JPH0355680A - Image input device - Google Patents

Abstract

PURPOSE:To quickly confirm the focus state of a lens by providing a photoelectric transducer means, an envelope curve level detecting means, a level dividing means, a binarizing means, a counter/comparator means, and a coincidence display means. CONSTITUTION:The output of a CCD image sensor 12 is sampled 14 for production of a video signal 100. An envelope curve detecting circuit 1 detects an envelope curve of a ground level of the signal 100. A resistance type potential dividing circuit 2 obtains the signals 102 and 103 having the similar amplitudes from an envelope curve signal 101 showing the ground level of an original. The signals 102 and 103 are compared with the signal 100 for output of the signals 104 and 105 of H and L levels if the signals 102 and 103 are larger and smaller than the signal 100 respectively. The counter circuits 5 and 6 are reset by a scan synchronizing signal 112 and at the same time count the starting frequencies 107 and 108 of both outputs 104 and 105. The frequencies 107 and 108 are compared 7 and 8 with the number N of set grid patterns, and an AND arithmetic 9 is carried out. Then an output 111 is set at an L level and an LED 10 is turned on when both outputs 109 and 110 are kept at H levels. As a result, the focus state can be quickly confirmed via the sensor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image input device, and more particularly to an image input device such as an image scanner and an optical character reading device that use an optical lens to read an image on a document. .

[Conventional technology]

In this type of image input device, an optical image on a document is formed by an optical lens on an image sensor such as a one-dimensional CCD image sensor, and a video signal is obtained by photoelectric conversion.

In order to obtain a clear optical image on the image sensor, it is necessary to adjust the focus of the optical lens.

[Problem to be solved by the invention]

For details on how to check and adjust whether the focus is on, see the second section.
A grid pattern as shown in the figure is scanned and the resulting video signal is observed. Then, confirm that the amplitude on the video signal corresponding to the grid pattern is a constant value. If the value is not constant, adjust the position of the lens in the optical axis direction.

However, with this method, it is necessary to connect an oscilloscope to a test terminal etc. in order to observe the video signal every time the focus is checked or adjusted. Therefore, there are problems such as it takes time to confirm the focus, adjust it, and prepare for it. It also has drawbacks such as the inability to check and adjust the focus unless you know the internals of the device and how to operate the oscilloscope. [Means for Solving the Problems] In order to solve the above problems, the present invention provides an image input device that forms an optical image of a document surface onto a one-dimensional image sensor using an optical lens, performs photoelectric conversion, and obtains a video signal. In,
means for photoelectrically exchanging the grating pattern; means for detecting the envelope level of the background color of the grating pattern from the photoelectric conversion signal obtained by the photoelectric conversion means; and means for converting the output level obtained by the background color level detection means into multiple lines. a level dividing means for dividing the signal at a ratio of means for calculating the number of grid patterns, means for comparing the counted value with the number of grid patterns that are objects set in advance, and a display that indicates a match when a match is detected by the comparison means. and means.

〔Example〕

Next, one embodiment of the present invention will be described.

FIG. 1 shows an embodiment of the invention. In the figure, reflected light from the surface of a document 16 is imaged onto a CCD image sensor 12 by an optical lens 11. CCD image sensor 12
The video signal output from the amplifier 13 is input to a sample and hold circuit 14. Since the video signal output from the COD image sensor 12 is output intermittently for each COD surface element, the sample and hold circuit 14 samples and holds each pixel to form a continuous video signal 100.

The envelope detection circuit 1 detects the envelope of the ground level of a video signal. FIG. 6 shows an example of an envelope detection circuit. Details of the circuit will be described later.

The resistive voltage dividing circuit 2 outputs two divided voltage signals 102 and 103 having amplitudes similar to the original ground level by resistive voltage division from an envelope signal 101, that is, a signal representing the ground level of the original.

Voltage dividing circuit outputs 102 and 103 are input to comparison circuits 3 and 4. In comparator circuits 3 and 4, voltage divider circuit output 102
and 103 are compared with the video signal 100, and if the latter is lower in level than the former, the outputs 104 and 105 are set to "high", and if higher, the outputs are set to "low".

The counting circuits 5 and 6 are reset to the count value "O" by the scanning synchronization signal 112, and thereafter count the number of times the comparator circuit outputs 104 and 105 rise from "low" to "high". The comparison circuits 7 and 8 compare each of the outputs 107 and 108 of the counting circuits 5 and 6 with a preset numerical value 106. Here, the number N of lattice patterns is set as the numerical value 106, and if a match is found as a result of the comparison, the outputs 109 and 110 become "high". The AND operation circuit 9 performs an AND operation on the comparison circuit outputs 109 and 110, and sets the output 111 to "low" only when both are "high", and lights up the LED 10. Also, the image sensor timing generation circuit 15 , C
Drive pulses 113 such as a scanning synchronization signal and a charge transfer clock are supplied to the CD image sensor 12. Now, write a K line pair/m on the manuscript as shown in Figure 2.
Assume that a grating pattern perpendicular to the scanning direction is printed with a spatial frequency of m. When this pattern is scanned along the arrows in FIG. 3, a video signal as shown in the figure is obtained. An amplitude is generated on the video signal corresponding to the black and white of the grid pattern on the original. When the optical lens 11 is in focus, the maximum and minimum amplitude values are at a constant ratio to the ground level of the video signal. It is assumed that each output of the resistive voltage divider circuit 2 in FIG. 1 is set in advance to be approximately equal to these two ratios. That is, the third
As shown in the figure, the voltage dividing circuit output l02 is set to a ratio A% that is a certain margin smaller than the local maximum value of the amplitude when in focus, and the voltage dividing circuit output l02 is a ratio B% that is a certain margin larger than the local minimum value. The voltage dividing circuit output 10 is set to the voltage dividing ratio such that
It is assumed that 3 is set.

