JPH0646256B2 - Focus adjustment device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus adjustment device used in a camera or the like, and more particularly, to project a light on an object and receive the reflected light to generate a focus adjustment signal. The present invention relates to a focus adjusting device to be formed.

<Prior Art> Conventionally, various forms of focus adjustment devices have been proposed for forming a focus adjustment signal by projecting light on an object and receiving the reflected light.

FIG. 1 shows an example thereof.

In FIG. 1, 1 is a first light receiving element, 2 is a second light receiving element, 3 is a light projecting element, 4 is a light projecting lens, 5 is a light receiving lens,
6 is a subject.

In this device, the light receiving element moves in the base line length direction in association with the extension and retraction of the taking lens. Then, this light receiving element is in the state (1-a
In the figure), the state in which the first light receiving element (2) and the taking lens which are long enough to receive the reflected light of the signal light projected from the light projecting element 3 from the subject at infinity is fully retracted ( 1-
(b), the signal light projected from the light projecting element 3 is composed of a second light receiving element (1) having a length long enough to receive reflected light from a subject at the close-up shooting limit of the shooting lens. ing. That is, this light receiving element was composed of two linear light receiving elements each having a length sufficient to receive the reflected light regardless of the subject at any distance from infinity to the close-up shooting limit.

By making the light receiving element long and taking a large area in this way, the field of view of the light receiving element is widened, and it is possible to catch the signal light by any one of at least two light receiving elements, regardless of the amount of extension of the taking lens. This allows the light receiving element to receive the signal reflected light from the subject within the image capturing range of the taking lens from the close-up shooting limit to the infinity.

On the other hand, when the area of the light receiving element is increased in this way, the light receiving element receives a large amount of outside light other than the signal. This external light is generally sunlight or reflected light from artificial lighting such as a light bulb and a fluorescent lamp. First, in the case of artificial lighting such as a light bulb and a fluorescent lamp, an AC component of 100 Hz or the like is often included due to the power source. Further, in the case of a fluorescent lamp or the like, a high frequency component is included in addition to that, and it works as noise in the signal processing circuit. Also, when the amount of direct current light such as sunlight increases, shot noise due to the current generated in the light receiving element due to the direct current light cannot be ignored, and as described above, when a large light receiving element is used, the signal reflected light is It was difficult to realize a device that can detect accurately.

Therefore, if the length of the light receiving element is shortened to suppress the above-mentioned noise component to a low level, the influence of external light is reduced accordingly, but on the contrary, the light receiving element cannot receive reflected light from a wide distance range, and a smooth distance measuring operation is possible. There was an inconvenience that it could not be done.

<Objects of the Invention> The present invention has been made in view of the above circumstances, and provides a focus adjustment device that forms a signal for focus adjustment by projecting light on an object and receiving the reflected light. The contradictory inconveniences described above, that is, in order to be able to measure a wide distance range from a short distance to a long distance, the length of the light receiving means is increased so that reflected light from a wide distance range from a short distance to a long distance can be obtained. If it is possible to receive light, the amount of received noise light such as sunlight or artificial light will increase accordingly, and the inconvenience that accurate focus adjustment will not be possible, conversely, to reduce the received amount of noise light When the length of the means is shortened, the distance range that can be measured by the light receiving means becomes narrow, and it is possible to solve the inconvenience that focus adjustment cannot be performed on an object within a certain distance range such as an extremely short distance or an extremely long distance. The present invention aims to provide a fixed focus adjustment device.

Therefore, the present invention is a focus adjusting device which forms a focus adjusting signal by projecting light on an object and receiving the reflected light, and a light projecting means for projecting light and the light projected by the light projecting means. A light receiving unit that receives the reflected light of the light and outputs a signal that can determine the light receiving position, and whether the light receiving position of the light receiving unit is within a predetermined range of the light receiving region of the light receiving unit based on the output of the light receiving unit. Determination means for determining whether or not,
In response to the determination result of the determination means, when it is determined that the light receiving position of the reflected light is within a predetermined range of the light receiving area of the light receiving means, the narrow light receiving area of the light receiving means corresponding to the light receiving position is detected. A focus adjustment signal is formed based on the output, and a focus adjustment signal based on the output of the wide light receiving area of the light receiving means when the light receiving position of the reflected light is determined not to be within a predetermined range of the light receiving area of the light receiving means. And a signal processing unit that forms a light receiving unit, determines the light receiving position of the reflected light based on the output of the light receiving unit, and can receive the reflected light in a narrow light receiving region of the light receiving unit corresponding to the light receiving position. The output of the narrow light-receiving area enables accurate focus adjustment with less influence of noise light, and conversely, when the reflected light cannot be received within the light-receiving area of the light-receiving means, the output of the wide light-receiving area is used. It is an focusing device that allows for the focusing of a wide distance range without omission.

