JPS58129407A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To carry out focusing automatically by comparing the first and second threshold values near the average density level of shaded picture detected through an optical system and a photographing signal and determining signal amount between threshold values. CONSTITUTION:A shaded picture is photographed by a photoelectric converter 3 through a lens 1 set at a proper position. Output changed to binary system by the first and second binary encoding circuit 41, 42 is processed by an exclusive OR circuit 43 and counted by a counter 44. The counted value corresponds to the sum of picture elements having a level between threshold values, and stored temporarily in a register 51. When the storage of the calculated value is completed, a controlling circuit 53 generates movement information to a driving mechanism 6, and shifts the position of the lens 1. The calculated value obtained basing on a photographing signal under this condition is compared with the value read out from the register 51, and focusing information is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technology of the Invention: Minute Hand] The present invention relates to the modification of an automatic focusing stirrup for automatically adjusting the focal length of an optical system.

[Technical background of the invention and its problems]

Conventionally, as a device that automatically adjusts the focal length of an optical system such as a lens, it detects the density difference between pixels that are in close contact with each other in grayscale image information captured through the optical system over the entire screen, and detects these density differences. There are some that adjust the focal length by moving the optical system in the direction that maximizes. However, when detecting the difference between each pixel of the imaging information, the device described above must perform the detection while moving the detection position of the entire lIIwi in the horizontal scanning direction and in the vertical scanning direction κ, respectively. Therefore, there are disadvantages in that it takes a lot of time for adjustment and the circuit configuration becomes complicated.

On the other hand, as another method for automatically adjusting the focal length,
There is a system that detects the high illt IL component contained in the image signal and adjusts the focal length of the optical system according to the detection result. However, even with this kind of O method, it takes a lot of time to perform the Fourier permutation calculation, and it is difficult to eliminate the influence of noise.
Since a complicated filter is required to eject high IR wave components with high H, shortening of adjustment time and simplification of the configuration cannot be expected.

[Purpose of the invention]

The present invention has a simple configuration and a short time KMII<11.
Automatic focus adjustment that allows you to do 1111! ! It provides eyes.

[Summary of the invention]

In general, when the optical system is in focus, the density distribution of the image is approximately evenly distributed in a wide range from dark to bright, as shown in Figure 1 (a), while the focus of the optical system is When the values do not match, the aIIlf distribution concentrates on a constant 11E@l that includes the average density level of the grayscale image, as shown in FIG. 1(b). In addition, at this time, the above-mentioned average level becomes approximately constant regardless of the focal point. Therefore, #fLIj
The focus of the optical system can be set to the optimum state by adjusting the optical system and the relative distance between the light and shade and the relative distance between us so that the distribution within a predetermined range including the average density level of g1 is minimized.

The present invention focuses on the above points, and the first and second imaging signals of gradation l111g1 received and detected through the optical system are set to different density levels near the average f111 degree level of the gradation image. A means is provided to determine the signal amount of each threshold value open by comparing it with each threshold value, and a plurality of signal amounts obtained by the above means are mutually determined by varying the relative distances between the optical system and the gradation TMS. The purpose of this comparison is to obtain focus adjustment information of the optical system and to variably control the relative distance between the optical system and the contrast m81 according to this focus adjustment information.

[Example of the invention]

Figure III is a professional configuration diagram of an automatic focus adjustment device in one embodiment of the present invention. This dynamic point adjustment device is
A photoelectric converter S consisting of a lens 1 configured to be movable in the direction of the original axis, a solid-state imaging probe that receives an optical image of a gradation image 2 through the lens 1 and outputs an imaging signal thereof, and the above-mentioned imaging A signal amount detection circuit 4 that detects the signal amount corresponding to the average density region of gradation l111m7 from the signal, a focus adjustment information generation circuit l that creates focus adjustment information based on the output of this signal amount detection circuit 4, and It is comprised of a drive mechanism 6 that moves the lens 1 in the direction of its optical axis according to adjustment information.

The signal amount detection circuit 4 has a first and a second circuit that binarizes the imaging signal from the photoelectric converter 3 using different threshold values.
It has a value conversion circuit 41.4jl. The threshold value set in the binarization circuit 41 of the compilation is the average 'mI of the grayscale image 2.
F Nirepel is also sufficient for any high level. The threshold value set in the binarization circuit 42 of II2 is determined corresponding to an arbitrary level lower than the above-mentioned average density level. Then, the signal amount detection circuit 4 detects each of the above two signals.
The binary output of the digitization circuit 41.41 is converted into an exclusive single-layer phase circuit 4.
3 and performs logical sum processing, the logical sum output is led to the counter 44 and counted, thereby memorizing m and having a fast value opening level I! i! I'm looking for a prime number.

- The universal point adjustment information generation circuit 5 includes the signal amount detection circuit 4
A register 51 that temporarily stores the count value of i*greatness output from the force inputter 44, and a comparison that compares the count value stored in this register 51 with the count value obtained at another position of the lens 1. It consists of a circuit 52 and a control circuit 5S that generates focus adjustment information according to the output of the comparison circuit 52. Here, the focus adjustment information consists of a signal for specifying the moving direction of the lens 1.

