JPH0213282B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a focusing device, and more particularly, to a focusing device that can automatically focus well even when the amount of defocus is large with a long focal length lens, etc. .

(Prior art) A focusing device such as a camera emits infrared rays, etc.
A device that measures reflected light from an object, or a device that allows light from the object to enter a light receiving unit that has multiple pairs of light receiving elements such as CCDs, and calculates the shift (phase difference) between the received light signals of each pair. There are devices that detect this and calculate the shift of the focus ring.

The present invention relates to the improvement of the latter method using a light receiving sensor such as a CCD.

For those using conventional light receiving sensors such as CCD,
There is a so-called Honeywell patent. An overview of this Honeywell patent will be explained below.

FIG. 4 specifically shows the CCD sensor 15.

The CCD sensor 15 includes a plurality of pairs of light receiving sensors A and B arranged at regular intervals. 20 each pair of light receiving sensors A,
The lenslets are arranged corresponding to each lenslet.

FIG. 5 shows the relationship between the optical lens system 13 and the light receiving section 15. Now, the target object 12 is the optical lens system 13
If it is at the 0' position which is the front pin position before the gear spin position 0 position, then the 0'
The light flux from the part An′ enters the light receiving sensor An, and from Bn′ enters Bn. Since An' and Bn' are different parts on the target object 12, they generally have different brightnesses. Therefore, the light receiving sensor An, Bn
The amount of luminous flux incident on the two has different values. In this way, when the target objects 12 are not at the jaspin distance, they form a pair. The amount of luminous flux incident on the CCD light receiving sensors An and Bn has different values for each pair.

In contrast, the target object 12 has a gear spin position of 0.
, the diffusely reflected light from the same part of ABn is incident on An and Bn, so the same amount of luminous flux is incident on An and Bn.

In this way, when O and F become optically conjugate surfaces in the optical lens system 13, the amount of incident light flux is equal for any pair of light receiving sensors An and Bn. become.

In FIG. 6, a shows the center of gravity of the light beam cone incident on the front principal point plane P of the lenslet when the target object 12 is in the back focused state with respect to the optical lens system 13, b is in the backward focused state, and c is in the front focused state. FIG.

As is clear from the figure, between the rear focus and the front focus, the light flux from the target object 12 passes through the upper half (solid line) and the lower half (broken line) of the optical lens system 13, with the optical axis being different. The position of incidence on P is switched. i-th lenslet from the end; Li
The light receiving sensor behind Ai; the light receiving sensor receiving the same amount of light flux as the amount of light incident on Ai; Bj
Lenslet located in front of the lens; depending on which side of the lenslet Lj is located in relation to the position of Li, it can be determined whether the lenslet is front focused or rear focused. When the position of Li is taken as a reference, the position of Lj is a geometric quantity with a direction; if it deviates by δ, then δ is the plane F and P on which the target object 12 is imaged by the optical lens system 13. The directional distance between

FIG. 8 shows light received from the target object 12.
This is a plot of each analog output voltage of the CCD line sensor. The analog output voltage of each CCD light receiving sensor is plotted in the order of arrangement, divided into groups A and B, and the plots of the groups are connected by a curve. δ in the figure corresponds to the above-mentioned δ. To calculate δ, do the following: That is, A,
When the B group curve is an=f(n), bn=f(n-δ), the B group curve is moved in the right (positive) direction of the horizontal axis by an integer; i
When translated in parallel, bn=f(ni-δ). f
(n), the average value of f(n-i-δ) is Cn, the differential coefficient of Fu is α, and the difference is β, then if i+δ≧0, Σα・
If β≧0 and i+δ<0, the relationship Σα·β<0 holds true. That is, the function y=g(i+δ)=Σα·β is a monotonically increasing function for the amount of deviation i+δ of bn+i in the right (positive) direction of the horizontal axis with respect to an. Therefore, if the smallest i among the i's for which g(i+δ) is positive is i ₀ , then g(i+δ) is i ₀ +δ and i ₀ +δ−
Since δ becomes zero between 1 and 1, δ can be calculated as follows using the interpolation method.

