Image reading apparatus

1. An image reading apparatus comprising:

a first reading unit configured to output an analog signal by reading an original;

a second reading unit different from the first reading unit;

a conversion unit configured to convert analog signals outputted from the first reading unit and from the second reading unit to digital signals;

a wire connection control unit configured to control a wire connection between the first reading unit and the second reading unit and the conversion unit, by a switch that is provided on a signal line and switches an output target in a plurality of input signals, wherein the analog signals outputted from the first reading unit and from the second reading unit are inputted into the conversion unit via the wire connection control unit;

an output control unit configured to control an output of an analog signal from the first reading unit,

wherein, in a first reading mode, the wire connection control unit is configured to control the wire connection such that analog signals outputted from a plurality of output channels of the first reading unit are respectively inputted to a plurality of input channels of the conversion unit,

in a second reading mode different from the first reading mode, the wire connection control unit is configured to control the wire connection such that the analog signals outputted from the plurality of output channels of the first reading unit and analog signals outputted from a plurality of output channels of the second reading unit are inputted to the plurality of input channels of the conversion unit, and

in the second reading mode, the output control unit is configured to control an output of analog signals such that a timing of an output of an analog signal from each of the plurality of output channels of the first reading unit to be inputted to one input channel of the conversion unit is shifted.

2. The image reading apparatus according to claim 1 , wherein the wire connection control unit is configured to perform a switchover of the switch using a signal that indicates either the first reading mode or the second reading mode.

3. The image reading apparatus according to claim 1 , wherein an analog signal controlled by the output control unit in the second reading mode is transmitted on a signal line connected by a wired-OR to one input channel of the conversion unit.

4. The image reading apparatus according to claim 1 , wherein

the first reading unit includes a plurality of chips, and

the plurality of chips are grouped to correspond to an output channel, and a timing of an output of an analog signal is controlled for each group.

5. The image reading apparatus according to claim 4 , wherein in the first reading mode, the plurality of grouped chips are configured such that an output of an analog signal from a first chip and an output of an analog signal from a second chip adjacent to the first chip are started in parallel.

6. The image reading apparatus according to claim 4 , wherein in the second reading mode, the plurality of grouped chips are configured such that after an analog signal is outputted from a first chip, an output of an analog signal from a second chip adjacent to the first chip is started.

7. The image reading apparatus according to claim 6 , wherein the output control unit, in the second reading mode, after an analog signal has been outputted from a last chip of the grouped chips of a first group, causes a leading chip among chips of a second group adjacent to the first group to output an analog signal.

8. The image reading apparatus according to claim 7 , wherein an analog signal is outputted from the leading chip among the chips of the second group based on a level of a signal of a logical sum of a level of a signal that indicates either the first reading mode or the second reading mode and a level of a signal that indicates that an analog signal has been outputted from the last chip.

9. The image reading apparatus according to claim 8 , wherein the output control unit, by changing the level of the signal that indicates either the first reading mode or the second reading mode, is configured to control a timing of an output of an analog signal from the leading chip among the chips of the second group.

10. The image reading apparatus according to claim 1 , wherein the first reading unit and the second reading unit are contact image sensors.

11. The image reading apparatus according to claim 1 , wherein the first reading unit is used at a time of reading a first side of an original, and the second reading unit is used at a time of reading a second side, which is a back side of the first side, of the original.

12. The image reading apparatus according to claim 1 , wherein the first reading unit is used at a time of reading an original of a first size and a second size that is larger than the first size, and the second reading unit is not used at a time of reading an original of the first size and is used at a time of reading an original of the second size.

13. The image reading apparatus according to claim 1 , wherein

the wire connection control unit is configured to,

in the first reading mode, control the wire connection such that an analog signal outputted from a first output channel of the first reading unit is inputted to a first input channel of the conversion unit, an analog signal outputted from a second output channel of the first reading unit is inputted to a second input channel of the conversion unit, an analog signal outputted from a third output channel of the first reading unit is inputted to a third input channel of the conversion unit, and an analog signal outputted from a fourth output channel of the first reading unit is inputted to a fourth input channel of the conversion unit, and,

in the second reading mode, control the wire connection such that the analog signal outputted from the first output channel and the analog signal outputted from the second output channel of the first reading unit are inputted to the first input channel of the conversion unit, the analog signal outputted from the third output channel and the analog signal outputted from the fourth output channel of the first reading unit are inputted to the second input channel of the conversion unit, the analog signal outputted from the first output channel of the second reading unit is inputted to the third input channel of the conversion unit, and the analog signal outputted from the second output channel of the second reading unit is inputted to the fourth input channel of the conversion unit.