JPS63186219A - Autofocusing camera - Google Patents

Abstract

PURPOSE:To miniaturize an AF mechanism by selectively setting up any prescribed position excluding an infinite position from a focusing zone at the time of selecting snap photographing by a switching means, and in the case of non- snap photographing, selectively setting any prescribed position in the whole focusing zone including the infinite position. CONSTITUTION:The titled camera is provided with a means SW2 for selecting and switching any one of snap photographing and non-snap photographing and a means 15 for selectively setting up a prescribed photographing position obtained by excluding the infinite position from the focusing zone at the time of selecting the snap photographing by the switching means SW2. In the case of selecting the snap photographing by the switching means SW2 for selecting the snap photographing or the non-snap photographing, a photographing lens is set up on any position in the focusing zone excluding the infinite position, so that even if misfocusing operation is generated, out-of-focus photographing is not generated. In the case of the non-snap photographing, ordinary zone focusing is executed and the photographing lens is set up also on the infinite position, so that a clear picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an automatic focusing camera, and more particularly to an automatic focusing camera having an optical projection type distance measuring device using a triangular distance measuring method.

[Prior Art] Generally, automatic focusing cameras use light projection distance measurement using a triangular distance measurement method, which measures the distance to the subject by projecting a light beam toward the subject and receiving the reflected light with a light receiving element. Autofocusing cameras with devices are known. In this type of automatic focusing camera, as the distance to the subject increases, the amount of reflected light decreases, making it difficult to accurately measure the distance. In order to accurately measure the distance to a distant object, it is possible to increase the projection output and increase the amount of reflected light, but this increases the size of the automatic focus adjustment mechanism and increases the cost, so this is not practical.

[Problems to be solved by the invention] For this reason, when trying to photograph an extremely distant (infinite distance) subject such as a landscape photograph, in an automatic focusing camera equipped with an actual optical projection type distance measuring device, The focus tends to be poor, and especially when the subject brightness is low and the photographic lens must be used close to its maximum aperture, such as in the morning, evening, or on cloudy days, the poor focus becomes noticeable. .

In addition, when taking snapshots, accurate distance measurement is not possible unless the person you want to focus on falls within the entire rangefinder frame, and if the person is removed from the rangefinder frame, the focus may be far away. Unfortunately, errors in the focus operation sometimes resulted in out-of-focus photos. Above all,
It is difficult to fit a person at a distance of 5 m or more within the entire range measurement frame because the person is small, so it is currently impossible to accurately measure the distance for a person at a distance of 5 m or more. In snapshots other than landscape photographs, especially portraits, the person is often within 10m, so in normal snapshots, if the aperture of the photographic lens is wide open, it is practical to focus up to 10m. is sufficient.

In other words, autofocus cameras having optical projection type distance measuring devices have conventionally had the following problems. First, in order to improve the infinity depiction characteristics, if the infinity shooting position is set beyond hyperfocal point, for example, when shooting two people side by side, there will be no person in the center of the screen, so the presence of this person will be ignored. This increases the possibility of creating an out-of-focus photograph by causing a focus operation error such as locating the all-lens frame in the center of the image, or so-called centering. Therefore, if the infinity photographing position is set near the common focus so that a satisfactory photograph can be obtained even if a focus operation error occurs, the infinity depiction characteristics will be impaired. These two points are mutually contradictory problems.

Considering the above points, the far side of the in-focus range, that is,
If you set the depth of field at the rear to be closer than infinity, you can avoid poor focus even in landscape photos, prevent out-of-focus photos even if you make a mistake in focus operation in snapshots, and improve the distance measured by the distance measuring device. The AF mechanism can be miniaturized without having to move the camera far away. Therefore, an object of the present invention is to provide such a small and inexpensive S dynamic focusing camera.

[Means for Solving the Problems] An automatic focusing camera according to the present invention is an automatic focusing camera in which a photographing lens is set to a predetermined photographing position in at least three or more focusing zones in response to a distance measurement output. There is a switching means for selecting between snapshot photography and non-snap photography, and this switching means selects and sets the focusing zone to any predetermined position excluding the infinity position when snapshot photography is selected, and when non-snap photography is selected. means for selecting and setting one of all predetermined positions including an infinite position.

[Function] When snapshot photography is selected using the switching means for selecting snapshot photography or non-snap photography, the photographing lens is set to any of the focusing zones except for the infinity position, and even if there is a so-called focus operation error, it will not result in an out-of-focus photograph. No. On the other hand, when taking non-snap shots such as landscape depictions, zone focus is used as before, and the photographing lens is naturally set at an infinity position, so that clear pictures can be obtained.