<Embodiment> FIG. 2 is a schematic view of an embodiment of the present invention. In FIG. 2, 3 is a light projecting element, for example, an infrared light emitting diode is used, 4 is a light projecting lens, 5 is a light receiving lens, 6 is a subject. Reference numerals 10 and 11 denote two light receiving elements that constitute the first light receiving element, and 20 denotes a second light receiving element. The above three light receiving elements are arranged in a straight line in a direction perpendicular to the optical axis, and they are integrally displaced in the direction perpendicular to the optical axis as shown by A according to the amount of extension of the taking lens (not shown), and the taking lens is always present. Each of the first light receiving element 10 and the second light receiving element 20 is configured to receive 1/2 of the signal reflected light from the subject located at the in-focus distance. In the above configuration, when the subject is slightly behind the focus position of the taking lens, the reflected light from the subject 6 of the signal from the light projecting element 3 is incident on the second light receiving element 20 more than the first light receiving element 10. To do. Further, when the subject is located slightly before the position where the photographing lens is in focus, that is, when the subject is rear-focused, the reflected light from the subject 6 of the signal from the light projecting element 3 is first received by the second light receiving element 20. Many incidents on the element 10. Then, when the subject is located further in front, the reflected light from the subject 6 from the light projecting element 3 enters the first light receiving element 11.

Here, when the subject is located at a position that is far behind the in-focus position of the photographing lens, the signal reflected light does not enter any of the light receiving elements 10, 11, and 20.

In this way, when the amount of deviation is small according to the distance between the focus of the photographing lens and the distance to the subject, it depends on which side of the first light receiving element and the second light receiving element the incident light quantity is biased. , In-focus, front focus, or rear focus can be determined, and when the amount of deviation is large on the rear focus side, signal reflection light enters the first light receiving element 11 to determine that state. When the signal reflected light does not enter any of the light receiving elements, it can be determined that the signal is largely deviated to the front pin side.

FIG. 3 is a block diagram of a first embodiment of an electric circuit for processing the signals of the light receiving elements 10, 11, and 20 shown in FIG. In FIG. 3, 3 is a light emitting element, 10 is a first light receiving element which is adjacent to the second light receiving element 20, and 11 is a light receiving element which together with 10 constitutes the first light receiving element. Then, the element is a light receiving element adjacent to 10 apart from the second light receiving element 20. 100, 11
0 and 200 are current amplifiers, 101, 111 and 201 are DC cut capacitors, 102, 103, 112 and 11
3, 202, 203 are resistors, 104, 107, 114,
117, 204, 207 are operational amplifiers, 105, 11
5, 205 are operational amplifiers switched by the control circuit 300, 106, 116, 206 are no-signal levels, that is, capacitors for holding DC optical signal components, 1
Reference numerals 08, 118, and 208 denote signal integration capacitors, 300 denotes a control circuit, and 302 denotes a motor, which extends and retracts the taking lens. 100 to 108 are the light receiving elements 10, 110 to 118 are the light receiving elements 11, and 200 to
Reference numeral 208 constitutes a circuit that amplifies and integrates the signal of the light receiving element 20, respectively.

Light incident on the light-receiving element 10 is converted into a photocurrent by the element 10 and amplified by the current amplifier 100, so that the capacitor 1
The direct current component is cut by 01 and is output to the synchronizing circuit constituted by 102 to 106. The operational amplifier 105 that constitutes such a synchronization circuit repeats operation and non-operation in synchronization with lighting and non-lighting of the light projecting element 3 which is interlocked with the synchronization signal 400. While the light emitting element is not lit and the operational amplifier 105 is operating, feedback is applied from the output of the operational amplifier 104 to the input, and the potentials at the inverting input terminal and the non-inverting input terminal become equal. In this case, an electric charge corresponding to the photocurrent level generated in the light receiving element 10 is stored in the capacitor 106.
That is, the external light component is stored in the condenser 106.

