JPH0566343A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To provide an automatic focusing device which can variously change a distance measurement object as user's desire as for the automatic focusing device which executes the focusing of a camera or the like. CONSTITUTION:The device is the automatic focusing device which includes at least an optical sensor 1 including many photodetectors which are one- dimensionally arranged and a signal processing circuit 5 which processes a sensor output signal from the sensor 1 and supplies a focus signal showing the focusing state of a formed image. Besides, a focus detection area designation circuit 3 which can designate which area of the sensor 1 is set as the area from which the sensor output signal is fetched is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device for focusing a camera or the like.

[0002]

2. Description of the Related Art FIG. 8 shows an example of conventional technology. Figure 8
(A) shows a configuration example of an external light type focus detection device. The taking lens 51 of the camera forms an image of the subject on the film 52. A pair of distance measuring lenses 53 and 54 are provided separately from the taking lens 51, and a corresponding pair of line sensors 55 and 56 are arranged on the image forming planes of the distance measuring lenses 53 and 54. ..

The line sensor 55 is used as a reference line sensor and supplies image information photoelectrically converted in a fixed phase to a processing circuit 57. The line sensor 56 is a reference line sensor, which sequentially changes the read phase and supplies the photoelectrically converted image information to the processing circuit 57. Processing circuit 5
In 7, the distance to the subject is detected based on the image signals supplied from the standard line sensor 55 and the reference line sensor 56.

As described above, according to the structure in which the distance measuring lenses 53 and 54 are used separately from the photographing lens 51, it is sufficient as compared with the method of measuring the distance by using a part of the light passing through the photographing lens 51. It has the advantages that a large amount of light can be obtained, the degree of freedom in camera design is increased, and the manufacturing cost of the camera can be easily reduced.

The principle of distance measurement with the configuration shown in FIG. 8A will be described with reference to the partially enlarged view of FIG. 8B. Standard line sensor 55, reference line sensor 5
Reference numeral 6 is arranged so that the optical axes thereof are aligned with the distance measuring lenses 53 and 54, respectively. If the subject is at infinity,
The distance measuring lenses 53 and 54 form images of the subject on the center portions of the standard line sensor 55 and the reference line sensor 56, respectively. When the subject approaches the camera, the light incident on the distance measuring lenses 53 and 54 from the subject changes from the broken line state to the solid line state.

That is, as the subject gets closer to the camera, the standard line sensor 55 and the reference line sensor 56.
The images formed on top of one another gradually separate. By detecting the distance between the image on the reference line sensor 55 and the image on the reference line sensor 56, the distance from the camera to the object can be measured by the principle of triangulation. A phase difference detection method is used to detect the distance between the images.

That is, the image signal B (k) is read from each pixel of the reference line sensor 55 in a fixed phase, a predetermined phase difference m is set from the reference line sensor 56, and the image signal R (k + m) is read. .. If these images are the same, B (k) -R (k + m) will be zero. The image reading area is set to n pixels, and this calculation is performed for each of the image signals read from the corresponding n pixels, and the correlation degree H (m) that is the sum of them is obtained.

H (m) = Σ (k = 1 to n) | B (k) −R (k + m) | (1) where Σ (k = 1 to n) is a function in which k is 1 to n. Represents the sum of. The degree of correlation H (m) indicates the degree of coincidence between the image on the standard line sensor 55 and the image on the reference line sensor 56 at the phase m.

The phase m is sequentially changed, the correlation H (m) for each case is obtained, and the correlation curve is drawn. Then, the position where the correlation curve has the minimum value is the phase at which the image on the standard line sensor 55 and the image on the reference line sensor 56 are most in agreement. By detecting this phase, the distance from the camera to the subject can be measured.

The signal processing circuit 57 is, for example, shown in FIG.
As shown in, an A / D converter 59 for converting the signal from the line sensor from an analog amount to a digital amount, and a RAM which is a temporary storage device for storing the digitally converted image signal.
(Random Access Memory) 61 is included. Using the image signal stored in the RAM 61, the CPU (Central Processi)
ng Unit) 60 performs the above-described calculation of the degree of correlation to detect the phase with the smallest degree of correlation.

In the focus detection apparatus shown in FIGS. 8A and 8B, the charge accumulated in the photosensor is converted into a charge-voltage as it is to form a detection signal, which is converted into a digital signal and stored in the RAM 61. The calculation is performed by reading the lever signal.

