JPS60126611A - Picture processing device - Google Patents

Abstract

PURPOSE:To make a device small-sized, and to confirm easily a focused point by constituting a titled device so that a focus mark having a specified space frequency is read by an image sensor, and the focused point can be detected and displayed at a position of the maximum difference voltage of a video signal. CONSTITUTION:Positive and negative peak values of a video signal of a focus detecting mark which is read by an image sensor 9 and fetched by a gate circuit 11 and a BPF13 are detected by peak value detecting and holding circuits 14, 15, respectively, and a difference voltage of the circuits 14, 15 is detected by a differential amplifier 16 and held by a holding circuit 17. Also, a comparator circuit 18 compares an output of the circuit 17 and an output of the amplifier 16 and detects the maximum value of the voltage difference. Subsequently, an output of the circuit 18 is inputted to a displaying circuit 19 for focus detection, it flickers in accordance with its output signal, and it is displayed that a focus of a lens has been matched at a position where the maximum voltage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image processing apparatus equipped with a mechanism for automatically detecting and displaying a focus.

[Prior art]

Conventionally, as shown in FIG.
An image is formed on the light receiving part of an OD image sensor, etc.), and a photoelectric f(
When the image of the microfilm 1 is taken out as an analog video signal by a device 3 and the light receiving section of the image sensor 4 is to be focused, a monitor screen 5 for detecting the focus of the subject has been provided.

That is, a half mirror 6 and an attachment lens 7 are interposed between the monitor screen 5 and the light receiving section of the image sensor 4, and by optically focusing on the monitor screen 5, the focus of the light receiving section of the image sensor 4 is adjusted. could be matched at the same time.

However, in such a conventional image processing device, a monitor image 5, a half mirror 6, an attachment lens 7, etc. are required for focusing, which increases the number of parts and makes it difficult to accurately focus. This requires a long optical path length, making it difficult to make the image processing device more compact.

[Purpose of the invention]

The present invention attempts to solve these conventional drawbacks, and uses an image sensor to read a focus detection mark having a constant spatial frequency of 1%, and then detects the focus detection mark at the point where the maximum voltage difference between the -7 video signals can be obtained. The object of this invention is to make it possible to detect and display that the image is in focus, thereby making it easier to downsize the image processing apparatus, and to make it easier to confirm that the image is in focus.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 to 5.

As shown in FIG. 1, the image embedding device according to the present invention irradiates a microfilm 1 with a light source 21, forms an image on the light receiving part of an image sensor 4 with a lens 3, converts the light, and irradiates the microfilm 1 with a light source 21. Analog video 1# of the image! When focusing on the light-receiving part of the image sensor 4 while taking out the signal as a signal, as shown in FIG. 2, the focus detection mark 8 having a specific spatial frequency and the image sensor 4 are used. When the image is in focus, it can be detected and displayed.

That is, as shown in FIG. 2, a focus detection mark 8 having a specific spatial frequency provided on a microfilm 10 is read by an image sensor 4, and the positive peak 1 direct and negative peak of the output voltage waveform of the image sensor 4 are read. In addition to outputting the differential voltage from the peak 1 shift.

The system is designed to detect and display that the camera is in focus by positioning the camera at the position where the voltage difference is maximum.

FIGS. 3 and 4 are diagrams for explaining the principle of focus detection described above. In other words, FIG. 3 shows the output voltage waveform of the image sensor 4, where the solid line waveform a is the output waveform when the focus is on, and the voltage is A In the output waveform, its double pressure is B (Vl
It is. Both 'double pressures have a relationship of 8〉B. Figure 4 shows
This figure shows the relationship between the differential voltage (tV) between the positive peak value and the negative peak value of this output voltage waveform and the moving distance l of the lens 3.

As is clear from each figure, lens 3 is 1. At this position, the differential voltage is maximum, and the focus is poor at this position. The m+ elephant processing device of the present invention is based on such a principle.

FIG. 5 specifically shows the difference 1 voltage detection means for detecting the maximum difference voltage, and the focus detection display means 2 for detecting and displaying that the focus is in the position where the maximum difference voltage is obtained. It is.

