing for scanning, etc., and DS is a movement amount detection circuit that detects the relative movement distance in the sub-scanning direction between the document and the image sensor IS. The image sensor IS is used as the detection circuit DS.
a function that can send an output signal when the amount of movement between the document and the document in the sub-scanning direction corresponds to a predetermined scanning line interval defined by the system;
Alternatively, a device with an equivalent function can be used, such as a pulse that generates a pulse depending on the rotation angle of a motor used in a drive system for moving the document in the sub-scanning direction. A generator, an encoder, or a pulse generator that generates pulses in response to movement of the document over a predetermined distance may be used.

When the movement amount detection pulse Pd (Fig. 2 d) is applied from the movement amount detection circuit DS to the timing pulse generator TPG via the line _l0 , the timing pulse generator TPG receives the image signal from the image sensor IS. generate a control pulse for the start of the read operation of and give it to the drive circuit DC via line _l1 ,
The image sensor IS starts reading an image signal corresponding to the image information of the document by the drive pulse from the drive circuit DC, and reads the image signal Sa {Fig. 2a
} is sent out and applied to the readout amplifier A.

The read amplifier A amplifies the image signal Sa supplied from the image sensor IS and supplies it to the peak hold circuit PH and the comparator COMP. The peak hold circuit PH holds the peak value of the image signal applied thereto, and applies a voltage corresponding to the held peak value to the variable resistor VR.

The slider of the variable resistor VR is variably adjusted to obtain the threshold voltage Vs shown in FIG.
It is given as a reference signal (reference voltage) to COMP, and the comparator COMP compares the given image signal with the threshold voltage Vs. The image signal is converted into a binary signal and sent out so that the signal portion that does not reach the threshold voltage Vs is treated as a black signal, and the signal portion that is equal to or higher than the threshold voltage Vs is treated as a white signal.

In addition, the above-mentioned timing pulse generator TPG
Now, a control pulse for starting the readout operation of the image signal from the image sensor IS described above is generated, and a no-image signal period Tb in the readout cycle starting from the start of the readout operation {see FIG. 2; , Tv is the image signal period, Tt is the period of (Tv + Tb)}, a reset pulse Pr as shown in Fig. 2c is generated and it is applied to the peak hold circuit.
PH to reset the peak hold circuit PH.

As a result, the peak value held in the peak hold circuit PH is reset each time one main scan in the line image sensor IS is completed, and therefore the peak value held in the peak hold circuit PH is reset.
The threshold voltage Vs, which is created by dividing the peak value held in PH, is also applied to each image sensor IS.
It is reset every time one main scan is completed {see FIGS. 2a to 2c}.

In this way, in the previously proposed binary signal generation circuit shown in Figure 1, the document and the image sensor IS are moved by a predetermined amount of movement in the sub-scanning direction (an amount of movement corresponding to the scanning line interval defined by the system). ), the timing pulse generator TPG generates a control pulse to start the readout operation of the image signal from the image sensor IS, based on the movement amount detection pulse Pd from the movement amount detection circuit DS. As a result, the drive circuit DC is connected to the image sensor.
A driving pulse is supplied to the IS so that the image sensor starts reading out the image information and the corresponding image signal at the new scan line position, and the image sensor IS causes the image sensor IS to read out the image information at the new scan line position and the corresponding image signal. During the no-image signal period after the end of the reading operation of the image signal corresponding to the image information of Therefore, the threshold voltage created based on the peak value held by the peak hold circuit PH is reset every time one main scan of the image sensor is completed. Comparator
The threshold voltage Vs given as a reference signal to the COMP is used to binarize the image signal based on the image information read out by a new main scan performed by the image sensor IS thereafter. Therefore, if the reading operation of the image sensor IS is started every time the relative movement amount between the image sensor IS and the document in the sub-scanning direction reaches a predetermined value, A threshold voltage created corresponding to the white peak value that occurs in the image signal when the exposure time is long is used to binarize the image signal read out in the subsequent readout cycle in the image sensor IS. The deterioration in image quality caused by this does not occur in the binarized signal generation circuit as shown in FIG.

By the way, in the image signal generation device equipped with the above-mentioned binarized signal generation circuit, the slowest sub-scanning speed corresponding to the longest readout period allowed from the electrical characteristics of the device and the S/N ratio of the output signal are determined. The range of change in sub-scanning speed that is permissible for the device (the ratio of the fastest sub-scanning speed to the slowest sub-scanning speed) If the sub-scanning speed is within about 10 to 1, a good binary signal can be obtained by the operation of the above-mentioned binary signal generation circuit. The sub-scanning speed of manual sub-scanning type readers normally varies widely depending on how the operator operates, and the range of variation is within the range of the above-mentioned device. In some cases, the change range of the sub-scanning speed may be larger than the permissible range of change in the sub-scanning speed, and in that case, it is natural that a good binarized signal cannot be obtained.

Therefore, in order for a manual sub-scanning type reader to output a good binary signal, the sub-scanning speed of the manual device must be permissible for a device equipped with a binary signal generation circuit. The operator must perform sub-scanning so that the sub-scanning speed is within the change range that is specified, but from the viewpoint of operability of the device, manually performing sub-scanning under such constraints It's not a desirable thing to look at.