Next, while the light projecting element is turned on and the operational amplifier 105 is not operating, the operational amplifier 104 is configured to detect the voltage at the inverting input terminal of the operational amplifier 104 and the capacitor 1 when the light projecting element is turned on.
06, that is, the difference between the output of the light receiving element 10 when the light projecting element 3 is on and the output of the light receiving element 10 when the light projecting element 3 is off, in other words, Only the reflected light component of the light projecting element 3 is supplied to the operational amplifier 107 and the capacitor 1.
It outputs to the integrating circuit constituted by 08. The integrator circuit integrates the output and transfers it to the control circuit 300. Although the operation of the circuit elements shown in the light receiving elements 10 and 100 to 108 is as described above, the light receiving element 11, the circuit elements 110 to 118, the light receiving element 20, and the circuit element 200 are described.
˜208 are also the light receiving element 10 and the circuit elements 100 to 1 respectively.
Since the same operation as that of 08 is performed and the integrated output thereof is given to the control circuit 300, description thereof will be omitted. The control circuit 300 includes operational amplifiers 105, 115, 20 of the synchronous circuit.
A synchronization signal is given to the light emitting element 5 and the light projecting element 3 to control integration, and based on the total integrated output, focus, front focus, rear focus, etc. are determined, and the motor 302 controls the amount of extension of the taking lens. The operation of the control circuit 300 will be described later.

FIG. 4 is a block diagram of another embodiment of an electric circuit for processing the signals of the light receiving elements 10, 11, and 20 of FIG. Incidentally, in FIG. 4, elements having the same functions as those shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. 301 is a switching means for switching between the output of only the light receiving element 10 in the off state and the output of the light receiving elements 10 and 11 in the on state, and for example, a MOS transistor is used.

Thus, the circuit for processing a signal can be reduced to about ⅔ by using the hitching means 301. In this case, at first, 301 is turned on and both light receiving elements 10 and 11 are used as a first light receiving element. By controlling the taking lens, the extension amount of the taking lens reaches the vicinity of the focus, and the second light receiving element is reached. When the signal output of 20 is obtained, 301 is turned off and only the light receiving element 10 is used as the first light receiving element. The operation of the control circuit 300 'shown in FIG. 4 will be described later.

When the signal processing circuit configuration as shown in FIG. 4 is used, a processing circuit of almost the same scale as that of the conventional two light receiving element is possible.

Next, the control circuit 300 shown in FIG. 3 will be described with reference to FIGS. Control circuit 3
00 is configured, for example, as shown in the block diagram of FIG. 5, and operates according to the flowchart shown in FIG.

In FIG. 5, reference numerals 3001 to 3003 respectively convert the integrated voltage of the integrating circuit (composed of the operational amplifier 207 and the capacitor 208, the operational amplifier 107 and the capacitor 108, the operational amplifier 117 and the capacitor 118) of FIG. 3 into a digital signal. These are A / D converters, each of which gives a digital value to the microcomputer 3004 according to the amount of light received by the light receiving elements 20, 10, 11.

The microcomputer 3004 operates the motor 302 via the motor drive circuit 3005 according to the flowchart shown in FIG.
Is operated to extend and retract the distance ring of the lens, and the AND gate 3006 supplies the synchronizing signal 400 from the synchronizing signal generating circuit 3007 to the control terminals of the light projecting element 3 and the operational amplifiers 205, 105 and 115. Whether or not the distance measuring operation is performed is controlled.

Next, the operation of the control circuit 300 will be described with reference to FIG. In the following description, the operation of the steps shown in FIG. 6 will be described first, and the corresponding step numbers will be given in parentheses next.

First, as an initial setting, a flag (hereinafter referred to as N
-FLAG) is reset. That is, it is assumed that the focus is not in the vicinity (# 1). Next, the microcomputer 30
The timer for counting the integration time built in 04 is reset, the integration capacitors 108, 118 and 208 are reset by a reset circuit (not shown) (# 2), and the AND gate 3006 is turned on to output the synchronization signal ( #
3). Next, the timer incorporated in the microcomputer 3004 counts this synchronizing signal and measures the time by the number of its pulses.

