JPH0123132Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a TTL camera that is ideal for single-lens reflex cameras, etc.
The present invention relates to an in-focus/out-of-focus display device for an autofocus camera that employs a (through the taking lens) autofocus system.

For example, an autofocus system in a single-lens reflex camera includes a so-called autofocus mechanism that uses a motor or the like to automatically extend or retract the optical system, that is, the lens, and then stops when the lens is in focus. There is a so-called focus display mechanism in which the user manually performs a focus detection display on the camera side and the user stops the lens based on the display, but the present invention is mainly directed to the latter, that is, the focus display mechanism.

In a TTL autofocus system, calculations are made based on the image information of the subject that is detected through the lens, and it is determined whether the subject is in one of three states: front focus, in focus, or back focus. Based on this, a series of operations for displaying these three states and, in some cases, additionally controlling the drive of the lens (extending, stopping, retracting), are repeated sequentially.

An example of an autofocus camera to which such an autofocus system is applied will be described.

FIG. 1 is a conceptual diagram showing a portion related to an autofocus function in a single-lens reflex autofocus camera. In the figure, a part of the light passing through the lens 1 passes through a quick return mirror, that is, a semi-transparent part formed in the center of the main mirror 2, and is mirrored by a sub-mirror 3 attached behind the main mirror 2. Light receiving section 4 located at the bottom of the box
guided by. The light receiving section 4 includes, for example, a row of solid-state imaging devices such as CCDs (charge-coupled devices) arranged via a beam splitter in a plane optically equivalent to the front and back positions of the film surface, respectively. The illuminance distribution of the image on two surfaces equivalent to the front and back of the film surface is scanned and detected by each solid-state image sensor array. This detection information is given to the calculation unit 5, which compares the detection values of adjacent elements for each solid-state image sensor column to obtain a contrast evaluation function, that is, contrast information, and further compares the contrast information of each column. Therefore, it is determined whether the object is in front focus, in focus, or in back focus. The determination results in this calculation unit 5 are given to a display 6 in the viewfinder, for example, and are displayed for the out-of-focus front pin N, the in-focus J, and the out-of-focus back pin F.
The difference is indicated by a symbol such as lighting of a light emitting diode. In FIG. 1, the out-of-focus display symbol corresponds to the direction of rotation of the distance adjustment ring of the lens.

By the way, as a display method for in-focus/out-of-focus in such an autofocus camera, it is common to display the determination result of the arithmetic unit 5 on the display 6 as it is. That is, in this case, lens 1
As shown in Figure 2, the judgment output changes in the order of rear focus, focus, and front focus, and the rear focus display, focus display, and front focus display correspond to each of them. will be done.

However, in this case, if the focus detection accuracy is sufficiently high, slight changes in the part of the subject that falls into the focus detection area (distance measurement area) due to slight movements of the camera or subject (especially when held hand-held) will cause The in-focus and out-of-focus indications flicker frequently, making it extremely difficult to see and making it difficult to judge whether the camera is in focus or not. In addition, when photographing a distant subject, the in-focus display may appear only for a moment and then quickly change to an out-of-focus display, even though the subject is actually in focus, leading to erroneous decisions. Sometimes things like that happen.

In reality, when using this type of display, if the focus is displayed even momentarily, it can often be said that the focus is sufficiently focused for practical purposes as long as you do not change the subject. tends to judge that the subject is out of focus unless the in-focus display is displayed continuously.

This inconvenience with focus display can be prevented by, for example, lowering the focus detection accuracy and determining focus over a wide range, but if you do this, for example, when shooting a stationary subject using a tripod, This results in a new inconvenience in that the focusing accuracy is lowered even in situations where the above-mentioned problem does not occur, such as when photographing.

The present invention was developed against the background of these circumstances, and aims to provide a display device for an autofocus camera that makes it easier to determine the focus state and improves the stability of the display without reducing focusing accuracy. is intended to provide.