[Example] The present invention will be described below with reference to the drawings.

First, the present invention will be explained in detail with reference to FIG.

FIG. 2 is a diagram showing the amount of movement of the photographing lens with respect to the subject distance in zone focusing applied in the present invention. The horizontal axis of the diagram shown in FIG. 2 is the reciprocal of the subject distance, and the vertical axis is the amount of extension of the photographic lens. The solid line J in the diagram indicates the amount of extension of the photographing lens that is most in focus at a certain distance to the subject (hereinafter referred to as "jasbin"), and the broken line δ1゜δ2 represents the range of focus (hereinafter referred to as "field of focus") at a certain amount of extension of the photographic lens. This is a line plotting the limit values of depth (referred to as depth). In the zone focus shown in Fig. 2, the amount of extension of the photographic lens is do l dt
, d2. You can take in-focus photos with the 4 steps of da. In snapshot photography, the photographic lens is set to dl, d2, etc. using the output from the range finder. set at one point in da. When the shooting lens extension amount is dl, Jasbin's field of view is from b to b2 at the subject distance g1, and when the extension amount is d9,
Jaspin is at a distance Ω and the depth of field is from b2 to b3, and furthermore, when the feed amount is d3, the Jaspin is at a distance Ω and the depth of field is from b2 to b4. In other words, the shooting range is b
to b4. In the case of non-snap photography of landscapes, etc., if the amount of extension of the photographic lens is set to do according to the photographer's intention, the depth of field will be clear at a distance of Ω. becomes.

In other words, the shooting range at this time is from infinity ■.

Until. And the feeding amount is d. If it is set to -0, Jaspin becomes ■, and the focus is accurately determined as a landscape photograph.

FIG. 3 is a diagram for explaining the principle of the distance measuring optical system used in the present invention. In FIG. 3, a beam of light projected from a light emitting element LD is converged into a spot by a projection lens 1 and irradiated toward a subject 2. The reflected light from the subject 2 is imaged through a light-receiving lens 3 onto a semiconductor device detector (hereinafter abbreviated as PSD) 4, which is a light-receiving element.

Now, the baseline length is S, the subject distance is Ω, and the total length of PSD4 is t.
If the distance between the PSD 4 and the light receiving lens 3 is f, then the PSD
The imaging position X on d is as follows. As is well known, the PSD divides a photocurrent that is inversely proportional to the distance from the center of gravity of the incident light to the electrodes at both ends, and outputs it from the electrodes at both ends. When matched, 11:I2 = (-+x): (H-x)...
-(2), and if I l / I 2 can be measured, P
Since the total length t of SD4 is known, X can be found from equation (2). Substituting this X into equation (1) yields the baseline length S and PSD4
Since the distance f between the lens 3 and the light receiving lens 3 is known, the distance g to the subject can be determined.

FIG. 1 is an electrical circuit diagram of an embodiment of an automatic focusing camera according to the present invention. The electric circuit of this embodiment will be briefly explained below. When the switch SW1 is turned on,
The light emitting drive circuit 5 is activated, and the transistor Q2, which had been turned off by the pull-down resistor R1, is turned on, and the light emitting element LD is supplied with power and emits light.

The circuit 11 is a current-to-voltage conversion circuit that removes the influence of background light from the signal current 11 obtained by photoelectrically converting the incident light flux to the PSD 4, and logarithmically transforms only the variation and outputs it. A current-voltage conversion circuit that removes the influence of background light from the signal current I2 obtained by photoelectrically converting the incident luminous flux of
This is a circuit similar to 1. These current-voltage conversion circuits 11
And each output of the circuit 12 is connected to a differential amplifier 13 consisting of an operational amplifier OP4 and external resistors R6 to R9.
An analog voltage proportional to the quotient of the distance is formed to form a distance measuring circuit. Then, A/D converter 14 consisting of comparator CP-CF2 and resistor R10"" R12 converts A/
The signal is D-converted and supplied to the lens drive signal setting circuit 15 at the next stage. The lens drive signal setting circuit 15 has its output terminal 0.
It is fed out to the position from 1 to 04.