When the timer is incremented by one pulse of the synchronizing signal, the output of the rear pin sensor is set to the output of the sensor 10 only when N-FLAG is set, and the output of the sensor 10 is changed to N-FLAG.
Is reset, the sum of the outputs of the sensor 10 and the sensor 11 is obtained (# 5), and the sum of the outputs of the rear pin side sensor and the front pin side sensor is obtained (# 6).

Next, it is judged whether or not the sum of the sensor outputs is at a level sufficient for making a focus judgment by comparing with a pre-programmed comparison value V (# 7), where the comparison value V is still full. If not, it is judged whether or not the measured value of the timer has reached the preprogrammed maximum integration time (# 8). When it is determined that the maximum integration time has not been reached, the flow returns to # 4 again, the integration time is repeatedly measured, and the process proceeds from # 4 until the output sum reaches the comparison value V or the integration time reaches the maximum integration time. Repeat the # 8 loop.

This loop is repeated, and when the maximum integration time is finally reached, the AND gate 3006 is turned off, the synchronization signal is cut off, the signal integration is terminated (# 9), and then it is determined by N-FLAG whether or not the focus is near focus. Judge (# 10). N-FLAG
If at least sensor 10,
This means that a sufficient amount of signal light is not received in the range covered by the sensor 11 and the sensor 20,
The motor control circuit considers that the signal light is imaged at a position largely deviated from the front pin that is not covered by the sensor 20, or that there is a subject at a distance such that the signal light can only be received by a weak amount that cannot be sensed. Through the motor 3
02, and the light receiving spot on the sensor surface is the sensor 20.
The distance ring is retracted by an amount corresponding to the movement of the length (# 11). After executing # 11, the flow returns to # 1 again to start distance measurement. When the N-FLAG is in the set state, the spot of a sufficient light amount is not imaged in the vicinity of the focus covered by the sensor 10 and the sensor 20, so the output of the sensor 11 is checked ( # 12),
If there is a sufficient output here, it is considered that the light receiving spot was on the sensor 11, that is, it was largely deviated to the rear pin, and an amount corresponding to the movement of the spot by the length of the sensor 10 on the sensor surface (# 13), When the output of the sensor 11 is equivalently zero, the flow returns to # 11, and the range ring is rewound in the same manner as when the N-FLAG is reset.

As described above, when the maximum integration time is reached, it is considered that the focus is not in the vicinity of the in-focus state, and the flow is jumped to # 1 to execute N-FL.
Reset AG and repeat from the beginning.

Next, a case where the sum of the outputs of the sensors reaches the comparison value V in # 7 will be described. Also in this case, the synchronization signal is first cut off, and the signal integration is ended (# 14).

Then, the outputs of the sensor 10 and the sensor 11 are compared (# 1
5) When the output of the sensor 11 is obviously high, the spot is fed out on the sensor surface by an amount corresponding to the length of the sensor 10 (# 13), and the flow jumps to # 1 and N
-Reset FLAG (# 1) and repeat again from the beginning. At # 15, when the output of the sensor 10 is larger or almost equal, that is, when the light receiving spots are on the sensor 10 and the sensor 20, the N-FLAG is first checked (# 16). , If this is reset, the sensor output on the rear pin side is the sensor 10
Is the sum of the output of the sensor 11 and the output of the sensor 11, and the signal is noisy due to the influence of external light. Also, the position of the light-receiving spot should be within a range that can be sufficiently covered by only the sensor 10 and the sensor 20, so that the N-FLA
Set G (# 17) and set the sensor on the rear pin side to sensor 1.
Only 0 is considered, and the flow jumps again to # 1 to restart the process from the beginning in order to obtain a signal that is less affected by external light. N
-If FLAG has already been set, the obtained signal is a signal that has less adverse effects such as noise due to external light. After that, compare the outputs of the pin side sensor and the front pin side sensor (# 18) and focus. In consideration of accuracy, when the difference between them appears to be 0, it is recognized as in-focus, and the range ring is stopped (# 2
1), a series of distance measuring operations is completed (# 19). If it cannot be regarded as 0, the distance ring is extended or rolled (# 20, # 21) according to the magnitude relation, the flow jumps again to # 1, and the flow repeats from the beginning.
This is done until it comes into focus.