Further, the control circuit 51 independently generates focus movement information regardless of the output from the comparison circuit 52, and controls the position of the P lens 1 to be varied based on this information.

Next, the operation of the device configured as described above will be explained according to the adjustment procedure. First, set the lens el at an appropriate position. In this state, a grayscale image 2 is generated from the photoelectric converter IK through the lens 1. Take an image.

Then, from the photoelectric converter 1, as shown in FIG.
An imaging signal is output, and this imaging signal is converted into binary values by the binarization circuits 41゜4j of votes 1 and H2 according to the respective threshold values ① and ② as shown in Fig. 3(b) and (e), respectively. be converted into These binary outputs are subjected to exclusive OR processing in an exclusive OR circuit 43 as shown in FIG. The counting operation at this time is performed in synchronization with the establishment of a shift output tie of 1 mg of Mayu Ekigen Electricity Consumption. Then, when the counting for l-images is completed, the counter 44Fi outputs its counted value, the total value of the pixels having the above-mentioned threshold value open level, and this hand value is temporarily stored in the register 51. Ru. Incidentally, when the output of the above-mentioned count value is completed, the count contents of the input counter 44 are self-cleared.

When the above-mentioned needle value has been memorized, the control circuit is generates movement information for the drive mechanism I to slightly move the positions of lenses and el in the direction of the optical axis, and then causes the photoelectric converter 1 to perform an imaging operation. have them do it. Then, the photoelectric converter 1 outputs an image signal received through the lens 1 after the movement, which is different from the image signal IjtI, and this image signal is also shown in FIGS. ), the signals are processed and a counter 44 counts pixels having a level between each threshold. When the counting for one stroke is completed, the counted value is read out from the register 11.
It is supplied to the comparator circuit i1 together with the count value before the O movement, and is compared between the two. When the comparison result signal is output, the control circuit jJii generates focus adjustment information according to the comparison result signal. For example, if the comparison result signal is
The count value before lens movement> indicates the count value after movement.If 9, it is determined that the position after movement is closer to the alignment position, and the lens is further moved in the direction in which it was moved earlier. Emit information for moving. On the other hand, if the comparison result signal indicates the needle value before movement <the needle value after movement, it is determined that the value before movement is closer to the focus specie position,
Information for moving the lens 1 in a direction opposite to the previous lens movement direction is issued. As a result, there is a slight movement in the direction specified by the focus-to-view information from Ren I1.

Thereafter, the series of adjustment operations are repeated every time the minute movement is performed, and the adjustment operation ends when the control circuit 53 detects that the count value of the counter 44 has become the minimum.

In this way, with this device, a series of signal processing can be performed using general analog or expanded digital circuits without using a Fourier transformer or special filter, and the processing itself is extremely simple. Because it is simple, the configuration can be made much easier than in the past, and moreover, it can be adjusted at high speed and with high precision.

Note that the present invention is not limited to the above embodiments.
For example, in the above embodiment, the focus adjustment information is generated by comparing two counted values with each other, but three or more needle values obtained by moving the position of the lens 1 little by little are Compare each, and from the comparison result, determine not only the amount of movement of the lens 1t, but also the amount of movement thereof, and supply this information as focus adjustment information to the driver II#- to control the lens 1t. By doing so, the time required for adjustment can be further reduced. In addition, the level of each threshold value, the configuration of the signal amount detection circuit and the focus adjustment information generation circuit, the configuration of the photoelectric converter, etc. can be modified in various ways without departing from the gist of the present invention.

〔Effect of the invention〕

The present invention compares the imaging signal with each of the Ill and second thresholds set corresponding to the different S contrast levels near the average density level of light and dark, and compares the signal amount at each of the above thresholds. By means of the above means, p is determined by varying the optical system and the relative distance between the shading and the image, and the nine plurality of signal quantities are compared with each other. From this comparison result, the focus adjustment information of the optical system is obtained. According to this information, the relative distance between the optical system and the dark fkll image is variably controlled.

Therefore, according to the present invention, it is possible to provide an automatic focus adjustment device that has a simple configuration and can perform accurate adjustment in a short time.

[Brief explanation of the drawing]

FIG. 1(a) is a characteristic diagram for explaining the present invention in detail, FIG. 2 is a professional configuration diagram of an automatic focusing device in an embodiment of the present invention, and FIG. 3(a) is a characteristic diagram for explaining the present invention in detail. ) to (d) are tie diagrams for use in explaining the operation of the device. DESCRIPTION OF SYMBOLS 1...Lens, 2...Density-me, 1...Photoelectric converter, 4...Signal amount detection circuit, i...Focal point-adjustment information generation circuit, d...Drive mechanism.

Claims (1)

[Claims] a photoelectric converter that receives an optical image with a density of mg1 through an optical system and obtains an image signal;
(ii) a means for determining the signal amount at each of the above thresholds by comparing the levels with each of the 9th and 1112th thresholds set corresponding to respective different concentration levels near the average concentration level of the optical system; means for mutually comparing the respective signal amounts obtained by the circuit at a plurality of different relative distances between the optical system and the gradation image, and obtaining the control point information of the optical system based on the comparison results; An automatic focus I# adjusting device comprising an optical system and means for variably controlling the relative distance between the lllfL images.