In the figure, 9 is an image sensor (for example, a CCD image sensor, etc.) for reading the focus detection mark 8; 10 is an amplifier 11 for amplifying the output of the image sensor 9;
1 is a gate circuit for extracting only the focus detection mark 8; This gate circuit 11 is a timing control circuit 1
This circuit opens and closes the detection mark signal using the gate opening/closing signal generated in step 2. 13 is the image sensor 9111! This is a bandpass filter that removes any existing noise and allows only fixed frequencies to pass through. These gate circuits 1
1 and the bandpass filter 13 extract only the focus detection mark 8, and send this signal to one of the positive peak value detection and holding circuits 14.
The positive peak value is extracted laterally, and the other negative peak value I is detected by the detection and holding circuit 15. Both circuits 14, 15 are adapted to be reset by the timing control circuit 12 as required. 16 is a differential amplifier that detects the differential output of both circuits 14 and 15, that is, the differential voltage; 6, 17 is a hold circuit for holding the differential voltage obtained by the differential amplifier 416; and 18 is a differential amplifier that detects the differential voltage. This is a comparator circuit for comparing the output of the hold circuit 17 and the output of the differential amplifier rlj 16. This comparator circuit 18 is a circuit for detecting the maximum value of the differential voltage, and has a hysteresis characteristic depending on the depth of focus of the lens. Reference numeral 19 denotes a focus detection display circuit which receives the output of the comparator circuit 18 and detects and displays that the lens is in focus at the position where the maximum differential voltage is obtained. This circuit 19 is composed of a light emitting diode or a lamp, and is adapted to blink in response to the output signal of the comparator circuit 18. Reference numeral 20 denotes a threshold processing circuit for converting an image of a subject (microfilm) into a binary image signal through threshold processing.

With this configuration, the positive peak value of the video signal of the focus detection mark 8 read by the image sensor 9 and extracted by the gate circuit 11 and bandpass filter 13 is detected by the positive peak value detection and holding circuit 14. detected by
The negative peak value is detected by the corner peak value detection and holding circuit 15.

The differential voltage between these two holding circuits 14 and 15 is determined by the differential amplifier 16.
is detected and held by the hold circuit 11. The comparator circuit 18 compares the output of the hold circuit 1γ and the output of the differential amplifier 16 to detect the maximum value of the voltage difference.

The output of the comparator circuit 13 that has detected this maximum differential voltage is input to the detection display circuit 19, which blinks according to the output signal to indicate that the lens is in focus at the position where the maximum differential voltage is obtained. do.

In the above embodiment, the image 1#! is equipped with a transmission type focus detector used in the microfiln. Although the processing device has been described, there is no difference in operation and effect even if it is a general reflective type image processing device in which a focus detection mark is provided on the original pressure bonding plate.

〔Effect of the invention〕

As explained above, according to the present invention, a focus detection mark having a specific spatial frequency is read by an image sensor, and the focus is detected and displayed at the position where the maximum voltage difference of the image signal is obtained. This eliminates the need for monitor screens, half-mirrors, attachment lenses, etc. that were previously required; the number of parts is relatively reduced; and a long optical path length is not required for accurate focusing. Therefore, it is possible to make image processing smaller or more compact, and it is also possible to obtain the effect that it is easier to confirm that the image is in focus.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a conventional image processing device, FIG. 2 is a schematic block diagram of an embodiment of the present invention, and FIG. 3 is a graph showing the output voltage waveform of the image sensor shown in FIG. 4 is a graph showing the relationship between the differential voltage between the positive peak value and the negative peak value of the output voltage waveform in FIG. 3 and the moving distance of the lens,
FIG. 5 is a block diagram showing the main structure of an embodiment of the present invention. 3...Lens 4...Image sensor 8...Focus detection mark 19...Focus detection display circuit Fig. 3 □N

Claims (1)

[Claims] In 'Jklt, which scans an image and obtains an analog video signal by C photoelectric transformation, a difference voltage detection means for detecting the maximum difference voltage of the video signal of a focus detection mark having a specific spatial frequency, and the obtainable value of the maximum difference voltage are used. An image processing apparatus comprising a focus detection mechanism comprising a focus detection display means for detecting and displaying that the image is in focus at a position where the image is focused.