δ=−i ₀ +g(i ₀ +δ)/g(i ₀ +δ)−g(i ₀ +δ
-1) By calculating the δ value and further calculating the ε value as described above, the movement amount and direction of the focus ring are determined.

A device using a light receiving sensor such as a CCD can be suitably used in a TTL camera.

(Problems to be Solved by the Invention) However, the above conventional example also has the following problems.

That is, when the focus lens is a long focal length lens such as a telephoto lens, the imaging plane of the focus lens may be deviated from the film plane by 20 to 30 mm. When the amount of defocus is large like this, for example, when the focus ring is on the close side,
In cases where the subject is near ∞, the calculation result of δ may appear in the opposite direction from the actual direction.

If the total amount of movement of the focus ring on the image plane is 15 mm, the calculation starts assuming that the focus ring is initially shifted in the direction of extending 15 mm from its current position on the image plane. Because it does. That is, the aforementioned y=g(i+δ)
When substituting δ from -15 mm to +15 mm, the solution is the value of δ that satisfies y = 0. However, if the amount of defocus is large, the image on the light receiving sensor becomes extremely blurred. Therefore, in reality, the curves of an=f(n) and bn=f(n-δ) mentioned above are often close to sine curves, and in that case, when the curve of bn is translated in parallel, it overlaps the curve of an. This is because a complex number of solutions for δ are obtained, and a value of δ that satisfies the focusing condition is obtained in a direction opposite to the actual focal direction. This tendency becomes more pronounced as the amount of defocus increases. As a condition for the defocus to become large, the probability of occurrence is highest when the focus ring is close to the object or near ∞.

Therefore, conventionally, in the case of a long-focus lens, the focus ring is manually turned to bring the lens close to the focus position by visual inspection, and only fine adjustments are made using autofocus.

(Means for Solving the Problems) A focusing device according to the present invention includes the following configuration in order to solve the above problems.

That is, an image of the subject is formed by an optical system on a photoreceiver having a plurality of pairs of photoreceptors, an analog signal output from the photoreceptor is extracted and input to a microprocessor, and the focus position is determined by the microprocessor. In a focusing device that performs a phase difference detection calculation and moves a focus ring out or out based on the calculation result to focus, the current position of the focus ring is detected and this position signal is input to the microprocessor. do,
A focus ring position detection device is provided, and the microprocessor takes into account the focus ring position information based on the input position signal and abstracts out a focus phase difference that is impossible depending on the focus ring position. It is characterized by being set to perform calculations as follows.

(effect) Next, we will discuss the effect.

First, the focus ring position detecting device detects whether the current position of the focus ring is near, near the middle, or near ∞. This detection signal is then input to the microprocessor as position information.

In a microprocessor, for example, when the focus ring is at the ∞ position, it is actually impossible to focus on the ∞ side of the current focus ring, so the calculations on the ∞ side are stopped and the calculations are performed in the closest direction. I do. By doing this, it is possible to reduce the number of calculation solutions in the wrong direction, allowing accurate focusing operations, and eliminating unnecessary calculations, speeding up the calculation process. .

(Example) Preferred examples embodying the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a block diagram.

30 is a light receiving section such as a CCD, and has a group of light receiving sensors consisting of a plurality of pairs. The light receiving section 30 has an integral function section, a shift register section, etc., receives light from a subject, and emits analog signals corresponding to the above-mentioned an and bn. 32 is an analog signal processing device, which includes a function of extracting the difference between the masked dark current signal of the reference sensor and the sensor signal as a reference level, and an automatic gain control circuit (AGC). The analog signal processed by this analog signal processing device 32 is inputted to a microprocessor 36 as a digital signal via an A/D converter 34. Reference numeral 38 denotes a focus ring position detection device, which detects whether the current position of the focus ring is on the close side, an intermediate position, or near the ∞ side, and inputs it to the microprocessor 36 as a position signal. In the microprocessor 36,
The above-mentioned calculation is performed taking into consideration the position information.

A focus position switch 40 counts pulses to detect whether the focus lens control motor 42 has driven the focus lens by the amount obtained by converting the calculation result of the phase difference δ into the number of pulses. The focal length control motor 42 drives the focus ring based on the calculation result to focus.

Next, an example of calculation using a microprocessor is shown.

