JP3435726B2 - Focus measuring device for video equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus measuring device for a video device for measuring the focus state of an electron beam of the video device.

[0002]

2. Description of the Related Art A television receiver using a color cathode ray tube, which is the most popular among video devices, is
Adjusting the focus of the electron beam is an essential requirement. Then, it is premised that focus measurement is performed in order to adjust the focus of the electron beam.

A conventional focus measuring apparatus includes a pattern generator for outputting a line pattern signal to a television receiver as an object to be measured, and an image pickup means having a light receiving surface opposed to a display surface of the television receiver. An image memory that takes in the luminance data of the video signal output by the photographing means, and a reference luminance value of a percent is obtained with the luminance peak value of the image memory being 100%, and the luminance range above this reference luminance value is calculated as the line width And a line width calculating means.

In the above structure, a line pattern is displayed on the display surface of the television receiver as shown in FIG. The state of this line pattern is photographed by the photographing means, and the brightness data of the video signal output by this photographing means is taken into the image memory. Of the brightness data captured in the image memory, the brightness distribution in the direction orthogonal to the line pattern (direction AA 'in FIG. 3) is as shown in FIG. Then, each luminance data in the orthogonal direction of the line pattern is compared with the reference luminance value, and the distance from P to P ′ shown in FIG. 4 is calculated as the line width.

[0005]

However, according to the above-mentioned conventional example, since each luminance data is simply compared with the reference luminance value, noise in the vicinity of the point P or the point P ′ directly becomes a measurement error. However, there is a drawback that noise greatly affects the measurement error.

Therefore, it is an object of the present invention to provide a focus measuring device for a video device in which a measurement error due to noise is minimized.

[0007]

A focus measuring apparatus for a video apparatus according to the present invention for achieving the above object comprises a pattern generator for outputting a predetermined video pattern signal to the video apparatus, and a display surface of the video apparatus. An image pickup device having light-receiving surfaces arranged opposite to each other, an image memory for taking in luminance data of a video signal output from the image pickup device in two orthogonal address areas corresponding to image positions, and the image memory. If the variation coefficient of a plurality of brightness data is calculated based on the address data in two directions orthogonal to the brightness data of
And a variation coefficient calculation means for calculating the variation coefficient.
Means are provided for each address and luminance data on one side in two orthogonal directions.
The difference between the peak value of the
Sum of brightness for each address on one side due to difference in address
Multiply the values, find the sum, and divide the sum by the sum of luminance.
Then, the variation coefficient is calculated .

[0008]

The predetermined image pattern is projected on the display surface of the image device, the state of this image pattern is photographed by the photographing means, and the luminance data in the two orthogonal directions of the video signal output by this photographing means is taken into the image memory. A variation coefficient of a plurality of brightness data is calculated based on the brightness data of the image memory and the address data . Since the variation coefficient is calculated based on a plurality of luminance data, the value of the variation coefficient is not directly affected by noise.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram of a focus measuring device of a video device. In FIG. 1, the image device to be measured is a television receiver 1 using a color CRT 1a, and a dot pattern signal is supplied from a pattern generator 2 to the television receiver 1.

The photographing means 3 is composed of a line sensor, a CCD camera, etc., and its light receiving surface 3a is arranged so as to face the front surface of the color cathode ray tube 1a. This photographing means 3
The video signal (luminance data) output by is supplied to the image memory 5 via the A / D converter 4. As shown in Table 1 below, the image memory 5 has an address area specified by a horizontal address HA and a vertical address VA corresponding to the image position, and fetches the brightness data into the address area corresponding to the image position.

[0011]

[Table 1]

Brightness in the orthogonal direction of the line pattern shown in FIG .
Degree distribution is regarded as a dispersion curve and calculated by the formula of [Equation 2].
Σ is defined as the variation coefficient. The variation coefficient calculating means 6 searches for the peak value of all the brightness data fetched in the image memory 5 and detects the horizontal address indicating this peak value. Then, the horizontal address HA _i luminance data L _ij (i horizontal address, j is the vertical address), when the horizontal address of the peak value of the luminance data and HA _p, roses
Add coefficient σ (unit: address)

[0013]

[Equation 2]

It is obtained from the equation.