As described above, by selectively using the light-receiving elements 20, 10 and 11 according to the focus adjustment state, it is possible to perform the focus determination in all areas, and at the same time, in the vicinity of the focus, the light-receiving surface is focused. It was made to be the minimum necessary for focus determination, and it was possible to obtain high focusing accuracy while minimizing the influence of external light.

The above description of the flow chart was for the operation of the embodiment shown in FIG. 3, but the control circuit 300 'of the embodiment shown in FIG. 4 will now be described with reference to FIGS. Explain.

The control circuit 300 'shown in FIG. 4 is constructed, for example, as shown in FIG. 7 and operates according to the flow chart shown in FIG.

In FIG. 7, 7001 and 7002 are A / D converters for converting the integrated voltages of the integrating circuits (207, 208) and (107, 108) of FIG. 4 into digital signals, respectively.
The microcomputer 7 calculates a digital value corresponding to the amount of light received by each of the light receiving elements 20 and 10 (or 10 + 11).
Give to 004.

The microcomputer 7004, based on these A / D-converted received light integrated signals, follows the flowchart of FIG.
Is operated to extend and retract the distance ring of the lens, and the AND gate 7006 applies the synchronization signal from the synchronization signal generation circuit 7007 to the light projecting unit 3 and the operational amplifier 2.
05, 105 control terminals, that is, whether or not distance measurement (synchronous integration) is performed, and a control signal is supplied to the switching means 301 of FIG. It controls whether only 10 or the sum of the light receiving elements 10 and 11 is used.

Next, referring to FIG. 8, the operation of the microcomputer 7004 will be described. First, by turning on the SW 301, the sensors on the rear pin side are the light receiving element 10 and the light receiving element 11 (# 1). Next, a timer which is built in the microcomputer 7004 and measures the integration time by the number of pulses of the synchronization signal is reset, and the integration capacitors 208 and 108 are reset by a reset circuit (not shown) (# 2). Then, the AND gate 7006 is turned on to output the synchronizing signal (# 3).

When the timer is incremented by one pulse of the synchronizing signal (# 4), next, the sum of the output of the light receiving element (2) on the front pin side and the output of the light receiving element (1) on the rear pin side is obtained (#
5).

It is determined whether or not the sum of the outputs of the light receiving elements has reached a level sufficient for performing the focus determination (# 6). When it is determined that the output is not sufficient, the integration time reaches the maximum integration time. It is determined whether or not (# 7). If it is determined that it has not reached here, the process returns to # 4 and the loop of # 4 to # 7 is repeated.
If the maximum integration time has been reached, the AND gate 7006 is turned off, the synchronization signal is cut off, and the distance measurement (integration) ends (# 8). When the SW301 is in the off state, light is received on the light receiving element 11. It means that there is a spot or there is no light receiving spot on any of the light receiving elements or the amount of received light is so small that it cannot be sensed, and since the determination is impossible at this point, the flow jumps to # 1. , SW301 is turned on and repeated again.

If the SW 301 has already been turned on, there is no light receiving spot with a sufficient amount of light within the range covered by the three light receiving elements, that is, the light receiving spot is not covered by the light receiving element 20 and is largely displaced to the front pin side. It is determined that the light receiving power is too small, or the subject is extremely far away and cannot be detected by the sensor, and the light receiving power is renormalized as much as # 11 in FIG. 6 (# 9), and then the distance measurement is repeated from # 1.

When it is determined in # 6 that the sum of the outputs has reached a level sufficient for performing the focus determination, first the AND gate 7006
Is turned off, the sync signal is cut off, the distance measurement is finished (# 10),
When the light receiving element output (1) on the rear pin side is much larger than the light receiving element output (12) on the front pin side (when the front pin side sensor output is equal to 0), the flow is # 12 to # 12. After branching to, the amount of light corresponding to the radius of the light receiving spot and the movement of the light receiving spot on the sensor surface is extended (# 12), and then #
Repeat from 1 again. When there is no large difference between the output of the light receiving element on the rear pin side (2) and the output of the light receiving element on the front pin side (11) or the output of the light receiving element on the front pin side is larger, the flow branches from # 11 to # 13. Then, it is confirmed whether or not the SW301 is turned off (# 13). If it is turned on, the rear pin side sensor detects the light receiving element 10 and the light receiving element 1.
Since it is the sum of 1 and is greatly affected by outside light and is not suitable for focus determination, SW301 is turned off (# 1
4) Then, the flow enters # 2 to perform distance measurement again.