The inventor of the present invention has proposed an automatic focusing device which non-destructively reads out electric charges accumulated by irradiating light and directly performs arithmetic processing with an analog amount.

FIG. 8C shows an example of the structure of the optical sensor section of such an automatic focusing device. The photodetection portion is formed by forming a p-type well 66 on the surface of the n ⁻ -type silicon substrate 64, forming an n ⁺ -type region 68 in a part of the p-type well 66, and forming a pn junction 69. When light is incident on the vicinity of the pn junction 69, electron-hole pairs are formed, and the electrons and holes are separated and accumulated according to the potential gradient around the pn junction.

The p-type well 66 extends to the left side of the pn junction 69 in the figure, on which insulated gate electrodes 71 to 74 and 76 of polysilicon are formed. A barrier section having a gate electrode 71 is formed adjacent to the photodiode, and a storage section having a gate electrode 72 is formed next to the barrier section.

That is, charges corresponding to the light incident on the light receiving portion are accumulated in the accumulating portion from the vicinity of the pn junction 69 via the barrier portion. The storage portion is a transfer gate electrode 73.
Through the gate electrode 74, and the shift register portion is continuous with the region below the floating gate electrode 76 having the bias applying aluminum electrode 75 thereon.

That is, when an electron-hole pair is formed in response to light incident on the photodiode portion, carriers are accumulated in the accumulation portion under the gate electrode 72 beyond the barrier portion, and further transferred to the transfer gate electrode 73. It is transferred over and under the gate electrode 74 of the shift register. The charges accumulated under the gate electrode 74 of the shift register section are transferred to the gate electrode 7
It is transferred below the floating gate electrode 76 depending on the voltage of 5. Electric charges corresponding to the transferred electric charges are induced in the floating gate electrode 76, and the incident light amount is read nondestructively by the electric charge amount.

When the photosensor as shown in FIG. 8C is used, the calculation of the equation (1) can be performed with the electric charge kept at an analog amount by using the switched capacitor integrating circuit.

[0018]

In the focus detecting device according to the prior art described above, the focus detecting device has a simple structure when the taking lens 51 is of a variable focal length type or has a zoom function, and There is a problem that it becomes difficult to detect the focus properly.

When the focus of the taking lens 51 is changed or the zoom function is applied, the angle of view of the lens 51 with respect to the film 52 changes.

If the distance measuring lenses 53 and 54 are similarly changed in response to such a change, the structure of the distance measuring system becomes extremely complicated. When the distance measuring lenses 53 and 54 are fixed focus type and the angle of view of the taking lens 51 is changed, for example, when the angle of view of the taking lens 51 is extremely narrow, the line sensors 55 and 56 are provided.
An image with a wide angle of view is projected on the top, and the distance to a subject different from the subject to be photographed will be measured.

That is, the distance measuring system cannot adjust the measuring object in response to the change of the main subject set by the photographing lens 51.

An object of the present invention is to provide an automatic focusing device capable of variously changing a distance measuring object as desired.

[0023]

SUMMARY OF THE INVENTION An automatic focusing apparatus according to the present invention includes an optical sensor including a large number of elements arranged at least one-dimensionally, and a sensor output signal from the optical sensor is subjected to signal processing to form an image. An automatic focusing device including a signal processing circuit that supplies a focus signal indicating a focus state, wherein a focus detection area designation capable of designating which area of the photosensor is an area for extracting a sensor output signal It has a circuit.

Further, another automatic focusing apparatus of the present invention determines the focused state of the object by detecting two images formed on the reference surface through the pair of lenses by the pair of optical sensors. In the automatic focusing device, at least one of the photosensors includes a number of elements equal to or more than the number of elements required to detect a focus state, and which area of the one photosensor is used as an area for extracting a sensor output signal A focus detection area designation circuit capable of designating whether or not is provided.

[0025]

By combining an optical sensor including a large number of elements arranged at least one-dimensionally and a focus detection area designating circuit capable of designating which area of the optical sensor is to be an area for extracting a sensor output signal. The focusing function of the automatic focusing device can be changed as necessary.

For example, by aligning the optical axis of the lens with the center of the optical sensor and using the element at the end of the optical sensor,
The camera can be focused on the subject at the edge of the field of view.

Further, when the relative relationship between the optical sensor and the optical axis of the lens changes, the design change of the camera or the like can be flexibly dealt with by designating the area for taking out the sensor output signal according to the optical axis of the lens. An automatic focusing device can be obtained.