The CPU 7 reads the image memory 5
The writing, the calculation procedure of the variation coefficient calculating means 6, the signal generation timing of the pattern generator 2 and the like are controlled.

The operation of the above structure will be described below. When the pattern generator 2 outputs a dot pattern signal,
A dot pattern is displayed on the color CRT 1a of the television receiver 1. The state of this dot pattern is photographed by the photographing means 3, and this output video signal (luminance data) is taken into the image memory 5. And the variation
The number calculating means 6 determines the horizontal address H of the peak value of the brightness data.
A _p is detected and the variation coefficient σ is obtained using this.

Here, if the luminance data taken in the image memory 5 has the contents shown in Table 1 above, the horizontal address of the peak value is HA _p = 3. Also, first, it obtains a luminance sum of each horizontal address, by using this roses
If you calculate the coefficient σ,
The fluctuation coefficient σ is obtained.

[0018]

[Equation 3]

[0019] Since the variation coefficients σ that is calculated on the basis of the plurality of luminance data, is not Direct influence of noise on the variation coefficient values.

The variation coefficient calculating means 6 calculates the Roses
The coefficient (σ = 0.63) is output to, for example, the diameter calculating means (not shown). The diameter calculation means, Ru seek dot diameter (assuming) by variation coefficient values. An example of how to obtain it will be described.

FIG. 2 shows a horizontal luminance distribution state in the case of the luminance data shown in Table 1. The variation coefficient σ of the brightness distribution of the dots as shown in FIG. 2 is ± 3
99.7% of the total luminance distribution is included in the interval of σ.
Therefore, the value (unit is address) represented by 6σ is defined as the diameter of the dot, and 6σ = 3.78 (address) is defined as the diameter in the above specific example. This value is the focus measurement evaluation value.

In this embodiment, the pattern generator 2 outputs the dot pattern signal and calculates the dot diameter, but the pattern generator 2 may output the line pattern signal and calculate the line width. .

[0023]

As described above, according to the present invention, the variation coefficient of the image pattern displayed on the image device is calculated, and the amount of focus is obtained from the variation coefficient value. Even if the level fluctuates due to noise, the effect on the focus measurement is small.

[Brief description of drawings]

FIG. 1 is a circuit block diagram (example) of a focus measuring device of a video device.

FIG. 2 is a graph showing a horizontal luminance distribution state (Example).

FIG. 3 is a diagram showing a display state of a line pattern (conventional example).

FIG. 4 is a direction orthogonal to a line pattern (direction AA in FIG. 3)
3 is a graph showing the luminance distribution of (conventional example).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Television receiver (video device) 2 ... Pattern generator 3 ... Imaging means 5 ... Image memory 6 ... Variation coefficient calculation means

Claims (4)

(57) [Claims] 1. A pattern generator for outputting a predetermined video pattern signal to a video device, a photographing means in which a light receiving surface is arranged so as to face a display surface of the video device, and luminance data of a video signal outputted by the photographing means. Corresponds to the image position
An image memory for taking in two orthogonal directions of the address area, two-way orthogonal to the luminance data of the image memory
A plurality of luminance data Nobaratsu based on direction of the address data
And a variation coefficient calculating means for calculating a coefficient, wherein the variation coefficient calculating means is one side in two orthogonal directions.
Each address and one side address of the peak value of luminance data
The difference between each address is
Multiply the total value of the brightness of each dress, find the sum, and
Calculate the variation coefficient by dividing the total sum by the total brightness
Focus measurement devices of the video apparatus according to claim. 2. The variation coefficient calculating means has HA _{i as} a horizontal address of the image memory and L _{ij as} luminance data.
(I is a horizontal address, j is a vertical address), and if the horizontal address of the peak value of the luminance data is HA _p , the variation
The coefficient σ is The focus measuring apparatus for a video device according to claim 1, wherein the focus measuring apparatus is calculated by the following equation. 3. The focus measuring device for a video device according to claim 1, wherein the video pattern signal of the pattern generator is a dot pattern signal. 4. The focus measuring apparatus for a video device according to claim 1, wherein the video pattern signal of the putter generator is a line pattern signal.