JPS59103474A - Device for discriminating focusing of image pickup device - Google Patents

Abstract

PURPOSE:To discriminate easily the propriety of focusing of an image pickup device by detecting a slow change of a boundary between a bright and a dark part by two comparators and counting the change while converting it into a pulse. CONSTITUTION:A video pulse signal having a level voltage in response to an input light amount is generated from a linear solid-state image pickup element in scanning a dark object 1 with a bright background. The change is steep in the boundary between the object and the background when a lens 2 is focused and slow when the focus is not matched. In setting reference voltages E1, E2 of comparators 6, 7 to 2/3, 1/3 of the voltage of a bright image, a pulse corresponding to a bright part, an intermediate part and a dark part is obtained respectively from AND gates 81, 82, 83. In setting a suitable amount to P1, P2 to discriminate dark and bright, an AND gate 12 is opened in a suitable timing, the number of pulses representing the intermediate brightness is displayed on a display device 13, and it is discriminated that the focus is matched when the value is small.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes a focus determination device that can easily and simply determine whether an image is in focus in a one-dimensional or two-dimensional imaging device having a large number of photoelectric elements. It is.

In an imaging device that performs measurement control by linking an image to a one-dimensional solid-state image sensor, which is made up of a large number of photoelectric elements arranged in a row, using an optical system, the image is displayed on a general CRT monitor using a video signal. Since it is difficult to focus, it is difficult to focus using an optical finder, or to observe and measure the video signal with a measurement device such as an oscilloscope, and to adjust the focus gradually based on the observed waveform. Measures were taken to do so. However, this method requires expensive equipment and requires skill to operate.

The present invention has been made to solve certain inconveniences, and is configured to focus on the difference in the level of the video signal when it is in focus and when it is out of focus, and to identify and separate this difference in level. It is an object of the present invention to provide a focus determination device for an imaging device that can easily determine whether or not the focus is appropriate. Hereinafter, the present invention will be explained in detail based on the drawings showing its implementation.

In FIG. 1, an object II/'i is imaged by a lens 2 onto a one-dimensional solid-state image sensor 3''. -Dimensional solid-state image sensor This device has three photoelectric elements arranged in a row, and is sequentially scanned by a pulse signal generated by a scanning pulse generation circuit 5, and each photoelectric element generates a voltage at a level corresponding to the amount of incident light. Video pulse signals having the following values are sequentially emitted.

This video pulse signal is input to the Hayashi amplification circuit 1i134 and amplified, and its amplified output is given to the input terminal of the first comparison circuit 6 and the input terminal of the second comparison circuit 7. The comparison reference voltage F is connected to the single power terminal of times fIv!
FEI is applied. A comparison reference voltage El (where p, t > E2) is applied to the input terminal of the comparison circuit 7 @2. Both of these comparison circuits 6.7 output a high level output when the 10 inputs are higher than the human power, and output low level outputs when the 10 inputs are lower than the 10 inputs.
The output of the comparison circuit 6 is given to the input terminal of an AND gate 81 and the negative logic input terminal of a three-way AND gate 82.
．． Further, the output of the comparator circuit 7 is applied to an input terminal of an AND gate 83 and another negative logic input terminal of a three-way AND gate 82.

A scanning pulse signal is applied from the scanning pulse generating circuit 5 as a counting pulse signal to another input terminal of these AND gates 81, 82 and 83. AN
The outputs of the D gates 81, 82 and 83 are input to the first counter circuit 9, the second counter circuit 10 and the third counter circuit 11, respectively. 1st. The third counter circuit is a preset counter and is set to a predetermined value PI+p.

The operation of the apparatus of the present invention constructed as described above will be described in the case where the vertical center of the object 1 shaped like the letter A is set as the imaging field of view as shown in FIGS. 1 and 2(a). Assuming that the subject 1 is dark and the background is bright, the output of the amplifier circuit 4 will be approximately K as shown in Figure 2(b), but the output of the amplifier circuit 4 will be K as shown in FIG.
When the signal corresponding to the upper part of the image is enlarged, it becomes as shown in FIG. 2(c) when the image is out of focus, and as shown in FIG. 2(g) when it is in focus. When the image is out of focus, the transition between the bright and dark areas is gradual, whereas when the image is in focus, the transition between the bright and dark areas is steep. Assume that the comparison reference voltage EI e Ez is set to 2/3 and 1/3 of the voltage level V when a bright image is captured. Then, when the focus is on, the voltage level of the video pulse signal E ld E > E, = 1/3 V during the time period t and i when the background part of KFi is being scanned. The output is no-y level, and the scanning pulse signal synchronized with the video pulse signal is AND
The signal is input from the gate 81 to the first counter circuit 9 and is counted as shown in FIG. 2(d).