In an automatic focusing apparatus using a pair of optical sensors, the number of elements of at least one optical sensor is increased, and which area of the optical sensor is used as an area for extracting a sensor output signal is a focus detection area designating circuit. It is possible to deal with a change in the base line length of the automatic focusing device, etc. Further, it becomes possible to diversify the focusing condition.

[0029]

1 shows an automatic focusing device according to an embodiment of the present invention. FIG. 1A shows a structure and FIG. 1B shows a function.

In FIG. 1A, the sensor output 8 from the optical sensor 1 is processed by the signal processing circuit 5 to generate contrast information 10.

The optical sensor 1 is provided with a selection circuit 3, and a focus detection area designating signal generated by the selection circuit 3 can specify which area of the signal of the optical sensor 1 is to be taken out as the sensor output 8. That is, the optical sensor 1 can selectively supply the sensor output 8 from any position thereof. For example, the focus state can be detected by obtaining the contrast of the sensor output 8 by the processing circuit 5.

FIG. 1B is a block diagram of the configuration shown in FIG.
Indicates a function. The optical axis 11 of the optical sensor lens 15 is arranged vertically to the center of the optical sensor 1. Subject 13
When a and 13b are present at positions apart from the optical axis 11,
The sensor output 8a corresponding to the subject 13b is obtained from the right side portion of the optical sensor 1, and the subject 13 is obtained from the left side portion.
A sensor output 8b corresponding to a is obtained. The person who handles the camera can arbitrarily select at which position in the field of view the focusing is performed by designating which subject is focused. The focus detection area designation can be changed almost continuously.

A configuration example of the selection circuit 3 is shown in FIG. The configuration of FIG. 2 also has a multiplexer function. The D flip-flops (DFF) 21 are arranged in series, and the DFF 2 in the first stage is
The D input of 1 receives the data input D1, and its Q output is supplied to the D input of the DFF 21 in the second stage. Similarly, the Q output of the second-stage DFF 21 is supplied to the D input of the third-stage DFF 21. Further, the clock signal CK1 is supplied to the trigger input terminal T of each DFF. The Q output and the XQ output of each DFF 21 are supplied to a predetermined signal line 22.

The AND circuit 23 has its input connected to a predetermined combination of the signal lines 22, and its output is supplied to the OR circuit 24 via an inverter. An enable signal XEN1 that determines the start of reading the photosensor is applied to the other input terminal of the OR circuit 24. The output of the OR circuit 24 is applied to a preset terminal PR of a flip-flop circuit 25 which is a combination of a D flip-flop and an AND circuit via an inverter.

That is, there is the output of the AND circuit 23,
And the enable signal XEN1 falls and the OR circuit 2
When the output of 4 goes low, the input is applied to the preset terminal of the corresponding flip-flop circuit 25. The flip-flop circuit 25 receives the clock signal CK2 and the enable signal EN2, and outputs its Θ output to the transfer transistor 26.
Applied to the gate of. The drain of the transistor 26 is
It is connected to the floating gate FG of the photosensor.

The operation of the selection circuit shown in FIG. 2 will be described with reference to the signal timing chart shown in FIG.

Each time the clock signal CK1 is applied, the data signals D11 to D23 of the data input D1 are transferred to the DFF2.
1 is sequentially transmitted, and when a series of data signals is applied, a predetermined address signal is generated at the output of the series of DFFs 21. This address signal is formed on the signal line 22.

When a series of address signals are input, the clear signal XCL2 falls and the flip-flop circuit 25 is cleared. Then, the first enable signal X
When EN1 falls, only the output of the OR circuit 24 connected to the AND circuit 23 generating the output is applied to the preset terminal PR of the corresponding flip-flop circuit 25.

In this way, the start position of the optical sensor is determined. When the second enable signal EN2 is present, the flip-flop circuit 25 generates "1" at its output Θ. Thereafter, each time the clock signal CK2 is applied, the Q output of the flip-flop circuit 25 is transmitted to the next-stage flip-flop circuit 25, and the floating gates FG are sequentially selected. When the second enable signal EN2 falls, the output of the flip-flop circuit 25 does not occur thereafter.

In this way, the second enable signal E
The length of N2 determines the number of elements read from the photosensor.

As described above, in the configuration shown in FIG. 1A, by supplying the read start position and the number of read elements from the selection circuit 3, the sensor output 8 of a desired portion of the optical sensor 1 is read and the signal is output. By performing the processing, it is possible to perform the automatic focusing operation while changing the function of the optical sensor 1 into a desired form.