Next, to explain FIG. 1 in more detail, the above-mentioned current -
In the voltage conversion circuit 11, the photocurrent 11 from the PSD 4
is the operational amplifier op1. Transistor Q and resistor R
After being converted to voltage by an IV converter consisting of 5,
Operational amplifier OP3, diode D1, transistor Q6
is applied to a hold circuit consisting of Q7 and capacitor C2. The transistor Q6 of this hold circuit is turned on by a circuit (not shown) connected to its base when the light emitting diode D1 is not lit, that is, when the distance measuring device is not operating, so it supplies bias to the operational amplifier OP3. The operational amplifier OP3 operates accordingly. In this state, the base of transistor Q8 is connected to the operational amplifier OP.
2 to the reference voltage V1, and the emitter is the operational amplifier O.
Since they are each fixed to the reference voltage V2 by P3, the AC component of the background light flows to the emitter junction of diode D1 and transistor Q7 and charges capacitor C2 which defines the holding level. In this state, since the light emitting element LD is not yet emitting light, the voltage generated across the resistor R5 by IV conversion of the photocurrent 1 is the result of photoelectric conversion of only the background light. When the light emitting element LD emits light, the transistor Q
6 is turned off and the bias of the operational amplifier OP3 is cut off, the emitter potential of the transistor Q8 becomes free, and the logarithmic conversion circuit consisting of the operational amplifier OP2 and the transistor Q8 is activated. In addition, the base of the transistor Q7 of the hold circuit is fixed to the potential obtained by photoelectrically converting the background light by the capacitor C2, so the base of the transistor Q7 is
A signal current 11 obtained by photoelectrically converting only the reflected light from the object after removing the background light is logarithmically compressed by the operational amplifier OP2 and the transistor Q8 and is outputted through the capacitor C. In the end, the emitter current of the transistor Q is determined by the bias current IEl determined by the reference voltages V1 and V2, and the signal current (1) that is emitted from the light emitting element LD, reflected by the object, incident on the PSD4, converted into a photocurrent, and divided into the transistor β current amplified by β times at Q
The sum with I becomes IE1+β11. If the reverse saturation current of the transistor is I and the thermal voltage is VT, then the base-emitter voltage of the transistor Q BE1
is V −VN f(IE1+β11)/I,I
It becomes EITn. Here, the Boltzmann constant is 1 and the absolute temperature is T,
If the constant of electronic charge is q, then the thermal voltage V
is VTtsukT/Q.

Similarly, v − v for the current-voltage conversion circuit 12
D f(IE2+]I2)/r81E2Tn is output. These 100 outputs are input to a differential amplifier 15 consisting of resistors R6 to R9 and an operational amplifier OP4.
and VBE2 is output. Considering that the resistor R is biased to the reference voltage V4 at BEI, the potential at the output terminal point ■ of the operational amplifier OP4 is ``BEI''BF2 +V4-VTI), ((lEt+β11)/(IE2+β)
■2)) +v4. Here I (β1,1(βI
If we set El l E2 2, then VBEl-VBE2+v4″″vTgn(11/I2)
+V4, so there is a P at the output terminal of the operational amplifier OP4.
A voltage corresponding to the center position of the light intensity of the light flux incident on the SD 4 is extracted.

Next, the output of the operational amplifier OP4 is connected to the comparator cp
-cp4 and a resistor R10"-R12, it is A/D converted and output to the next stage lens drive signal setting circuit 15. This lens drive signal setting circuit 1
5 is the output of comparators CP1 to CP4 and the snap
It sets a drive signal to be sent to the drive section of the photographing lens according to the combination of on and off of the non-snap changeover switch SW2, and has a two-man power OR gate OR1 and output terminals O1-04. The two input terminals of the OR gate OR■ are the output terminal of the comparator CP1 and the snap terminal.
They are respectively connected to the non-snap changeover switch SW2. Note that the resistor R13 connected to the changeover switch SW2
is for pull-ups. The output terminal of this OR gate OR1 is connected to the output terminal 01 of the lens drive signal setting circuit 15.

Output terminals of comparators CP2 to CP4 are connected to 0 to 0, respectively.

From the above configuration, comparator CP1 of A/D converter 14
~Output of CP4, on/off of snap/non-snap changeover switch SW2, and lens drive signal setting circuit 15
The levels of the output terminals 0 and 04 have the relationship shown in Table 1 below.

Table 1 When the photographer takes a snapshot, if the photographer turns off the snap/non-snap switch SW2, the
The photographing lens is extended in the lens extension fits d2 to d5 shown in FIG. 5, as indicated by o, l to no. Next, when the photographer takes non-snap shots of landscapes, etc.,
When the snap/non-snap changeover switch SW2 is turned on, the photographing lens is extended to positions d1 to d5 including the infinity photographing position d, as shown in No., [i to No., 1O in Table 1 above.