The present invention provides good binarization at all times, even if the range of change in sub-scanning speed manually by the operator is wide, and regardless of the manner in which the sub-scanning speed changes. The above-mentioned problems are solved by providing a manual sub-scanning type reader that can obtain a signal.The following describes the specific details of the manual sub-scanning type reader of the present invention with reference to the accompanying drawings. Provide a detailed explanation of the content.

FIG. 3 is a block diagram of one embodiment of the manual sub-scanning type reader of the present invention, and in this FIG. 3, components corresponding to those shown in the block diagram of FIG. The first component is
The same drawing numerals as those used in the figures are used.

In Figure 3, the parts consisting of the line image sensor IS, drive circuit DC, readout amplifier A, peak hold circuit PH, variable resistor VR, comparator COMP, movement amount detection circuit DS, timing pulse generator TPG, etc. , which has the same configuration as the device shown in the first figure described above.

In Figure 3, the output signal of the sample and hold circuit PH is given to the light amount control circuit PVC of the light source,
The light source light amount control circuit PVC controls the light source L for illuminating the document according to the output signal of the sample hold circuit PH.
control the amount of light. In the illustrated example, the light amount control circuit PVC of the light source includes resistors 1 to 4, transistors
When _the signal level of the output signal of the peak hold circuit _PH is high, it reduces the light intensity of the light source L for illuminating the document, and also reduces the output signal level of the peak hold circuit PH. When it is low, it operates to increase the light amount of the light source L for illuminating the document.

Figures 4a to 4e are waveform diagrams for explaining the operation of the device of the present invention, and Figure 4a is the image signal Sa,
Figure 4b shows the output signal of the peak hold circuit PH, Figure 4c shows the reset pulse Pr, and Figure 4d shows the output signal of the peak hold circuit PH.
The figure shows the movement amount detection pulse Pd, and Fig. 4e
The figure shows the amount of light from the light source L for illuminating the original.

Now, the signal level of the output signal of the peak hold circuit PH indicates the signal level of the image signal corresponding to the whitest part of the document, and if the sub-scanning speed is constant, the signal level of the output signal of the peak hold circuit PH will peak at each reading cycle. The signal level of the output signal output from the hold circuit PH is a constant value. However, when the sub-scanning speed is changing, the time length for each readout cycle is different, and the exposure amount for each readout cycle is also changing, so the whitest part of the document will not correspond to the same whitest part. Even in the case of an image signal generated by an image sensor, the signal level changes depending on the exposure amount, that is, the time length of the readout cycle (which may be considered as the sub-scanning speed).

Therefore, if the amount of light emitted by the light source L for illuminating the document is controlled to decrease or increase depending on the signal level of the output signal of the peak hold circuit PH, the amount of exposure can be adjusted according to changes in the sub-scanning speed. can be kept in a proper state at all times. Control of the amount of light emitted by the light source L for illuminating the original as described above according to the signal level of the output signal of the peak hold circuit PH is as follows:
A state in which the sub-scanning speed changes relatively slowly over a relatively long period of time,
For example, in a manual sub-scanning type reader, the sub-scanning speed changes from a low sub-scanning speed at the start of reading, gradually becomes faster, and then gradually becomes slower. In the case where the speed changes relatively slowly and has a large change range, it functions to obtain a good binarized signal.

For instantaneous changes in the sub-scanning speed, that is, discontinuous hand movements that lack smoothness, the threshold voltage of the comparator COMP is set according to the output signal of the peak hold circuit PH. It goes without saying that the binarization processing operation can be performed satisfactorily by doing so.

As described above, the manual sub-scanning type reader of the present invention can always perform good binarization even if the sub-scanning speed changes rapidly or changes slowly and widely. Therefore, according to the present invention, the manual control device with good operability allows the operator to operate in any manner without being constrained by the sub-scanning speed. It is possible to provide a sub-scanning type reading device, and the device of the present invention can also perform well in response to changes in the light source over time, a decrease in transmittance due to dirt in the optical system, and the density of the background of the document. .

[Brief explanation of drawings]

FIG. 1 is a block diagram of an already proposed circuit, FIG. 3 is a block diagram of an embodiment of the device of the present invention, and FIGS.
FIG. d and FIGS. 4A to 4E are explanatory waveform charts. IS...image sensor, DC...drive circuit, A...readout amplifier, PH...peak hold circuit, COMP
…Comparator, DS…Movement detection circuit, TPG…Timing pulse generator, PVC…Light source light amount control circuit,
L...Light source for illuminating the original.

Claims (1)

[Claims] 1 an image reading means for outputting an image signal corresponding to the image information read; a peak value detection means for detecting the peak value of the image signal output from the image reading means; a holding means for holding the peak value for each line; and a threshold value is set independently for each line and variably within one line based on the output signal of the holding means, and A binary signal generating means for performing binarization by comparing the image signal output from the reading means, and a binary signal generating means for performing binarization for each line independently and based on the output signal of the holding means.
1. A manual sub-scanning type reader comprising: a control means for variably controlling the amount of light from an illumination light source even during a line.