In other words, the features of the present invention include an optical system that focuses on the subject, a light receiving section that detects image information of the subject that passes through this optical system, and a light receiving section that detects image information of the subject that passes through this optical system. Autofocus equipped with a calculation unit that sequentially determines focus, front focus, and rear focus, and a display that displays focus, front focus, and rear focus based on the determination results of this calculation unit. In the in-focus/out-of-focus display device for a camera, the out-of-focus display is displayed only when a state in which there is no focus output from the arithmetic unit continues for a predetermined time or more.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted. Out of the pre-out-of-focus pin output S _N , the in-focus output S _J , and the out-of-focus pin output S _F of the calculation unit 5 (one of which is H, that is, a high level), the in-focus output S _J is the re-focus output. Only when there is no in-focus output S _J that is applied to the waveform conversion circuit 9 consisting of a series circuit of a monostable multivibrator 7 with a triggerable predetermined time width and an inverter 8 that inverts its output for more than the predetermined time. Inverter 8
The output of is H, and at all other times it is converted into a pulse that is L, that is, a low level. Both the out-of-focus outputs S _N and S _F of the calculation unit 5 are connected to the inverter 8.
The out-of-focus outputs S _N and S _F are inverted and output only when the output of the inverter 8 is H. That is, these NAND gates 10, 11
is the output L of the inverter 8 and each non-focus output S _N , S _F
This constitutes a prohibition circuit that prevents The output of the inverter 8 is applied to the light emitting diode 6 _J for displaying focus on the display 6, the output of the NAND gate 10 is applied to the light emitting diode 6 _N for indicating the front focus, and the output of the NAND gate 11 is applied to the light emitting diode 6 _F for indicating the rear focus. It will be done. Resistors 61, 62, and 63 of the display device 6 are resistors for limiting the current of the light emitting diodes _6N , _6J , and _6F , respectively.

In such a configuration, when the focus output S _J is output from the calculation unit 5, the monostable multivibrator 7 of the waveform conversion circuit 9 is triggered and the output becomes H, which is inverted by the inverter 8 and becomes L, which is displayed on the display. The light emitting diode 6 _J of 6 is turned on to indicate focus. The L output of this inverter 8 is also applied to NAND gates 10 and 11 to close these gates and force the output to H. Therefore, at this time, the light emitting diodes 6 _N and 6 _F do not light up. Then, even if the focusing output S _J is no longer output from the calculation unit 5 and, for example, the front pin output S _N is output, the previous output state is maintained for the set time of the monostable multivibrator 7, and the output of the inverter 8 is remains at L. During this time, due to the L output of the inverter 8, the front pin output S _N from the calculation section 5 is also blocked by the NAND gate 10.
The display on the display 6 also remains the same as before. If the focus output S _J is output again from the calculation unit 5 during this time, the monostable multivibrator 7 will be triggered again, so the above-mentioned display state will be extended until after the set time after the focus output S _J disappears. Ru. If the focusing output S _J is not output from the calculation unit 5 for more than the set time, the output of the monostable multivibrator 7 becomes L, the output of the inverter 8 becomes H, and the light emitting diode 6 _J turns off. For example, the previous pin output
If S _N is being output from the arithmetic unit 5, the output of the NAND gate 10 becomes L, the light emitting diode 6 _N of the display 6 lights up, and the display becomes an out-of-focus focus display.

Next, an example of the operation will be explained with reference to the time chart shown in FIG. For example, if the subject in the distance measurement area is stationary and the lens is at the rear focus position and the lens is gradually extended, the focus display will change from the rear focus display based on the rear focus determination to the in-focus display based on the focus determination. Then, the determination is made that the focus is on the front, but the in-focus display is made for a set time T, and after the time T, the display becomes the focus on the front.

In this way, the focus display becomes distorted from the moment the focus judgment output S _J is output from the calculation unit 5, and short-term out-of-focus judgments within the time T output by the monostable multivibrator 7 are ignored. Do not show. Then, only when the out-of-focus determination continues for the time T or more, out-of-focus is displayed. Therefore, the focus display becomes stable and easy to see, making it easy to determine focus. Moreover, the focusing accuracy will not deteriorate as long as the determination is made for a time sufficiently longer than the time T. In this case, the appropriate setting time T is usually about 0.1 to 0.5 seconds.

Note that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented in various modifications.

For example, FIG. 5 shows the configuration of another embodiment of the present invention.