■ For example, if the subject is at infinity, the differential amplifier 1
Since the signal gog (■l/I2) obtained at the output terminal ■ of No. 3 is almost zero, the outputs of the comparators cp-cp4 are all " There is an L″ level. Now, as above, A/D
When the transducer 14 is in the infinity output state, the snap
If the non-snap changeover switch SW2 is left off,
That is, when taking a snapshot, one input of the OR gate OR1 is applied with an "H" level from the power supply via the resistor R13, so the output terminal 0 is applied as shown in No. and l in Table 1 above.
is at the "H" level, the output terminals 0° to 04 are at the "v level," and the photographing lens (not shown) moves to the extended position id2 in FIG. 5. On the other hand, the snap/non-snap changeover switch SW
2 is turned on, that is, during non-snap shooting such as landscape depiction, one input of the OR gate OR1 becomes "L" level, so all output terminals 01 to 04 are turned on as shown in No. 8 in Table 1 above. becomes the "L" level, and the photographing lens is extended to dl, that is, to infinity.

In other words, when taking snapshots without turning on the switch SW2, even if there is a mistake in focus operation such as a person not completely entering the rangefinder frame, the photographing lens will extend to the amount d1 when shooting at infinity. Therefore, the photographic lens stops when the focus zone in front of it is extended ff1d2, and out-of-focus photography can be avoided. When you want to take a picture of scenery at infinity, use the above switch SW2.
By turning on, shooting will be performed with the lens extension amount depending on the zone distance within the distance measurement frame, as before.

FIG. 4 shows the relationship between the potential at the output terminal 0 point of the operational amplifier oP4 and the object distance. In Figure 4, the solid line shows an ideal output curve, but in reality, due to circuit noise etc.
The broken line has noise widths as shown by '' and ''. The farther the subject distance becomes, the weaker the complete incidence on the PSD 4 becomes, and the wider the noise width becomes. comparator cpl
-Cp4 judgment voltage V v V and C
PI″ CP2° CF2 ■ If the object distance range e i , e
2.

Because of CF4 e and e4, the output after A/D conversion is not constant. This unstable subject distance range is called a switching width.

In this embodiment, the actual extension amount of the photographing lens is as shown in FIG. 5 with respect to the output of the operational amplifier OP4 as shown in FIG. 4 above.

In Fig. 5, as in Fig. 2, the horizontal axis represents the reciprocal of the subject distance, and the vertical axis represents the amount of extension of the photographing lens (the solid line J represents the amount of lens extension at the time of focusing, and the broken line represents the limit of the depth of field). Expressed by δ1 and δ2, e t −e i is the switching width.As is clear from FIG. In other words, as mentioned above, in most cases when shooting snapshots, the focus is within 10m. Since there is a subject to be photographed, even if the projected light beam does not hit the subject and is projected to infinity and there is no amount of reflected light, the subject will be in focus.In addition, in landscape photography, the subject is covered by the shooting lens extension mdt. The camera will focus within the range (in terms of subject distance, from infinity to 8m).

In this way, when a photographer wants to take a picture of a landscape, he can take a picture with good infinity depiction characteristics simply by turning on the snap/non-snap selection switch SW2 shown in FIG. Also, even if you were to take a picture of a landscape close to infinity in snapshot mode, the aperture would be set between F5.6 and F8, so the depth of field would be deep and the depth of field would be deep, even if the distance is d2. You can take good photos even with this camera.

[Effects of the Invention] As described above, according to the present invention, by simply adding a simple circuit to a conventional zone focus camera, it is possible to prevent out-of-focus photography due to focus operation errors, and also to shoot landscapes close to infinity with good focus. becomes possible, and the above-mentioned 2
Two conflicting problems can be resolved.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the amount of movement of the photographing lens with respect to the reciprocal of the subject distance, and FIG. 3 is a diagram for explaining the invention in detail. A principle diagram of the distance measuring optical system used in the embodiment shown in FIG. 1 above. FIG. 4 is a diagram showing the operational amplifier output potential with respect to object distance in the circuit of the embodiment shown in FIG. 1 above. FIG. 2 is a diagram showing the movement of the photographic lens against the reciprocal of the subject distance in the embodiment circuit shown in FIG. 1. FIG. 11.12...Current-voltage conversion circuit 13...
.........Differential amplifier 14...
......A/D converter 15...
...... Lens drive signal setting circuit (selection setting means) SW2 ...... Snap/non-snap changeover switch (selection means)

Claims (1)

[Claims] In an automatic focusing camera in which a photographing lens is set to a predetermined photographing position in at least three focusing zones in response to a distance measurement output, either snap photographing or non-snap photographing is selected. and means for selecting and setting a predetermined photographing position excluding the infinity position from the focusing zone when snapshot photography is selected by the switching means. camera.