JP2002341236A - Focusing degree display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always display focusing degree data as a standard for focusing in an electronic viewfinder(EVD) when focusing is performed over a look at the EVF. SOLUTION: An image pickup signal after basic video signal processing is outputted to a plurality of BPFs and respective frequency components are extracted. Then a focus area is set to a subject to be focused on which is displayed in the EVF 15. Extraction from low-frequency components outputted from the BPFs 5 is performed, their maximum values and positions are detected, and different frequency components are detected in image pickup signals of the same position. A focusing degree computing circuit 13 compares the detected frequency components with respective prepared frequency components in focusing and outputs the result as focusing degree data. A display converting circuit 14 adds the focusing degree data to the image pickup signal outputted from a signal processing circuit 4 and the result is displayed in the EVF 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focus degree display device used for a camera that performs focusing while looking at an electronic viewfinder.

[0002]

2. Description of the Related Art When photographing a subject using a broadcast video camera, a photographer looks at the subject image displayed on an electronic viewfinder provided in the video camera.
Focusing is performed by empirically determining the distance to the subject. However, in general, electronic viewfinders have small screens and low resolution, making focusing difficult.
It was a complicated operation requiring skill.

Therefore, as a method for automatically performing focusing, an infrared active method and a contrast detection method are known. In the infrared active method, a subject is irradiated with infrared rays, and a reflected light beam is detected by a PSD (semiconductor position detecting element) to perform distance measurement based on the principle of triangulation. On the other hand, the contrast method utilizes the property that the high-frequency component of the image signal becomes maximum in the focused state.

[0004]

However, these methods have problems in the signal processing time required for focusing, the driving time of the lens, and the accuracy. In particular, the method can be regarded as being in focus. At present, a high-definition camera with an extremely shallow depth of field falls short of the ability of an experienced professional photographer.

The present invention has been made in view of such a point, and focuses on a frequency characteristic of an optical low-pass filter for correcting a characteristic unique to a lens when performing focusing while looking at an electronic viewfinder. It is an object of the present invention to provide a focus degree display device that calculates the calculated focus degree and displays the focus degree on an electronic viewfinder as needed.

[0006]

The invention according to claim 1 of the present application is a focus degree display device used in a camera having an electronic viewfinder for displaying at least a captured image, and forms an optical image of a subject. A lens that images, an optical low-pass filter that removes high-frequency components from the optical image of the subject, an image sensor that photoelectrically converts an optical image of the subject from which high-frequency components have been removed by the optical low-pass filter, and outputs an imaging signal, A first method of extracting an arbitrary frequency component from an image signal output from an image sensor
A plurality of band-pass filters for extracting different frequency components higher than an extraction frequency of the first band-pass filter from an image signal output from the image sensor; and an electronic viewfinder. A focus area having an area of an arbitrary size at an arbitrary position of an image displayed on the image, and a focus area setting circuit for outputting a focus area signal; and an imaging signal extracted from the first band-pass filter. A gate circuit that cuts out the focus area from a, a peak value detection circuit that detects a maximum value of a signal output from the gate circuit, and a maximum value of the imaging signal detected by the peak value detection circuit, A position detection circuit for detecting whether the position is present, and a position output from the position detection circuit. A degree-of-focus calculating means for calculating a degree of maximum value of the first and other bandpass filters to be compared with the ratio at the time of focusing prepared in advance, thereby outputting degree-of-focus data. , Is characterized by having.