In FIG. 5, the focused output S _J is transmitted from the calculation unit 5 to the transistor Q ₁ of the waveform conversion unit ₁₂ via the resistor R
When applied to the base of , transistor Q ₁ turns on, and the collector potential of transistor Q ₂ decreases, triggering monostable multivibrator MM and inverting the output state. When the output state of the monostable multivibrator MM is reversed and the transistor _Q3 is turned off and the transistor _Q2 is turned on, the focus display light emitting diode _6J lights up. At the same time, the transistor Q ₄ of the inhibiting circuit 13 having a gate circuit consisting of diodes D ₁ , D ₂ and resistor R ₂ is turned off, and the light emitting diodes 6 _N ,
6 _F turns off. Monostable multivibrator MM
When the output of is in a stable state, that is, when there is no in-focus output S _J for more than the set time T, the transistor Q ₄ of the prohibition circuit 13 is turned on, and either one of the light-emitting diodes 6 _N and 6 _F for out-of-focus indication is turned on. lights up.
In this case, the set time T is the capacitor C ₁ , the resistor
From _R3 , it is expressed as T=0.7, _C1 , and _R3 .

Further, FIG. 6 shows the configuration of another embodiment of the present invention.

In FIG. 6, when the focus output S _J is output from the calculation unit 5, the capacitor C ₂ is charged through the diode D ₃ of the waveform conversion circuit 14, and the resistor
It is applied to the base of transistor _Q5 through _R4 , and transistor _Q5 is turned on. Transistor Q ₅
When turned on, the focus display light emitting diode _6J lights up and the diode 6J lights up, almost as shown in Fig.
The transistor Q ₆ of the inhibition circuit 15 having a gate circuit composed of D ₄ , D ₅ , and resistor R ₅ is turned off.
This prevents the light emitting diodes 6 _N and 6 _F for out-of-focus indication from lighting up. Even after the focus output S _J disappears, the charge stored in the capacitor C ₂ of the waveform conversion circuit 14 causes the base current to flow through the transistor Q ₅ for a scheduled time T.
During this period, transistor _Q5 remains on. When the transistor Q ₅ is turned off after the time T has elapsed, the transistor Q ₆ of the inhibition circuit 15 is turned on, and one of the light emitting diodes 6 _N and 6 _F lights up according to the output of the calculation section 5 at that time. In this case the resistance
If R ₄ and R ₆ are (R ₄ <<R ₆ ), the time T is expressed as T=-C ₂ R ₄ ln0.7/Vcc (where ln is a natural logarithm and Vcc is a power supply voltage).

Various other modifications are possible, such as replacing the transistor from PNP to NPN and changing the power supply accordingly.

As detailed above, according to the present invention, it is possible to provide a display device for an autofocus camera that allows easy determination of the in-focus state and provides a highly stable display without substantially reducing focusing accuracy. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the main part configuration of an example of an autofocus camera to which the present invention is applied, and FIG. 2 is a timing chart for explaining its operation.
FIG. 3 is a block diagram schematically showing the main structure of one embodiment of the present invention, FIG. 4 is a timing chart for explaining its operation, and FIGS. 5 and 6 are different versions of the present invention. FIG. 2 is a circuit configuration diagram showing the configuration of an embodiment. 9, 12, 14...Waveform conversion circuit, 13, 15
...Prohibition circuit, 1 ... Lens, 2 ... Main mirror, 3 ... Submirror, 4 ... Light receiving section, 5 ... Arithmetic section, 6 ... Display unit, 7, MM ... Monostable multivibrator, 8 ...Inverter, 10, 11...
... NAND gate, 6 _N , 6 _J , 6 _F ... Light emitting diode, 61 to 63, R ₁ to R ₆ ... Resistor, C ₁ , C ₂ ...
…Capacitor, D ₁ ~ D ₄ … Diode, Q ₁ ~ _{Q 6}
...transistor.

Claims (1)

[Scope of utility model registration request] An optical system that should focus on the subject, a light receiving unit that detects image information of the subject that has passed through this optical system,
There is a calculation unit that sequentially determines focus, front focus, and rear focus based on the information detected by this light receiving unit, and a calculation unit that determines focus, front focus, and rear focus based on the judgment results of this calculation unit. In an in-focus/out-of-focus display device for an autofocus camera equipped with a display device for displaying, a waveform conversion circuit that maintains the in-focus output of the arithmetic unit for a predetermined time even after it disappears, and this waveform 1. A display device for an autofocus camera, comprising: a prohibition circuit that prevents front focus and rear focus outputs from being supplied to a display device from an arithmetic unit while a focus output is being output by a conversion circuit.