For example, assume that the total movement of the image plane of the focus lens is 15 mm.

When the amount of image plane shift is δ, the case where it is extended is negative,
If it is carried over, it is considered positive.

Conventionally, calculations are started assuming that the lens is initially shifted by 15 mm in the direction of extension on the image plane from its current position, and δ = By substituting values from −15 mm to +15 mm, δ that satisfies y=0 was found as a solution, but as mentioned above, there was a problem in that the calculation results appeared in the opposite direction.

In the present invention, taking into account the position information from the position detecting device 38 mentioned above, when the focus ring is near the close range, the value of δ is set at −15 mm, for example, so as not to be too large toward the close range. -5 mm, increase the value to +15 mm on the ∞ side, and perform calculations between -5 mm and +15 mm. Also, if the focus ring is near the middle depending on the position information,
Calculations are performed between -10 mm and +10 mm, and when the focus ring is near the ∞ side, δ corresponding to the ∞ side is abstracted and calculations are performed between -15 mm and +5 mm. This reduces the probability of obtaining a solution in the wrong direction.

Note that the above calculation value range is merely an example, and is not limited to the above range.

FIG. 2 is a schematic diagram showing the appearance of the focus lens 44. In the figure, reference numeral 42 denotes the aforementioned focal length control motor which rotationally drives the focus lens 46. 38 is a focus ring position detection device, which rotates together with the focus ring 46. Third
The figure shows a developed view of it. S1 and S2 are position detection brushes, and P1 and P2 of the microprocessor 36 read 0 at positions where they contact the conductive sheet 48 of the position detection device, and read 1 at positions where they do not contact. Therefore, when the focus ring 46 is in a close position,
(P1, P2) becomes (1, 0), if it is in the middle position, it becomes (1, 1), and if it is in the side position, it becomes (0, 1), and the position information is input to the microprocessor 36. .

Note that the position detection device is not limited to the above.

50 is a pulse encoder, and S3 and S4 indicate its brushes. The pulse encoder 50 converts the amount of defocus calculated by the microprocessor 36 into a number of pulses, and controls the focus ring 46 by the focal length control motor 42 by the corresponding number of pulses.
It rotates accurately.

(Effects of the Invention) As described above, in the present invention, a focus ring position detection device is provided to input the focus ring position information to the microprocessor, and the microprocessor detects the position of the focus ring according to the position of the focus ring. Because the calculation is performed by discarding the improbable phase difference,
It reduces the occurrence of calculation solutions in the wrong direction, and enables accurate focusing even with long focal length lenses.
It also has the remarkable effect of speeding up arithmetic processing.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the outline of the device of the present invention, Fig. 2 is a schematic diagram of the focus ring,
FIG. 3 shows a developed view of the position detection device and pulse encoder. Fig. 4 is an explanatory diagram showing a specific example of a CCD sensor, Fig. 5 is an explanatory diagram showing the relationship between the optical lens system and the light receiving section, and Fig. 6 is an explanatory diagram showing the states of the rear pin, the gear pin, and the front pin. FIG. 7 is an explanatory diagram showing the proportional relationship between δ and ε, and FIG. 8 is a graph showing the waveform of light received by the CCD sensor. 15...CCD sensor, 20...lenslet,
13... Optical lens system, 12... Target object, 30
... Light receiving section, 32 ... Analog signal processing device, 3
4... A/D converter, 36... Microprocessor, 38... Position detection device, 40... Focus position switch, 42... Focal length control motor, 46... Focus ring, 48... ...Conductive sheet, 50...Pulse encoder.

Claims (1)

[Scope of Claims] 1. An image of a subject is formed by an optical system on a light-receiving section having a plurality of pairs of light-receiving elements, and an analog signal output from the light-receiving element is extracted and inputted to a microprocessor. In a focusing device that performs a focus phase difference detection calculation in a processor and moves the focus ring forward or retracted based on the calculation result to focus, the current position of the focus ring is detected and this position signal is sent. A focus ring position detection device is provided to input the position signal to the microprocessor, and the microprocessor takes into account the position information of the focus ring based on the input position signal, and depending on the position of the focus ring. A focusing device characterized in that the focusing device is set to abstract and calculate an impossible focus phase difference.