Next, during the period from time t1 to time t, when the background part near the subject 1 and the part near the outer edge of the subject 1 are being scanned, the video pulse signal voltage level E is E, < E < E, so @
1. Since the outputs of the second comparator circuits 6 and 7 are both at low level, the scanning pulse signals are inputted from the AND gate 82 to the second counter circuit 10 and counted as shown in FIG. 2(e). Furthermore, during the period [, ~t3] when the inside of the object 1' is being cleaned, the voltage level E of the video pulse signal is E < E, so the output of the second comparison circuit becomes high level and the scanning pulse bus signal HAND gate 83
are inputted to the third counter circuit 11 and counted as shown in FIG. 2(f). Thereafter, in the same manner, the counter circuit 10 counts in the period from t3 to t4, and the counter circuit 9 counts in the period after t4.

Now, when setting P,, P, to a value corresponding to the size (the number of photoelectric elements on the image sensor 3) that is sufficient to determine that there are bright and dark parts in the field of view, t, ~t3.
After an appropriate timing during the period, the AND gate 12 opens and the count value of the second counter circuit 10 is displayed on the display 13, and as shown in FIG.
n,) will be displayed. On the other hand, when the focus is on, the change in the boundary part is steep, so t
, ~t, and the periods from t3 to t4 are shortened, and the counting input Fi to the counter circuits 9.10 and 11 is reduced (h) in FIG.
As shown in (i) and (j), the second counter circuit 10
input is reduced.

And in this case #t ml + my (< n++
nt ) will be displayed on the display 13. In other words, if the numerical value displayed on the display 13 is small, it means that the subject is in focus. Note that when the entire imaging field of view is bright (or dark), the counter times Wt11 (or counter circuit 9
) does not reach pt (straight PI) and the count value of the counter circuit 10 is not output to the display 13, so in this case, the field of view may be changed.

As described above, the focusing determination device according to the present invention is an imaging device that sequentially scans a large number of photoelectric elements using a scanning pulse signal and outputs an image pulse signal having a voltage corresponding to the light incident needle of each optical element. a circuit that compares the video pulse signal with the voltage @1 and the voltage @2 lower than the first voltage; a first counter circuit that counts the number of times a video pulse signal higher than the voltage @1 is generated; A counter circuit of gK2 counts the number of occurrences of a video pulse signal that is lower than the voltage of the voltage and higher than the second voltage, and a counter circuit of @3 counts the number of times that the video pulse signal that is lower than the second voltage is generated. , the suitability of focusing is determined in relation to the count value of the second counter circuit when the count value of the first and third counter circuits is larger than a predetermined value, so the device of the present invention In this case, it is possible to easily determine whether or not focusing is appropriate based on the numerical value displayed on the display 13, and the circuit configuration is not complicated and can be realized at low cost.

It goes without saying that the present invention is also applicable to a two-dimensional imaging device using a two-dimensional solid-state imaging device.

In addition, there are other methods other than the Vi numbers that indicate the suitability of focusing.
For example, it may be possible to use flashing lights, sounds, etc., and it is not limited to the method in which humans judge suitability using a display device, but it is also possible to feed back to the adjustment mechanism of the optical system to automatically perform tζ focusing. Of course.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the device of the present invention, and FIG. 2 (a) to (j
) is a timing chart for explaining the operation. 3... Solid-state image sensor 4... Video amplification circuit 5...
・Scanning pulse generation circuit 6.7...Comparison circuit 9,1
0.11...Counter times FjlS 13-...Display SR12, 81, 82, 83=-AND gate patent applicant Koyo Electronics Co., Ltd. agent Patent attorney Noboru Kono Go to Tada? ? Tsuri
452- City

Claims (1)

[Claims] 1. In an imaging device that sequentially scans a large number of photoelectric elements with a scanning pulse signal and outputs an Eirin pulse signal having a voltage corresponding to the amount of light incident on each optical element, the Eirin pulse signal is applied to a first voltage and a first voltage. a circuit that compares the voltage with a second voltage lower than the voltage of , a kakunta circuit of @1 that counts the number of occurrences of a video pulse signal that is higher than the first voltage, and a circuit that compares the voltage with a second voltage that is lower than the voltage of the first voltage and a voltage of @2 that is higher than the first voltage. A second kakunta circuit that counts the number of occurrences of a pulse signal and a third kakunta circuit that counts the number of occurrences of a video pulse signal lower than the second voltage. What is claimed is: 1. A focusing determination device, characterized in that it determines whether or not focusing is appropriate in relation to the count value of the second kakunta circuit when the numerical value is larger than a predetermined value.