FIG. 4 schematically shows an automatic focusing device according to another embodiment of the present invention. Light receiving diode 31 and CCD
The first photosensor 1 including the storage unit 32 and the shift register 33 includes the required number of elements or more and forms a reference section. Light receiving diode 34 and CCD storage unit 35
And the second photosensor 2 including the shift register 36 includes the required number of elements and constitutes a reference portion. Both CCD
The sensor output read from the accumulators 32 and 35 is supplied to the signal processing circuit 5a and subjected to signal processing to generate autofocus-related data 10.

A start position setting circuit 37 is connected to the reference light sensor 1 and specifies from which position of the light receiving diode 31 the sensor output is read. The number of read elements is constant.

FIG. 7 shows an example of the plan configuration of the optical sensor 1.
A large number of light receiving diodes 31 are provided on the surface of the semiconductor chip.
They are arranged in a three-dimensional array. Adjacent to the light receiving diode 31, a CCD 32 for receiving and accumulating electric charge from each light receiving diode is formed. CCD
The number of stages of 32 is set equal to the number of elements of the light receiving diode 31.

Further, a shift register 33 is formed adjacent to the CCD 32. The number of stages of the shift register 33 is also set to be the same as the number of stages of the CCD 32. In the central portion of the shift register 33, the floating gates 50 are arranged adjacent to each other via the transfer section.

The charge signal generated by receiving the light by the light receiving diode 51 is accumulated in the CCD 32 as it is, and the charge of the CCD 32 is transferred to the shift register 33 and circulates in the shift register 33 when the signal is read. The charges in the shift register 33 are selectively read out by the floating gate 50.

FIG. 4B shows one of utilization modes of the configuration shown in FIG. Lenses 39a and 39b are arranged at a predetermined distance from each other and define optical axes 41a and 41b parallel to each other. The light receiving diode 31 of the first optical sensor is
Of the second photosensor and the light receiving diode 34 of the second photosensor are arranged under the second lens 39b. In addition, these light receiving diodes 31, 34 are
It may be composed of two parts of a series of light receiving diodes 40.

For example, consider a case where one lens 39a is arranged on the optical axis 41c due to a design change of the camera. At this time, by moving the signal reading (focus detection) area in the light receiving diode 31 in correspondence with the change of the optical axis, it is possible to cope with the design change of the camera without changing the hardware configuration.

In the embodiment shown in FIG. 4, one of the pair of photosensors has a variable signal read area, but both of the pair of photosensors have variable signal read areas to further diversify the functions. can do.

FIG. 5 shows an automatic focusing device according to another embodiment of the present invention. In the configuration of FIG. 5A, the first photosensor 31 is combined with the transfer CCD 32 and the shift register 34, and the second photosensor 34 is used as the transfer CCD 3.
5, combined with the shift register 36. The shift register start position setting circuits 37 and 38 supply the shift register start positions to the shift registers 33 and 36, and the focus detection region width setting circuit 45 supplies the region width to be read, that is, the number of elements. ..

Shift register start position setting circuit 3
7, 38 can be realized by the circuit configuration shown in FIG. 2, for example. Further, the focus detection area width setting circuit 45 can be realized by using, for example, a down counter. Optical sensor 3
The sensor outputs read out from the selected areas 1 and 34 are supplied from the transfer CCDs 32 and 35 to the signal processing circuit 5b, processed by the signals, and converted into digital data by the A / D converter 7. Generate relevant data 10. The circuit 9 of FIG. 5A is all integrated in one chip.

FIG. 5B shows one usage mode of the configuration shown in FIG. The series of photodiode rows 40 includes a first optical sensor 31 and a second optical sensor 3 shown in FIG.
Make up 4. A pair of lenses 39a and 39b are arranged on the front surface of the photodiode array 40, and optical axes 41a and 41b are defined. When focusing on the image in the center of the visual field, the automatic focusing operation can be performed by reading the sensor output from the photodiodes around the optical axes 41a and 41b. When focusing on the subject at the end of the visual field, for example, the focus detection area in the photodiode array 40 is changed in accordance with the light rays 42a and 42b incident on the lenses 39a and 39b from the subject.

As described above, by changing the focus object based on the intention of the camera operator, for example, as shown in FIG.
It is possible to perform a focusing operation on the moving body as in the case shown in FIG.