Figure 4 (a) shows the signal waveforms of each part when the focus is on.
- Shown in (c). Video signal 100, envelope signal 101
, the relationship between the voltage dividing circuit outputs 102 and 103 is shown in FIG. 4(b).
It will look like this. As shown in the figure, the maximum amplitude values for the grid pattern are all larger than the voltage divider circuit output 102, and the minimum values are all smaller than the voltage divider circuit output 103, so the comparison circuit outputs 104 and 105 have a grid pattern. N pulses appear that match the amplitude of . Counting circuits 5 and 6 count the number of rises of comparison circuit outputs 104 and 105, and output a count value N at the rear end of the grid pattern. The state of the counting circuit outputs 107 and 108 at this time is shown in FIG. 4(C). Thereafter, the count value N is held until the end of one scan.

Comparing circuits 7 and 8 have counting circuit outputs 107 and 108,
It is compared with the preset value 106, but in this case, since both are count values N, the outputs 109 and 110 are
Then, the comparison circuit outputs 109 and 110
While both are “high”, the AND operation circuit 9 outputs the output 11.
1 is set to “low” and the LEDIO is turned on.

Figure 5 (a) shows the state when the lens 11 is out of focus.
) to (c). In this case, even if the grid pattern in Figure 2 is used in the same way as when the focus is in focus, Figure 5(b)
The amplitude corresponding to the grid pattern becomes smaller. Therefore, even if N lattice patterns are scanned as shown in FIG. 5(C), N pulses corresponding to the amplitudes do not appear in the comparison circuit outputs 104 and 105. Therefore, the outputs 107 and 108 of the counting circuits 5 and 6 are not equal to the count value N, so the comparison circuits 7 and 8 cannot match the set value 106, and the AND operation circuit output 111 also remains "high". Therefore, LED10 does not light up.

As mentioned above, if the lens 11 is in focus, the LED
Since the LED 10 is lit, it can be determined whether the lens 11 is in focus or not based on the lighting state of the LED 10. Furthermore, if the object is out of focus, the focus of the lens 11 may be adjusted so that the LED 10 lights up. Note that the focus adjustment of the lens 11 is performed using the lenses 11 and C in FIG.
The distance {between the CD image sensors 12 may be adjusted.

Finally, the envelope detection circuit shown in FIG. 6 will be explained.

Although the resistor 61 in the figure is sufficiently smaller than the resistor 64, the time constant of the integrating circuit consisting of the resistor 61, diode 62, and capacitor 63 is small, and the output signal 101 follows the rapid increase in the input signal 100. On the other hand, the time constant of the integrating circuit made up of the capacitor 63 and the resistor 64 is large, and the output signal 101 cannot follow the sudden decrease in the input signal 100, and thus maintains the previous output level. This makes it possible to detect the ground level of the manuscript. Note that the constant voltage source 65 in FIG. 6 is for canceling the voltage drop across the diode 62. [Effects of the Invention] As explained above, according to the present invention, there is no need to connect a measuring instrument such as an oscilloscope to the test terminal of the device each time the lens focus is adjusted and confirmed, and the focus state can be confirmed. This has the advantage of being able to do this at a glance without taking much time.Also, since there is no need to connect an oscilloscope or other device to the device, even people who are not familiar with the inside of the device or the operation of an oscilloscope can check the focus state of the device. It is also effective.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a document used for adjusting and checking the focus of the lens and a grid pattern on the document, and FIG. Explanatory diagrams showing the relationship between the amplitude of the grid pattern of the video signal and the output of the voltage dividing circuit when
c) shows the waveforms of various parts when the lens is in focus. FIGS. 5A to 5C are explanatory diagrams showing waveforms of various parts when the lens is out of focus, and FIG. 6 is a circuit diagram showing the envelope line detection circuit in this embodiment. 1... Envelope detection circuit, 2... Resistance voltage divider circuit, 3...
4, 7, 8... Comparison circuit, 5, 6... Counting circuit, 9
...AND operation circuit, 10...LED, 11...
Optical lens, 12... COD image sensor, 13.
...Amplifier, 14...Sample and hold circuit, 15
...Timing generation circuit, 16...Manuscript.

Claims (1)

[Claims] In an image input device for forming an optical image of a document surface onto a one-dimensional image sensor using an optical lens and photoelectrically converting the image to obtain a video signal, means for photoelectrically exchanging a grating pattern;
means for detecting the envelope level of the ground color of the grid pattern from the photoelectric conversion signal obtained by the photoelectric conversion means; level division means for dividing the output level obtained by the ground color level detection means at a plurality of different ratios; means for comparing each output level obtained by the level dividing means with the photoelectric conversion signal and binarizing it; means for calculating the number of electrical grid patterns obtained by the binarizing means;
It is characterized by comprising a means for comparing the counted value and a preset number of grid patterns as objects, and a display means for displaying a match when a match is detected by the comparing means. image input device.