According to a second aspect of the present invention, in the focusing degree display apparatus according to the first aspect, the focusing degree data output from the focusing degree calculating means is converted into an arbitrary format and output from the image sensor. A display conversion circuit to be added to an image signal to be processed,
An electronic viewfinder for displaying an image pickup signal output from the display conversion circuit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a focus degree display device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a focus degree display device according to the present embodiment. In FIG. 1, an image sensor 3 is provided at a focal position of a lens 1 via an optical low-pass filter 2. The output of the image sensor 3 is supplied to a signal processing circuit 4, first to fourth band pass filters 5 to 8, and a display conversion circuit 14. The first band-pass filter 5 is a band-pass filter having a predetermined low-frequency pass characteristic, and the band-pass filters 6, 7, and 8 are other band-pass filters whose pass bands are sequentially changed to the high-frequency side. The output terminal of the bandpass filter 5 is connected to a peak value detection circuit 11 via a gate circuit 10. A focus area setting circuit 9 having a focus area is connected to the gate circuit 10. The output of the peak value detection circuit 11 is supplied to the focus degree calculation circuit 13 as it is and via the position detection circuit 12. The degree-of-focus calculation circuit 13 includes the bandpass filters 6 to 6 at the time of peak value detection obtained by the position detection circuit 12.
8 and the peak value of the peak value detection circuit 11 to calculate the degree of focusing. The result is superimposed on the original image signal by the display conversion circuit 14 and sent to the electronic viewfinder (EVF) 15. Given.

The operation of displaying the degree of focus on the electronic viewfinder 15 by the focus degree display device configured as shown in FIG. 1 will be described below with reference to FIGS. First, an optical image of a subject is formed by the lens 1,
The light is passed through an optical low-pass filter 2. FIG. 2 shows frequency characteristics of the optical low-pass filter 2. The optical low-pass filter 2 removes moire generated by mixing high-frequency components of the innumerable frequency components included in the formed optical image of the subject as a return signal into the signal of the subject. High-frequency components are removed at a stage. The optical image composed of the low-frequency components thus obtained is output as an imaging signal by photoelectric conversion by the imaging device 3, and the signal processing circuit 4 performs basic video signal processing such as gamma correction and knee correction. Then, the image is displayed on the electronic viewfinder 15 via a display conversion circuit 14 described later.

Next, the image signal subjected to the basic video signal processing in the signal processing circuit 4 is converted into a first band-pass filter 5 having the frequency characteristic shown in FIG. Second bandpass filter 6 having characteristics, FIG.
Each of the frequency components f _{1 to} f ₄ is extracted by the third band-pass filter 7 having the frequency characteristic shown in FIG. 3C and the fourth band-pass filter 8 having the frequency characteristic shown in FIG. Next, a focus area 16 of an arbitrary size is set at an arbitrary position by the focus area setting circuit 9 for the subject to be focused, which is displayed on the electronic viewfinder 15 as shown in FIG. The signal indicating the focus area is output to the gate circuit 10, and the focus area 16 is cut out from the image signal of the low frequency component extracted by the first band pass filter 5. Then, the maximum value of the change of the low frequency component is detected from the signal by the peak value detection circuit 11, and the position of the maximum value in the focus area 16 is detected by the position detection circuit 12.

FIG. 5 shows first to fourth band-pass filters 5.
It is a waveform diagram which shows the input-output waveform of No.-8. For the position of the input signal a at which the maximum value is detected, the output b of the first band-pass filter 5 has a gain of 0.86, the output c of the second band-pass filter 6 has a gain of 0.68, and the third The output d of the bandpass filter 7 had a gain of 0.34, and the output e of the fourth bandpass filter 8 had a gain of 0.05. Here, the ratio of each frequency component at the time of focusing is uniquely determined by the lens 1 and the optical low-pass filter 2, and depends on the frequency characteristics of the system by the optical low-pass filter 2 and the signal processing circuit 4 shown in FIG. I do. Therefore, by comparing the ratio of each frequency component at the time of focusing and the ratio of each frequency component calculated for each field, the degree of focusing can be grasped.