FIG. 6 schematically shows an automatic focusing device according to another embodiment of the present invention. The reference unit 46a and the standard unit 46b each include a photodiode array, a transfer CCD, a shift register, and the like. These output terminals RFG1 to RFGn and BFG1 to BFGn are applied to multiplexer circuits 47a and 47b connected in parallel, respectively. In the configuration shown in the figure, the multiplexers 47a and 47b are shown by connecting three identical circuits in parallel.

Each multiplexer circuit has the same structure as the circuit shown in FIG. Similarly, in the focus detection area width setting circuit 45, circuits having the same function are connected in three layers in parallel, and signals are supplied to the multiplexer circuits 47a and 47b in the three layers, respectively. The output signals of the multiplexer circuits 47a and 47b are respectively supplied to the correlators 48 of the three layers, and the correlation function is calculated in each correlator. One of the outputs of the three-layer correlator 48 is selected by the switch SW and output via the analog-to-digital converter 49. The read start position can be further adjusted by inputting data.

For example, multiplexers 47a and 47b
The three sets of circuits simultaneously detect in-focus states for a person, a near view, and a distant view. The camera operator selects a desired subject with the switch SW, thereby performing an automatic focusing operation according to the subject.

Incidentally, in the configuration of FIG. 6, the angle of view can be changed as described in the embodiment of FIG. These functional changes can be changed continuously.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
Whether to use the TTL method is arbitrary. It is also arbitrary to use a multiplexer other than the above-mentioned configuration. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

[0059]

As described above, according to the present invention,
An automatic focusing device is provided in which a single optical sensor can be used in various ways.

By setting various usage modes, it is possible to perform a matching operation according to the situation.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1A is a block diagram showing the structure, and FIG. 1B is a schematic diagram for explaining the function.

FIG. 2 is a block diagram showing a configuration example of a selection circuit in the embodiment of FIG.

FIG. 3 is a timing chart of various signals in the selection circuit of FIG.

FIG. 4 shows another embodiment of the present invention. FIG. 4A is a block diagram showing the configuration, and FIG. 4B is a schematic diagram showing one of usage modes.

FIG. 5 shows another embodiment of the present invention. FIG. 5 (A) is a block diagram showing a configuration, and FIG. 5 (B) is a schematic diagram showing one of usage modes.

FIG. 6 is a schematic block diagram showing an embodiment of the present invention.

FIG. 7 is a plan view showing a configuration example of an optical sensor.

FIG. 8 shows a conventional technique. 8A and 8B are a block diagram showing a configuration example of a conventional automatic focusing device and a partially enlarged view thereof, and FIG. 8C is a schematic sectional view showing another example of the optical sensor.

[Explanation of symbols]

 1, 2 Optical sensor 3 Selection circuit (multiplexer) 5 Signal processing circuit 8 Sensor output 10 Contrast information 31, 34 Light receiving diode 32, 35 CCD storage unit 33, 36 Shift register 37 Start position setting circuit 39 Lens 45 Focus detection area width setting Circuit 51 Photographic lens 52 Film 53, 54 Distance measuring lens 55, 56 Line sensor 57 Processing circuit 59 A / D converter 60 CPU 61 RAM 66 p-type well 69 pn junction 71-75 Gate electrode 76 Floating gate electrode

Claims (4)

[Claims] 1. An optical sensor including a large number of light receiving elements arranged at least one-dimensionally, and a signal processing circuit for processing a sensor output signal from the optical sensor to supply a focus signal representing a focused state of image formation. An automatic focusing device including a focus detection region designating circuit capable of designating which region of the optical sensor is to be a region for extracting a sensor output signal. .. 2. An automatic focusing device for determining a focused state of a subject by detecting two image formations formed on a reference surface through a pair of lenses by a pair of optical sensors, The focus detection area designation can specify which area of the one photosensor is to be an area for extracting a sensor output signal An automatic focusing device comprising a circuit. 3. The automatic focusing device according to claim 2, wherein each of the pair of photosensors includes elements equal to or more than the number of elements required to detect a focus state, and which region of the pair of photosensors is further included. An automatic focusing apparatus comprising a focus detection area designating circuit capable of designating whether or not to be an area for extracting a sensor output signal. 4. The automatic focusing device according to claim 3, wherein:
4. The automatic focusing apparatus according to claim 3, wherein a plurality of sets of readout circuits are coupled to each of the pair of photosensors, and the focus detection area designating circuit includes a selection unit that selects one of a plurality of sets of readout circuits. ..