If the SW 301 is off in # 13, focus determination is performed next (# 15), and the difference between the output of the rear pin side light receiving element (1) and the output of the front pin side light receiving element (2) is the focusing accuracy. If it is within the range, that is, if they can be regarded as equal to each other, it is determined to be in focus, the distance ring is stopped (# 16), and all the operations are ended. When the output of the rear pin side light receiving element is large, it is extended (# 17), when the output of the front pin side light receiving element is large, it is extended (# 18), and then the flow jumps to # 14 to repeat the distance measurement. Continue until focus is achieved.

Also in the embodiments shown in FIGS. 7 and 8 described above, the light receiving elements 10, 11 and 20 are selectively used according to the focus adjustment state similarly to the embodiments described in FIGS. 5 and 6. By doing so, it is possible to determine the focus in all areas, and in the vicinity of the focus, the light receiving surface is set to the minimum necessary for the focus determination, and the effect of external light is minimized to obtain high focus accuracy. Made it possible.

In the above embodiment, the light projecting element 3 corresponds to the light projecting means of the present invention, and the light receiving elements 10, 11 and 20 correspond to the light receiving means of the present invention, and the step # 15 of the microcomputer 3004 or the microcomputer 3004. Steps of 7004 #
Reference numeral 11 corresponds to the determination means of the present invention, and steps # 13, # 16, # 18 and # 1 of the microcomputer 3004.
9, # 20, # 21 or microcomputer 700
Steps # 12, # 13, # 15, # 16, # 1 of 4
7 and # 18 correspond to the signal processing means of the present invention.

<Effects of the Invention> As described above, according to the present invention, in the focus adjusting device that forms a signal for focus adjustment by projecting light on an object and receiving the reflected light, The light receiving position of the reflected light is determined based on the output of the light receiving means for receiving, and if the light receiving position of the reflected light can be received in a narrow light receiving area of the light receiving means, the narrow light receiving area Accurate focus adjustment with little influence of noise light by output, and conversely, if reflected light cannot be received in the light receiving area of the light receiving means in a narrow range, output of a wide light receiving area provides a wide distance range without omission. Since the focus adjustment is performed, it is possible to achieve both the measurement of a wide distance range from a short distance to a long distance and the accurate focus adjustment.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a conventional focus detection device, FIG. 2 is a schematic diagram of an embodiment of the present invention, and FIG. 3 is an electric circuit for processing signals of the light receiving elements 10, 11 and 20 shown in FIG. A block diagram of a first embodiment of the circuit, FIG. 4 is a block diagram of a second embodiment of an electric circuit for processing the signals of the light receiving elements 10, 11, and 20 shown in FIG. 2, and FIG. 3 is a block diagram of the control circuit 300 shown in FIG. 3, and FIG. 6 is a microcomputer 3004 shown in FIG.
7 is a block diagram of the control circuit 300 'shown in FIG. 4, and FIG. 8 is a microcomputer 700 shown in FIG.
It is a flowchart of 4 '. 10, 11, 20 ... Light receiving element 300, 300 '... Control circuit 3004, 7004 ... Microcomputer

Claims (1)

[Claims] 1. A focus adjusting device for forming a focus adjusting signal by projecting light on an object and receiving reflected light thereof, and a light projecting means for projecting light, and a light projecting means for projecting light. Light receiving means for receiving the reflected light and outputting a signal capable of determining the light receiving position, and whether or not the light receiving position of the light receiving means is within a predetermined range of the light receiving area of the light receiving means based on the output of the light receiving means. And a light receiving position corresponding to the light receiving position of the reflected light when the light receiving position of the reflected light is determined to be within a predetermined range of the light receiving region of the light receiving unit in response to the determination result of the determination unit. The focus adjustment signal is formed based on the output of the narrow light receiving area of the light receiving means and the output of the wide light receiving area of the light receiving means is determined when the light receiving position of the reflected light is not within the predetermined range of the light receiving area of the light receiving means. Focus based on Focusing device, characterized in that a signal processing means for forming a signal.