For example, as shown by a solid line in FIG. 6, the first bandpass filter output b has a gain of 0.9 when focused.
0, the second bandpass filter output c has a gain of 0.80,
The third band-pass filter output d has a gain of 0.60,
Has a gain of 0.40. In the state where the above-mentioned focus is not achieved, the ratio becomes lower than those prepared in advance as shown by the broken line. In the degree-of-focus calculation circuit, the ratio with the in-focus state is, for example,
In the display conversion circuit 14, the calculation is performed based on the area ratio between the in-focus state and the current acquisition curve shown in FIG. For example, the in-focus state is set as the in-focus degree 100, and the in-focus degree is currently output as 80. Then, the focus degree data is added to the image pickup signal as a bar graph, a pie graph, or a numerical value, for example. The electronic viewfinder 15 displays an image pickup signal for visually confirming the degree of focus. Further, the graph shown in FIG. 6 may be directly displayed, or may be directly displayed on the camera when the focus is over a predetermined range.

[0013]

As described above, the focus degree display device according to the present invention focuses on the frequency characteristics of the optical low-pass filter for compensating the characteristics unique to the lens. Can be compared and the degree of focus can be displayed at any time on the electronic viewfinder, so that it is possible to visually grasp whether the subject is in focus and to reduce the work load of the cameraman on focusing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a focus degree display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing frequency characteristics of the optical low-pass filter according to the present embodiment.

FIG. 3 is an explanatory diagram schematically showing frequency characteristics of the bandpass filter according to the present embodiment.

FIG. 4 is an explanatory diagram schematically showing a focus area setting in an electronic viewfinder according to the present embodiment.

FIG. 5 is a waveform chart showing input and output waveforms of the bandpass filter according to the present embodiment.

FIG. 6 is a graph showing a relationship between frequency and gain at the time of focusing and defocusing according to the present embodiment.

[Description of Signs] 1 lens 2 optical low-pass filter 3 image sensor 4 signal processing circuit 5 first band-pass filter 6 second band-pass filter 7 third band-pass filter 8 fourth band-pass filter 9 focus area setting Circuit 10 Gate circuit 11 Peak value detection circuit 12 Position detection circuit 13 Focus degree calculation circuit 14 Display conversion circuit 15 Electronic viewfinder 16 Focus area

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 G02B 7/11 Z G03B 3/00 A (72) Inventor Hiroyuki Ono Kadoma, Kadoma City, Osaka Prefecture 1006 Matsushita Electric Industrial Co., Ltd.F-term (reference)

Claims (2)

[Claims] 1. A focusing degree display device used in a camera provided with an electronic viewfinder for displaying at least a captured image, comprising: a lens for forming an optical image of a subject; and a high-frequency component for the optical image of the subject. An optical low-pass filter that performs removal, an image sensor that photoelectrically converts an optical image of a subject from which high-frequency components have been removed by the optical low-pass filter and outputs an image signal, and an image signal that is output from the image sensor. A first bandpass filter for extracting a frequency component of the first bandpass filter; and a plurality of bands for respectively extracting different frequency components higher than the extraction frequency of the first bandpass filter for an image signal output from the image sensor. A pass filter, and an area of an arbitrary size at an arbitrary position of an image displayed on the electronic viewfinder. A focus area setting circuit that sets a focus area having a focus area and outputs a focus area signal; a gate circuit that cuts out the focus area from an imaging signal extracted from the first band-pass filter; A peak value detection circuit that detects a maximum value of the signal, a position detection circuit that detects a position in the focus area where the maximum value of the imaging signal detected by the peak value detection circuit is located, and from the position detection circuit. The first at the output position
And a focus degree calculating means for calculating the ratio of the maximum value of the other band-pass filters and comparing the calculated ratio with the focus ratio prepared in advance to output focus degree data. A focus degree display device characterized by the above-mentioned. 2. A display conversion circuit for converting focus degree data output from the focus degree calculation means into an arbitrary format and adding the converted data to an image signal output from the image sensor, and a display conversion circuit output from the display conversion circuit. 2. The focus degree display device according to claim 1, further comprising: an electronic viewfinder for displaying an image pickup signal.